THE DESCENT OF MAN AND SELECTION IN RELATION TO SEX

By Charles Darwin


CONTENTS

 PREFACE TO THE SECOND EDITION.
 DETAILED TABLE OF CONTENTS
 THE DESCENT OF MAN; AND SELECTION IN RELATION TO SEX.
 INTRODUCTION.

 PART I. THE DESCENT OR ORIGIN OF MAN.
 CHAPTER I. THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.
 CHAPTER II. — ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.
 CHAPTER III. — COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.
 CHAPTER IV. — COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS, continued.
 CHAPTER V. — ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FACULTIES DURING PRIMEVAL AND CIVILISED TIMES.
 CHAPTER VI. — ON THE AFFINITIES AND GENEALOGY OF MAN.
 CHAPTER VII. — ON THE RACES OF MAN.

 PART II. SEXUAL SELECTION.
 CHAPTER VIII. — PRINCIPLES OF SEXUAL SELECTION.
 CHAPTER IX. — SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.
 CHAPTER X. — SECONDARY SEXUAL CHARACTERS OF INSECTS.
 CHAPTER XI. — INSECTS, continued. ORDER LEPIDOPTERA. (BUTTERFLIES AND MOTHS.)
 CHAPTER XII. — SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, AND REPTILES.
 CHAPTER XIII. — SECONDARY SEXUAL CHARACTERS OF BIRDS.
 CHAPTER XIV. — BIRDS—continued.
 CHAPTER XV. — BIRDS—continued.
 CHAPTER XVI. — BIRDS—concluded.
 CHAPTER XVII. — SECONDARY SEXUAL CHARACTERS OF MAMMALS.
 CHAPTER XVIII. — SECONDARY SEXUAL CHARACTERS OF MAMMALS, continued.

 PART III. — SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.
 CHAPTER XIX. — SECONDARY SEXUAL CHARACTERS OF MAN.
 CHAPTER XX. — SECONDARY SEXUAL CHARACTERS OF MAN, continued.
 CHAPTER XXI. — GENERAL A SUMMARY AND CONCLUSION.




PREFACE TO THE SECOND EDITION.


During the successive reprints of the first edition of this work,
published in 1871, I was able to introduce several important
corrections; and now that more time has elapsed, I have endeavoured to
profit by the fiery ordeal through which the book has passed, and have
taken advantage of all the criticisms which seem to me sound. I am also
greatly indebted to a large number of correspondents for the
communication of a surprising number of new facts and remarks. These
have been so numerous, that I have been able to use only the more
important ones; and of these, as well as of the more important
corrections, I will append a list. Some new illustrations have been
introduced, and four of the old drawings have been replaced by better
ones, done from life by Mr. T.W. Wood. I must especially call attention
to some observations which I owe to the kindness of Prof. Huxley (given
as a supplement at the end of Part I.), on the nature of the
differences between the brains of man and the higher apes. I have been
particularly glad to give these observations, because during the last
few years several memoirs on the subject have appeared on the
Continent, and their importance has been, in some cases, greatly
exaggerated by popular writers.

I may take this opportunity of remarking that my critics frequently
assume that I attribute all changes of corporeal structure and mental
power exclusively to the natural selection of such variations as are
often called spontaneous; whereas, even in the first edition of the
‘Origin of Species,’ I distinctly stated that great weight must be
attributed to the inherited effects of use and disuse, with respect
both to the body and mind. I also attributed some amount of
modification to the direct and prolonged action of changed conditions
of life. Some allowance, too, must be made for occasional reversions of
structure; nor must we forget what I have called “correlated” growth,
meaning, thereby, that various parts of the organisation are in some
unknown manner so connected, that when one part varies, so do others;
and if variations in the one are accumulated by selection, other parts
will be modified. Again, it has been said by several critics, that when
I found that many details of structure in man could not be explained
through natural selection, I invented sexual selection; I gave,
however, a tolerably clear sketch of this principle in the first
edition of the ‘Origin of Species,’ and I there stated that it was
applicable to man. This subject of sexual selection has been treated at
full length in the present work, simply because an opportunity was here
first afforded me. I have been struck with the likeness of many of the
half-favourable criticisms on sexual selection, with those which
appeared at first on natural selection; such as, that it would explain
some few details, but certainly was not applicable to the extent to
which I have employed it. My conviction of the power of sexual
selection remains unshaken; but it is probable, or almost certain, that
several of my conclusions will hereafter be found erroneous; this can
hardly fail to be the case in the first treatment of a subject. When
naturalists have become familiar with the idea of sexual selection, it
will, as I believe, be much more largely accepted; and it has already
been fully and favourably received by several capable judges.

DOWN, BECKENHAM, KENT, September, 1874.

First Edition February 24, 1871. Second Edition September, 1874.




DETAILED TABLE OF CONTENTS

INTRODUCTION.

PART I. THE DESCENT OR ORIGIN OF MAN.

CHAPTER I.
THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.
Nature of the evidence bearing on the origin of man—Homologous
structures in man and the lower animals—Miscellaneous points of
correspondence—Development—Rudimentary structures, muscles,
sense-organs, hair, bones, reproductive organs, etc.—The bearing of
these three great classes of facts on the origin of man.

CHAPTER II.
ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.
Variability of body and mind in man—Inheritance—Causes of
variability—Laws of variation the same in man as in the lower
animals—Direct action of the conditions of life—Effects of the
increased use and disuse of parts—Arrested
development—Reversion—Correlated variation—Rate of increase—Checks to
increase—Natural selection—Man the most dominant animal in the
world—Importance of his corporeal structure—The causes which have led
to his becoming erect—Consequent changes of structure—Decrease in size
of the canine teeth—Increased size and altered shape of the
skull—Nakedness —Absence of a tail—Defenceless condition of man.

CHAPTER III.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.
The difference in mental power between the highest ape and the lowest
savage, immense—Certain instincts in common—The
emotions—Curiosity—Imitation—Attention—Memory—
Imagination—Reason—Progressive improvement —Tools and weapons used by
animals—Abstraction, Self-consciousness—Language—Sense of beauty—Belief
in God, spiritual agencies, superstitions.

CHAPTER IV.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS,
continued.
The moral sense—Fundamental proposition—The qualities of social
animals—Origin of sociability—Struggle between opposed instincts—Man a
social animal—The more enduring social instincts conquer other less
persistent instincts—The social virtues alone regarded by savages—The
self-regarding virtues acquired at a later stage of development—The
importance of the judgment of the members of the same community on
conduct—Transmission of moral tendencies—Summary.

CHAPTER V.
ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FACULTIES DURING
PRIMEVAL AND CIVILISED TIMES.
Advancement of the intellectual powers through natural
selection—Importance of imitation—Social and moral faculties—Their
development within the limits of the same tribe—Natural selection as
affecting civilised nations—Evidence that civilised nations were once
barbarous.

CHAPTER VI.
ON THE AFFINITIES AND GENEALOGY OF MAN.
Position of man in the animal series—The natural system
genealogical—Adaptive characters of slight value—Various small points
of resemblance between man and the Quadrumana—Rank of man in the
natural system—Birthplace and antiquity of man—Absence of fossil
connecting-links—Lower stages in the genealogy of man, as inferred
firstly from his affinities and secondly from his structure—Early
androgynous condition of the Vertebrata —Conclusion.

CHAPTER VII.
ON THE RACES OF MAN.
The nature and value of specific characters—Application to the races of
man—Arguments in favour of, and opposed to, ranking the so-called races
of man as distinct species—Sub-species—Monogenists and
polygenists—Convergence of character—Numerous points of resemblance in
body and mind between the most distinct races of man—The state of man
when he first spread over the earth—Each race not descended from a
single pair—The extinction of races—The formation of races—The effects
of crossing—Slight influence of the direct action of the conditions of
life—Slight or no influence of natural selection—Sexual selection.

PART II. SEXUAL SELECTION.

CHAPTER VIII.
PRINCIPLES OF SEXUAL SELECTION.
Secondary sexual characters—Sexual selection—Manner of action—Excess of
males—Polygamy—The male alone generally modified through sexual
selection—Eagerness of the male—Variability of the male—Choice exerted
by the female—Sexual compared with natural selection—Inheritance at
corresponding periods of life, at corresponding seasons of the year,
and as limited by sex—Relations between the several forms of
inheritance—Causes why one sex and the young are not modified through
sexual selection—Supplement on the proportional numbers of the two
sexes throughout the animal kingdom—The proportion of the sexes in
relation to natural selection.

CHAPTER IX.
SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.
These characters are absent in the lowest classes—Brilliant
colours—Mollusca—Annelids—Crustacea, secondary sexual characters
strongly developed; dimorphism; colour; characters not acquired before
maturity—Spiders, sexual colours of; stridulation by the
males—Myriapoda.

CHAPTER X.
SECONDARY SEXUAL CHARACTERS OF INSECTS.
Diversified structures possessed by the males for seizing the
females—Differences between the sexes, of which the meaning is not
understood—Difference in size between the
sexes—Thysanura—Diptera—Hemiptera—Homoptera, musical powers possessed
by the males alone—Orthoptera, musical instruments of the males, much
diversified in structure; pugnacity; colours—Neuroptera, sexual
differences in colour—Hymenoptera, pugnacity and odours—Coleoptera,
colours; furnished with great horns, apparently as an ornament;
battles; stridulating organs generally common to both sexes.

CHAPTER XI.
INSECTS, continued. ORDER LEPIDOPTERA. (BUTTERFLIES AND MOTHS.)
Courtship of Butterflies—Battles—Ticking noise—Colours common to both
sexes, or more brilliant in the males—Examples—Not due to the direct
action of the conditions of life—Colours adapted for protection—Colours
of moths—Display—Perceptive powers of the
Lepidoptera—Variability—Causes of the difference in colour between the
males and females—Mimicry, female butterflies more brilliantly coloured
than the males—Bright colours of caterpillars—Summary and concluding
remarks on the secondary sexual character of insects—Birds and insects
compared.

CHAPTER XII.
SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, AND REPTILES.
Fishes: Courtship and battles of the males—Larger size of the
females—Males, bright colours and ornamental appendages; other strange
characters—Colours and appendages acquired by the males during the
breeding-season alone—Fishes with both sexes brilliantly
coloured—Protective colours—The less conspicuous colours of the female
cannot be accounted for on the principle of protection—Male fishes
building nests, and taking charge of the ova and young. AMPHIBIANS:
Differences in structure and colour between the sexes—Vocal organs.
REPTILES: Chelonians—Crocodiles—Snakes, colours in some cases
protective—Lizards, battles of—Ornamental appendages—Strange
differences in structure between the sexes—Colours—Sexual differences
almost as great as with birds.

CHAPTER XIII.
SECONDARY SEXUAL CHARACTERS OF BIRDS.
Sexual differences—Law of battle—Special weapons—Vocal
organs—Instrumental music—Love-antics and dances—Decorations, permanent
and seasonal—Double and single annual moults—Display of ornaments by
the males.

CHAPTER XIV.
BIRDS—continued.
Choice exerted by the female—Length of courtship—Unpaired birds—Mental
qualities and taste for the beautiful—Preference or antipathy shewn by
the female for particular males—Variability of birds—Variations
sometimes abrupt—Laws of variation—Formation of ocelli—Gradations of
character—Case of Peacock, Argus pheasant, and Urosticte.

CHAPTER XV.
BIRDS—continued.
Discussion as to why the males alone of some species, and both sexes of
others are brightly coloured—On sexually-limited inheritance, as
applied to various structures and to brightly-coloured
plumage—Nidification in relation to colour—Loss of nuptial plumage
during the winter.

CHAPTER XVI.
BIRDS—concluded.
The immature plumage in relation to the character of the plumage in
both sexes when adult—Six classes of cases—Sexual differences between
the males of closely-allied or representative species—The female
assuming the characters of the male—Plumage of the young in relation to
the summer and winter plumage of the adults—On the increase of beauty
in the birds of the world—Protective colouring—Conspicuously coloured
birds—Novelty appreciated—Summary of the four chapters on birds.

CHAPTER XVII.
SECONDARY SEXUAL CHARACTERS OF MAMMALS.
The law of battle—Special weapons, confined to the males—Cause of
absence of weapons in the female—Weapons common to both sexes, yet
primarily acquired by the male—Other uses of such weapons—Their high
importance—Greater size of the male—Means of defence—On the preference
shewn by either sex in the pairing of quadrupeds.

CHAPTER XVIII.
SECONDARY SEXUAL CHARACTERS OF MAMMALS, continued.
Voice—Remarkable sexual peculiarities in seals—Odour—Development of the
hair—Colour of the hair and skin—Anomalous case of the female being
more ornamented than the male—Colour and ornaments due to sexual
selection—Colour acquired for the sake of protection—Colour, though
common to both sexes, often due to sexual selection—On the
disappearance of spots and stripes in adult quadrupeds—On the colours
and ornaments of the Quadrumana—Summary.

PART III. SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.

CHAPTER XIX.
SECONDARY SEXUAL CHARACTERS OF MAN.
Differences between man and woman—Causes of such differences, and of
certain characters common to both sexes—Law of battle—Differences in
mental powers, and voice—On the influence of beauty in determining the
marriages of mankind—Attention paid by savages to ornaments—Their ideas
of beauty in women—The tendency to exaggerate each natural peculiarity.

CHAPTER XX.
SECONDARY SEXUAL CHARACTERS OF MAN, continued.
On the effects of the continued selection of women according to a
different standard of beauty in each race—On the causes which interfere
with sexual selection in civilised and savage nations—Conditions
favourable to sexual selection during primeval times—On the manner of
action of sexual selection with mankind—On the women in savage tribes
having some power to choose their husbands—Absence of hair on the body,
and development of the beard—Colour of the skin—Summary.

CHAPTER XXI.
GENERAL A SUMMARY AND CONCLUSION.
Main conclusion that man is descended from some lower form—Manner of
development—Genealogy of man—Intellectual and moral faculties—Sexual
selection—Concluding remarks.




THE DESCENT OF MAN; AND SELECTION IN RELATION TO SEX.




INTRODUCTION.


The nature of the following work will be best understood by a brief
account of how it came to be written. During many years I collected
notes on the origin or descent of man, without any intention of
publishing on the subject, but rather with the determination not to
publish, as I thought that I should thus only add to the prejudices
against my views. It seemed to me sufficient to indicate, in the first
edition of my ‘Origin of Species,’ that by this work “light would be
thrown on the origin of man and his history;” and this implies that man
must be included with other organic beings in any general conclusion
respecting his manner of appearance on this earth. Now the case wears a
wholly different aspect. When a naturalist like Carl Vogt ventures to
say in his address as President of the National Institution of Geneva
(1869), “personne, en Europe au moins, n’ose plus soutenir la creation
indépendante et de toutes pièces, des espèces,” it is manifest that at
least a large number of naturalists must admit that species are the
modified descendants of other species; and this especially holds good
with the younger and rising naturalists. The greater number accept the
agency of natural selection; though some urge, whether with justice the
future must decide, that I have greatly overrated its importance. Of
the older and honoured chiefs in natural science, many unfortunately
are still opposed to evolution in every form.

In consequence of the views now adopted by most naturalists, and which
will ultimately, as in every other case, be followed by others who are
not scientific, I have been led to put together my notes, so as to see
how far the general conclusions arrived at in my former works were
applicable to man. This seemed all the more desirable, as I had never
deliberately applied these views to a species taken singly. When we
confine our attention to any one form, we are deprived of the weighty
arguments derived from the nature of the affinities which connect
together whole groups of organisms—their geographical distribution in
past and present times, and their geological succession. The
homological structure, embryological development, and rudimentary
organs of a species remain to be considered, whether it be man or any
other animal, to which our attention may be directed; but these great
classes of facts afford, as it appears to me, ample and conclusive
evidence in favour of the principle of gradual evolution. The strong
support derived from the other arguments should, however, always be
kept before the mind.

The sole object of this work is to consider, firstly, whether man, like
every other species, is descended from some pre-existing form;
secondly, the manner of his development; and thirdly, the value of the
differences between the so-called races of man. As I shall confine
myself to these points, it will not be necessary to describe in detail
the differences between the several races—an enormous subject which has
been fully described in many valuable works. The high antiquity of man
has recently been demonstrated by the labours of a host of eminent men,
beginning with M. Boucher de Perthes; and this is the indispensable
basis for understanding his origin. I shall, therefore, take this
conclusion for granted, and may refer my readers to the admirable
treatises of Sir Charles Lyell, Sir John Lubbock, and others. Nor shall
I have occasion to do more than to allude to the amount of difference
between man and the anthropomorphous apes; for Prof. Huxley, in the
opinion of most competent judges, has conclusively shewn that in every
visible character man differs less from the higher apes, than these do
from the lower members of the same order of Primates.

This work contains hardly any original facts in regard to man; but as
the conclusions at which I arrived, after drawing up a rough draft,
appeared to me interesting, I thought that they might interest others.
It has often and confidently been asserted, that man’s origin can never
be known: but ignorance more frequently begets confidence than does
knowledge: it is those who know little, and not those who know much,
who so positively assert that this or that problem will never be solved
by science. The conclusion that man is the co-descendant with other
species of some ancient, lower, and extinct form, is not in any degree
new. Lamarck long ago came to this conclusion, which has lately been
maintained by several eminent naturalists and philosophers; for
instance, by Wallace, Huxley, Lyell, Vogt, Lubbock, Buchner, Rolle,
etc. (1. As the works of the first-named authors are so well known, I
need not give the titles; but as those of the latter are less well
known in England, I will give them:—‘Sechs Vorlesungen über die
Darwin’sche Theorie:’ zweite Auflage, 1868, von Dr L. Buchner;
translated into French under the title ‘Conférences sur la Théorie
Darwinienne,’ 1869. ‘Der Mensch im Lichte der Darwin’sche Lehre,’ 1865,
von Dr. F. Rolle. I will not attempt to give references to all the
authors who have taken the same side of the question. Thus G.
Canestrini has published (‘Annuario della Soc. d. Nat.,’ Modena, 1867,
page 81) a very curious paper on rudimentary characters, as bearing on
the origin of man. Another work has (1869) been published by Dr.
Francesco Barrago, bearing in Italian the title of “Man, made in the
image of God, was also made in the image of the ape.”), and especially
by Haeckel. This last naturalist, besides his great work, ‘Generelle
Morphologie’ (1866), has recently (1868, with a second edition in
1870), published his ‘Natürliche Schöpfungsgeschichte,’ in which he
fully discusses the genealogy of man. If this work had appeared before
my essay had been written, I should probably never have completed it.
Almost all the conclusions at which I have arrived I find confirmed by
this naturalist, whose knowledge on many points is much fuller than
mine. Wherever I have added any fact or view from Prof. Haeckel’s
writings, I give his authority in the text; other statements I leave as
they originally stood in my manuscript, occasionally giving in the
foot-notes references to his works, as a confirmation of the more
doubtful or interesting points.

During many years it has seemed to me highly probable that sexual
selection has played an important part in differentiating the races of
man; but in my ‘Origin of Species’ (first edition, page 199) I
contented myself by merely alluding to this belief. When I came to
apply this view to man, I found it indispensable to treat the whole
subject in full detail. (2. Prof. Haeckel was the only author who, at
the time when this work first appeared, had discussed the subject of
sexual selection, and had seen its full importance, since the
publication of the ‘Origin’; and this he did in a very able manner in
his various works.) Consequently the second part of the present work,
treating of sexual selection, has extended to an inordinate length,
compared with the first part; but this could not be avoided.

I had intended adding to the present volumes an essay on the expression
of the various emotions by man and the lower animals. My attention was
called to this subject many years ago by Sir Charles Bell’s admirable
work. This illustrious anatomist maintains that man is endowed with
certain muscles solely for the sake of expressing his emotions. As this
view is obviously opposed to the belief that man is descended from some
other and lower form, it was necessary for me to consider it. I
likewise wished to ascertain how far the emotions are expressed in the
same manner by the different races of man. But owing to the length of
the present work, I have thought it better to reserve my essay for
separate publication.




PART I.
THE DESCENT OR ORIGIN OF MAN.




CHAPTER I.
THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.


Nature of the evidence bearing on the origin of man—Homologous
structures in man and the lower animals—Miscellaneous points of
correspondence—Development—Rudimentary structures, muscles, sense-
organs, hair, bones, reproductive organs, etc.—The bearing of these
three great classes of facts on the origin of man.

He who wishes to decide whether man is the modified descendant of some
pre-existing form, would probably first enquire whether man varies,
however slightly, in bodily structure and in mental faculties; and if
so, whether the variations are transmitted to his offspring in
accordance with the laws which prevail with the lower animals. Again,
are the variations the result, as far as our ignorance permits us to
judge, of the same general causes, and are they governed by the same
general laws, as in the case of other organisms; for instance, by
correlation, the inherited effects of use and disuse, etc.? Is man
subject to similar malconformations, the result of arrested
development, of reduplication of parts, etc., and does he display in
any of his anomalies reversion to some former and ancient type of
structure? It might also naturally be enquired whether man, like so
many other animals, has given rise to varieties and sub-races,
differing but slightly from each other, or to races differing so much
that they must be classed as doubtful species? How are such races
distributed over the world; and how, when crossed, do they react on
each other in the first and succeeding generations? And so with many
other points.

The enquirer would next come to the important point, whether man tends
to increase at so rapid a rate, as to lead to occasional severe
struggles for existence; and consequently to beneficial variations,
whether in body or mind, being preserved, and injurious ones
eliminated. Do the races or species of men, whichever term may be
applied, encroach on and replace one another, so that some finally
become extinct? We shall see that all these questions, as indeed is
obvious in respect to most of them, must be answered in the
affirmative, in the same manner as with the lower animals. But the
several considerations just referred to may be conveniently deferred
for a time: and we will first see how far the bodily structure of man
shews traces, more or less plain, of his descent from some lower form.
In succeeding chapters the mental powers of man, in comparison with
those of the lower animals, will be considered.

THE BODILY STRUCTURE OF MAN.

It is notorious that man is constructed on the same general type or
model as other mammals. All the bones in his skeleton can be compared
with corresponding bones in a monkey, bat, or seal. So it is with his
muscles, nerves, blood-vessels and internal viscera. The brain, the
most important of all the organs, follows the same law, as shewn by
Huxley and other anatomists. Bischoff (1. ‘Grosshirnwindungen des
Menschen,’ 1868, s. 96. The conclusions of this author, as well as
those of Gratiolet and Aeby, concerning the brain, will be discussed by
Prof. Huxley in the Appendix alluded to in the Preface to this
edition.), who is a hostile witness, admits that every chief fissure
and fold in the brain of man has its analogy in that of the orang; but
he adds that at no period of development do their brains perfectly
agree; nor could perfect agreement be expected, for otherwise their
mental powers would have been the same. Vulpian (2. ‘Lec. sur la Phys.’
1866, page 890, as quoted by M. Dally, ‘L’Ordre des Primates et le
Transformisme,’ 1868, page 29.), remarks: “Les différences réelles qui
existent entre l’encephale de l’homme et celui des singes supérieurs,
sont bien minimes. Il ne faut pas se faire d’illusions a cet égard.
L’homme est bien plus près des singes anthropomorphes par les
caractères anatomiques de son cerveau que ceux-ci ne le sont non
seulement des autres mammifères, mais même de certains quadrumanes, des
guenons et des macaques.” But it would be superfluous here to give
further details on the correspondence between man and the higher
mammals in the structure of the brain and all other parts of the body.

It may, however, be worth while to specify a few points, not directly
or obviously connected with structure, by which this correspondence or
relationship is well shewn.

Man is liable to receive from the lower animals, and to communicate to
them, certain diseases, as hydrophobia, variola, the glanders,
syphilis, cholera, herpes, etc. (3. Dr. W. Lauder Lindsay has treated
this subject at some length in the ‘Journal of Mental Science,’ July
1871; and in the ‘Edinburgh Veterinary Review,’ July 1858.); and this
fact proves the close similarity (4. A Reviewer has criticised
(‘British Quarterly Review,’ Oct. 1st, 1871, page 472) what I have here
said with much severity and contempt; but as I do not use the term
identity, I cannot see that I am greatly in error. There appears to me
a strong analogy between the same infection or contagion producing the
same result, or one closely similar, in two distinct animals, and the
testing of two distinct fluids by the same chemical reagent.) of their
tissues and blood, both in minute structure and composition, far more
plainly than does their comparison under the best microscope, or by the
aid of the best chemical analysis. Monkeys are liable to many of the
same non-contagious diseases as we are; thus Rengger (5.
‘Naturgeschichte der Säugethiere von Paraguay,’ 1830, s. 50.), who
carefully observed for a long time the Cebus Azarae in its native land,
found it liable to catarrh, with the usual symptoms, and which, when
often recurrent, led to consumption. These monkeys suffered also from
apoplexy, inflammation of the bowels, and cataract in the eye. The
younger ones when shedding their milk-teeth often died from fever.
Medicines produced the same effect on them as on us. Many kinds of
monkeys have a strong taste for tea, coffee, and spiritous liquors:
they will also, as I have myself seen, smoke tobacco with pleasure. (6.
The same tastes are common to some animals much lower in the scale. Mr.
A. Nichols informs me that he kept in Queensland, in Australia, three
individuals of the Phaseolarctus cinereus; and that, without having
been taught in any way, they acquired a strong taste for rum, and for
smoking tobacco.) Brehm asserts that the natives of north-eastern
Africa catch the wild baboons by exposing vessels with strong beer, by
which they are made drunk. He has seen some of these animals, which he
kept in confinement, in this state; and he gives a laughable account of
their behaviour and strange grimaces. On the following morning they
were very cross and dismal; they held their aching heads with both
hands, and wore a most pitiable expression: when beer or wine was
offered them, they turned away with disgust, but relished the juice of
lemons. (7. Brehm, ‘Thierleben,’ B. i. 1864, s. 75, 86. On the Ateles,
s. 105. For other analogous statements, see s. 25, 107.) An American
monkey, an Ateles, after getting drunk on brandy, would never touch it
again, and thus was wiser than many men. These trifling facts prove how
similar the nerves of taste must be in monkeys and man, and how
similarly their whole nervous system is affected.

Man is infested with internal parasites, sometimes causing fatal
effects; and is plagued by external parasites, all of which belong to
the same genera or families as those infesting other mammals, and in
the case of scabies to the same species. (8. Dr. W. Lauder Lindsay,
‘Edinburgh Vet. Review,’ July 1858, page 13.) Man is subject, like
other mammals, birds, and even insects (9. With respect to insects see
Dr. Laycock, “On a General Law of Vital Periodicity,” ‘British
Association,’ 1842. Dr. Macculloch, ‘Silliman’s North American Journal
of Science,’ vol. XVII. page 305, has seen a dog suffering from tertian
ague. Hereafter I shall return to this subject.), to that mysterious
law, which causes certain normal processes, such as gestation, as well
as the maturation and duration of various diseases, to follow lunar
periods. His wounds are repaired by the same process of healing; and
the stumps left after the amputation of his limbs, especially during an
early embryonic period, occasionally possess some power of
regeneration, as in the lowest animals. (10. I have given the evidence
on this head in my ‘Variation of Animals and Plants under
Domestication,’ vol. ii. page 15, and more could be added.)

The whole process of that most important function, the reproduction of
the species, is strikingly the same in all mammals, from the first act
of courtship by the male (11. Mares e diversis generibus Quadrumanorum
sine dubio dignoscunt feminas humanas a maribus. Primum, credo,
odoratu, postea aspectu. Mr. Youatt, qui diu in Hortis Zoologicis
(Bestiariis) medicus animalium erat, vir in rebus observandis cautus et
sagax, hoc mihi certissime probavit, et curatores ejusdem loci et alii
e ministris confirmaverunt. Sir Andrew Smith et Brehm notabant idem in
Cynocephalo. Illustrissimus Cuvier etiam narrat multa de hac re, qua ut
opinor, nihil turpius potest indicari inter omnia hominibus et
Quadrumanis communia. Narrat enim Cynocephalum quendam in furorem
incidere aspectu feminarum aliquarem, sed nequaquam accendi tanto
furore ab omnibus. Semper eligebat juniores, et dignoscebat in turba,
et advocabat voce gestuque.), to the birth and nurturing of the young.
Monkeys are born in almost as helpless a condition as our own infants;
and in certain genera the young differ fully as much in appearance from
the adults, as do our children from their full-grown parents. (12. This
remark is made with respect to Cynocephalus and the anthropomorphous
apes by Geoffroy Saint-Hilaire and F. Cuvier, ‘Histoire Nat. des
Mammifères,’ tom. i. 1824.) It has been urged by some writers, as an
important distinction, that with man the young arrive at maturity at a
much later age than with any other animal: but if we look to the races
of mankind which inhabit tropical countries the difference is not
great, for the orang is believed not to be adult till the age of from
ten to fifteen years. (13. Huxley, ‘Man’s Place in Nature,’ 1863, p.
34.) Man differs from woman in size, bodily strength, hairiness, etc.,
as well as in mind, in the same manner as do the two sexes of many
mammals. So that the correspondence in general structure, in the minute
structure of the tissues, in chemical composition and in constitution,
between man and the higher animals, especially the anthropomorphous
apes, is extremely close.

EMBRYONIC DEVELOPMENT.

[Fig. 1. Shows a human embryo, from Ecker, and a dog embryo, from
Bischoff. Labelled in each are:

a. Fore-brain, cerebral hemispheres, etc. b. Mid-brain, corpora
quadrigemina. c. Hind-brain, cerebellum, medulla oblongata. d. Eye. e.
Ear. f. First visceral arch. g. Second visceral arch. H. Vertebral
columns and muscles in process of development. i. Anterior extremities.
K. Posterior extremities. L. Tail or os coccyx.]

Man is developed from an ovule, about the 125th of an inch in diameter,
which differs in no respect from the ovules of other animals. The
embryo itself at a very early period can hardly be distinguished from
that of other members of the vertebrate kingdom. At this period the
arteries run in arch-like branches, as if to carry the blood to
branchiae which are not present in the higher Vertebrata, though the
slits on the sides of the neck still remain (see f, g, fig. 1), marking
their former position. At a somewhat later period, when the extremities
are developed, “the feet of lizards and mammals,” as the illustrious
Von Baer remarks, “the wings and feet of birds, no less than the hands
and feet of man, all arise from the same fundamental form.” It is, says
Prof. Huxley (14. ‘Man’s Place in Nature,’ 1863, p. 67.), “quite in the
later stages of development that the young human being presents marked
differences from the young ape, while the latter departs as much from
the dog in its developments, as the man does. Startling as this last
assertion may appear to be, it is demonstrably true.”

As some of my readers may never have seen a drawing of an embryo, I
have given one of man and another of a dog, at about the same early
stage of development, carefully copied from two works of undoubted
accuracy. (15. The human embryo (upper fig.) is from Ecker, ‘Icones
Phys.,’ 1851-1859, tab. xxx. fig. 2. This embryo was ten lines in
length, so that the drawing is much magnified. The embryo of the dog is
from Bischoff, ‘Entwicklungsgeschichte des Hunde-Eies,’ 1845, tab. xi.
fig. 42B. This drawing is five times magnified, the embryo being
twenty-five days old. The internal viscera have been omitted, and the
uterine appendages in both drawings removed. I was directed to these
figures by Prof. Huxley, from whose work, ‘Man’s Place in Nature,’ the
idea of giving them was taken. Haeckel has also given analogous
drawings in his ‘Schopfungsgeschichte.’)

After the foregoing statements made by such high authorities, it would
be superfluous on my part to give a number of borrowed details, shewing
that the embryo of man closely resembles that of other mammals. It may,
however, be added, that the human embryo likewise resembles certain low
forms when adult in various points of structure. For instance, the
heart at first exists as a simple pulsating vessel; the excreta are
voided through a cloacal passage; and the os coccyx projects like a
true tail, “extending considerably beyond the rudimentary legs.” (16.
Prof. Wyman in ‘Proceedings of the American Academy of Sciences,’ vol.
iv. 1860, p. 17.) In the embryos of all air-breathing vertebrates,
certain glands, called the corpora Wolffiana, correspond with, and act
like the kidneys of mature fishes. (17. Owen, ‘Anatomy of Vertebrates,’
vol. i. p. 533.) Even at a later embryonic period, some striking
resemblances between man and the lower animals may be observed.
Bischoff says that “the convolutions of the brain in a human foetus at
the end of the seventh month reach about the same stage of development
as in a baboon when adult.” (18. ‘Die Grosshirnwindungen des Menschen,’
1868, s. 95.) The great toe, as Professor Owen remarks (19. ‘Anatomy of
Vertebrates,’ vol. ii. p. 553.), “which forms the fulcrum when standing
or walking, is perhaps the most characteristic peculiarity in the human
structure;” but in an embryo, about an inch in length, Prof. Wyman (20.
‘Proc. Soc. Nat. Hist.’ Boston, 1863, vol. ix. p. 185.) found “that the
great toe was shorter than the others; and, instead of being parallel
to them, projected at an angle from the side of the foot, thus
corresponding with the permanent condition of this part in the
quadrumana.” I will conclude with a quotation from Huxley (21. ‘Man’s
Place in Nature,’ p. 65.) who after asking, does man originate in a
different way from a dog, bird, frog or fish? says, “the reply is not
doubtful for a moment; without question, the mode of origin, and the
early stages of the development of man, are identical with those of the
animals immediately below him in the scale: without a doubt in these
respects, he is far nearer to apes than the apes are to the dog.”

RUDIMENTS.

This subject, though not intrinsically more important than the two
last, will for several reasons be treated here more fully. (22. I had
written a rough copy of this chapter before reading a valuable paper,
“Caratteri rudimentali in ordine all’ origine dell’ uomo” (‘Annuario
della Soc. d. Naturalisti,’ Modena, 1867, p. 81), by G. Canestrini, to
which paper I am considerably indebted. Haeckel has given admirable
discussions on this whole subject, under the title of Dysteleology, in
his ‘Generelle Morphologie’ and ‘Schöpfungsgeschichte.’) Not one of the
higher animals can be named which does not bear some part in a
rudimentary condition; and man forms no exception to the rule.
Rudimentary organs must be distinguished from those that are nascent;
though in some cases the distinction is not easy. The former are either
absolutely useless, such as the mammae of male quadrupeds, or the
incisor teeth of ruminants which never cut through the gums; or they
are of such slight service to their present possessors, that we can
hardly suppose that they were developed under the conditions which now
exist. Organs in this latter state are not strictly rudimentary, but
they are tending in this direction. Nascent organs, on the other hand,
though not fully developed, are of high service to their possessors,
and are capable of further development. Rudimentary organs are
eminently variable; and this is partly intelligible, as they are
useless, or nearly useless, and consequently are no longer subjected to
natural selection. They often become wholly suppressed. When this
occurs, they are nevertheless liable to occasional reappearance through
reversion—a circumstance well worthy of attention.

The chief agents in causing organs to become rudimentary seem to have
been disuse at that period of life when the organ is chiefly used (and
this is generally during maturity), and also inheritance at a
corresponding period of life. The term “disuse” does not relate merely
to the lessened action of muscles, but includes a diminished flow of
blood to a part or organ, from being subjected to fewer alternations of
pressure, or from becoming in any way less habitually active.
Rudiments, however, may occur in one sex of those parts which are
normally present in the other sex; and such rudiments, as we shall
hereafter see, have often originated in a way distinct from those here
referred to. In some cases, organs have been reduced by means of
natural selection, from having become injurious to the species under
changed habits of life. The process of reduction is probably often
aided through the two principles of compensation and economy of growth;
but the later stages of reduction, after disuse has done all that can
fairly be attributed to it, and when the saving to be effected by the
economy of growth would be very small (23. Some good criticisms on this
subject have been given by Messrs. Murie and Mivart, in ‘Transact.
Zoological Society,’ 1869, vol. vii. p. 92.), are difficult to
understand. The final and complete suppression of a part, already
useless and much reduced in size, in which case neither compensation
nor economy can come into play, is perhaps intelligible by the aid of
the hypothesis of pangenesis. But as the whole subject of rudimentary
organs has been discussed and illustrated in my former works (24.
‘Variation of Animals and Plants under Domestication,’ vol. ii pp. 317
and 397. See also ‘Origin of Species,’ 5th Edition p. 535.), I need
here say no more on this head.

Rudiments of various muscles have been observed in many parts of the
human body (25. For instance, M. Richard (‘Annales des Sciences Nat.,’
3rd series, Zoolog. 1852, tom. xviii. p. 13) describes and figures
rudiments of what he calls the “muscle pedieux de la main,” which he
says is sometimes “infiniment petit.” Another muscle, called “le tibial
posterieur,” is generally quite absent in the hand, but appears from
time to time in a more or less rudimentary condition.); and not a few
muscles, which are regularly present in some of the lower animals can
occasionally be detected in man in a greatly reduced condition. Every
one must have noticed the power which many animals, especially horses,
possess of moving or twitching their skin; and this is effected by the
panniculus carnosus. Remnants of this muscle in an efficient state are
found in various parts of our bodies; for instance, the muscle on the
forehead, by which the eyebrows are raised. The platysma myoides, which
is well developed on the neck, belongs to this system. Prof. Turner, of
Edinburgh, has occasionally detected, as he informs me, muscular
fasciculi in five different situations, namely in the axillae, near the
scapulae, etc., all of which must be referred to the system of the
panniculus. He has also shewn (26. Prof. W. Turner, ‘Proceedings of the
Royal Society of Edinburgh,’ 1866-67, p. 65.) that the musculus
sternalis or sternalis brutorum, which is not an extension of the
rectus abdominalis, but is closely allied to the panniculus, occurred
in the proportion of about three per cent. in upwards of 600 bodies: he
adds, that this muscle affords “an excellent illustration of the
statement that occasional and rudimentary structures are especially
liable to variation in arrangement.”

Some few persons have the power of contracting the superficial muscles
on their scalps; and these muscles are in a variable and partially
rudimentary condition. M. A. de Candolle has communicated to me a
curious instance of the long-continued persistence or inheritance of
this power, as well as of its unusual development. He knows a family,
in which one member, the present head of the family, could, when a
youth, pitch several heavy books from his head by the movement of the
scalp alone; and he won wagers by performing this feat. His father,
uncle, grandfather, and his three children possess the same power to
the same unusual degree. This family became divided eight generations
ago into two branches; so that the head of the above-mentioned branch
is cousin in the seventh degree to the head of the other branch. This
distant cousin resides in another part of France; and on being asked
whether he possessed the same faculty, immediately exhibited his power.
This case offers a good illustration how persistent may be the
transmission of an absolutely useless faculty, probably derived from
our remote semi-human progenitors; since many monkeys have, and
frequently use the power, of largely moving their scalps up and down.
(27. See my ‘Expression of the Emotions in Man and Animals,’ 1872, p.
144.)

The extrinsic muscles which serve to move the external ear, and the
intrinsic muscles which move the different parts, are in a rudimentary
condition in man, and they all belong to the system of the panniculus;
they are also variable in development, or at least in function. I have
seen one man who could draw the whole ear forwards; other men can draw
it upwards; another who could draw it backwards (28. Canestrini quotes
Hyrtl. (‘Annuario della Soc. dei Naturalisti,’ Modena, 1867, p. 97) to
the same effect.); and from what one of these persons told me, it is
probable that most of us, by often touching our ears, and thus
directing our attention towards them, could recover some power of
movement by repeated trials. The power of erecting and directing the
shell of the ears to the various points of the compass, is no doubt of
the highest service to many animals, as they thus perceive the
direction of danger; but I have never heard, on sufficient evidence, of
a man who possessed this power, the one which might be of use to him.
The whole external shell may be considered a rudiment, together with
the various folds and prominences (helix and anti-helix, tragus and
anti-tragus, etc.) which in the lower animals strengthen and support
the ear when erect, without adding much to its weight. Some authors,
however, suppose that the cartilage of the shell serves to transmit
vibrations to the acoustic nerve; but Mr. Toynbee (29. ‘The Diseases of
the Ear,’ by J. Toynbee, F.R.S., 1860, p. 12. A distinguished
physiologist, Prof. Preyer, informs me that he had lately been
experimenting on the function of the shell of the ear, and has come to
nearly the same conclusion as that given here.), after collecting all
the known evidence on this head, concludes that the external shell is
of no distinct use. The ears of the chimpanzee and orang are curiously
like those of man, and the proper muscles are likewise but very
slightly developed. (30. Prof. A. Macalister, ‘Annals and Magazine of
Natural History,’ vol. vii. 1871, p. 342.) I am also assured by the
keepers in the Zoological Gardens that these animals never move or
erect their ears; so that they are in an equally rudimentary condition
with those of man, as far as function is concerned. Why these animals,
as well as the progenitors of man, should have lost the power of
erecting their ears, we cannot say. It may be, though I am not
satisfied with this view, that owing to their arboreal habits and great
strength they were but little exposed to danger, and so during a
lengthened period moved their ears but little, and thus gradually lost
the power of moving them. This would be a parallel case with that of
those large and heavy birds, which, from inhabiting oceanic islands,
have not been exposed to the attacks of beasts of prey, and have
consequently lost the power of using their wings for flight. The
inability to move the ears in man and several apes is, however, partly
compensated by the freedom with which they can move the head in a
horizontal plane, so as to catch sounds from all directions. It has
been asserted that the ear of man alone possesses a lobule; but “a
rudiment of it is found in the gorilla” (31. Mr. St. George Mivart,
‘Elementary Anatomy,’ 1873, p. 396.); and, as I hear from Prof. Preyer,
it is not rarely absent in the negro.

[Fig. 2. Human Ear, modelled and drawn by Mr. Woolner. The projecting
point is labelled a.]

The celebrated sculptor, Mr. Woolner, informs me of one little
peculiarity in the external ear, which he has often observed both in
men and women, and of which he perceived the full significance. His
attention was first called to the subject whilst at work on his figure
of Puck, to which he had given pointed ears. He was thus led to examine
the ears of various monkeys, and subsequently more carefully those of
man. The peculiarity consists in a little blunt point, projecting from
the inwardly folded margin, or helix. When present, it is developed at
birth, and, according to Prof. Ludwig Meyer, more frequently in man
than in woman. Mr. Woolner made an exact model of one such case, and
sent me the accompanying drawing. (Fig. 2). These points not only
project inwards towards the centre of the ear, but often a little
outwards from its plane, so as to be visible when the head is viewed
from directly in front or behind. They are variable in size, and
somewhat in position, standing either a little higher or lower; and
they sometimes occur on one ear and not on the other. They are not
confined to mankind, for I observed a case in one of the spider-monkeys
(Ateles beelzebuth) in our Zoological Gardens; and Mr. E. Ray Lankester
informs me of another case in a chimpanzee in the gardens at Hamburg.
The helix obviously consists of the extreme margin of the ear folded
inwards; and this folding appears to be in some manner connected with
the whole external ear being permanently pressed backwards. In many
monkeys, which do not stand high in the order, as baboons and some
species of macacus (32. See also some remarks, and the drawings of the
ears of the Lemuroidea, in Messrs. Murie and Mivart’s excellent paper
in ‘Transactions of the Zoological Society,’ vol. vii. 1869, pp. 6 and
90.), the upper portion of the ear is slightly pointed, and the margin
is not at all folded inwards; but if the margin were to be thus folded,
a slight point would necessarily project inwards towards the centre,
and probably a little outwards from the plane of the ear; and this I
believe to be their origin in many cases. On the other hand, Prof. L.
Meyer, in an able paper recently published (33. ‘Über das Darwin’sche
Spitzohr,’ Archiv fur Path. Anat. und Phys., 1871, p. 485.), maintains
that the whole case is one of mere variability; and that the
projections are not real ones, but are due to the internal cartilage on
each side of the points not having been fully developed. I am quite
ready to admit that this is the correct explanation in many instances,
as in those figured by Prof. Meyer, in which there are several minute
points, or the whole margin is sinuous. I have myself seen, through the
kindness of Dr. L. Down, the ear of a microcephalous idiot, on which
there is a projection on the outside of the helix, and not on the
inward folded edge, so that this point can have no relation to a former
apex of the ear. Nevertheless in some cases, my original view, that the
points are vestiges of the tips of formerly erect and pointed ears,
still seems to me probable. I think so from the frequency of their
occurrence, and from the general correspondence in position with that
of the tip of a pointed ear. In one case, of which a photograph has
been sent me, the projection is so large, that supposing, in accordance
with Prof. Meyer’s view, the ear to be made perfect by the equal
development of the cartilage throughout the whole extent of the margin,
it would have covered fully one-third of the whole ear. Two cases have
been communicated to me, one in North America, and the other in
England, in which the upper margin is not at all folded inwards, but is
pointed, so that it closely resembles the pointed ear of an ordinary
quadruped in outline. In one of these cases, which was that of a young
child, the father compared the ear with the drawing which I have given
(34. ‘The Expression of the Emotions,’ p. 136.) of the ear of a monkey,
the Cynopithecus niger, and says that their outlines are closely
similar. If, in these two cases, the margin had been folded inwards in
the normal manner, an inward projection must have been formed. I may
add that in two other cases the outline still remains somewhat pointed,
although the margin of the upper part of the ear is normally folded
inwards—in one of them, however, very narrowly. [Fig.3. Foetus of an
Orang(?). Exact copy of a photograph, shewing the form of the ear at
this early age.] The following woodcut (No. 3) is an accurate copy of a
photograph of the foetus of an orang (kindly sent me by Dr. Nitsche),
in which it may be seen how different the pointed outline of the ear is
at this period from its adult condition, when it bears a close general
resemblance to that of man. It is evident that the folding over of the
tip of such an ear, unless it changed greatly during its further
development, would give rise to a point projecting inwards. On the
whole, it still seems to me probable that the points in question are in
some cases, both in man and apes, vestiges of a former condition.

The nictitating membrane, or third eyelid, with its accessory muscles
and other structures, is especially well developed in birds, and is of
much functional importance to them, as it can be rapidly drawn across
the whole eye-ball. It is found in some reptiles and amphibians, and in
certain fishes, as in sharks. It is fairly well developed in the two
lower divisions of the mammalian series, namely, in the monotremata and
marsupials, and in some few of the higher mammals, as in the walrus.
But in man, the quadrumana, and most other mammals, it exists, as is
admitted by all anatomists, as a mere rudiment, called the semilunar
fold. (35. Muller’s ‘Elements of Physiology,’ Eng. translat. 1842, vol.
ii. p. 1117. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 260; ibid. on
the Walrus, ‘Proceedings of the Zoological Society,’ November 8, 1854.
See also R. Knox, ‘Great Artists and Anatomists,’ p. 106. This rudiment
apparently is somewhat larger in Negroes and Australians than in
Europeans, see Carl Vogt, ‘Lectures on Man,’ Eng. translat. p. 129.)

The sense of smell is of the highest importance to the greater number
of mammals—to some, as the ruminants, in warning them of danger; to
others, as the Carnivora, in finding their prey; to others, again, as
the wild boar, for both purposes combined. But the sense of smell is of
extremely slight service, if any, even to the dark coloured races of
men, in whom it is much more highly developed than in the white and
civilised races. (36. The account given by Humboldt of the power of
smell possessed by the natives of South America is well known, and has
been confirmed by others. M. Houzeau (‘Études sur les Facultés
Mentales,’ etc., tom. i. 1872, p. 91) asserts that he repeatedly made
experiments, and proved that Negroes and Indians could recognise
persons in the dark by their odour. Dr. W. Ogle has made some curious
observations on the connection between the power of smell and the
colouring matter of the mucous membrane of the olfactory region as well
as of the skin of the body. I have, therefore, spoken in the text of
the dark-coloured races having a finer sense of smell than the white
races. See his paper, ‘Medico-Chirurgical Transactions,’ London, vol.
liii. 1870, p. 276.) Nevertheless it does not warn them of danger, nor
guide them to their food; nor does it prevent the Esquimaux from
sleeping in the most fetid atmosphere, nor many savages from eating
half-putrid meat. In Europeans the power differs greatly in different
individuals, as I am assured by an eminent naturalist who possesses
this sense highly developed, and who has attended to the subject. Those
who believe in the principle of gradual evolution, will not readily
admit that the sense of smell in its present state was originally
acquired by man, as he now exists. He inherits the power in an
enfeebled and so far rudimentary condition, from some early progenitor,
to whom it was highly serviceable, and by whom it was continually used.
In those animals which have this sense highly developed, such as dogs
and horses, the recollection of persons and of places is strongly
associated with their odour; and we can thus perhaps understand how it
is, as Dr. Maudsley has truly remarked (37. ‘The Physiology and
Pathology of Mind,’ 2nd ed. 1868, p. 134.), that the sense of smell in
man “is singularly effective in recalling vividly the ideas and images
of forgotten scenes and places.”

Man differs conspicuously from all the other primates in being almost
naked. But a few short straggling hairs are found over the greater part
of the body in the man, and fine down on that of the woman. The
different races differ much in hairiness; and in the individuals of the
same race the hairs are highly variable, not only in abundance, but
likewise in position: thus in some Europeans the shoulders are quite
naked, whilst in others they bear thick tufts of hair. (38. Eschricht,
Über die Richtung der Haare am menschlichen Körper, Muller’s ‘Archiv
fur Anat. und Phys.’ 1837, s. 47. I shall often have to refer to this
very curious paper.) There can be little doubt that the hairs thus
scattered over the body are the rudiments of the uniform hairy coat of
the lower animals. This view is rendered all the more probable, as it
is known that fine, short, and pale-coloured hairs on the limbs and
other parts of the body, occasionally become developed into “thickset,
long, and rather coarse dark hairs,” when abnormally nourished near
old-standing inflamed surfaces. (39. Paget, ‘Lectures on Surgical
Pathology,’ 1853, vol. i. p. 71.)

I am informed by Sir James Paget that often several members of a family
have a few hairs in their eyebrows much longer than the others; so that
even this slight peculiarity seems to be inherited. These hairs, too,
seem to have their representatives; for in the chimpanzee, and in
certain species of Macacus, there are scattered hairs of considerable
length rising from the naked skin above the eyes, and corresponding to
our eyebrows; similar long hairs project from the hairy covering of the
superciliary ridges in some baboons.

The fine wool-like hair, or so-called lanugo, with which the human
foetus during the sixth month is thickly covered, offers a more curious
case. It is first developed, during the fifth month, on the eyebrows
and face, and especially round the mouth, where it is much longer than
that on the head. A moustache of this kind was observed by Eschricht
(40. Eschricht, ibid. s. 40, 47.) on a female foetus; but this is not
so surprising a circumstance as it may at first appear, for the two
sexes generally resemble each other in all external characters during
an early period of growth. The direction and arrangement of the hairs
on all parts of the foetal body are the same as in the adult, but are
subject to much variability. The whole surface, including even the
forehead and ears, is thus thickly clothed; but it is a significant
fact that the palms of the hands and the soles of the feet are quite
naked, like the inferior surfaces of all four extremities in most of
the lower animals. As this can hardly be an accidental coincidence, the
woolly covering of the foetus probably represents the first permanent
coat of hair in those mammals which are born hairy. Three or four cases
have been recorded of persons born with their whole bodies and faces
thickly covered with fine long hairs; and this strange condition is
strongly inherited, and is correlated with an abnormal condition of the
teeth. (41. See my ‘Variation of Animals and Plants under
Domestication,’ vol. ii. p. 327. Prof. Alex. Brandt has recently sent
me an additional case of a father and son, born in Russia, with these
peculiarities. I have received drawings of both from Paris.) Prof.
Alex. Brandt informs me that he has compared the hair from the face of
a man thus characterised, aged thirty-five, with the lanugo of a
foetus, and finds it quite similar in texture; therefore, as he
remarks, the case may be attributed to an arrest of development in the
hair, together with its continued growth. Many delicate children, as I
have been assured by a surgeon to a hospital for children, have their
backs covered by rather long silky hairs; and such cases probably come
under the same head.

It appears as if the posterior molar or wisdom-teeth were tending to
become rudimentary in the more civilised races of man. These teeth are
rather smaller than the other molars, as is likewise the case with the
corresponding teeth in the chimpanzee and orang; and they have only two
separate fangs. They do not cut through the gums till about the
seventeenth year, and I have been assured that they are much more
liable to decay, and are earlier lost than the other teeth; but this is
denied by some eminent dentists. They are also much more liable to
vary, both in structure and in the period of their development, than
the other teeth. (42. Dr. Webb, ‘Teeth in Man and the Anthropoid Apes,’
as quoted by Dr. C. Carter Blake in Anthropological Review, July 1867,
p. 299.) In the Melanian races, on the other hand, the wisdom-teeth are
usually furnished with three separate fangs, and are generally sound;
they also differ from the other molars in size, less than in the
Caucasian races. (43. Owen, ‘Anatomy of Vertebrates,’ vol. iii. pp.
320, 321, and 325.) Prof. Schaaffhausen accounts for this difference
between the races by “the posterior dental portion of the jaw being
always shortened” in those that are civilised (44. ‘On the Primitive
Form of the Skull,’ Eng. translat., in ‘Anthropological Review,’ Oct.
1868, p. 426), and this shortening may, I presume, be attributed to
civilised men habitually feeding on soft, cooked food, and thus using
their jaws less. I am informed by Mr. Brace that it is becoming quite a
common practice in the United States to remove some of the molar teeth
of children, as the jaw does not grow large enough for the perfect
development of the normal number. (45. Prof. Montegazza writes to me
from Florence, that he has lately been studying the last molar teeth in
the different races of man, and has come to the same conclusion as that
given in my text, viz., that in the higher or civilised races they are
on the road towards atrophy or elimination.)

With respect to the alimentary canal, I have met with an account of
only a single rudiment, namely the vermiform appendage of the caecum.
The caecum is a branch or diverticulum of the intestine, ending in a
cul-de-sac, and is extremely long in many of the lower
vegetable-feeding mammals. In the marsupial koala it is actually more
than thrice as long as the whole body. (46. Owen, ‘Anatomy of
Vertebrates,’ vol. iii. pp. 416, 434, 441.) It is sometimes produced
into a long gradually-tapering point, and is sometimes constricted in
parts. It appears as if, in consequence of changed diet or habits, the
caecum had become much shortened in various animals, the vermiform
appendage being left as a rudiment of the shortened part. That this
appendage is a rudiment, we may infer from its small size, and from the
evidence which Prof. Canestrini (47. ‘Annuario della Soc. d. Nat.’
Modena, 1867, p. 94.) has collected of its variability in man. It is
occasionally quite absent, or again is largely developed. The passage
is sometimes completely closed for half or two-thirds of its length,
with the terminal part consisting of a flattened solid expansion. In
the orang this appendage is long and convoluted: in man it arises from
the end of the short caecum, and is commonly from four to five inches
in length, being only about the third of an inch in diameter. Not only
is it useless, but it is sometimes the cause of death, of which fact I
have lately heard two instances: this is due to small hard bodies, such
as seeds, entering the passage, and causing inflammation. (48. M. C.
Martins (“De l’Unité Organique,” in ‘Revue des Deux Mondes,’ June 15,
1862, p. 16) and Haeckel (‘Generelle Morphologie,’ B. ii. s. 278), have
both remarked on the singular fact of this rudiment sometimes causing
death.)

In some of the lower Quadrumana, in the Lemuridae and Carnivora, as
well as in many marsupials, there is a passage near the lower end of
the humerus, called the supra-condyloid foramen, through which the
great nerve of the fore limb and often the great artery pass. Now in
the humerus of man, there is generally a trace of this passage, which
is sometimes fairly well developed, being formed by a depending
hook-like process of bone, completed by a band of ligament. Dr.
Struthers (49. With respect to inheritance, see Dr. Struthers in the
‘Lancet,’ Feb. 15, 1873, and another important paper, ibid. Jan. 24,
1863, p. 83. Dr. Knox, as I am informed, was the first anatomist who
drew attention to this peculiar structure in man; see his ‘Great
Artists and Anatomists,’ p. 63. See also an important memoir on this
process by Dr. Gruber, in the ‘Bulletin de l’Acad. Imp. de St.
Petersbourg,’ tom. xii. 1867, p. 448.), who has closely attended to the
subject, has now shewn that this peculiarity is sometimes inherited, as
it has occurred in a father, and in no less than four out of his seven
children. When present, the great nerve invariably passes through it;
and this clearly indicates that it is the homologue and rudiment of the
supra-condyloid foramen of the lower animals. Prof. Turner estimates,
as he informs me, that it occurs in about one per cent. of recent
skeletons. But if the occasional development of this structure in man
is, as seems probable, due to reversion, it is a return to a very
ancient state of things, because in the higher Quadrumana it is absent.

There is another foramen or perforation in the humerus, occasionally
present in man, which may be called the inter-condyloid. This occurs,
but not constantly, in various anthropoid and other apes (50. Mr. St.
George Mivart, ‘Transactions Phil. Soc.’ 1867, p. 310.), and likewise
in many of the lower animals. It is remarkable that this perforation
seems to have been present in man much more frequently during ancient
times than recently. Mr. Busk (51. “On the Caves of Gibraltar,”
‘Transactions of the International Congress of Prehistoric
Archaeology,’ Third Session, 1869, p. 159. Prof. Wyman has lately shewn
(Fourth Annual Report, Peabody Museum, 1871, p. 20), that this
perforation is present in thirty-one per cent. of some human remains
from ancient mounds in the Western United States, and in Florida. It
frequently occurs in the negro.) has collected the following evidence
on this head: Prof. Broca “noticed the perforation in four and a half
per cent. of the arm-bones collected in the ‘Cimetière du Sud,’ at
Paris; and in the Grotto of Orrony, the contents of which are referred
to the Bronze period, as many as eight humeri out of thirty-two were
perforated; but this extraordinary proportion, he thinks, might be due
to the cavern having been a sort of ‘family vault.’ Again, M. Dupont
found thirty per cent. of perforated bones in the caves of the Valley
of the Lesse, belonging to the Reindeer period; whilst M. Leguay, in a
sort of dolmen at Argenteuil, observed twenty-five per cent. to be
perforated; and M. Pruner-Bey found twenty-six per cent. in the same
condition in bones from Vaureal. Nor should it be left unnoticed that
M. Pruner-Bey states that this condition is common in Guanche
skeletons.” It is an interesting fact that ancient races, in this and
several other cases, more frequently present structures which resemble
those of the lower animals than do the modern. One chief cause seems to
be that the ancient races stand somewhat nearer in the long line of
descent to their remote animal-like progenitors.

In man, the os coccyx, together with certain other vertebrae hereafter
to be described, though functionless as a tail, plainly represent this
part in other vertebrate animals. At an early embryonic period it is
free, and projects beyond the lower extremities; as may be seen in the
drawing (Fig. 1.) of a human embryo. Even after birth it has been
known, in certain rare and anomalous cases (52. Quatrefages has lately
collected the evidence on this subject. ‘Revue des Cours
Scientifiques,’ 1867-1868, p. 625. In 1840 Fleischmann exhibited a
human foetus bearing a free tail, which, as is not always the case,
included vertebral bodies; and this tail was critically examined by the
many anatomists present at the meeting of naturalists at Erlangen (see
Marshall in Niederlandischen Archiv für Zoologie, December 1871).), to
form a small external rudiment of a tail. The os coccyx is short,
usually including only four vertebrae, all anchylosed together: and
these are in a rudimentary condition, for they consist, with the
exception of the basal one, of the centrum alone. (53. Owen, ‘On the
Nature of Limbs,’ 1849, p. 114.) They are furnished with some small
muscles; one of which, as I am informed by Prof. Turner, has been
expressly described by Theile as a rudimentary repetition of the
extensor of the tail, a muscle which is so largely developed in many
mammals.

The spinal cord in man extends only as far downwards as the last dorsal
or first lumbar vertebra; but a thread-like structure (the filum
terminale) runs down the axis of the sacral part of the spinal canal,
and even along the back of the coccygeal bones. The upper part of this
filament, as Prof. Turner informs me, is undoubtedly homologous with
the spinal cord; but the lower part apparently consists merely of the
pia mater, or vascular investing membrane. Even in this case the os
coccyx may be said to possess a vestige of so important a structure as
the spinal cord, though no longer enclosed within a bony canal. The
following fact, for which I am also indebted to Prof. Turner, shews how
closely the os coccyx corresponds with the true tail in the lower
animals: Luschka has recently discovered at the extremity of the
coccygeal bones a very peculiar convoluted body, which is continuous
with the middle sacral artery; and this discovery led Krause and Meyer
to examine the tail of a monkey (Macacus), and of a cat, in both of
which they found a similarly convoluted body, though not at the
extremity.

The reproductive system offers various rudimentary structures; but
these differ in one important respect from the foregoing cases. Here we
are not concerned with the vestige of a part which does not belong to
the species in an efficient state, but with a part efficient in the one
sex, and represented in the other by a mere rudiment. Nevertheless, the
occurrence of such rudiments is as difficult to explain, on the belief
of the separate creation of each species, as in the foregoing cases.
Hereafter I shall have to recur to these rudiments, and shall shew that
their presence generally depends merely on inheritance, that is, on
parts acquired by one sex having been partially transmitted to the
other. I will in this place only give some instances of such rudiments.
It is well known that in the males of all mammals, including man,
rudimentary mammae exist. These in several instances have become well
developed, and have yielded a copious supply of milk. Their essential
identity in the two sexes is likewise shewn by their occasional
sympathetic enlargement in both during an attack of the measles. The
vesicula prostatica, which has been observed in many male mammals, is
now universally acknowledged to be the homologue of the female uterus,
together with the connected passage. It is impossible to read
Leuckart’s able description of this organ, and his reasoning, without
admitting the justness of his conclusion. This is especially clear in
the case of those mammals in which the true female uterus bifurcates,
for in the males of these the vesicula likewise bifurcates. (54.
Leuckart, in Todd’s ‘Cyclopaedia of Anatomy’ 1849-52, vol. iv. p. 1415.
In man this organ is only from three to six lines in length, but, like
so many other rudimentary parts, it is variable in development as well
as in other characters.) Some other rudimentary structures belonging to
the reproductive system might have been here adduced. (55. See, on this
subject, Owen, ‘Anatomy of Vertebrates,’ vol. iii. pp. 675, 676, 706.)

The bearing of the three great classes of facts now given is
unmistakeable. But it would be superfluous fully to recapitulate the
line of argument given in detail in my ‘Origin of Species.’ The
homological construction of the whole frame in the members of the same
class is intelligible, if we admit their descent from a common
progenitor, together with their subsequent adaptation to diversified
conditions. On any other view, the similarity of pattern between the
hand of a man or monkey, the foot of a horse, the flipper of a seal,
the wing of a bat, etc., is utterly inexplicable. (56. Prof. Bianconi,
in a recently published work, illustrated by admirable engravings (‘La
Théorie Darwinienne et la création dite indépendante,’ 1874),
endeavours to shew that homological structures, in the above and other
cases, can be fully explained on mechanical principles, in accordance
with their uses. No one has shewn so well, how admirably such
structures are adapted for their final purpose; and this adaptation
can, as I believe, be explained through natural selection. In
considering the wing of a bat, he brings forward (p. 218) what appears
to me (to use Auguste Comte’s words) a mere metaphysical principle,
namely, the preservation “in its integrity of the mammalian nature of
the animal.” In only a few cases does he discuss rudiments, and then
only those parts which are partially rudimentary, such as the little
hoofs of the pig and ox, which do not touch the ground; these he shews
clearly to be of service to the animal. It is unfortunate that he did
not consider such cases as the minute teeth, which never cut through
the jaw in the ox, or the mammae of male quadrupeds, or the wings of
certain beetles, existing under the soldered wing-covers, or the
vestiges of the pistil and stamens in various flowers, and many other
such cases. Although I greatly admire Prof. Bianconi’s work, yet the
belief now held by most naturalists seems to me left unshaken, that
homological structures are inexplicable on the principle of mere
adaptation.) It is no scientific explanation to assert that they have
all been formed on the same ideal plan. With respect to development, we
can clearly understand, on the principle of variations supervening at a
rather late embryonic period, and being inherited at a corresponding
period, how it is that the embryos of wonderfully different forms
should still retain, more or less perfectly, the structure of their
common progenitor. No other explanation has ever been given of the
marvellous fact that the embryos of a man, dog, seal, bat, reptile,
etc., can at first hardly be distinguished from each other. In order to
understand the existence of rudimentary organs, we have only to suppose
that a former progenitor possessed the parts in question in a perfect
state, and that under changed habits of life they became greatly
reduced, either from simple disuse, or through the natural selection of
those individuals which were least encumbered with a superfluous part,
aided by the other means previously indicated.

Thus we can understand how it has come to pass that man and all other
vertebrate animals have been constructed on the same general model, why
they pass through the same early stages of development, and why they
retain certain rudiments in common. Consequently we ought frankly to
admit their community of descent: to take any other view, is to admit
that our own structure, and that of all the animals around us, is a
mere snare laid to entrap our judgment. This conclusion is greatly
strengthened, if we look to the members of the whole animal series, and
consider the evidence derived from their affinities or classification,
their geographical distribution and geological succession. It is only
our natural prejudice, and that arrogance which made our forefathers
declare that they were descended from demi-gods, which leads us to
demur to this conclusion. But the time will before long come, when it
will be thought wonderful that naturalists, who were well acquainted
with the comparative structure and development of man, and other
mammals, should have believed that each was the work of a separate act
of creation.




CHAPTER II.
ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.


Variability of body and mind in man—Inheritance—Causes of
variability—Laws of variation the same in man as in the lower
animals—Direct action of the conditions of life—Effects of the
increased use and disuse of parts—Arrested
development—Reversion—Correlated variation—Rate of increase—Checks to
increase—Natural selection—Man the most dominant animal in the
world—Importance of his corporeal structure—The causes which have led
to his becoming erect—Consequent changes of structure—Decrease in size
of the canine teeth—Increased size and altered shape of the
skull—Nakedness —Absence of a tail—Defenceless condition of man.

It is manifest that man is now subject to much variability. No two
individuals of the same race are quite alike. We may compare millions
of faces, and each will be distinct. There is an equally great amount
of diversity in the proportions and dimensions of the various parts of
the body; the length of the legs being one of the most variable points.
(1. ‘Investigations in Military and Anthropological Statistics of
American Soldiers,’ by B.A. Gould, 1869, p. 256.) Although in some
quarters of the world an elongated skull, and in other quarters a short
skull prevails, yet there is great diversity of shape even within the
limits of the same race, as with the aborigines of America and South
Australia—the latter a race “probably as pure and homogeneous in blood,
customs, and language as any in existence”—and even with the
inhabitants of so confined an area as the Sandwich Islands. (2. With
respect to the “Cranial forms of the American aborigines,” see Dr.
Aitken Meigs in ‘Proc. Acad. Nat. Sci.’ Philadelphia, May 1868. On the
Australians, see Huxley, in Lyell’s ‘Antiquity of Man,’ 1863, p. 87. On
the Sandwich Islanders, Prof. J. Wyman, ‘Observations on Crania,’
Boston, 1868, p. 18.) An eminent dentist assures me that there is
nearly as much diversity in the teeth as in the features. The chief
arteries so frequently run in abnormal courses, that it has been found
useful for surgical purposes to calculate from 1040 corpses how often
each course prevails. (3. ‘Anatomy of the Arteries,’ by R. Quain.
Preface, vol. i. 1844.) The muscles are eminently variable: thus those
of the foot were found by Prof. Turner (4. ‘Transactions of the Royal
Society of Edinburgh,’ vol. xxiv. pp. 175, 189.) not to be strictly
alike in any two out of fifty bodies; and in some the deviations were
considerable. He adds, that the power of performing the appropriate
movements must have been modified in accordance with the several
deviations. Mr. J. Wood has recorded (5. ‘Proceedings Royal Society,’
1867, p. 544; also 1868, pp. 483, 524. There is a previous paper, 1866,
p. 229.) the occurrence of 295 muscular variations in thirty-six
subjects, and in another set of the same number no less than 558
variations, those occurring on both sides of the body being only
reckoned as one. In the last set, not one body out of the thirty-six
was “found totally wanting in departures from the standard descriptions
of the muscular system given in anatomical text books.” A single body
presented the extraordinary number of twenty-five distinct
abnormalities. The same muscle sometimes varies in many ways: thus
Prof. Macalister describes (6. ‘Proc. R. Irish Academy,’ vol. x. 1868,
p. 141.) no less than twenty distinct variations in the palmaris
accessorius.

The famous old anatomist, Wolff (7. ‘Act. Acad. St. Petersburg,’ 1778,
part ii. p. 217.), insists that the internal viscera are more variable
than the external parts: Nulla particula est quae non aliter et aliter
in aliis se habeat hominibus. He has even written a treatise on the
choice of typical examples of the viscera for representation. A
discussion on the beau-ideal of the liver, lungs, kidneys, etc., as of
the human face divine, sounds strange in our ears.

The variability or diversity of the mental faculties in men of the same
race, not to mention the greater differences between the men of
distinct races, is so notorious that not a word need here be said. So
it is with the lower animals. All who have had charge of menageries
admit this fact, and we see it plainly in our dogs and other domestic
animals. Brehm especially insists that each individual monkey of those
which he kept tame in Africa had its own peculiar disposition and
temper: he mentions one baboon remarkable for its high intelligence;
and the keepers in the Zoological Gardens pointed out to me a monkey,
belonging to the New World division, equally remarkable for
intelligence. Rengger, also, insists on the diversity in the various
mental characters of the monkeys of the same species which he kept in
Paraguay; and this diversity, as he adds, is partly innate, and partly
the result of the manner in which they have been treated or educated.
(8. Brehm, ‘Thierleben,’ B. i. ss. 58, 87. Rengger, ‘Säugethiere von
Paraguay,’ s. 57.)

I have elsewhere (9. ‘Variation of Animals and Plants under
Domestication,’ vol. ii. chap. xii.) so fully discussed the subject of
Inheritance, that I need here add hardly anything. A greater number of
facts have been collected with respect to the transmission of the most
trifling, as well as of the most important characters in man, than in
any of the lower animals; though the facts are copious enough with
respect to the latter. So in regard to mental qualities, their
transmission is manifest in our dogs, horses, and other domestic
animals. Besides special tastes and habits, general intelligence,
courage, bad and good temper, etc., are certainly transmitted. With man
we see similar facts in almost every family; and we now know, through
the admirable labours of Mr. Galton (10. ‘Hereditary Genius: an Inquiry
into its Laws and Consequences,’ 1869.), that genius which implies a
wonderfully complex combination of high faculties, tends to be
inherited; and, on the other hand, it is too certain that insanity and
deteriorated mental powers likewise run in families.

With respect to the causes of variability, we are in all cases very
ignorant; but we can see that in man as in the lower animals, they
stand in some relation to the conditions to which each species has been
exposed, during several generations. Domesticated animals vary more
than those in a state of nature; and this is apparently due to the
diversified and changing nature of the conditions to which they have
been subjected. In this respect the different races of man resemble
domesticated animals, and so do the individuals of the same race, when
inhabiting a very wide area, like that of America. We see the influence
of diversified conditions in the more civilised nations; for the
members belonging to different grades of rank, and following different
occupations, present a greater range of character than do the members
of barbarous nations. But the uniformity of savages has often been
exaggerated, and in some cases can hardly be said to exist. (11. Mr.
Bates remarks (‘The Naturalist on the Amazons,’ 1863, vol. ii p. 159),
with respect to the Indians of the same South American tribe, “no two
of them were at all similar in the shape of the head; one man had an
oval visage with fine features, and another was quite Mongolian in
breadth and prominence of cheek, spread of nostrils, and obliquity of
eyes.”) It is, nevertheless, an error to speak of man, even if we look
only to the conditions to which he has been exposed, as “far more
domesticated” (12. Blumenbach, ‘Treatises on Anthropology.’ Eng.
translat., 1865, p. 205.) than any other animal. Some savage races,
such as the Australians, are not exposed to more diversified conditions
than are many species which have a wide range. In another and much more
important respect, man differs widely from any strictly domesticated
animal; for his breeding has never long been controlled, either by
methodical or unconscious selection. No race or body of men has been so
completely subjugated by other men, as that certain individuals should
be preserved, and thus unconsciously selected, from somehow excelling
in utility to their masters. Nor have certain male and female
individuals been intentionally picked out and matched, except in the
well-known case of the Prussian grenadiers; and in this case man
obeyed, as might have been expected, the law of methodical selection;
for it is asserted that many tall men were reared in the villages
inhabited by the grenadiers and their tall wives. In Sparta, also, a
form of selection was followed, for it was enacted that all children
should be examined shortly after birth; the well-formed and vigorous
being preserved, the others left to perish. (13. Mitford’s ‘History of
Greece,’ vol. i. p. 282. It appears also from a passage in Xenophon’s
‘Memorabilia,’ B. ii. 4 (to which my attention has been called by the
Rev. J.N. Hoare), that it was a well recognised principle with the
Greeks, that men ought to select their wives with a view to the health
and vigour of their children. The Grecian poet, Theognis, who lived 550
B.C., clearly saw how important selection, if carefully applied, would
be for the improvement of mankind. He saw, likewise, that wealth often
checks the proper action of sexual selection. He thus writes:

    “With kine and horses, Kurnus! we proceed
    By reasonable rules, and choose a breed
    For profit and increase, at any price:
    Of a sound stock, without defect or vice.
    But, in the daily matches that we make,
    The price is everything:  for money’s sake,
    Men marry:  women are in marriage given
    The churl or ruffian, that in wealth has thriven,
    May match his offspring with the proudest race:
    Thus everything is mix’d, noble and base!
    If then in outward manner, form, and mind,
    You find us a degraded, motley kind,
    Wonder no more, my friend! the cause is plain,
    And to lament the consequence is vain.”

(The Works of J. Hookham Frere, vol. ii. 1872, p. 334.))

If we consider all the races of man as forming a single species, his
range is enormous; but some separate races, as the Americans and
Polynesians, have very wide ranges. It is a well-known law that
widely-ranging species are much more variable than species with
restricted ranges; and the variability of man may with more truth be
compared with that of widely-ranging species, than with that of
domesticated animals.

Not only does variability appear to be induced in man and the lower
animals by the same general causes, but in both the same parts of the
body are affected in a closely analogous manner. This has been proved
in such full detail by Godron and Quatrefages, that I need here only
refer to their works. (14. Godron, ‘De l’Espèce,’ 1859, tom. ii. livre
3. Quatrefages, ‘Unité de l’Espèce Humaine,’ 1861. Also Lectures on
Anthropology, given in the ‘Revue des Cours Scientifiques,’ 1866-1868.)
Monstrosities, which graduate into slight variations, are likewise so
similar in man and the lower animals, that the same classification and
the same terms can be used for both, as has been shewn by Isidore
Geoffroy St.-Hilaire. (15. ‘Hist. Gen. et Part. des Anomalies de
l’Organisation,’ in three volumes, tom. i. 1832.) In my work on the
variation of domestic animals, I have attempted to arrange in a rude
fashion the laws of variation under the following heads:—The direct and
definite action of changed conditions, as exhibited by all or nearly
all the individuals of the same species, varying in the same manner
under the same circumstances. The effects of the long-continued use or
disuse of parts. The cohesion of homologous parts. The variability of
multiple parts. Compensation of growth; but of this law I have found no
good instance in the case of man. The effects of the mechanical
pressure of one part on another; as of the pelvis on the cranium of the
infant in the womb. Arrests of development, leading to the diminution
or suppression of parts. The reappearance of long-lost characters
through reversion. And lastly, correlated variation. All these
so-called laws apply equally to man and the lower animals; and most of
them even to plants. It would be superfluous here to discuss all of
them (16. I have fully discussed these laws in my ‘Variation of Animals
and Plants under Domestication,’ vol. ii. chap. xxii. and xxiii. M.
J.P. Durand has lately (1868) published a valuable essay, ‘De
l’Influence des Milieux,’ etc. He lays much stress, in the case of
plants, on the nature of the soil.); but several are so important, that
they must be treated at considerable length.

THE DIRECT AND DEFINITE ACTION OF CHANGED CONDITIONS.

This is a most perplexing subject. It cannot be denied that changed
conditions produce some, and occasionally a considerable effect, on
organisms of all kinds; and it seems at first probable that if
sufficient time were allowed this would be the invariable result. But I
have failed to obtain clear evidence in favour of this conclusion; and
valid reasons may be urged on the other side, at least as far as the
innumerable structures are concerned, which are adapted for special
ends. There can, however, be no doubt that changed conditions induce an
almost indefinite amount of fluctuating variability, by which the whole
organisation is rendered in some degree plastic.

In the United States, above 1,000,000 soldiers, who served in the late
war, were measured, and the States in which they were born and reared
were recorded. (17. ‘Investigations in Military and Anthrop.
Statistics,’ etc., 1869, by B.A. Gould, pp. 93, 107, 126, 131, 134.)
From this astonishing number of observations it is proved that local
influences of some kind act directly on stature; and we further learn
that “the State where the physical growth has in great measure taken
place, and the State of birth, which indicates the ancestry, seem to
exert a marked influence on the stature.” For instance, it is
established, “that residence in the Western States, during the years of
growth, tends to produce increase of stature.” On the other hand, it is
certain that with sailors, their life delays growth, as shewn “by the
great difference between the statures of soldiers and sailors at the
ages of seventeen and eighteen years.” Mr. B.A. Gould endeavoured to
ascertain the nature of the influences which thus act on stature; but
he arrived only at negative results, namely that they did not relate to
climate, the elevation of the land, soil, nor even “in any controlling
degree” to the abundance or the need of the comforts of life. This
latter conclusion is directly opposed to that arrived at by Villerme,
from the statistics of the height of the conscripts in different parts
of France. When we compare the differences in stature between the
Polynesian chiefs and the lower orders within the same islands, or
between the inhabitants of the fertile volcanic and low barren coral
islands of the same ocean (18. For the Polynesians, see Prichard’s
‘Physical History of Mankind,’ vol. v. 1847, pp. 145, 283. Also Godron,
‘De l’Espèce,’ tom. ii. p. 289. There is also a remarkable difference
in appearance between the closely-allied Hindoos inhabiting the Upper
Ganges and Bengal; see Elphinstone’s ‘History of India,’ vol. i. p.
324.) or again between the Fuegians on the eastern and western shores
of their country, where the means of subsistence are very different, it
is scarcely possible to avoid the conclusion that better food and
greater comfort do influence stature. But the preceding statements shew
how difficult it is to arrive at any precise result. Dr. Beddoe has
lately proved that, with the inhabitants of Britain, residence in towns
and certain occupations have a deteriorating influence on height; and
he infers that the result is to a certain extent inherited, as is
likewise the case in the United States. Dr. Beddoe further believes
that wherever a “race attains its maximum of physical development, it
rises highest in energy and moral vigour.” (19. ‘Memoirs,
Anthropological Society,’ vol. iii. 1867-69, pp. 561, 565, 567.)

Whether external conditions produce any other direct effect on man is
not known. It might have been expected that differences of climate
would have had a marked influence, inasmuch as the lungs and kidneys
are brought into activity under a low temperature, and the liver and
skin under a high one. (20. Dr. Brakenridge, ‘Theory of Diathesis,’
‘Medical Times,’ June 19 and July 17, 1869.) It was formerly thought
that the colour of the skin and the character of the hair were
determined by light or heat; and although it can hardly be denied that
some effect is thus produced, almost all observers now agree that the
effect has been very small, even after exposure during many ages. But
this subject will be more properly discussed when we treat of the
different races of mankind. With our domestic animals there are grounds
for believing that cold and damp directly affect the growth of the
hair; but I have not met with any evidence on this head in the case of
man.

EFFECTS OF THE INCREASED USE AND DISUSE OF A PARTS.

It is well known that use strengthens the muscles in the individual,
and complete disuse, or the destruction of the proper nerve, weakens
them. When the eye is destroyed, the optic nerve often becomes
atrophied. When an artery is tied, the lateral channels increase not
only in diameter, but in the thickness and strength of their coats.
When one kidney ceases to act from disease, the other increases in
size, and does double work. Bones increase not only in thickness, but
in length, from carrying a greater weight. (21. I have given
authorities for these several statements in my ‘Variation of Animals
and Plants under Domestication,’ vol. ii. pp. 297-300. Dr. Jaeger,
“Über das Langenwachsthum der Knochen,” ‘Jenäischen Zeitschrift,’ B. v.
Heft. i.) Different occupations, habitually followed, lead to changed
proportions in various parts of the body. Thus it was ascertained by
the United States Commission (22. ‘Investigations,’ etc., by B.A.
Gould, 1869, p. 288.) that the legs of the sailors employed in the late
war were longer by 0.217 of an inch than those of the soldiers, though
the sailors were on an average shorter men; whilst their arms were
shorter by 1.09 of an inch, and therefore, out of proportion, shorter
in relation to their lesser height. This shortness of the arms is
apparently due to their greater use, and is an unexpected result: but
sailors chiefly use their arms in pulling, and not in supporting
weights. With sailors, the girth of the neck and the depth of the
instep are greater, whilst the circumference of the chest, waist, and
hips is less, than in soldiers.

Whether the several foregoing modifications would become hereditary, if
the same habits of life were followed during many generations, is not
known, but it is probable. Rengger (23. ‘Säugethiere von Paraguay,’
1830, s. 4.) attributes the thin legs and thick arms of the Payaguas
Indians to successive generations having passed nearly their whole
lives in canoes, with their lower extremities motionless. Other writers
have come to a similar conclusion in analogous cases. According to
Cranz (24. ‘History of Greenland,’ Eng. translat., 1767, vol. i. p.
230.), who lived for a long time with the Esquimaux, “the natives
believe that ingenuity and dexterity in seal-catching (their highest
art and virtue) is hereditary; there is really something in it, for the
son of a celebrated seal-catcher will distinguish himself, though he
lost his father in childhood.” But in this case it is mental aptitude,
quite as much as bodily structure, which appears to be inherited. It is
asserted that the hands of English labourers are at birth larger than
those of the gentry. (25. ‘Intermarriage,’ by Alex. Walker, 1838, p.
377.) From the correlation which exists, at least in some cases (26.
‘The Variation of Animals under Domestication,’ vol. i. p. 173.),
between the development of the extremities and of the jaws, it is
possible that in those classes which do not labour much with their
hands and feet, the jaws would be reduced in size from this cause. That
they are generally smaller in refined and civilised men than in
hard-working men or savages, is certain. But with savages, as Mr.
Herbert Spencer (27. ‘Principles of Biology,’ vol. i. p. 455.) has
remarked, the greater use of the jaws in chewing coarse, uncooked food,
would act in a direct manner on the masticatory muscles, and on the
bones to which they are attached. In infants, long before birth, the
skin on the soles of the feet is thicker than on any other part of the
body; (28. Paget, ‘Lectures on Surgical Pathology,’ vol. ii, 1853, p.
209.) and it can hardly be doubted that this is due to the inherited
effects of pressure during a long series of generations.

It is familiar to every one that watchmakers and engravers are liable
to be short-sighted, whilst men living much out of doors, and
especially savages, are generally long-sighted. (29. It is a singular
and unexpected fact that sailors are inferior to landsmen in their mean
distance of distinct vision. Dr. B.A. Gould (‘Sanitary Memoirs of the
War of the Rebellion,’ 1869, p. 530), has proved this to be the case;
and he accounts for it by the ordinary range of vision in sailors being
“restricted to the length of the vessel and the height of the masts.”)
Short-sight and long-sight certainly tend to be inherited. (30. ‘The
Variation of Animals under Domestication,’ vol. i. p. 8.) The
inferiority of Europeans, in comparison with savages, in eyesight and
in the other senses, is no doubt the accumulated and transmitted effect
of lessened use during many generations; for Rengger (31. ‘Säugethiere
von Paraguay,’ s. 8, 10. I have had good opportunities for observing
the extraordinary power of eyesight in the Fuegians. See also Lawrence
(‘Lectures on Physiology,’ etc., 1822, p. 404) on this same subject. M.
Giraud-Teulon has recently collected (‘Revue des Cours Scientifiques,’
1870, p. 625) a large and valuable body of evidence proving that the
cause of short-sight, “C’est le travail assidu, de près.”) states that
he has repeatedly observed Europeans, who had been brought up and spent
their whole lives with the wild Indians, who nevertheless did not equal
them in the sharpness of their senses. The same naturalist observes
that the cavities in the skull for the reception of the several
sense-organs are larger in the American aborigines than in Europeans;
and this probably indicates a corresponding difference in the
dimensions of the organs themselves. Blumenbach has also remarked on
the large size of the nasal cavities in the skulls of the American
aborigines, and connects this fact with their remarkably acute power of
smell. The Mongolians of the plains of northern Asia, according to
Pallas, have wonderfully perfect senses; and Prichard believes that the
great breadth of their skulls across the zygomas follows from their
highly-developed sense organs. (32. Prichard, ‘Physical History of
Mankind,’ on the authority of Blumenbach, vol. i. 1851, p. 311; for the
statement by Pallas, vol. iv. 1844, p. 407.)

The Quechua Indians inhabit the lofty plateaux of Peru; and Alcide
d’Orbigny states (33. Quoted by Prichard, ‘Researches into the Physical
History of Mankind,’ vol. v. p. 463.) that, from continually breathing
a highly rarefied atmosphere, they have acquired chests and lungs of
extraordinary dimensions. The cells, also, of the lungs are larger and
more numerous than in Europeans. These observations have been doubted,
but Mr. D. Forbes carefully measured many Aymaras, an allied race,
living at the height of between 10,000 and 15,000 feet; and he informs
me (34. Mr. Forbes’ valuable paper is now published in the ‘Journal of
the Ethnological Society of London,’ new series, vol. ii. 1870, p.193.)
that they differ conspicuously from the men of all other races seen by
him in the circumference and length of their bodies. In his table of
measurements, the stature of each man is taken at 1000, and the other
measurements are reduced to this standard. It is here seen that the
extended arms of the Aymaras are shorter than those of Europeans, and
much shorter than those of Negroes. The legs are likewise shorter; and
they present this remarkable peculiarity, that in every Aymara
measured, the femur is actually shorter than the tibia. On an average,
the length of the femur to that of the tibia is as 211 to 252; whilst
in two Europeans, measured at the same time, the femora to the tibiae
were as 244 to 230; and in three Negroes as 258 to 241. The humerus is
likewise shorter relatively to the forearm. This shortening of that
part of the limb which is nearest to the body, appears to be, as
suggested to me by Mr. Forbes, a case of compensation in relation with
the greatly increased length of the trunk. The Aymaras present some
other singular points of structure, for instance, the very small
projection of the heel.

These men are so thoroughly acclimatised to their cold and lofty abode,
that when formerly carried down by the Spaniards to the low eastern
plains, and when now tempted down by high wages to the gold-washings,
they suffer a frightful rate of mortality. Nevertheless Mr. Forbes
found a few pure families which had survived during two generations:
and he observed that they still inherited their characteristic
peculiarities. But it was manifest, even without measurement, that
these peculiarities had all decreased; and on measurement, their bodies
were found not to be so much elongated as those of the men on the high
plateau; whilst their femora had become somewhat lengthened, as had
their tibiae, although in a less degree. The actual measurements may be
seen by consulting Mr. Forbes’s memoir. From these observations, there
can, I think, be no doubt that residence during many generations at a
great elevation tends, both directly and indirectly, to induce
inherited modifications in the proportions of the body. (35. Dr.
Wilckens (‘Landwirthschaft. Wochenblatt,’ No. 10, 1869) has lately
published an interesting essay shewing how domestic animals, which live
in mountainous regions, have their frames modified.)

Although man may not have been much modified during the latter stages
of his existence through the increased or decreased use of parts, the
facts now given shew that his liability in this respect has not been
lost; and we positively know that the same law holds good with the
lower animals. Consequently we may infer that when at a remote epoch
the progenitors of man were in a transitional state, and were changing
from quadrupeds into bipeds, natural selection would probably have been
greatly aided by the inherited effects of the increased or diminished
use of the different parts of the body.

ARRESTS OF DEVELOPMENT.

There is a difference between arrested development and arrested growth,
for parts in the former state continue to grow whilst still retaining
their early condition. Various monstrosities come under this head; and
some, as a cleft palate, are known to be occasionally inherited. It
will suffice for our purpose to refer to the arrested brain-development
of microcephalous idiots, as described in Vogt’s memoir. (36. ‘Mémoire
sur les Microcephales,’ 1867, pp. 50, 125, 169, 171, 184-198.) Their
skulls are smaller, and the convolutions of the brain are less complex
than in normal men. The frontal sinus, or the projection over the
eye-brows, is largely developed, and the jaws are prognathous to an
“effrayant” degree; so that these idiots somewhat resemble the lower
types of mankind. Their intelligence, and most of their mental
faculties, are extremely feeble. They cannot acquire the power of
speech, and are wholly incapable of prolonged attention, but are much
given to imitation. They are strong and remarkably active, continually
gambolling and jumping about, and making grimaces. They often ascend
stairs on all-fours; and are curiously fond of climbing up furniture or
trees. We are thus reminded of the delight shewn by almost all boys in
climbing trees; and this again reminds us how lambs and kids,
originally alpine animals, delight to frisk on any hillock, however
small. Idiots also resemble the lower animals in some other respects;
thus several cases are recorded of their carefully smelling every
mouthful of food before eating it. One idiot is described as often
using his mouth in aid of his hands, whilst hunting for lice. They are
often filthy in their habits, and have no sense of decency; and several
cases have been published of their bodies being remarkably hairy. (37.
Prof. Laycock sums up the character of brute-like idiots by calling
them “theroid;” ‘Journal of Mental Science,’ July 1863. Dr. Scott (‘The
Deaf and Dumb,’ 2nd ed. 1870, p. 10) has often observed the imbecile
smelling their food. See, on this same subject, and on the hairiness of
idiots, Dr. Maudsley, ‘Body and Mind,’ 1870, pp. 46-51. Pinel has also
given a striking case of hairiness in an idiot.)

REVERSION.

Many of the cases to be here given, might have been introduced under
the last heading. When a structure is arrested in its development, but
still continues growing, until it closely resembles a corresponding
structure in some lower and adult member of the same group, it may in
one sense be considered as a case of reversion. The lower members in a
group give us some idea how the common progenitor was probably
constructed; and it is hardly credible that a complex part, arrested at
an early phase of embryonic development, should go on growing so as
ultimately to perform its proper function, unless it had acquired such
power during some earlier state of existence, when the present
exceptional or arrested structure was normal. The simple brain of a
microcephalous idiot, in as far as it resembles that of an ape, may in
this sense be said to offer a case of reversion. (38. In my ‘Variation
of Animals under Domestication’ (vol. ii. p. 57), I attributed the not
very rare cases of supernumerary mammae in women to reversion. I was
led to this as a probable conclusion, by the additional mammae being
generally placed symmetrically on the breast; and more especially from
one case, in which a single efficient mamma occurred in the inguinal
region of a woman, the daughter of another woman with supernumerary
mammae. But I now find (see, for instance, Prof. Preyer, ‘Der Kampf um
das Dasein,’ 1869, s. 45) that mammae erraticae, occur in other
situations, as on the back, in the armpit, and on the thigh; the mammae
in this latter instance having given so much milk that the child was
thus nourished. The probability that the additional mammae are due to
reversion is thus much weakened; nevertheless, it still seems to me
probable, because two pairs are often found symmetrically on the
breast; and of this I myself have received information in several
cases. It is well known that some Lemurs normally have two pairs of
mammae on the breast. Five cases have been recorded of the presence of
more than a pair of mammae (of course rudimentary) in the male sex of
mankind; see ‘Journal of Anat. and Physiology,’ 1872, p. 56, for a case
given by Dr. Handyside, in which two brothers exhibited this
peculiarity; see also a paper by Dr. Bartels, in ‘Reichert’s and du
Bois-Reymond’s Archiv.,’ 1872, p. 304. In one of the cases alluded to
by Dr. Bartels, a man bore five mammae, one being medial and placed
above the navel; Meckel von Hemsbach thinks that this latter case is
illustrated by a medial mamma occurring in certain Cheiroptera. On the
whole, we may well doubt if additional mammae would ever have been
developed in both sexes of mankind, had not his early progenitors been
provided with more than a single pair.

In the above work (vol. ii. p. 12), I also attributed, though with much
hesitation, the frequent cases of polydactylism in men and various
animals to reversion. I was partly led to this through Prof. Owen’s
statement, that some of the Ichthyopterygia possess more than five
digits, and therefore, as I supposed, had retained a primordial
condition; but Prof. Gegenbaur (‘Jenaischen Zeitschrift,’ B. v. Heft 3,
s. 341), disputes Owen’s conclusion. On the other hand, according to
the opinion lately advanced by Dr. Gunther, on the paddle of Ceratodus,
which is provided with articulated bony rays on both sides of a central
chain of bones, there seems no great difficulty in admitting that six
or more digits on one side, or on both sides, might reappear through
reversion. I am informed by Dr. Zouteveen that there is a case on
record of a man having twenty-four fingers and twenty-four toes! I was
chiefly led to the conclusion that the presence of supernumerary digits
might be due to reversion from the fact that such digits, not only are
strongly inherited, but, as I then believed, had the power of regrowth
after amputation, like the normal digits of the lower vertebrata. But I
have explained in the second edition of my Variation under
Domestication why I now place little reliance on the recorded cases of
such regrowth. Nevertheless it deserves notice, inasmuch as arrested
development and reversion are intimately related processes; that
various structures in an embryonic or arrested condition, such as a
cleft palate, bifid uterus, etc., are frequently accompanied by
polydactylism. This has been strongly insisted on by Meckel and Isidore
Geoffroy St.-Hilaire. But at present it is the safest course to give up
altogether the idea that there is any relation between the development
of supernumerary digits and reversion to some lowly organised
progenitor of man.) There are other cases which come more strictly
under our present head of reversion. Certain structures, regularly
occurring in the lower members of the group to which man belongs,
occasionally make their appearance in him, though not found in the
normal human embryo; or, if normally present in the human embryo, they
become abnormally developed, although in a manner which is normal in
the lower members of the group. These remarks will be rendered clearer
by the following illustrations.

In various mammals the uterus graduates from a double organ with two
distinct orifices and two passages, as in the marsupials, into a single
organ, which is in no way double except from having a slight internal
fold, as in the higher apes and man. The rodents exhibit a perfect
series of gradations between these two extreme states. In all mammals
the uterus is developed from two simple primitive tubes, the inferior
portions of which form the cornua; and it is in the words of Dr. Farre,
“by the coalescence of the two cornua at their lower extremities that
the body of the uterus is formed in man; while in those animals in
which no middle portion or body exists, the cornua remain ununited. As
the development of the uterus proceeds, the two cornua become gradually
shorter, until at length they are lost, or, as it were, absorbed into
the body of the uterus.” The angles of the uterus are still produced
into cornua, even in animals as high up in the scale as the lower apes
and lemurs.

Now in women, anomalous cases are not very infrequent, in which the
mature uterus is furnished with cornua, or is partially divided into
two organs; and such cases, according to Owen, repeat “the grade of
concentrative development,” attained by certain rodents. Here perhaps
we have an instance of a simple arrest of embryonic development, with
subsequent growth and perfect functional development; for either side
of the partially double uterus is capable of performing the proper
office of gestation. In other and rarer cases, two distinct uterine
cavities are formed, each having its proper orifice and passage. (39.
See Dr. A. Farre’s well-known article in the ‘Cyclopaedia of Anatomy
and Physiology,’ vol. v. 1859, p. 642. Owen, ‘Anatomy of Vertebrates,’
vol. iii. 1868, p. 687. Professor Turner, in ‘Edinburgh Medical
Journal,’ February, 1865.) No such stage is passed through during the
ordinary development of the embryo; and it is difficult to believe,
though perhaps not impossible, that the two simple, minute, primitive
tubes should know how (if such an expression may be used) to grow into
two distinct uteri, each with a well-constructed orifice and passage,
and each furnished with numerous muscles, nerves, glands and vessels,
if they had not formerly passed through a similar course of
development, as in the case of existing marsupials. No one will pretend
that so perfect a structure as the abnormal double uterus in woman
could be the result of mere chance. But the principle of reversion, by
which a long-lost structure is called back into existence, might serve
as the guide for its full development, even after the lapse of an
enormous interval of time.

Professor Canestrini, after discussing the foregoing and various
analogous cases, arrives at the same conclusion as that just given. He
adduces another instance, in the case of the malar bone (40. ‘Annuario
della Soc. dei Naturalisti,’ Modena, 1867, p. 83. Prof. Canestrini
gives extracts on this subject from various authorities. Laurillard
remarks, that as he has found a complete similarity in the form,
proportions, and connection of the two malar bones in several human
subjects and in certain apes, he cannot consider this disposition of
the parts as simply accidental. Another paper on this same anomaly has
been published by Dr. Saviotti in the ‘Gazzetta delle Cliniche,’ Turin,
1871, where he says that traces of the division may be detected in
about two per cent. of adult skulls; he also remarks that it more
frequently occurs in prognathous skulls, not of the Aryan race, than in
others. See also G. Delorenzi on the same subject; ‘Tre nuovi casi
d’anomalia dell’ osso malare,’ Torino, 1872. Also, E. Morselli, ‘Sopra
una rara anomalia dell’ osso malare,’ Modena, 1872. Still more recently
Gruber has written a pamphlet on the division of this bone. I give
these references because a reviewer, without any grounds or scruples,
has thrown doubts on my statements.), which, in some of the Quadrumana
and other mammals, normally consists of two portions. This is its
condition in the human foetus when two months old; and through arrested
development, it sometimes remains thus in man when adult, more
especially in the lower prognathous races. Hence Canestrini concludes
that some ancient progenitor of man must have had this bone normally
divided into two portions, which afterwards became fused together. In
man the frontal bone consists of a single piece, but in the embryo, and
in children, and in almost all the lower mammals, it consists of two
pieces separated by a distinct suture. This suture occasionally
persists more or less distinctly in man after maturity; and more
frequently in ancient than in recent crania, especially, as Canestrini
has observed, in those exhumed from the Drift, and belonging to the
brachycephalic type. Here again he comes to the same conclusion as in
the analogous case of the malar bones. In this, and other instances
presently to be given, the cause of ancient races approaching the lower
animals in certain characters more frequently than do the modern races,
appears to be, that the latter stand at a somewhat greater distance in
the long line of descent from their early semi-human progenitors.

Various other anomalies in man, more or less analogous to the
foregoing, have been advanced by different authors, as cases of
reversion; but these seem not a little doubtful, for we have to descend
extremely low in the mammalian series, before we find such structures
normally present. (41. A whole series of cases is given by Isidore
Geoffroy St.-Hilaire, ‘Hist. des Anomalies,’ tom, iii, p. 437. A
reviewer (‘Journal of Anatomy and Physiology,’ 1871, p. 366) blames me
much for not having discussed the numerous cases, which have been
recorded, of various parts arrested in their development. He says that,
according to my theory, “every transient condition of an organ, during
its development, is not only a means to an end, but once was an end in
itself.” This does not seem to me necessarily to hold good. Why should
not variations occur during an early period of development, having no
relation to reversion; yet such variations might be preserved and
accumulated, if in any way serviceable, for instance, in shortening and
simplifying the course of development? And again, why should not
injurious abnormalities, such as atrophied or hypertrophied parts,
which have no relation to a former state of existence, occur at an
early period, as well as during maturity?)

In man, the canine teeth are perfectly efficient instruments for
mastication. But their true canine character, as Owen (42. ‘Anatomy of
Vertebrates,’ vol. iii. 1868, p. 323.) remarks, “is indicated by the
conical form of the crown, which terminates in an obtuse point, is
convex outward and flat or sub-concave within, at the base of which
surface there is a feeble prominence. The conical form is best
expressed in the Melanian races, especially the Australian. The canine
is more deeply implanted, and by a stronger fang than the incisors.”
Nevertheless, this tooth no longer serves man as a special weapon for
tearing his enemies or prey; it may, therefore, as far as its proper
function is concerned, be considered as rudimentary. In every large
collection of human skulls some may be found, as Haeckel (43.
‘Generelle Morphologie,’ 1866, B. ii. s. clv.) observes, with the
canine teeth projecting considerably beyond the others in the same
manner as in the anthropomorphous apes, but in a less degree. In these
cases, open spaces between the teeth in the one jaw are left for the
reception of the canines of the opposite jaw. An inter-space of this
kind in a Kaffir skull, figured by Wagner, is surprisingly wide. (44.
Carl Vogt’s ‘Lectures on Man,’ Eng. translat., 1864, p. 151.)
Considering how few are the ancient skulls which have been examined,
compared to recent skulls, it is an interesting fact that in at least
three cases the canines project largely; and in the Naulette jaw they
are spoken of as enormous. (45. C. Carter Blake, on a jaw from La
Naulette, ‘Anthropological Review,’ 1867, p. 295. Schaaffhausen, ibid.
1868, p. 426.)

Of the anthropomorphous apes the males alone have their canines fully
developed; but in the female gorilla, and in a less degree in the
female orang, these teeth project considerably beyond the others;
therefore the fact, of which I have been assured, that women sometimes
have considerably projecting canines, is no serious objection to the
belief that their occasional great development in man is a case of
reversion to an ape-like progenitor. He who rejects with scorn the
belief that the shape of his own canines, and their occasional great
development in other men, are due to our early forefathers having been
provided with these formidable weapons, will probably reveal, by
sneering, the line of his descent. For though he no longer intends, nor
has the power, to use these teeth as weapons, he will unconsciously
retract his “snarling muscles” (thus named by Sir C. Bell) (46. The
Anatomy of Expression, 1844, pp. 110, 131.), so as to expose them ready
for action, like a dog prepared to fight.

Many muscles are occasionally developed in man, which are proper to the
Quadrumana or other mammals. Professor Vlacovich (47. Quoted by Prof.
Canestrini in the ‘Annuario della Soc. dei Naturalisti,’ 1867, p. 90.)
examined forty male subjects, and found a muscle, called by him the
ischio-pubic, in nineteen of them; in three others there was a ligament
which represented this muscle; and in the remaining eighteen no trace
of it. In only two out of thirty female subjects was this muscle
developed on both sides, but in three others the rudimentary ligament
was present. This muscle, therefore, appears to be much more common in
the male than in the female sex; and on the belief in the descent of
man from some lower form, the fact is intelligible; for it has been
detected in several of the lower animals, and in all of these it serves
exclusively to aid the male in the act of reproduction.

Mr. J. Wood, in his valuable series of papers (48. These papers deserve
careful study by any one who desires to learn how frequently our
muscles vary, and in varying come to resemble those of the Quadrumana.
The following references relate to the few points touched on in my
text: ‘Proc. Royal Soc.’ vol. xiv. 1865, pp. 379-384; vol. xv. 1866,
pp. 241, 242; vol. xv. 1867, p. 544; vol. xvi. 1868, p. 524. I may here
add that Dr. Murie and Mr. St. George Mivart have shewn in their Memoir
on the Lemuroidea (‘Transactions, Zoological Society,’ vol. vii. 1869,
p. 96), how extraordinarily variable some of the muscles are in these
animals, the lowest members of the Primates. Gradations, also, in the
muscles leading to structures found in animals still lower in the
scale, are numerous in the Lemuroidea.), has minutely described a vast
number of muscular variations in man, which resemble normal structures
in the lower animals. The muscles which closely resemble those
regularly present in our nearest allies, the Quadrumana, are too
numerous to be here even specified. In a single male subject, having a
strong bodily frame, and well-formed skull, no less than seven muscular
variations were observed, all of which plainly represented muscles
proper to various kinds of apes. This man, for instance, had on both
sides of his neck a true and powerful “levator claviculae,” such as is
found in all kinds of apes, and which is said to occur in about one out
of sixty human subjects. (49. See also Prof. Macalister in
‘Proceedings, Royal Irish Academy,’ vol. x. 1868, p. 124.) Again, this
man had “a special abductor of the metatarsal bone of the fifth digit,
such as Professor Huxley and Mr. Flower have shewn to exist uniformly
in the higher and lower apes.” I will give only two additional cases;
the acromio-basilar muscle is found in all mammals below man, and seems
to be correlated with a quadrupedal gait, (50. Mr. Champneys in
‘Journal of Anatomy and Physiology,’ Nov. 1871, p. 178.) and it occurs
in about one out of sixty human subjects. In the lower extremities Mr.
Bradley (51. Ibid. May 1872, p. 421.) found an abductor ossis metatarsi
quinti in both feet of man; this muscle had not up to that time been
recorded in mankind, but is always present in the anthropomorphous
apes. The muscles of the hands and arms—parts which are so eminently
characteristic of man—are extremely liable to vary, so as to resemble
the corresponding muscles in the lower animals. (52. Prof. Macalister
(ibid. p. 121) has tabulated his observations, and finds that muscular
abnormalities are most frequent in the fore-arms, secondly, in the
face, thirdly, in the foot, etc.) Such resemblances are either perfect
or imperfect; yet in the latter case they are manifestly of a
transitional nature. Certain variations are more common in man, and
others in woman, without our being able to assign any reason. Mr. Wood,
after describing numerous variations, makes the following pregnant
remark. “Notable departures from the ordinary type of the muscular
structures run in grooves or directions, which must be taken to
indicate some unknown factor, of much importance to a comprehensive
knowledge of general and scientific anatomy.” (53. The Rev. Dr.
Haughton, after giving (‘Proc. R. Irish Academy,’ June 27, 1864, p.
715) a remarkable case of variation in the human flexor pollicis
longus, adds, “This remarkable example shews that man may sometimes
possess the arrangement of tendons of thumb and fingers characteristic
of the macaque; but whether such a case should be regarded as a macaque
passing upwards into a man, or a man passing downwards into a macaque,
or as a congenital freak of nature, I cannot undertake to say.” It is
satisfactory to hear so capable an anatomist, and so embittered an
opponent of evolutionism, admitting even the possibility of either of
his first propositions. Prof. Macalister has also described
(‘Proceedings Royal Irish Academy,’ vol. x. 1864, p. 138) variations in
the flexor pollicis longus, remarkable from their relations to the same
muscle in the Quadrumana.)

That this unknown factor is reversion to a former state of existence
may be admitted as in the highest degree probable. (54. Since the first
edition of this book appeared, Mr. Wood has published another memoir in
the Philosophical Transactions, 1870, p. 83, on the varieties of the
muscles of the human neck, shoulder, and chest. He here shews how
extremely variable these muscles are, and how often and how closely the
variations resemble the normal muscles of the lower animals. He sums up
by remarking, “It will be enough for my purpose if I have succeeded in
shewing the more important forms which, when occurring as varieties in
the human subject, tend to exhibit in a sufficiently marked manner what
may be considered as proofs and examples of the Darwinian principle of
reversion, or law of inheritance, in this department of anatomical
science.”) It is quite incredible that a man should through mere
accident abnormally resemble certain apes in no less than seven of his
muscles, if there had been no genetic connection between them. On the
other hand, if man is descended from some ape-like creature, no valid
reason can be assigned why certain muscles should not suddenly reappear
after an interval of many thousand generations, in the same manner as
with horses, asses, and mules, dark-coloured stripes suddenly reappear
on the legs, and shoulders, after an interval of hundreds, or more
probably of thousands of generations.

These various cases of reversion are so closely related to those of
rudimentary organs given in the first chapter, that many of them might
have been indifferently introduced either there or here. Thus a human
uterus furnished with cornua may be said to represent, in a rudimentary
condition, the same organ in its normal state in certain mammals. Some
parts which are rudimentary in man, as the os coccyx in both sexes, and
the mammae in the male sex, are always present; whilst others, such as
the supracondyloid foramen, only occasionally appear, and therefore
might have been introduced under the head of reversion. These several
reversionary structures, as well as the strictly rudimentary ones,
reveal the descent of man from some lower form in an unmistakable
manner.

CORRELATED VARIATION.

In man, as in the lower animals, many structures are so intimately
related, that when one part varies so does another, without our being
able, in most cases, to assign any reason. We cannot say whether the
one part governs the other, or whether both are governed by some
earlier developed part. Various monstrosities, as I. Geoffroy
repeatedly insists, are thus intimately connected. Homologous
structures are particularly liable to change together, as we see on the
opposite sides of the body, and in the upper and lower extremities.
Meckel long ago remarked, that when the muscles of the arm depart from
their proper type, they almost always imitate those of the leg; and so,
conversely, with the muscles of the legs. The organs of sight and
hearing, the teeth and hair, the colour of the skin and of the hair,
colour and constitution, are more or less correlated. (55. The
authorities for these several statements are given in my ‘Variation of
Animals under Domestication,’ vol. ii. pp. 320-335.) Professor
Schaaffhausen first drew attention to the relation apparently existing
between a muscular frame and the strongly-pronounced supra-orbital
ridges, which are so characteristic of the lower races of man.

Besides the variations which can be grouped with more or less
probability under the foregoing heads, there is a large class of
variations which may be provisionally called spontaneous, for to our
ignorance they appear to arise without any exciting cause. It can,
however, be shewn that such variations, whether consisting of slight
individual differences, or of strongly-marked and abrupt deviations of
structure, depend much more on the constitution of the organism than on
the nature of the conditions to which it has been subjected. (56. This
whole subject has been discussed in chap. xxiii. vol. ii. of my
‘Variation of Animals and Plants under Domestication.’)

RATE OF INCREASE.

Civilised populations have been known under favourable conditions, as
in the United States, to double their numbers in twenty-five years;
and, according to a calculation, by Euler, this might occur in a little
over twelve years. (57. See the ever memorable ‘Essay on the Principle
of Population,’ by the Rev. T. Malthus, vol. i. 1826. pp. 6, 517.) At
the former rate, the present population of the United States (thirty
millions), would in 657 years cover the whole terraqueous globe so
thickly, that four men would have to stand on each square yard of
surface. The primary or fundamental check to the continued increase of
man is the difficulty of gaining subsistence, and of living in comfort.
We may infer that this is the case from what we see, for instance, in
the United States, where subsistence is easy, and there is plenty of
room. If such means were suddenly doubled in Great Britain, our number
would be quickly doubled. With civilised nations this primary check
acts chiefly by restraining marriages. The greater death-rate of
infants in the poorest classes is also very important; as well as the
greater mortality, from various diseases, of the inhabitants of crowded
and miserable houses, at all ages. The effects of severe epidemics and
wars are soon counterbalanced, and more than counterbalanced, in
nations placed under favourable conditions. Emigration also comes in
aid as a temporary check, but, with the extremely poor classes, not to
any great extent.

There is reason to suspect, as Malthus has remarked, that the
reproductive power is actually less in barbarous, than in civilised
races. We know nothing positively on this head, for with savages no
census has been taken; but from the concurrent testimony of
missionaries, and of others who have long resided with such people, it
appears that their families are usually small, and large ones rare.
This may be partly accounted for, as it is believed, by the women
suckling their infants during a long time; but it is highly probable
that savages, who often suffer much hardship, and who do not obtain so
much nutritious food as civilised men, would be actually less prolific.
I have shewn in a former work (58. ‘Variation of Animals and Plants
under Domestication,’ vol ii. pp. 111-113, 163.), that all our
domesticated quadrupeds and birds, and all our cultivated plants, are
more fertile than the corresponding species in a state of nature. It is
no valid objection to this conclusion that animals suddenly supplied
with an excess of food, or when grown very fat; and that most plants on
sudden removal from very poor to very rich soil, are rendered more or
less sterile. We might, therefore, expect that civilised men, who in
one sense are highly domesticated, would be more prolific than wild
men. It is also probable that the increased fertility of civilised
nations would become, as with our domestic animals, an inherited
character: it is at least known that with mankind a tendency to produce
twins runs in families. (59. Mr. Sedgwick, ‘British and Foreign
Medico-Chirurgical Review,’ July 1863, p. 170.)

Notwithstanding that savages appear to be less prolific than civilised
people, they would no doubt rapidly increase if their numbers were not
by some means rigidly kept down. The Santali, or hill-tribes of India,
have recently afforded a good illustration of this fact; for, as shewn
by Mr. Hunter (60. ‘The Annals of Rural Bengal,’ by W.W. Hunter, 1868,
p. 259.), they have increased at an extraordinary rate since
vaccination has been introduced, other pestilences mitigated, and war
sternly repressed. This increase, however, would not have been possible
had not these rude people spread into the adjoining districts, and
worked for hire. Savages almost always marry; yet there is some
prudential restraint, for they do not commonly marry at the earliest
possible age. The young men are often required to shew that they can
support a wife; and they generally have first to earn the price with
which to purchase her from her parents. With savages the difficulty of
obtaining subsistence occasionally limits their number in a much more
direct manner than with civilised people, for all tribes periodically
suffer from severe famines. At such times savages are forced to devour
much bad food, and their health can hardly fail to be injured. Many
accounts have been published of their protruding stomachs and emaciated
limbs after and during famines. They are then, also, compelled to
wander much, and, as I was assured in Australia, their infants perish
in large numbers. As famines are periodical, depending chiefly on
extreme seasons, all tribes must fluctuate in number. They cannot
steadily and regularly increase, as there is no artificial increase in
the supply of food. Savages, when hard pressed, encroach on each
other’s territories, and war is the result; but they are indeed almost
always at war with their neighbours. They are liable to many accidents
on land and water in their search for food; and in some countries they
suffer much from the larger beasts of prey. Even in India, districts
have been depopulated by the ravages of tigers.

Malthus has discussed these several checks, but he does not lay stress
enough on what is probably the most important of all, namely
infanticide, especially of female infants, and the habit of procuring
abortion. These practices now prevail in many quarters of the world;
and infanticide seems formerly to have prevailed, as Mr. M’Lennan (61.
‘Primitive Marriage,’ 1865.) has shewn, on a still more extensive
scale. These practices appear to have originated in savages recognising
the difficulty, or rather the impossibility of supporting all the
infants that are born. Licentiousness may also be added to the
foregoing checks; but this does not follow from failing means of
subsistence; though there is reason to believe that in some cases (as
in Japan) it has been intentionally encouraged as a means of keeping
down the population.

If we look back to an extremely remote epoch, before man had arrived at
the dignity of manhood, he would have been guided more by instinct and
less by reason than are the lowest savages at the present time. Our
early semi-human progenitors would not have practised infanticide or
polyandry; for the instincts of the lower animals are never so
perverted (62. A writer in the ‘Spectator’ (March 12, 1871, p. 320)
comments as follows on this passage:—“Mr. Darwin finds himself
compelled to reintroduce a new doctrine of the fall of man. He shews
that the instincts of the higher animals are far nobler than the habits
of savage races of men, and he finds himself, therefore, compelled to
re-introduce,—in a form of the substantial orthodoxy of which he
appears to be quite unconscious,—and to introduce as a scientific
hypothesis the doctrine that man’s gain of KNOWLEDGE was the cause of a
temporary but long-enduring moral deterioration as indicated by the
many foul customs, especially as to marriage, of savage tribes. What
does the Jewish tradition of the moral degeneration of man through his
snatching at a knowledge forbidden him by his highest instinct assert
beyond this?”) as to lead them regularly to destroy their own
offspring, or to be quite devoid of jealousy. There would have been no
prudential restraint from marriage, and the sexes would have freely
united at an early age. Hence the progenitors of man would have tended
to increase rapidly; but checks of some kind, either periodical or
constant, must have kept down their numbers, even more severely than
with existing savages. What the precise nature of these checks were, we
cannot say, any more than with most other animals. We know that horses
and cattle, which are not extremely prolific animals, when first turned
loose in South America, increased at an enormous rate. The elephant,
the slowest breeder of all known animals, would in a few thousand years
stock the whole world. The increase of every species of monkey must be
checked by some means; but not, as Brehm remarks, by the attacks of
beasts of prey. No one will assume that the actual power of
reproduction in the wild horses and cattle of America, was at first in
any sensible degree increased; or that, as each district became fully
stocked, this same power was diminished. No doubt, in this case, and in
all others, many checks concur, and different checks under different
circumstances; periodical dearths, depending on unfavourable seasons,
being probably the most important of all. So it will have been with the
early progenitors of man.

NATURAL SELECTION.

We have now seen that man is variable in body and mind; and that the
variations are induced, either directly or indirectly, by the same
general causes, and obey the same general laws, as with the lower
animals. Man has spread widely over the face of the earth, and must
have been exposed, during his incessant migrations (63. See some good
remarks to this effect by W. Stanley Jevons, “A Deduction from Darwin’s
Theory,” ‘Nature,’ 1869, p. 231.), to the most diversified conditions.
The inhabitants of Tierra del Fuego, the Cape of Good Hope, and
Tasmania in the one hemisphere, and of the arctic regions in the other,
must have passed through many climates, and changed their habits many
times, before they reached their present homes. (64. Latham, ‘Man and
his Migrations,’ 1851, p. 135.) The early progenitors of man must also
have tended, like all other animals, to have increased beyond their
means of subsistence; they must, therefore, occasionally have been
exposed to a struggle for existence, and consequently to the rigid law
of natural selection. Beneficial variations of all kinds will thus,
either occasionally or habitually, have been preserved and injurious
ones eliminated. I do not refer to strongly-marked deviations of
structure, which occur only at long intervals of time, but to mere
individual differences. We know, for instance, that the muscles of our
hands and feet, which determine our powers of movement, are liable,
like those of the lower animals, (65. Messrs. Murie and Mivart in their
‘Anatomy of the Lemuroidea’ (‘Transact. Zoolog. Soc.’ vol. vii. 1869,
pp. 96-98) say, “some muscles are so irregular in their distribution
that they cannot be well classed in any of the above groups.” These
muscles differ even on the opposite sides of the same individual.) to
incessant variability. If then the progenitors of man inhabiting any
district, especially one undergoing some change in its conditions, were
divided into two equal bodies, the one half which included all the
individuals best adapted by their powers of movement for gaining
subsistence, or for defending themselves, would on an average survive
in greater numbers, and procreate more offspring than the other and
less well endowed half.

Man in the rudest state in which he now exists is the most dominant
animal that has ever appeared on this earth. He has spread more widely
than any other highly organised form: and all others have yielded
before him. He manifestly owes this immense superiority to his
intellectual faculties, to his social habits, which lead him to aid and
defend his fellows, and to his corporeal structure. The supreme
importance of these characters has been proved by the final arbitrament
of the battle for life. Through his powers of intellect, articulate
language has been evolved; and on this his wonderful advancement has
mainly depended. As Mr. Chauncey Wright remarks (66. Limits of Natural
Selection, ‘North American Review,’ Oct. 1870, p. 295.): “a
psychological analysis of the faculty of language shews, that even the
smallest proficiency in it might require more brain power than the
greatest proficiency in any other direction.” He has invented and is
able to use various weapons, tools, traps, etc., with which he defends
himself, kills or catches prey, and otherwise obtains food. He has made
rafts or canoes for fishing or crossing over to neighbouring fertile
islands. He has discovered the art of making fire, by which hard and
stringy roots can be rendered digestible, and poisonous roots or herbs
innocuous. This discovery of fire, probably the greatest ever made by
man, excepting language, dates from before the dawn of history. These
several inventions, by which man in the rudest state has become so
pre-eminent, are the direct results of the development of his powers of
observation, memory, curiosity, imagination, and reason. I cannot,
therefore, understand how it is that Mr. Wallace (67. ‘Quarterly
Review,’ April 1869, p. 392. This subject is more fully discussed in
Mr. Wallace’s ‘Contributions to the Theory of Natural Selection,’ 1870,
in which all the essays referred to in this work are re-published. The
‘Essay on Man,’ has been ably criticised by Prof. Claparede, one of the
most distinguished zoologists in Europe, in an article published in the
‘Bibliotheque Universelle,’ June 1870. The remark quoted in my text
will surprise every one who has read Mr. Wallace’s celebrated paper on
‘The Origin of Human Races Deduced from the Theory of Natural
Selection,’ originally published in the ‘Anthropological Review,’ May
1864, p. clviii. I cannot here resist quoting a most just remark by Sir
J. Lubbock (‘Prehistoric Times,’ 1865, p. 479) in reference to this
paper, namely, that Mr. Wallace, “with characteristic unselfishness,
ascribes it (i.e. the idea of natural selection) unreservedly to Mr.
Darwin, although, as is well known, he struck out the idea
independently, and published it, though not with the same elaboration,
at the same time.”) maintains, that “natural selection could only have
endowed the savage with a brain a little superior to that of an ape.”

Although the intellectual powers and social habits of man are of
paramount importance to him, we must not underrate the importance of
his bodily structure, to which subject the remainder of this chapter
will be devoted; the development of the intellectual and social or
moral faculties being discussed in a later chapter.

Even to hammer with precision is no easy matter, as every one who has
tried to learn carpentry will admit. To throw a stone with as true an
aim as a Fuegian in defending himself, or in killing birds, requires
the most consummate perfection in the correlated action of the muscles
of the hand, arm, and shoulder, and, further, a fine sense of touch. In
throwing a stone or spear, and in many other actions, a man must stand
firmly on his feet; and this again demands the perfect co-adaptation of
numerous muscles. To chip a flint into the rudest tool, or to form a
barbed spear or hook from a bone, demands the use of a perfect hand;
for, as a most capable judge, Mr. Schoolcraft (68. Quoted by Mr. Lawson
Tait in his ‘Law of Natural Selection,’ ‘Dublin Quarterly Journal of
Medical Science,’ Feb. 1869. Dr. Keller is likewise quoted to the same
effect.), remarks, the shaping fragments of stone into knives, lances,
or arrow-heads, shews “extraordinary ability and long practice.” This
is to a great extent proved by the fact that primeval men practised a
division of labour; each man did not manufacture his own flint tools or
rude pottery, but certain individuals appear to have devoted themselves
to such work, no doubt receiving in exchange the produce of the chase.
Archaeologists are convinced that an enormous interval of time elapsed
before our ancestors thought of grinding chipped flints into smooth
tools. One can hardly doubt, that a man-like animal who possessed a
hand and arm sufficiently perfect to throw a stone with precision, or
to form a flint into a rude tool, could, with sufficient practice, as
far as mechanical skill alone is concerned, make almost anything which
a civilised man can make. The structure of the hand in this respect may
be compared with that of the vocal organs, which in the apes are used
for uttering various signal-cries, or, as in one genus, musical
cadences; but in man the closely similar vocal organs have become
adapted through the inherited effects of use for the utterance of
articulate language.

Turning now to the nearest allies of men, and therefore to the best
representatives of our early progenitors, we find that the hands of the
Quadrumana are constructed on the same general pattern as our own, but
are far less perfectly adapted for diversified uses. Their hands do not
serve for locomotion so well as the feet of a dog; as may be seen in
such monkeys as the chimpanzee and orang, which walk on the outer
margins of the palms, or on the knuckles. (69. Owen, ‘Anatomy of
Vertebrates,’ vol. iii. p. 71.) Their hands, however, are admirably
adapted for climbing trees. Monkeys seize thin branches or ropes, with
the thumb on one side and the fingers and palm on the other, in the
same manner as we do. They can thus also lift rather large objects,
such as the neck of a bottle, to their mouths. Baboons turn over
stones, and scratch up roots with their hands. They seize nuts,
insects, or other small objects with the thumb in opposition to the
fingers, and no doubt they thus extract eggs and young from the nests
of birds. American monkeys beat the wild oranges on the branches until
the rind is cracked, and then tear it off with the fingers of the two
hands. In a wild state they break open hard fruits with stones. Other
monkeys open mussel-shells with the two thumbs. With their fingers they
pull out thorns and burs, and hunt for each other’s parasites. They
roll down stones, or throw them at their enemies: nevertheless, they
are clumsy in these various actions, and, as I have myself seen, are
quite unable to throw a stone with precision.

It seems to me far from true that because “objects are grasped
clumsily” by monkeys, “a much less specialised organ of prehension”
would have served them (70. ‘Quarterly Review,’ April 1869, p. 392.)
equally well with their present hands. On the contrary, I see no reason
to doubt that more perfectly constructed hands would have been an
advantage to them, provided that they were not thus rendered less
fitted for climbing trees. We may suspect that a hand as perfect as
that of man would have been disadvantageous for climbing; for the most
arboreal monkeys in the world, namely, Ateles in America, Colobus in
Africa, and Hylobates in Asia, are either thumbless, or their toes
partially cohere, so that their limbs are converted into mere grasping
hooks. (71. In Hylobates syndactylus, as the name expresses, two of the
toes regularly cohere; and this, as Mr. Blyth informs me, is
occasionally the case with the toes of H. agilis, lar, and leuciscus.
Colobus is strictly arboreal and extraordinarily active (Brehm,
‘Thierleben,’ B. i. s. 50), but whether a better climber than the
species of the allied genera, I do not know. It deserves notice that
the feet of the sloths, the most arboreal animals in the world, are
wonderfully hook-like.

As soon as some ancient member in the great series of the Primates came
to be less arboreal, owing to a change in its manner of procuring
subsistence, or to some change in the surrounding conditions, its
habitual manner of progression would have been modified: and thus it
would have been rendered more strictly quadrupedal or bipedal. Baboons
frequent hilly and rocky districts, and only from necessity climb high
trees (72. Brehm, ‘Thierleben,’ B. i. s. 80.); and they have acquired
almost the gait of a dog. Man alone has become a biped; and we can, I
think, partly see how he has come to assume his erect attitude, which
forms one of his most conspicuous characters. Man could not have
attained his present dominant position in the world without the use of
his hands, which are so admirably adapted to act in obedience to his
will. Sir C. Bell (73. ‘The Hand,’ etc., ‘Bridgewater Treatise,’ 1833,
p. 38.) insists that “the hand supplies all instruments, and by its
correspondence with the intellect gives him universal dominion.” But
the hands and arms could hardly have become perfect enough to have
manufactured weapons, or to have hurled stones and spears with a true
aim, as long as they were habitually used for locomotion and for
supporting the whole weight of the body, or, as before remarked, so
long as they were especially fitted for climbing trees. Such rough
treatment would also have blunted the sense of touch, on which their
delicate use largely depends. From these causes alone it would have
been an advantage to man to become a biped; but for many actions it is
indispensable that the arms and whole upper part of the body should be
free; and he must for this end stand firmly on his feet. To gain this
great advantage, the feet have been rendered flat; and the great toe
has been peculiarly modified, though this has entailed the almost
complete loss of its power of prehension. It accords with the principle
of the division of physiological labour, prevailing throughout the
animal kingdom, that as the hands became perfected for prehension, the
feet should have become perfected for support and locomotion. With some
savages, however, the foot has not altogether lost its prehensile
power, as shewn by their manner of climbing trees, and of using them in
other ways. (74. Haeckel has an excellent discussion on the steps by
which man became a biped: ‘Natürliche Schöpfungsgeschichte,’ 1868, s.
507. Dr. Buchner (‘Conférences sur la Théorie Darwinienne,’ 1869, p.
135) has given good cases of the use of the foot as a prehensile organ
by man; and has also written on the manner of progression of the higher
apes, to which I allude in the following paragraph: see also Owen
(‘Anatomy of Vertebrates,’ vol. iii. p. 71) on this latter subject.)

If it be an advantage to man to stand firmly on his feet and to have
his hands and arms free, of which, from his pre-eminent success in the
battle of life there can be no doubt, then I can see no reason why it
should not have been advantageous to the progenitors of man to have
become more and more erect or bipedal. They would thus have been better
able to defend themselves with stones or clubs, to attack their prey,
or otherwise to obtain food. The best built individuals would in the
long run have succeeded best, and have survived in larger numbers. If
the gorilla and a few allied forms had become extinct, it might have
been argued, with great force and apparent truth, that an animal could
not have been gradually converted from a quadruped into a biped, as all
the individuals in an intermediate condition would have been miserably
ill-fitted for progression. But we know (and this is well worthy of
reflection) that the anthropomorphous apes are now actually in an
intermediate condition; and no one doubts that they are on the whole
well adapted for their conditions of life. Thus the gorilla runs with a
sidelong shambling gait, but more commonly progresses by resting on its
bent hands. The long-armed apes occasionally use their arms like
crutches, swinging their bodies forward between them, and some kinds of
Hylobates, without having been taught, can walk or run upright with
tolerable quickness; yet they move awkwardly, and much less securely
than man. We see, in short, in existing monkeys a manner of progression
intermediate between that of a quadruped and a biped; but, as an
unprejudiced judge (75. Prof. Broca, La Constitution des Vertèbres
caudales; ‘La Revue d’Anthropologie,’ 1872, p. 26, (separate copy).)
insists, the anthropomorphous apes approach in structure more nearly to
the bipedal than to the quadrupedal type.

As the progenitors of man became more and more erect, with their hands
and arms more and more modified for prehension and other purposes, with
their feet and legs at the same time transformed for firm support and
progression, endless other changes of structure would have become
necessary. The pelvis would have to be broadened, the spine peculiarly
curved, and the head fixed in an altered position, all which changes
have been attained by man. Prof. Schaaffhausen (76. ‘On the Primitive
Form of the Skull,’ translated in ‘Anthropological Review,’ Oct. 1868,
p. 428. Owen (‘Anatomy of Vertebrates,’ vol. ii. 1866, p. 551) on the
mastoid processes in the higher apes.) maintains that “the powerful
mastoid processes of the human skull are the result of his erect
position;” and these processes are absent in the orang, chimpanzee,
etc., and are smaller in the gorilla than in man. Various other
structures, which appear connected with man’s erect position, might
here have been added. It is very difficult to decide how far these
correlated modifications are the result of natural selection, and how
far of the inherited effects of the increased use of certain parts, or
of the action of one part on another. No doubt these means of change
often co-operate: thus when certain muscles, and the crests of bone to
which they are attached, become enlarged by habitual use, this shews
that certain actions are habitually performed and must be serviceable.
Hence the individuals which performed them best, would tend to survive
in greater numbers.

The free use of the arms and hands, partly the cause and partly the
result of man’s erect position, appears to have led in an indirect
manner to other modifications of structure. The early male forefathers
of man were, as previously stated, probably furnished with great canine
teeth; but as they gradually acquired the habit of using stones, clubs,
or other weapons, for fighting with their enemies or rivals, they would
use their jaws and teeth less and less. In this case, the jaws,
together with the teeth, would become reduced in size, as we may feel
almost sure from innumerable analogous cases. In a future chapter we
shall meet with a closely parallel case, in the reduction or complete
disappearance of the canine teeth in male ruminants, apparently in
relation with the development of their horns; and in horses, in
relation to their habit of fighting with their incisor teeth and hoofs.

In the adult male anthropomorphous apes, as Rutimeyer (77. ‘Die Grenzen
der Thierwelt, eine Betrachtung zu Darwin’s Lehre,’ 1868, s. 51.), and
others, have insisted, it is the effect on the skull of the great
development of the jaw-muscles that causes it to differ so greatly in
many respects from that of man, and has given to these animals “a truly
frightful physiognomy.” Therefore, as the jaws and teeth in man’s
progenitors gradually become reduced in size, the adult skull would
have come to resemble more and more that of existing man. As we shall
hereafter see, a great reduction of the canine teeth in the males would
almost certainly affect the teeth of the females through inheritance.

As the various mental faculties gradually developed themselves the
brain would almost certainly become larger. No one, I presume, doubts
that the large proportion which the size of man’s brain bears to his
body, compared to the same proportion in the gorilla or orang, is
closely connected with his higher mental powers. We meet with closely
analogous facts with insects, for in ants the cerebral ganglia are of
extraordinary dimensions, and in all the Hymenoptera these ganglia are
many times larger than in the less intelligent orders, such as beetles.
(78. Dujardin, ‘Annales des Sciences Nat.’ 3rd series, Zoolog., tom.
xiv. 1850, p. 203. See also Mr. Lowne, ‘Anatomy and Phys. of the Musca
vomitoria,’ 1870, p. 14. My son, Mr. F. Darwin, dissected for me the
cerebral ganglia of the Formica rufa.) On the other hand, no one
supposes that the intellect of any two animals or of any two men can be
accurately gauged by the cubic contents of their skulls. It is certain
that there may be extraordinary mental activity with an extremely small
absolute mass of nervous matter: thus the wonderfully diversified
instincts, mental powers, and affections of ants are notorious, yet
their cerebral ganglia are not so large as the quarter of a small pin’s
head. Under this point of view, the brain of an ant is one of the most
marvellous atoms of matter in the world, perhaps more so than the brain
of a man.

The belief that there exists in man some close relation between the
size of the brain and the development of the intellectual faculties is
supported by the comparison of the skulls of savage and civilised
races, of ancient and modern people, and by the analogy of the whole
vertebrate series. Dr. J. Barnard Davis has proved (79. ‘Philosophical
Transactions,’ 1869, p. 513.), by many careful measurements, that the
mean internal capacity of the skull in Europeans is 92.3 cubic inches;
in Americans 87.5; in Asiatics 87.1; and in Australians only 81.9 cubic
inches. Professor Broca (80. ‘Les Selections,’ M. P. Broca, ‘Revue
d’Anthropologies,’ 1873; see also, as quoted in C. Vogt’s ‘Lectures on
Man,’ Engl. translat., 1864, pp. 88, 90. Prichard, ‘Physical History of
Mankind,’ vol. i. 1838, p. 305.) found that the nineteenth century
skulls from graves in Paris were larger than those from vaults of the
twelfth century, in the proportion of 1484 to 1426; and that the
increased size, as ascertained by measurements, was exclusively in the
frontal part of the skull—the seat of the intellectual faculties.
Prichard is persuaded that the present inhabitants of Britain have
“much more capacious brain-cases” than the ancient inhabitants.
Nevertheless, it must be admitted that some skulls of very high
antiquity, such as the famous one of Neanderthal, are well developed
and capacious. (81. In the interesting article just referred to, Prof.
Broca has well remarked, that in civilised nations, the average
capacity of the skull must be lowered by the preservation of a
considerable number of individuals, weak in mind and body, who would
have been promptly eliminated in the savage state. On the other hand,
with savages, the average includes only the more capable individuals,
who have been able to survive under extremely hard conditions of life.
Broca thus explains the otherwise inexplicable fact, that the mean
capacity of the skull of the ancient Troglodytes of Lozere is greater
than that of modern Frenchmen.) With respect to the lower animals, M.E.
Lartet (82. ‘Comptes-rendus des Sciences,’ etc., June 1, 1868.), by
comparing the crania of tertiary and recent mammals belonging to the
same groups, has come to the remarkable conclusion that the brain is
generally larger and the convolutions are more complex in the more
recent forms. On the other hand, I have shewn (83. The ‘Variation of
Animals and Plants under Domestication,’ vol. i. pp. 124-129.) that the
brains of domestic rabbits are considerably reduced in bulk, in
comparison with those of the wild rabbit or hare; and this may be
attributed to their having been closely confined during many
generations, so that they have exerted their intellect, instincts,
senses and voluntary movements but little.

The gradually increasing weight of the brain and skull in man must have
influenced the development of the supporting spinal column, more
especially whilst he was becoming erect. As this change of position was
being brought about, the internal pressure of the brain will also have
influenced the form of the skull; for many facts shew how easily the
skull is thus affected. Ethnologists believe that it is modified by the
kind of cradle in which infants sleep. Habitual spasms of the muscles,
and a cicatrix from a severe burn, have permanently modified the facial
bones. In young persons whose heads have become fixed either sideways
or backwards, owing to disease, one of the two eyes has changed its
position, and the shape of the skull has been altered apparently by the
pressure of the brain in a new direction. (84. Schaaffhausen gives from
Blumenbach and Busch, the cases of the spasms and cicatrix, in
‘Anthropological Review,’ Oct. 1868, p. 420. Dr. Jarrold
(‘Anthropologia,’ 1808, pp. 115, 116) adduces from Camper and from his
own observations, cases of the modification of the skull from the head
being fixed in an unnatural position. He believes that in certain
trades, such as that of a shoemaker, where the head is habitually held
forward, the forehead becomes more rounded and prominent.) I have shewn
that with long-eared rabbits even so trifling a cause as the lopping
forward of one ear drags forward almost every bone of the skull on that
side; so that the bones on the opposite side no longer strictly
correspond. Lastly, if any animal were to increase or diminish much in
general size, without any change in its mental powers, or if the mental
powers were to be much increased or diminished, without any great
change in the size of the body, the shape of the skull would almost
certainly be altered. I infer this from my observations on domestic
rabbits, some kinds of which have become very much larger than the wild
animal, whilst others have retained nearly the same size, but in both
cases the brain has been much reduced relatively to the size of the
body. Now I was at first much surprised on finding that in all these
rabbits the skull had become elongated or dolichocephalic; for
instance, of two skulls of nearly equal breadth, the one from a wild
rabbit and the other from a large domestic kind, the former was 3.15
and the latter 4.3 inches in length. (85. ‘Variation of Animals and
Plants under Domestication,’ vol. i. p. 117, on the elongation of the
skull; p. 119, on the effect of the lopping of one ear.) One of the
most marked distinctions in different races of men is that the skull in
some is elongated, and in others rounded; and here the explanation
suggested by the case of the rabbits may hold good; for Welcker finds
that short “men incline more to brachycephaly, and tall men to
dolichocephaly” (86. Quoted by Schaaffhausen, in ‘Anthropological
Review,’ Oct. 1868, p. 419.); and tall men may be compared with the
larger and longer-bodied rabbits, all of which have elongated skulls or
are dolichocephalic.

From these several facts we can understand, to a certain extent, the
means by which the great size and more or less rounded form of the
skull have been acquired by man; and these are characters eminently
distinctive of him in comparison with the lower animals.

Another most conspicuous difference between man and the lower animals
is the nakedness of his skin. Whales and porpoises (Cetacea), dugongs
(Sirenia) and the hippopotamus are naked; and this may be advantageous
to them for gliding through the water; nor would it be injurious to
them from the loss of warmth, as the species, which inhabit the colder
regions, are protected by a thick layer of blubber, serving the same
purpose as the fur of seals and otters. Elephants and rhinoceroses are
almost hairless; and as certain extinct species, which formerly lived
under an Arctic climate, were covered with long wool or hair, it would
almost appear as if the existing species of both genera had lost their
hairy covering from exposure to heat. This appears the more probable,
as the elephants in India which live on elevated and cool districts are
more hairy (87. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 619.) than
those on the lowlands. May we then infer that man became divested of
hair from having aboriginally inhabited some tropical land? That the
hair is chiefly retained in the male sex on the chest and face, and in
both sexes at the junction of all four limbs with the trunk, favours
this inference—on the assumption that the hair was lost before man
became erect; for the parts which now retain most hair would then have
been most protected from the heat of the sun. The crown of the head,
however, offers a curious exception, for at all times it must have been
one of the most exposed parts, yet it is thickly clothed with hair. The
fact, however, that the other members of the order of Primates, to
which man belongs, although inhabiting various hot regions, are well
clothed with hair, generally thickest on the upper surface (88. Isidore
Geoffroy St.-Hilaire remarks (‘Histoire Nat. Generale,’ tom. ii. 1859,
pp. 215-217) on the head of man being covered with long hair; also on
the upper surfaces of monkeys and of other mammals being more thickly
clothed than the lower surfaces. This has likewise been observed by
various authors. Prof. P. Gervais (‘Histoire Nat. des Mammifères,’ tom.
i. 1854, p. 28), however, states that in the Gorilla the hair is
thinner on the back, where it is partly rubbed off, than on the lower
surface.), is opposed to the supposition that man became naked through
the action of the sun. Mr. Belt believes (89. The ‘Naturalist in
Nicaragua,’ 1874, p. 209. As some confirmation of Mr. Belt’s view, I
may quote the following passage from Sir W. Denison (‘Varieties of
Vice-Regal Life,’ vol. i. 1870, p. 440): “It is said to be a practice
with the Australians, when the vermin get troublesome, to singe
themselves.”) that within the tropics it is an advantage to man to be
destitute of hair, as he is thus enabled to free himself of the
multitude of ticks (acari) and other parasites, with which he is often
infested, and which sometimes cause ulceration. But whether this evil
is of sufficient magnitude to have led to the denudation of his body
through natural selection, may be doubted, since none of the many
quadrupeds inhabiting the tropics have, as far as I know, acquired any
specialised means of relief. The view which seems to me the most
probable is that man, or rather primarily woman, became divested of
hair for ornamental purposes, as we shall see under Sexual Selection;
and, according to this belief, it is not surprising that man should
differ so greatly in hairiness from all other Primates, for characters,
gained through sexual selection, often differ to an extraordinary
degree in closely related forms.

According to a popular impression, the absence of a tail is eminently
distinctive of man; but as those apes which come nearest to him are
destitute of this organ, its disappearance does not relate exclusively
to man. The tail often differs remarkably in length within the same
genus: thus in some species of Macacus it is longer than the whole
body, and is formed of twenty-four vertebrae; in others it consists of
a scarcely visible stump, containing only three or four vertebrae. In
some kinds of baboons there are twenty-five, whilst in the mandrill
there are ten very small stunted caudal vertebrae, or, according to
Cuvier (90. Mr. St. George Mivart, ‘Proc. Zoolog. Soc.’ 1865, pp. 562,
583. Dr. J.E. Gray, ‘Cat. Brit. Mus.: ‘Skeletons.’ Owen, ‘Anatomy of
Vertebrates,’ vol. ii. p. 517. Isidore Geoffroy, ‘Hist. Nat. Gen.’ tom.
ii. p. 244.), sometimes only five. The tail, whether it be long or
short, almost always tapers towards the end; and this, I presume,
results from the atrophy of the terminal muscles, together with their
arteries and nerves, through disuse, leading to the atrophy of the
terminal bones. But no explanation can at present be given of the great
diversity which often occurs in its length. Here, however, we are more
specially concerned with the complete external disappearance of the
tail. Professor Broca has recently shewn (91. ‘Revue d’Anthropologie,’
1872; ‘La Constitution des vertèbres caudales.’) that the tail in all
quadrupeds consists of two portions, generally separated abruptly from
each other; the basal portion consists of vertebrae, more or less
perfectly channelled and furnished with apophyses like ordinary
vertebrae; whereas those of the terminal portion are not channelled,
are almost smooth, and scarcely resemble true vertebrae. A tail, though
not externally visible, is really present in man and the
anthropomorphous apes, and is constructed on exactly the same pattern
in both. In the terminal portion the vertebrae, constituting the os
coccyx, are quite rudimentary, being much reduced in size and number.
In the basal portion, the vertebrae are likewise few, are united firmly
together, and are arrested in development; but they have been rendered
much broader and flatter than the corresponding vertebrae in the tails
of other animals: they constitute what Broca calls the accessory sacral
vertebrae. These are of functional importance by supporting certain
internal parts and in other ways; and their modification is directly
connected with the erect or semi-erect attitude of man and the
anthropomorphous apes. This conclusion is the more trustworthy, as
Broca formerly held a different view, which he has now abandoned. The
modification, therefore, of the basal caudal vertebrae in man and the
higher apes may have been effected, directly or indirectly, through
natural selection.

But what are we to say about the rudimentary and variable vertebrae of
the terminal portion of the tail, forming the os coccyx? A notion which
has often been, and will no doubt again be ridiculed, namely, that
friction has had something to do with the disappearance of the external
portion of the tail, is not so ridiculous as it at first appears. Dr.
Anderson (92. ‘Proceedings Zoological Society,’ 1872, p. 210.) states
that the extremely short tail of Macacus brunneus is formed of eleven
vertebrae, including the imbedded basal ones. The extremity is
tendinous and contains no vertebrae; this is succeeded by five
rudimentary ones, so minute that together they are only one line and a
half in length, and these are permanently bent to one side in the shape
of a hook. The free part of the tail, only a little above an inch in
length, includes only four more small vertebrae. This short tail is
carried erect; but about a quarter of its total length is doubled on to
itself to the left; and this terminal part, which includes the
hook-like portion, serves “to fill up the interspace between the upper
divergent portion of the callosities;” so that the animal sits on it,
and thus renders it rough and callous. Dr. Anderson thus sums up his
observations: “These facts seem to me to have only one explanation;
this tail, from its short size, is in the monkey’s way when it sits
down, and frequently becomes placed under the animal while it is in
this attitude; and from the circumstance that it does not extend beyond
the extremity of the ischial tuberosities, it seems as if the tail
originally had been bent round by the will of the animal, into the
interspace between the callosities, to escape being pressed between
them and the ground, and that in time the curvature became permanent,
fitting in of itself when the organ happens to be sat upon.” Under
these circumstances it is not surprising that the surface of the tail
should have been roughened and rendered callous, and Dr. Murie (93.
‘Proceedings Zoological Society,’ 1872, p. 786.), who carefully
observed this species in the Zoological Gardens, as well as three other
closely allied forms with slightly longer tails, says that when the
animal sits down, the tail “is necessarily thrust to one side of the
buttocks; and whether long or short its root is consequently liable to
be rubbed or chafed.” As we now have evidence that mutilations
occasionally produce an inherited effect (94. I allude to Dr.
Brown-Sequard’s observations on the transmitted effect of an operation
causing epilepsy in guinea-pigs, and likewise more recently on the
analogous effects of cutting the sympathetic nerve in the neck. I shall
hereafter have occasion to refer to Mr. Salvin’s interesting case of
the apparently inherited effects of mot-mots biting off the barbs of
their own tail-feathers. See also on the general subject ‘Variation of
Animals and Plants under Domestication,’ vol. ii. pp. 22-24.), it is
not very improbable that in short-tailed monkeys, the projecting part
of the tail, being functionally useless, should after many generations
have become rudimentary and distorted, from being continually rubbed
and chafed. We see the projecting part in this condition in the Macacus
brunneus, and absolutely aborted in the M. ecaudatus and in several of
the higher apes. Finally, then, as far as we can judge, the tail has
disappeared in man and the anthropomorphous apes, owing to the terminal
portion having been injured by friction during a long lapse of time;
the basal and embedded portion having been reduced and modified, so as
to become suitable to the erect or semi-erect position.

I have now endeavoured to shew that some of the most distinctive
characters of man have in all probability been acquired, either
directly, or more commonly indirectly, through natural selection. We
should bear in mind that modifications in structure or constitution
which do not serve to adapt an organism to its habits of life, to the
food which it consumes, or passively to the surrounding conditions,
cannot have been thus acquired. We must not, however, be too confident
in deciding what modifications are of service to each being: we should
remember how little we know about the use of many parts, or what
changes in the blood or tissues may serve to fit an organism for a new
climate or new kinds of food. Nor must we forget the principle of
correlation, by which, as Isidore Geoffroy has shewn in the case of
man, many strange deviations of structure are tied together.
Independently of correlation, a change in one part often leads, through
the increased or decreased use of other parts, to other changes of a
quite unexpected nature. It is also well to reflect on such facts, as
the wonderful growth of galls on plants caused by the poison of an
insect, and on the remarkable changes of colour in the plumage of
parrots when fed on certain fishes, or inoculated with the poison of
toads (95. The ‘Variation of Animals and Plants under Domestication,’
vol. ii. pp. 280, 282.); for we can thus see that the fluids of the
system, if altered for some special purpose, might induce other
changes. We should especially bear in mind that modifications acquired
and continually used during past ages for some useful purpose, would
probably become firmly fixed, and might be long inherited.

Thus a large yet undefined extension may safely be given to the direct
and indirect results of natural selection; but I now admit, after
reading the essay by Nageli on plants, and the remarks by various
authors with respect to animals, more especially those recently made by
Professor Broca, that in the earlier editions of my ‘Origin of Species’
I perhaps attributed too much to the action of natural selection or the
survival of the fittest. I have altered the fifth edition of the
‘Origin’ so as to confine my remarks to adaptive changes of structure;
but I am convinced, from the light gained during even the last few
years, that very many structures which now appear to us useless, will
hereafter be proved to be useful, and will therefore come within the
range of natural selection. Nevertheless, I did not formerly consider
sufficiently the existence of structures, which, as far as we can at
present judge, are neither beneficial nor injurious; and this I believe
to be one of the greatest oversights as yet detected in my work. I may
be permitted to say, as some excuse, that I had two distinct objects in
view; firstly, to shew that species had not been separately created,
and secondly, that natural selection had been the chief agent of
change, though largely aided by the inherited effects of habit, and
slightly by the direct action of the surrounding conditions. I was not,
however, able to annul the influence of my former belief, then almost
universal, that each species had been purposely created; and this led
to my tacit assumption that every detail of structure, excepting
rudiments, was of some special, though unrecognised, service. Any one
with this assumption in his mind would naturally extend too far the
action of natural selection, either during past or present times. Some
of those who admit the principle of evolution, but reject natural
selection, seem to forget, when criticising my book, that I had the
above two objects in view; hence if I have erred in giving to natural
selection great power, which I am very far from admitting, or in having
exaggerated its power, which is in itself probable, I have at least, as
I hope, done good service in aiding to overthrow the dogma of separate
creations.

It is, as I can now see, probable that all organic beings, including
man, possess peculiarities of structure, which neither are now, nor
were formerly of any service to them, and which, therefore, are of no
physiological importance. We know not what produces the numberless
slight differences between the individuals of each species, for
reversion only carries the problem a few steps backwards, but each
peculiarity must have had its efficient cause. If these causes,
whatever they may be, were to act more uniformly and energetically
during a lengthened period (and against this no reason can be
assigned), the result would probably be not a mere slight individual
difference, but a well-marked and constant modification, though one of
no physiological importance. Changed structures, which are in no way
beneficial, cannot be kept uniform through natural selection, though
the injurious will be thus eliminated. Uniformity of character would,
however, naturally follow from the assumed uniformity of the exciting
causes, and likewise from the free intercrossing of many individuals.
During successive periods, the same organism might in this manner
acquire successive modifications, which would be transmitted in a
nearly uniform state as long as the exciting causes remained the same
and there was free intercrossing. With respect to the exciting causes
we can only say, as when speaking of so-called spontaneous variations,
that they relate much more closely to the constitution of the varying
organism, than to the nature of the conditions to which it has been
subjected.

—CONCLUSION—

In this chapter we have seen that as man at the present day is liable,
like every other animal, to multiform individual differences or slight
variations, so no doubt were the early progenitors of man; the
variations being formerly induced by the same general causes, and
governed by the same general and complex laws as at present. As all
animals tend to multiply beyond their means of subsistence, so it must
have been with the progenitors of man; and this would inevitably lead
to a struggle for existence and to natural selection. The latter
process would be greatly aided by the inherited effects of the
increased use of parts, and these two processes would incessantly react
on each other. It appears, also, as we shall hereafter see, that
various unimportant characters have been acquired by man through sexual
selection. An unexplained residuum of change must be left to the
assumed uniform action of those unknown agencies, which occasionally
induce strongly marked and abrupt deviations of structure in our
domestic productions.

Judging from the habits of savages and of the greater number of the
Quadrumana, primeval men, and even their ape-like progenitors, probably
lived in society. With strictly social animals, natural selection
sometimes acts on the individual, through the preservation of
variations which are beneficial to the community. A community which
includes a large number of well-endowed individuals increases in
number, and is victorious over other less favoured ones; even although
each separate member gains no advantage over the others of the same
community. Associated insects have thus acquired many remarkable
structures, which are of little or no service to the individual, such
as the pollen-collecting apparatus, or the sting of the worker-bee, or
the great jaws of soldier-ants. With the higher social animals, I am
not aware that any structure has been modified solely for the good of
the community, though some are of secondary service to it. For
instance, the horns of ruminants and the great canine teeth of baboons
appear to have been acquired by the males as weapons for sexual strife,
but they are used in defence of the herd or troop. In regard to certain
mental powers the case, as we shall see in the fifth chapter, is wholly
different; for these faculties have been chiefly, or even exclusively,
gained for the benefit of the community, and the individuals thereof
have at the same time gained an advantage indirectly.

It has often been objected to such views as the foregoing, that man is
one of the most helpless and defenceless creatures in the world; and
that during his early and less well-developed condition, he would have
been still more helpless. The Duke of Argyll, for instance, insists
(96. ‘Primeval Man,’ 1869, p. 66.) that “the human frame has diverged
from the structure of brutes, in the direction of greater physical
helplessness and weakness. That is to say, it is a divergence which of
all others it is most impossible to ascribe to mere natural selection.”
He adduces the naked and unprotected state of the body, the absence of
great teeth or claws for defence, the small strength and speed of man,
and his slight power of discovering food or of avoiding danger by
smell. To these deficiencies there might be added one still more
serious, namely, that he cannot climb quickly, and so escape from
enemies. The loss of hair would not have been a great injury to the
inhabitants of a warm country. For we know that the unclothed Fuegians
can exist under a wretched climate. When we compare the defenceless
state of man with that of apes, we must remember that the great canine
teeth with which the latter are provided, are possessed in their full
development by the males alone, and are chiefly used by them for
fighting with their rivals; yet the females, which are not thus
provided, manage to survive.

In regard to bodily size or strength, we do not know whether man is
descended from some small species, like the chimpanzee, or from one as
powerful as the gorilla; and, therefore, we cannot say whether man has
become larger and stronger, or smaller and weaker, than his ancestors.
We should, however, bear in mind that an animal possessing great size,
strength, and ferocity, and which, like the gorilla, could defend
itself from all enemies, would not perhaps have become social: and this
would most effectually have checked the acquirement of the higher
mental qualities, such as sympathy and the love of his fellows. Hence
it might have been an immense advantage to man to have sprung from some
comparatively weak creature.

The small strength and speed of man, his want of natural weapons, etc.,
are more than counterbalanced, firstly, by his intellectual powers,
through which he has formed for himself weapons, tools, etc., though
still remaining in a barbarous state, and, secondly, by his social
qualities which lead him to give and receive aid from his fellow-men.
No country in the world abounds in a greater degree with dangerous
beasts than Southern Africa; no country presents more fearful physical
hardships than the Arctic regions; yet one of the puniest of races,
that of the Bushmen, maintains itself in Southern Africa, as do the
dwarfed Esquimaux in the Arctic regions. The ancestors of man were, no
doubt, inferior in intellect, and probably in social disposition, to
the lowest existing savages; but it is quite conceivable that they
might have existed, or even flourished, if they had advanced in
intellect, whilst gradually losing their brute-like powers, such as
that of climbing trees, etc. But these ancestors would not have been
exposed to any special danger, even if far more helpless and
defenceless than any existing savages, had they inhabited some warm
continent or large island, such as Australia, New Guinea, or Borneo,
which is now the home of the orang. And natural selection arising from
the competition of tribe with tribe, in some such large area as one of
these, together with the inherited effects of habit, would, under
favourable conditions, have sufficed to raise man to his present high
position in the organic scale.




CHAPTER III.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.


The difference in mental power between the highest ape and the lowest
savage, immense—Certain instincts in common—The
emotions—Curiosity—Imitation—Attention—Memory—
Imagination—Reason—Progressive improvement —Tools and weapons used by
animals—Abstraction, Self-consciousness—Language—Sense of beauty—Belief
in God, spiritual agencies, superstitions.

We have seen in the last two chapters that man bears in his bodily
structure clear traces of his descent from some lower form; but it may
be urged that, as man differs so greatly in his mental power from all
other animals, there must be some error in this conclusion. No doubt
the difference in this respect is enormous, even if we compare the mind
of one of the lowest savages, who has no words to express any number
higher than four, and who uses hardly any abstract terms for common
objects or for the affections (1. See the evidence on those points, as
given by Lubbock, ‘Prehistoric Times,’ p. 354, etc.), with that of the
most highly organised ape. The difference would, no doubt, still remain
immense, even if one of the higher apes had been improved or civilised
as much as a dog has been in comparison with its parent-form, the wolf
or jackal. The Fuegians rank amongst the lowest barbarians; but I was
continually struck with surprise how closely the three natives on board
H.M.S. “Beagle,” who had lived some years in England, and could talk a
little English, resembled us in disposition and in most of our mental
faculties. If no organic being excepting man had possessed any mental
power, or if his powers had been of a wholly different nature from
those of the lower animals, then we should never have been able to
convince ourselves that our high faculties had been gradually
developed. But it can be shewn that there is no fundamental difference
of this kind. We must also admit that there is a much wider interval in
mental power between one of the lowest fishes, as a lamprey or
lancelet, and one of the higher apes, than between an ape and man; yet
this interval is filled up by numberless gradations.

Nor is the difference slight in moral disposition between a barbarian,
such as the man described by the old navigator Byron, who dashed his
child on the rocks for dropping a basket of sea-urchins, and a Howard
or Clarkson; and in intellect, between a savage who uses hardly any
abstract terms, and a Newton or Shakspeare. Differences of this kind
between the highest men of the highest races and the lowest savages,
are connected by the finest gradations. Therefore it is possible that
they might pass and be developed into each other.

My object in this chapter is to shew that there is no fundamental
difference between man and the higher mammals in their mental
faculties. Each division of the subject might have been extended into a
separate essay, but must here be treated briefly. As no classification
of the mental powers has been universally accepted, I shall arrange my
remarks in the order most convenient for my purpose; and will select
those facts which have struck me most, with the hope that they may
produce some effect on the reader.

With respect to animals very low in the scale, I shall give some
additional facts under Sexual Selection, shewing that their mental
powers are much higher than might have been expected. The variability
of the faculties in the individuals of the same species is an important
point for us, and some few illustrations will here be given. But it
would be superfluous to enter into many details on this head, for I
have found on frequent enquiry, that it is the unanimous opinion of all
those who have long attended to animals of many kinds, including birds,
that the individuals differ greatly in every mental characteristic. In
what manner the mental powers were first developed in the lowest
organisms, is as hopeless an enquiry as how life itself first
originated. These are problems for the distant future, if they are ever
to be solved by man.

As man possesses the same senses as the lower animals, his fundamental
intuitions must be the same. Man has also some few instincts in common,
as that of self-preservation, sexual love, the love of the mother for
her new-born offspring, the desire possessed by the latter to suck, and
so forth. But man, perhaps, has somewhat fewer instincts than those
possessed by the animals which come next to him in the series. The
orang in the Eastern islands, and the chimpanzee in Africa, build
platforms on which they sleep; and, as both species follow the same
habit, it might be argued that this was due to instinct, but we cannot
feel sure that it is not the result of both animals having similar
wants, and possessing similar powers of reasoning. These apes, as we
may assume, avoid the many poisonous fruits of the tropics, and man has
no such knowledge: but as our domestic animals, when taken to foreign
lands, and when first turned out in the spring, often eat poisonous
herbs, which they afterwards avoid, we cannot feel sure that the apes
do not learn from their own experience or from that of their parents
what fruits to select. It is, however, certain, as we shall presently
see, that apes have an instinctive dread of serpents, and probably of
other dangerous animals.

The fewness and the comparative simplicity of the instincts in the
higher animals are remarkable in contrast with those of the lower
animals. Cuvier maintained that instinct and intelligence stand in an
inverse ratio to each other; and some have thought that the
intellectual faculties of the higher animals have been gradually
developed from their instincts. But Pouchet, in an interesting essay
(2. ‘L’Instinct chez les Insectes,’ ‘Revue des Deux Mondes,’ Feb. 1870,
p. 690.), has shewn that no such inverse ratio really exists. Those
insects which possess the most wonderful instincts are certainly the
most intelligent. In the vertebrate series, the least intelligent
members, namely fishes and amphibians, do not possess complex
instincts; and amongst mammals the animal most remarkable for its
instincts, namely the beaver, is highly intelligent, as will be
admitted by every one who has read Mr. Morgan’s excellent work. (3.
‘The American Beaver and His Works,’ 1868.)

Although the first dawnings of intelligence, according to Mr. Herbert
Spencer (4. ‘The Principles of Psychology,’ 2nd edit., 1870, pp.
418-443.), have been developed through the multiplication and
co-ordination of reflex actions, and although many of the simpler
instincts graduate into reflex actions, and can hardly be distinguished
from them, as in the case of young animals sucking, yet the more
complex instincts seem to have originated independently of
intelligence. I am, however, very far from wishing to deny that
instinctive actions may lose their fixed and untaught character, and be
replaced by others performed by the aid of the free will. On the other
hand, some intelligent actions, after being performed during several
generations, become converted into instincts and are inherited, as when
birds on oceanic islands learn to avoid man. These actions may then be
said to be degraded in character, for they are no longer performed
through reason or from experience. But the greater number of the more
complex instincts appear to have been gained in a wholly different
manner, through the natural selection of variations of simpler
instinctive actions. Such variations appear to arise from the same
unknown causes acting on the cerebral organisation, which induce slight
variations or individual differences in other parts of the body; and
these variations, owing to our ignorance, are often said to arise
spontaneously. We can, I think, come to no other conclusion with
respect to the origin of the more complex instincts, when we reflect on
the marvellous instincts of sterile worker-ants and bees, which leave
no offspring to inherit the effects of experience and of modified
habits.

Although, as we learn from the above-mentioned insects and the beaver,
a high degree of intelligence is certainly compatible with complex
instincts, and although actions, at first learnt voluntarily can soon
through habit be performed with the quickness and certainty of a reflex
action, yet it is not improbable that there is a certain amount of
interference between the development of free intelligence and of
instinct,—which latter implies some inherited modification of the
brain. Little is known about the functions of the brain, but we can
perceive that as the intellectual powers become highly developed, the
various parts of the brain must be connected by very intricate channels
of the freest intercommunication; and as a consequence each separate
part would perhaps tend to be less well fitted to answer to particular
sensations or associations in a definite and inherited—that is
instinctive—manner. There seems even to exist some relation between a
low degree of intelligence and a strong tendency to the formation of
fixed, though not inherited habits; for as a sagacious physician
remarked to me, persons who are slightly imbecile tend to act in
everything by routine or habit; and they are rendered much happier if
this is encouraged.

I have thought this digression worth giving, because we may easily
underrate the mental powers of the higher animals, and especially of
man, when we compare their actions founded on the memory of past
events, on foresight, reason, and imagination, with exactly similar
actions instinctively performed by the lower animals; in this latter
case the capacity of performing such actions has been gained, step by
step, through the variability of the mental organs and natural
selection, without any conscious intelligence on the part of the animal
during each successive generation. No doubt, as Mr. Wallace has argued
(5. ‘Contributions to the Theory of Natural Selection,’ 1870, p. 212.),
much of the intelligent work done by man is due to imitation and not to
reason; but there is this great difference between his actions and many
of those performed by the lower animals, namely, that man cannot, on
his first trial, make, for instance, a stone hatchet or a canoe,
through his power of imitation. He has to learn his work by practice; a
beaver, on the other hand, can make its dam or canal, and a bird its
nest, as well, or nearly as well, and a spider its wonderful web, quite
as well (6. For the evidence on this head, see Mr. J. Traherne
Moggridge’s most interesting work, ‘Harvesting Ants and Trap-Door
Spiders,’ 1873, pp. 126, 128.), the first time it tries as when old and
experienced.

To return to our immediate subject: the lower animals, like man,
manifestly feel pleasure and pain, happiness and misery. Happiness is
never better exhibited than by young animals, such as puppies, kittens,
lambs, etc., when playing together, like our own children. Even insects
play together, as has been described by that excellent observer, P.
Huber (7. ‘Recherches sur les Moeurs des Fourmis,’ 1810, p. 173.), who
saw ants chasing and pretending to bite each other, like so many
puppies.

The fact that the lower animals are excited by the same emotions as
ourselves is so well established, that it will not be necessary to
weary the reader by many details. Terror acts in the same manner on
them as on us, causing the muscles to tremble, the heart to palpitate,
the sphincters to be relaxed, and the hair to stand on end. Suspicion,
the offspring of fear, is eminently characteristic of most wild
animals. It is, I think, impossible to read the account given by Sir E.
Tennent, of the behaviour of the female elephants, used as decoys,
without admitting that they intentionally practise deceit, and well
know what they are about. Courage and timidity are extremely variable
qualities in the individuals of the same species, as is plainly seen in
our dogs. Some dogs and horses are ill-tempered, and easily turn sulky;
others are good-tempered; and these qualities are certainly inherited.
Every one knows how liable animals are to furious rage, and how plainly
they shew it. Many, and probably true, anecdotes have been published on
the long-delayed and artful revenge of various animals. The accurate
Rengger, and Brehm (8. All the following statements, given on the
authority of these two naturalists, are taken from Rengger’s
‘Naturgesch. der Säugethiere von Paraguay,’ 1830, s. 41-57, and from
Brehm’s ‘Thierleben,’ B. i. s. 10-87.) state that the American and
African monkeys which they kept tame, certainly revenged themselves.
Sir Andrew Smith, a zoologist whose scrupulous accuracy was known to
many persons, told me the following story of which he was himself an
eye-witness; at the Cape of Good Hope an officer had often plagued a
certain baboon, and the animal, seeing him approaching one Sunday for
parade, poured water into a hole and hastily made some thick mud, which
he skilfully dashed over the officer as he passed by, to the amusement
of many bystanders. For long afterwards the baboon rejoiced and
triumphed whenever he saw his victim.

The love of a dog for his master is notorious; as an old writer
quaintly says (9. Quoted by Dr. Lauder Lindsay, in his ‘Physiology of
Mind in the Lower Animals,’ ‘Journal of Mental Science,’ April 1871, p.
38.), “A dog is the only thing on this earth that luvs you more than he
luvs himself.”

In the agony of death a dog has been known to caress his master, and
every one has heard of the dog suffering under vivisection, who licked
the hand of the operator; this man, unless the operation was fully
justified by an increase of our knowledge, or unless he had a heart of
stone, must have felt remorse to the last hour of his life.

As Whewell (10. ‘Bridgewater Treatise,’ p. 263.) has well asked, “who
that reads the touching instances of maternal affection, related so
often of the women of all nations, and of the females of all animals,
can doubt that the principle of action is the same in the two cases?”
We see maternal affection exhibited in the most trifling details; thus
Rengger observed an American monkey (a Cebus) carefully driving away
the flies which plagued her infant; and Duvaucel saw a Hylobates
washing the faces of her young ones in a stream. So intense is the
grief of female monkeys for the loss of their young, that it invariably
caused the death of certain kinds kept under confinement by Brehm in N.
Africa. Orphan monkeys were always adopted and carefully guarded by the
other monkeys, both males and females. One female baboon had so
capacious a heart that she not only adopted young monkeys of other
species, but stole young dogs and cats, which she continually carried
about. Her kindness, however, did not go so far as to share her food
with her adopted offspring, at which Brehm was surprised, as his
monkeys always divided everything quite fairly with their own young
ones. An adopted kitten scratched this affectionate baboon, who
certainly had a fine intellect, for she was much astonished at being
scratched, and immediately examined the kitten’s feet, and without more
ado bit off the claws. (11. A critic, without any grounds (‘Quarterly
Review,’ July 1871, p. 72), disputes the possibility of this act as
described by Brehm, for the sake of discrediting my work. Therefore I
tried, and found that I could readily seize with my own teeth the sharp
little claws of a kitten nearly five weeks old.) In the Zoological
Gardens, I heard from the keeper that an old baboon (C. chacma) had
adopted a Rhesus monkey; but when a young drill and mandrill were
placed in the cage, she seemed to perceive that these monkeys, though
distinct species, were her nearer relatives, for she at once rejected
the Rhesus and adopted both of them. The young Rhesus, as I saw, was
greatly discontented at being thus rejected, and it would, like a
naughty child, annoy and attack the young drill and mandrill whenever
it could do so with safety; this conduct exciting great indignation in
the old baboon. Monkeys will also, according to Brehm, defend their
master when attacked by any one, as well as dogs to whom they are
attached, from the attacks of other dogs. But we here trench on the
subjects of sympathy and fidelity, to which I shall recur. Some of
Brehm’s monkeys took much delight in teasing a certain old dog whom
they disliked, as well as other animals, in various ingenious ways.

Most of the more complex emotions are common to the higher animals and
ourselves. Every one has seen how jealous a dog is of his master’s
affection, if lavished on any other creature; and I have observed the
same fact with monkeys. This shews that animals not only love, but have
desire to be loved. Animals manifestly feel emulation. They love
approbation or praise; and a dog carrying a basket for his master
exhibits in a high degree self-complacency or pride. There can, I
think, be no doubt that a dog feels shame, as distinct from fear, and
something very like modesty when begging too often for food. A great
dog scorns the snarling of a little dog, and this may be called
magnanimity. Several observers have stated that monkeys certainly
dislike being laughed at; and they sometimes invent imaginary offences.
In the Zoological Gardens I saw a baboon who always got into a furious
rage when his keeper took out a letter or book and read it aloud to
him; and his rage was so violent that, as I witnessed on one occasion,
he bit his own leg till the blood flowed. Dogs shew what may be fairly
called a sense of humour, as distinct from mere play; if a bit of stick
or other such object be thrown to one, he will often carry it away for
a short distance; and then squatting down with it on the ground close
before him, will wait until his master comes quite close to take it
away. The dog will then seize it and rush away in triumph, repeating
the same manoeuvre, and evidently enjoying the practical joke.

We will now turn to the more intellectual emotions and faculties, which
are very important, as forming the basis for the development of the
higher mental powers. Animals manifestly enjoy excitement, and suffer
from ennui, as may be seen with dogs, and, according to Rengger, with
monkeys. All animals feel WONDER, and many exhibit CURIOSITY. They
sometimes suffer from this latter quality, as when the hunter plays
antics and thus attracts them; I have witnessed this with deer, and so
it is with the wary chamois, and with some kinds of wild-ducks. Brehm
gives a curious account of the instinctive dread, which his monkeys
exhibited, for snakes; but their curiosity was so great that they could
not desist from occasionally satiating their horror in a most human
fashion, by lifting up the lid of the box in which the snakes were
kept. I was so much surprised at his account, that I took a stuffed and
coiled-up snake into the monkey-house at the Zoological Gardens, and
the excitement thus caused was one of the most curious spectacles which
I ever beheld. Three species of Cercopithecus were the most alarmed;
they dashed about their cages, and uttered sharp signal cries of
danger, which were understood by the other monkeys. A few young monkeys
and one old Anubis baboon alone took no notice of the snake. I then
placed the stuffed specimen on the ground in one of the larger
compartments. After a time all the monkeys collected round it in a
large circle, and staring intently, presented a most ludicrous
appearance. They became extremely nervous; so that when a wooden ball,
with which they were familiar as a plaything, was accidentally moved in
the straw, under which it was partly hidden, they all instantly started
away. These monkeys behaved very differently when a dead fish, a mouse
(12. I have given a short account of their behaviour on this occasion
in my ‘Expression of the Emotions in Man and Animals,’ p. 43.), a
living turtle, and other new objects were placed in their cages; for
though at first frightened, they soon approached, handled and examined
them. I then placed a live snake in a paper bag, with the mouth loosely
closed, in one of the larger compartments. One of the monkeys
immediately approached, cautiously opened the bag a little, peeped in,
and instantly dashed away. Then I witnessed what Brehm has described,
for monkey after monkey, with head raised high and turned on one side,
could not resist taking a momentary peep into the upright bag, at the
dreadful object lying quietly at the bottom. It would almost appear as
if monkeys had some notion of zoological affinities, for those kept by
Brehm exhibited a strange, though mistaken, instinctive dread of
innocent lizards and frogs. An orang, also, has been known to be much
alarmed at the first sight of a turtle. (13. W.C.L. Martin, ‘Natural
History of Mammalia,’ 1841, p. 405.)

The principle of IMITATION is strong in man, and especially, as I have
myself observed, with savages. In certain morbid states of the brain
this tendency is exaggerated to an extraordinary degree: some
hemiplegic patients and others, at the commencement of inflammatory
softening of the brain, unconsciously imitate every word which is
uttered, whether in their own or in a foreign language, and every
gesture or action which is performed near them. (14. Dr. Bateman, ‘On
Aphasia,’ 1870, p. 110.) Desor (15. Quoted by Vogt, ‘Mémoire sur les
Microcephales,’ 1867, p. 168.) has remarked that no animal voluntarily
imitates an action performed by man, until in the ascending scale we
come to monkeys, which are well known to be ridiculous mockers.
Animals, however, sometimes imitate each other’s actions: thus two
species of wolves, which had been reared by dogs, learned to bark, as
does sometimes the jackal (16. The ‘Variation of Animals and Plants
under Domestication,’ vol. i. p. 27.), but whether this can be called
voluntary imitation is another question. Birds imitate the songs of
their parents, and sometimes of other birds; and parrots are notorious
imitators of any sound which they often hear. Dureau de la Malle gives
an account (17. ‘Annales des Sciences Nat.’ (1st Series), tom. xxii. p.
397.) of a dog reared by a cat, who learnt to imitate the well-known
action of a cat licking her paws, and thus washing her ears and face;
this was also witnessed by the celebrated naturalist Audouin. I have
received several confirmatory accounts; in one of these, a dog had not
been suckled by a cat, but had been brought up with one, together with
kittens, and had thus acquired the above habit, which he ever
afterwards practised during his life of thirteen years. Dureau de la
Malle’s dog likewise learnt from the kittens to play with a ball by
rolling it about with his fore paws, and springing on it. A
correspondent assures me that a cat in his house used to put her paws
into jugs of milk having too narrow a mouth for her head. A kitten of
this cat soon learned the same trick, and practised it ever afterwards,
whenever there was an opportunity.

The parents of many animals, trusting to the principle of imitation in
their young, and more especially to their instinctive or inherited
tendencies, may be said to educate them. We see this when a cat brings
a live mouse to her kittens; and Dureau de la Malle has given a curious
account (in the paper above quoted) of his observations on hawks which
taught their young dexterity, as well as judgment of distances, by
first dropping through the air dead mice and sparrows, which the young
generally failed to catch, and then bringing them live birds and
letting them loose.

Hardly any faculty is more important for the intellectual progress of
man than ATTENTION. Animals clearly manifest this power, as when a cat
watches by a hole and prepares to spring on its prey. Wild animals
sometimes become so absorbed when thus engaged, that they may be easily
approached. Mr. Bartlett has given me a curious proof how variable this
faculty is in monkeys. A man who trains monkeys to act in plays, used
to purchase common kinds from the Zoological Society at the price of
five pounds for each; but he offered to give double the price, if he
might keep three or four of them for a few days, in order to select
one. When asked how he could possibly learn so soon, whether a
particular monkey would turn out a good actor, he answered that it all
depended on their power of attention. If when he was talking and
explaining anything to a monkey, its attention was easily distracted,
as by a fly on the wall or other trifling object, the case was
hopeless. If he tried by punishment to make an inattentive monkey act,
it turned sulky. On the other hand, a monkey which carefully attended
to him could always be trained.

It is almost superfluous to state that animals have excellent MEMORIES
for persons and places. A baboon at the Cape of Good Hope, as I have
been informed by Sir Andrew Smith, recognised him with joy after an
absence of nine months. I had a dog who was savage and averse to all
strangers, and I purposely tried his memory after an absence of five
years and two days. I went near the stable where he lived, and shouted
to him in my old manner; he shewed no joy, but instantly followed me
out walking, and obeyed me, exactly as if I had parted with him only
half an hour before. A train of old associations, dormant during five
years, had thus been instantaneously awakened in his mind. Even ants,
as P. Huber (18. ‘Les Moeurs des Fourmis,’ 1810, p. 150.) has clearly
shewn, recognised their fellow-ants belonging to the same community
after a separation of four months. Animals can certainly by some means
judge of the intervals of time between recurrent events.

The IMAGINATION is one of the highest prerogatives of man. By this
faculty he unites former images and ideas, independently of the will,
and thus creates brilliant and novel results. A poet, as Jean Paul
Richter remarks (19. Quoted in Dr. Maudsley’s ‘Physiology and Pathology
of Mind,’ 1868, pp. 19, 220.), “who must reflect whether he shall make
a character say yes or no—to the devil with him; he is only a stupid
corpse.” Dreaming gives us the best notion of this power; as Jean Paul
again says, “The dream is an involuntary art of poetry.” The value of
the products of our imagination depends of course on the number,
accuracy, and clearness of our impressions, on our judgment and taste
in selecting or rejecting the involuntary combinations, and to a
certain extent on our power of voluntarily combining them. As dogs,
cats, horses, and probably all the higher animals, even birds (20. Dr.
Jerdon, ‘Birds of India,’ vol. i. 1862, p. xxi. Houzeau says that his
parokeets and canary-birds dreamt: ‘Etudes sur les Facultes Mentales
des Animaux,’ tom. ii. p. 136.) have vivid dreams, and this is shewn by
their movements and the sounds uttered, we must admit that they possess
some power of imagination. There must be something special, which
causes dogs to howl in the night, and especially during moonlight, in
that remarkable and melancholy manner called baying. All dogs do not do
so; and, according to Houzeau (21. ibid. 1872, tom. ii. p. 181.), they
do not then look at the moon, but at some fixed point near the horizon.
Houzeau thinks that their imaginations are disturbed by the vague
outlines of the surrounding objects, and conjure up before them
fantastic images: if this be so, their feelings may almost be called
superstitious.

Of all the faculties of the human mind, it will, I presume, be admitted
that REASON stands at the summit. Only a few persons now dispute that
animals possess some power of reasoning. Animals may constantly be seen
to pause, deliberate, and resolve. It is a significant fact, that the
more the habits of any particular animal are studied by a naturalist,
the more he attributes to reason and the less to unlearnt instincts.
(22. Mr. L.H. Morgan’s work on ‘The American Beaver,’ 1868, offers a
good illustration of this remark. I cannot help thinking, however, that
he goes too far in underrating the power of instinct.) In future
chapters we shall see that some animals extremely low in the scale
apparently display a certain amount of reason. No doubt it is often
difficult to distinguish between the power of reason and that of
instinct. For instance, Dr. Hayes, in his work on ‘The Open Polar Sea,’
repeatedly remarks that his dogs, instead of continuing to draw the
sledges in a compact body, diverged and separated when they came to
thin ice, so that their weight might be more evenly distributed. This
was often the first warning which the travellers received that the ice
was becoming thin and dangerous. Now, did the dogs act thus from the
experience of each individual, or from the example of the older and
wiser dogs, or from an inherited habit, that is from instinct? This
instinct, may possibly have arisen since the time, long ago, when dogs
were first employed by the natives in drawing their sledges; or the
Arctic wolves, the parent-stock of the Esquimaux dog, may have acquired
an instinct impelling them not to attack their prey in a close pack,
when on thin ice.

We can only judge by the circumstances under which actions are
performed, whether they are due to instinct, or to reason, or to the
mere association of ideas: this latter principle, however, is
intimately connected with reason. A curious case has been given by
Prof. Mobius (23. ‘Die Bewegungen der Thiere,’ etc., 1873, p. 11.), of
a pike, separated by a plate of glass from an adjoining aquarium
stocked with fish, and who often dashed himself with such violence
against the glass in trying to catch the other fishes, that he was
sometimes completely stunned. The pike went on thus for three months,
but at last learnt caution, and ceased to do so. The plate of glass was
then removed, but the pike would not attack these particular fishes,
though he would devour others which were afterwards introduced; so
strongly was the idea of a violent shock associated in his feeble mind
with the attempt on his former neighbours. If a savage, who had never
seen a large plate-glass window, were to dash himself even once against
it, he would for a long time afterwards associate a shock with a
window-frame; but very differently from the pike, he would probably
reflect on the nature of the impediment, and be cautious under
analogous circumstances. Now with monkeys, as we shall presently see, a
painful or merely a disagreeable impression, from an action once
performed, is sometimes sufficient to prevent the animal from repeating
it. If we attribute this difference between the monkey and the pike
solely to the association of ideas being so much stronger and more
persistent in the one than the other, though the pike often received
much the more severe injury, can we maintain in the case of man that a
similar difference implies the possession of a fundamentally different
mind?

Houzeau relates (24. ‘Études sur les Facultés Mentales des Animaux,’
1872, tom. ii. p. 265.) that, whilst crossing a wide and arid plain in
Texas, his two dogs suffered greatly from thirst, and that between
thirty and forty times they rushed down the hollows to search for
water. These hollows were not valleys, and there were no trees in them,
or any other difference in the vegetation, and as they were absolutely
dry there could have been no smell of damp earth. The dogs behaved as
if they knew that a dip in the ground offered them the best chance of
finding water, and Houzeau has often witnessed the same behaviour in
other animals.

I have seen, as I daresay have others, that when a small object is
thrown on the ground beyond the reach of one of the elephants in the
Zoological Gardens, he blows through his trunk on the ground beyond the
object, so that the current reflected on all sides may drive the object
within his reach. Again a well-known ethnologist, Mr. Westropp, informs
me that he observed in Vienna a bear deliberately making with his paw a
current in some water, which was close to the bars of his cage, so as
to draw a piece of floating bread within his reach. These actions of
the elephant and bear can hardly be attributed to instinct or inherited
habit, as they would be of little use to an animal in a state of
nature. Now, what is the difference between such actions, when
performed by an uncultivated man, and by one of the higher animals?

The savage and the dog have often found water at a low level, and the
coincidence under such circumstances has become associated in their
minds. A cultivated man would perhaps make some general proposition on
the subject; but from all that we know of savages it is extremely
doubtful whether they would do so, and a dog certainly would not. But a
savage, as well as a dog, would search in the same way, though
frequently disappointed; and in both it seems to be equally an act of
reason, whether or not any general proposition on the subject is
consciously placed before the mind. (25. Prof. Huxley has analysed with
admirable clearness the mental steps by which a man, as well as a dog,
arrives at a conclusion in a case analogous to that given in my text.
See his article, ‘Mr. Darwin’s Critics,’ in the ‘Contemporary Review,’
Nov. 1871, p. 462, and in his ‘Critiques and Essays,’ 1873, p. 279.)
The same would apply to the elephant and the bear making currents in
the air or water. The savage would certainly neither know nor care by
what law the desired movements were effected; yet his act would be
guided by a rude process of reasoning, as surely as would a philosopher
in his longest chain of deductions. There would no doubt be this
difference between him and one of the higher animals, that he would
take notice of much slighter circumstances and conditions, and would
observe any connection between them after much less experience, and
this would be of paramount importance. I kept a daily record of the
actions of one of my infants, and when he was about eleven months old,
and before he could speak a single word, I was continually struck with
the greater quickness, with which all sorts of objects and sounds were
associated together in his mind, compared with that of the most
intelligent dogs I ever knew. But the higher animals differ in exactly
the same way in this power of association from those low in the scale,
such as the pike, as well as in that of drawing inferences and of
observation.

The promptings of reason, after very short experience, are well shewn
by the following actions of American monkeys, which stand low in their
order. Rengger, a most careful observer, states that when he first gave
eggs to his monkeys in Paraguay, they smashed them, and thus lost much
of their contents; afterwards they gently hit one end against some hard
body, and picked off the bits of shell with their fingers. After
cutting themselves only ONCE with any sharp tool, they would not touch
it again, or would handle it with the greatest caution. Lumps of sugar
were often given them wrapped up in paper; and Rengger sometimes put a
live wasp in the paper, so that in hastily unfolding it they got stung;
after this had ONCE happened, they always first held the packet to
their ears to detect any movement within. (26. Mr. Belt, in his most
interesting work, ‘The Naturalist in Nicaragua,’ 1874, (p. 119),
likewise describes various actions of a tamed Cebus, which, I think,
clearly shew that this animal possessed some reasoning power.)

The following cases relate to dogs. Mr. Colquhoun (27. ‘The Moor and
the Loch,’ p. 45. Col. Hutchinson on ‘Dog Breaking,’ 1850, p. 46.)
winged two wild-ducks, which fell on the further side of a stream; his
retriever tried to bring over both at once, but could not succeed; she
then, though never before known to ruffle a feather, deliberately
killed one, brought over the other, and returned for the dead bird.
Col. Hutchinson relates that two partridges were shot at once, one
being killed, the other wounded; the latter ran away, and was caught by
the retriever, who on her return came across the dead bird; “she
stopped, evidently greatly puzzled, and after one or two trials,
finding she could not take it up without permitting the escape of the
winged bird, she considered a moment, then deliberately murdered it by
giving it a severe crunch, and afterwards brought away both together.
This was the only known instance of her ever having wilfully injured
any game.” Here we have reason though not quite perfect, for the
retriever might have brought the wounded bird first and then returned
for the dead one, as in the case of the two wild-ducks. I give the
above cases, as resting on the evidence of two independent witnesses,
and because in both instances the retrievers, after deliberation, broke
through a habit which is inherited by them (that of not killing the
game retrieved), and because they shew how strong their reasoning
faculty must have been to overcome a fixed habit.

I will conclude by quoting a remark by the illustrious Humboldt. (28.
‘Personal Narrative,’ Eng. translat., vol. iii. p. 106.) “The muleteers
in S. America say, ‘I will not give you the mule whose step is easiest,
but la mas racional,—the one that reasons best’”; and; as, he adds,
“this popular expression, dictated by long experience, combats the
system of animated machines, better perhaps than all the arguments of
speculative philosophy.” Nevertheless some writers even yet deny that
the higher animals possess a trace of reason; and they endeavour to
explain away, by what appears to be mere verbiage, (29. I am glad to
find that so acute a reasoner as Mr. Leslie Stephen (‘Darwinism and
Divinity, Essays on Free Thinking,’ 1873, p. 80), in speaking of the
supposed impassable barrier between the minds of man and the lower
animals, says, “The distinctions, indeed, which have been drawn, seem
to us to rest upon no better foundation than a great many other
metaphysical distinctions; that is, the assumption that because you can
give two things different names, they must therefore have different
natures. It is difficult to understand how anybody who has ever kept a
dog, or seen an elephant, can have any doubt as to an animal’s power of
performing the essential processes of reasoning.”) all such facts as
those above given.

It has, I think, now been shewn that man and the higher animals,
especially the Primates, have some few instincts in common. All have
the same senses, intuitions, and sensations,—similar passions,
affections, and emotions, even the more complex ones, such as jealousy,
suspicion, emulation, gratitude, and magnanimity; they practise deceit
and are revengeful; they are sometimes susceptible to ridicule, and
even have a sense of humour; they feel wonder and curiosity; they
possess the same faculties of imitation, attention, deliberation,
choice, memory, imagination, the association of ideas, and reason,
though in very different degrees. The individuals of the same species
graduate in intellect from absolute imbecility to high excellence. They
are also liable to insanity, though far less often than in the case of
man. (30. See ‘Madness in Animals,’ by Dr. W. Lauder Lindsay, in
‘Journal of Mental Science,’ July 1871.) Nevertheless, many authors
have insisted that man is divided by an insuperable barrier from all
the lower animals in his mental faculties. I formerly made a collection
of above a score of such aphorisms, but they are almost worthless, as
their wide difference and number prove the difficulty, if not the
impossibility, of the attempt. It has been asserted that man alone is
capable of progressive improvement; that he alone makes use of tools or
fire, domesticates other animals, or possesses property; that no animal
has the power of abstraction, or of forming general concepts, is
self-conscious and comprehends itself; that no animal employs language;
that man alone has a sense of beauty, is liable to caprice, has the
feeling of gratitude, mystery, etc.; believes in God, or is endowed
with a conscience. I will hazard a few remarks on the more important
and interesting of these points.

Archbishop Sumner formerly maintained (31. Quoted by Sir C. Lyell,
‘Antiquity of Man,’ p. 497.) that man alone is capable of progressive
improvement. That he is capable of incomparably greater and more rapid
improvement than is any other animal, admits of no dispute; and this is
mainly due to his power of speaking and handing down his acquired
knowledge. With animals, looking first to the individual, every one who
has had any experience in setting traps, knows that young animals can
be caught much more easily than old ones; and they can be much more
easily approached by an enemy. Even with respect to old animals, it is
impossible to catch many in the same place and in the same kind of
trap, or to destroy them by the same kind of poison; yet it is
improbable that all should have partaken of the poison, and impossible
that all should have been caught in a trap. They must learn caution by
seeing their brethren caught or poisoned. In North America, where the
fur-bearing animals have long been pursued, they exhibit, according to
the unanimous testimony of all observers, an almost incredible amount
of sagacity, caution and cunning; but trapping has been there so long
carried on, that inheritance may possibly have come into play. I have
received several accounts that when telegraphs are first set up in any
district, many birds kill themselves by flying against the wires, but
that in the course of a very few years they learn to avoid this danger,
by seeing, as it would appear, their comrades killed. (32. For
additional evidence, with details, see M. Houzeau, ‘Études sur les
Facultés Mentales des Animaux,’ tom. ii. 1872, p. 147.)

If we look to successive generations, or to the race, there is no doubt
that birds and other animals gradually both acquire and lose caution in
relation to man or other enemies (33. See, with respect to birds on
oceanic islands, my ‘Journal of Researches during the Voyage of the
“Beagle,”’ 1845, p. 398. ‘Origin of Species,’ 5th ed. p. 260.); and
this caution is certainly in chief part an inherited habit or instinct,
but in part the result of individual experience. A good observer, Leroy
(34. ‘Lettres Phil. sur l’Intelligence des Animaux,’ nouvelle edit.,
1802, p. 86.), states, that in districts where foxes are much hunted,
the young, on first leaving their burrows, are incontestably much more
wary than the old ones in districts where they are not much disturbed.

Our domestic dogs are descended from wolves and jackals (35. See the
evidence on this head in chap. i. vol. i., ‘On the Variation of Animals
and Plants under Domestication.’), and though they may not have gained
in cunning, and may have lost in wariness and suspicion, yet they have
progressed in certain moral qualities, such as in affection,
trust-worthiness, temper, and probably in general intelligence. The
common rat has conquered and beaten several other species throughout
Europe, in parts of North America, New Zealand, and recently in
Formosa, as well as on the mainland of China. Mr. Swinhoe (36.
‘Proceedings Zoological Society,’ 1864, p. 186.), who describes these
two latter cases, attributes the victory of the common rat over the
large Mus coninga to its superior cunning; and this latter quality may
probably be attributed to the habitual exercise of all its faculties in
avoiding extirpation by man, as well as to nearly all the less cunning
or weak-minded rats having been continuously destroyed by him. It is,
however, possible that the success of the common rat may be due to its
having possessed greater cunning than its fellow-species, before it
became associated with man. To maintain, independently of any direct
evidence, that no animal during the course of ages has progressed in
intellect or other mental faculties, is to beg the question of the
evolution of species. We have seen that, according to Lartet, existing
mammals belonging to several orders have larger brains than their
ancient tertiary prototypes.

It has often been said that no animal uses any tool; but the chimpanzee
in a state of nature cracks a native fruit, somewhat like a walnut,
with a stone. (37. Savage and Wyman in ‘Boston Journal of Natural
History,’ vol. iv. 1843-44, p. 383.) Rengger (38. ‘Säugethiere von
Paraguay,’ 1830, s. 51-56.) easily taught an American monkey thus to
break open hard palm-nuts; and afterwards of its own accord, it used
stones to open other kinds of nuts, as well as boxes. It thus also
removed the soft rind of fruit that had a disagreeable flavour. Another
monkey was taught to open the lid of a large box with a stick, and
afterwards it used the stick as a lever to move heavy bodies; and I
have myself seen a young orang put a stick into a crevice, slip his
hand to the other end, and use it in the proper manner as a lever. The
tamed elephants in India are well known to break off branches of trees
and use them to drive away the flies; and this same act has been
observed in an elephant in a state of nature. (39. The Indian Field,
March 4, 1871.) I have seen a young orang, when she thought she was
going to be whipped, cover and protect herself with a blanket or straw.
In these several cases stones and sticks were employed as implements;
but they are likewise used as weapons. Brehm (40. ‘Thierleben,’ B. i.
s. 79, 82.) states, on the authority of the well-known traveller
Schimper, that in Abyssinia when the baboons belonging to one species
(C. gelada) descend in troops from the mountains to plunder the fields,
they sometimes encounter troops of another species (C. hamadryas), and
then a fight ensues. The Geladas roll down great stones, which the
Hamadryas try to avoid, and then both species, making a great uproar,
rush furiously against each other. Brehm, when accompanying the Duke of
Coburg-Gotha, aided in an attack with fire-arms on a troop of baboons
in the pass of Mensa in Abyssinia. The baboons in return rolled so many
stones down the mountain, some as large as a man’s head, that the
attackers had to beat a hasty retreat; and the pass was actually closed
for a time against the caravan. It deserves notice that these baboons
thus acted in concert. Mr. Wallace (41. ‘The Malay Archipelago,’ vol.
i. 1869, p. 87.) on three occasions saw female orangs, accompanied by
their young, “breaking off branches and the great spiny fruit of the
Durian tree, with every appearance of rage; causing such a shower of
missiles as effectually kept us from approaching too near the tree.” As
I have repeatedly seen, a chimpanzee will throw any object at hand at a
person who offends him; and the before-mentioned baboon at the Cape of
Good Hope prepared mud for the purpose.

In the Zoological Gardens, a monkey, which had weak teeth, used to
break open nuts with a stone; and I was assured by the keepers that
after using the stone, he hid it in the straw, and would not let any
other monkey touch it. Here, then, we have the idea of property; but
this idea is common to every dog with a bone, and to most or all birds
with their nests.

The Duke of Argyll (42. ‘Primeval Man,’ 1869, pp. 145, 147.) remarks,
that the fashioning of an implement for a special purpose is absolutely
peculiar to man; and he considers that this forms an immeasurable gulf
between him and the brutes. This is no doubt a very important
distinction; but there appears to me much truth in Sir J. Lubbock’s
suggestion (43. ‘Prehistoric Times,’ 1865, p. 473, etc.), that when
primeval man first used flint-stones for any purpose, he would have
accidentally splintered them, and would then have used the sharp
fragments. From this step it would be a small one to break the flints
on purpose, and not a very wide step to fashion them rudely. This
latter advance, however, may have taken long ages, if we may judge by
the immense interval of time which elapsed before the men of the
neolithic period took to grinding and polishing their stone tools. In
breaking the flints, as Sir J. Lubbock likewise remarks, sparks would
have been emitted, and in grinding them heat would have been evolved:
thus the two usual methods of “obtaining fire may have originated.” The
nature of fire would have been known in the many volcanic regions where
lava occasionally flows through forests. The anthropomorphous apes,
guided probably by instinct, build for themselves temporary platforms;
but as many instincts are largely controlled by reason, the simpler
ones, such as this of building a platform, might readily pass into a
voluntary and conscious act. The orang is known to cover itself at
night with the leaves of the Pandanus; and Brehm states that one of his
baboons used to protect itself from the heat of the sun by throwing a
straw-mat over its head. In these several habits, we probably see the
first steps towards some of the simpler arts, such as rude architecture
and dress, as they arose amongst the early progenitors of man.

ABSTRACTION, GENERAL CONCEPTIONS, SELF-CONSCIOUSNESS, MENTAL
INDIVIDUALITY.

It would be very difficult for any one with even much more knowledge
than I possess, to determine how far animals exhibit any traces of
these high mental powers. This difficulty arises from the impossibility
of judging what passes through the mind of an animal; and again, the
fact that writers differ to a great extent in the meaning which they
attribute to the above terms, causes a further difficulty. If one may
judge from various articles which have been published lately, the
greatest stress seems to be laid on the supposed entire absence in
animals of the power of abstraction, or of forming general concepts.
But when a dog sees another dog at a distance, it is often clear that
he perceives that it is a dog in the abstract; for when he gets nearer
his whole manner suddenly changes, if the other dog be a friend. A
recent writer remarks, that in all such cases it is a pure assumption
to assert that the mental act is not essentially of the same nature in
the animal as in man. If either refers what he perceives with his
senses to a mental concept, then so do both. (44. Mr. Hookham, in a
letter to Prof. Max Muller, in the ‘Birmingham News,’ May 1873.) When I
say to my terrier, in an eager voice (and I have made the trial many
times), “Hi, hi, where is it?” she at once takes it as a sign that
something is to be hunted, and generally first looks quickly all
around, and then rushes into the nearest thicket, to scent for any
game, but finding nothing, she looks up into any neighbouring tree for
a squirrel. Now do not these actions clearly shew that she had in her
mind a general idea or concept that some animal is to be discovered and
hunted?

It may be freely admitted that no animal is self-conscious, if by this
term it is implied, that he reflects on such points, as whence he comes
or whither he will go, or what is life and death, and so forth. But how
can we feel sure that an old dog with an excellent memory and some
power of imagination, as shewn by his dreams, never reflects on his
past pleasures or pains in the chase? And this would be a form of
self-consciousness. On the other hand, as Buchner (45. ‘Conférences sur
la Théorie Darwinienne,’ French translat. 1869, p. 132.) has remarked,
how little can the hard-worked wife of a degraded Australian savage,
who uses very few abstract words, and cannot count above four, exert
her self-consciousness, or reflect on the nature of her own existence.
It is generally admitted, that the higher animals possess memory,
attention, association, and even some imagination and reason. If these
powers, which differ much in different animals, are capable of
improvement, there seems no great improbability in more complex
faculties, such as the higher forms of abstraction, and
self-consciousness, etc., having been evolved through the development
and combination of the simpler ones. It has been urged against the
views here maintained that it is impossible to say at what point in the
ascending scale animals become capable of abstraction, etc.; but who
can say at what age this occurs in our young children? We see at least
that such powers are developed in children by imperceptible degrees.

That animals retain their mental individuality is unquestionable. When
my voice awakened a train of old associations in the mind of the
before-mentioned dog, he must have retained his mental individuality,
although every atom of his brain had probably undergone change more
than once during the interval of five years. This dog might have
brought forward the argument lately advanced to crush all
evolutionists, and said, “I abide amid all mental moods and all
material changes...The teaching that atoms leave their impressions as
legacies to other atoms falling into the places they have vacated is
contradictory of the utterance of consciousness, and is therefore
false; but it is the teaching necessitated by evolutionism,
consequently the hypothesis is a false one.” (46. The Rev. Dr. J.
M’Cann, ‘Anti-Darwinism,’ 1869, p. 13.)

LANGUAGE.

This faculty has justly been considered as one of the chief
distinctions between man and the lower animals. But man, as a highly
competent judge, Archbishop Whately remarks, “is not the only animal
that can make use of language to express what is passing in his mind,
and can understand, more or less, what is so expressed by another.”
(47. Quoted in ‘Anthropological Review,’ 1864, p. 158.) In Paraguay the
Cebus azarae when excited utters at least six distinct sounds, which
excite in other monkeys similar emotions. (48. Rengger, ibid. s. 45.)
The movements of the features and gestures of monkeys are understood by
us, and they partly understand ours, as Rengger and others declare. It
is a more remarkable fact that the dog, since being domesticated, has
learnt to bark (49. See my ‘Variation of Animals and Plants under
Domestication,’ vol. i. p. 27.) in at least four or five distinct
tones. Although barking is a new art, no doubt the wild parent-species
of the dog expressed their feelings by cries of various kinds. With the
domesticated dog we have the bark of eagerness, as in the chase; that
of anger, as well as growling; the yelp or howl of despair, as when
shut up; the baying at night; the bark of joy, as when starting on a
walk with his master; and the very distinct one of demand or
supplication, as when wishing for a door or window to be opened.
According to Houzeau, who paid particular attention to the subject, the
domestic fowl utters at least a dozen significant sounds. (50.
‘Facultés Mentales des Animaux,’ tom. ii. 1872, p. 346-349.)

The habitual use of articulate language is, however, peculiar to man;
but he uses, in common with the lower animals, inarticulate cries to
express his meaning, aided by gestures and the movements of the muscles
of the face. (51. See a discussion on this subject in Mr. E.B. Tylor’s
very interesting work, ‘Researches into the Early History of Mankind,’
1865, chaps. ii. to iv.) This especially holds good with the more
simple and vivid feelings, which are but little connected with our
higher intelligence. Our cries of pain, fear, surprise, anger, together
with their appropriate actions, and the murmur of a mother to her
beloved child are more expressive than any words. That which
distinguishes man from the lower animals is not the understanding of
articulate sounds, for, as every one knows, dogs understand many words
and sentences. In this respect they are at the same stage of
development as infants, between the ages of ten and twelve months, who
understand many words and short sentences, but cannot yet utter a
single word. It is not the mere articulation which is our
distinguishing character, for parrots and other birds possess this
power. Nor is it the mere capacity of connecting definite sounds with
definite ideas; for it is certain that some parrots, which have been
taught to speak, connect unerringly words with things, and persons with
events. (52. I have received several detailed accounts to this effect.
Admiral Sir B.J. Sulivan, whom I know to be a careful observer, assures
me that an African parrot, long kept in his father’s house, invariably
called certain persons of the household, as well as visitors, by their
names. He said “good morning” to every one at breakfast, and “good
night” to each as they left the room at night, and never reversed these
salutations. To Sir B.J. Sulivan’s father, he used to add to the “ good
morning” a short sentence, which was never once repeated after his
father’s death. He scolded violently a strange dog which came into the
room through the open window; and he scolded another parrot (saying
“you naughty polly”) which had got out of its cage, and was eating
apples on the kitchen table. See also, to the same effect, Houzeau on
parrots, ‘Facultés Mentales,’ tom. ii. p. 309. Dr. A. Moschkau informs
me that he knew a starling which never made a mistake in saying in
German “good morning” to persons arriving, and “good bye, old fellow,”
to those departing. I could add several other such cases.) The lower
animals differ from man solely in his almost infinitely larger power of
associating together the most diversified sounds and ideas; and this
obviously depends on the high development of his mental powers.

As Horne Tooke, one of the founders of the noble science of philology,
observes, language is an art, like brewing or baking; but writing would
have been a better simile. It certainly is not a true instinct, for
every language has to be learnt. It differs, however, widely from all
ordinary arts, for man has an instinctive tendency to speak, as we see
in the babble of our young children; whilst no child has an instinctive
tendency to brew, bake, or write. Moreover, no philologist now supposes
that any language has been deliberately invented; it has been slowly
and unconsciously developed by many steps. (53. See some good remarks
on this head by Prof. Whitney, in his ‘Oriental and Linguistic
Studies,’ 1873, p. 354. He observes that the desire of communication
between man is the living force, which, in the development of language,
“works both consciously and unconsciously; consciously as regards the
immediate end to be attained; unconsciously as regards the further
consequences of the act.”) The sounds uttered by birds offer in several
respects the nearest analogy to language, for all the members of the
same species utter the same instinctive cries expressive of their
emotions; and all the kinds which sing, exert their power
instinctively; but the actual song, and even the call-notes, are learnt
from their parents or foster-parents. These sounds, as Daines
Barrington (54. Hon. Daines Barrington in ‘Philosoph. Transactions,’
1773, p. 262. See also Dureau de la Malle, in ‘Ann. des. Sc. Nat.’ 3rd
series, Zoolog., tom. x. p. 119.) has proved, “are no more innate than
language is in man.” The first attempts to sing “may be compared to the
imperfect endeavour in a child to babble.” The young males continue
practising, or as the bird-catchers say, “recording,” for ten or eleven
months. Their first essays shew hardly a rudiment of the future song;
but as they grow older we can perceive what they are aiming at; and at
last they are said “to sing their song round.” Nestlings which have
learnt the song of a distinct species, as with the canary-birds
educated in the Tyrol, teach and transmit their new song to their
offspring. The slight natural differences of song in the same species
inhabiting different districts may be appositely compared, as
Barrington remarks, “to provincial dialects”; and the songs of allied,
though distinct species may be compared with the languages of distinct
races of man. I have given the foregoing details to shew that an
instinctive tendency to acquire an art is not peculiar to man.

With respect to the origin of articulate language, after having read on
the one side the highly interesting works of Mr. Hensleigh Wedgwood,
the Rev. F. Farrar, and Prof. Schleicher (55. ‘On the Origin of
Language,’ by H. Wedgwood, 1866. ‘Chapters on Language,’ by the Rev.
F.W. Farrar, 1865. These works are most interesting. See also ‘De la
Phys. et de Parole,’ par Albert Lemoine, 1865, p. 190. The work on this
subject, by the late Prof. Aug. Schleicher, has been translated by Dr.
Bikkers into English, under the title of ‘Darwinism tested by the
Science of Language,’ 1869.), and the celebrated lectures of Prof. Max
Muller on the other side, I cannot doubt that language owes its origin
to the imitation and modification of various natural sounds, the voices
of other animals, and man’s own instinctive cries, aided by signs and
gestures. When we treat of sexual selection we shall see that primeval
man, or rather some early progenitor of man, probably first used his
voice in producing true musical cadences, that is in singing, as do
some of the gibbon-apes at the present day; and we may conclude from a
widely-spread analogy, that this power would have been especially
exerted during the courtship of the sexes,—would have expressed various
emotions, such as love, jealousy, triumph,—and would have served as a
challenge to rivals. It is, therefore, probable that the imitation of
musical cries by articulate sounds may have given rise to words
expressive of various complex emotions. The strong tendency in our
nearest allies, the monkeys, in microcephalous idiots (56. Vogt,
‘Mémoire sur les Microcephales,’ 1867, p. 169. With respect to savages,
I have given some facts in my ‘Journal of Researches,’ etc., 1845, p.
206.), and in the barbarous races of mankind, to imitate whatever they
hear deserves notice, as bearing on the subject of imitation. Since
monkeys certainly understand much that is said to them by man, and when
wild, utter signal-cries of danger to their fellows (57. See clear
evidence on this head in the two works so often quoted, by Brehm and
Rengger.); and since fowls give distinct warnings for danger on the
ground, or in the sky from hawks (both, as well as a third cry,
intelligible to dogs) (58. Houzeau gives a very curious account of his
observations on this subject in his ‘Facultés Mentales des Animaux,’
tom. ii. p. 348.), may not some unusually wise ape-like animal have
imitated the growl of a beast of prey, and thus told his fellow-monkeys
the nature of the expected danger? This would have been a first step in
the formation of a language.

As the voice was used more and more, the vocal organs would have been
strengthened and perfected through the principle of the inherited
effects of use; and this would have reacted on the power of speech. But
the relation between the continued use of language and the development
of the brain, has no doubt been far more important. The mental powers
in some early progenitor of man must have been more highly developed
than in any existing ape, before even the most imperfect form of speech
could have come into use; but we may confidently believe that the
continued use and advancement of this power would have reacted on the
mind itself, by enabling and encouraging it to carry on long trains of
thought. A complex train of thought can no more be carried on without
the aid of words, whether spoken or silent, than a long calculation
without the use of figures or algebra. It appears, also, that even an
ordinary train of thought almost requires, or is greatly facilitated by
some form of language, for the dumb, deaf, and blind girl, Laura
Bridgman, was observed to use her fingers whilst dreaming. (59. See
remarks on this head by Dr. Maudsley, ‘The Physiology and Pathology of
Mind,’ 2nd ed., 1868, p. 199.) Nevertheless, a long succession of vivid
and connected ideas may pass through the mind without the aid of any
form of language, as we may infer from the movements of dogs during
their dreams. We have, also, seen that animals are able to reason to a
certain extent, manifestly without the aid of language. The intimate
connection between the brain, as it is now developed in us, and the
faculty of speech, is well shewn by those curious cases of
brain-disease in which speech is specially affected, as when the power
to remember substantives is lost, whilst other words can be correctly
used, or where substantives of a certain class, or all except the
initial letters of substantives and proper names are forgotten. (60.
Many curious cases have been recorded. See, for instance, Dr. Bateman
‘On Aphasia,’ 1870, pp. 27, 31, 53, 100, etc. Also, ‘Inquiries
Concerning the Intellectual Powers,’ by Dr. Abercrombie, 1838, p. 150.)
There is no more improbability in the continued use of the mental and
vocal organs leading to inherited changes in their structure and
functions, than in the case of hand-writing, which depends partly on
the form of the hand and partly on the disposition of the mind; and
handwriting is certainly inherited. (61. ‘The Variation of Animals and
Plants under Domestication,’ vol. ii. p. 6.’)

Several writers, more especially Prof. Max Muller (62. Lectures on ‘Mr.
Darwin’s Philosophy of Language,’ 1873.), have lately insisted that the
use of language implies the power of forming general concepts; and that
as no animals are supposed to possess this power, an impassable barrier
is formed between them and man. (63. The judgment of a distinguished
philologist, such as Prof. Whitney, will have far more weight on this
point than anything that I can say. He remarks (‘Oriental and
Linguistic Studies,’ 1873, p. 297), in speaking of Bleek’s views:
“Because on the grand scale language is the necessary auxiliary of
thought, indispensable to the development of the power of thinking, to
the distinctness and variety and complexity of cognitions to the full
mastery of consciousness; therefore he would fain make thought
absolutely impossible without speech, identifying the faculty with its
instrument. He might just as reasonably assert that the human hand
cannot act without a tool. With such a doctrine to start from, he
cannot stop short of Max Muller’s worst paradoxes, that an infant (in
fans, not speaking) is not a human being, and that deaf-mutes do not
become possessed of reason until they learn to twist their fingers into
imitation of spoken words.” Max Muller gives in italics (‘Lectures on
Mr. Darwin’s Philosophy of Language,’ 1873, third lecture) this
aphorism: “There is no thought without words, as little as there are
words without thought.” What a strange definition must here be given to
the word thought!) With respect to animals, I have already endeavoured
to shew that they have this power, at least in a rude and incipient
degree. As far as concerns infants of from ten to eleven months old,
and deaf-mutes, it seems to me incredible, that they should be able to
connect certain sounds with certain general ideas as quickly as they
do, unless such ideas were already formed in their minds. The same
remark may be extended to the more intelligent animals; as Mr. Leslie
Stephen observes (64. ‘Essays on Free Thinking,’ etc., 1873, p. 82.),
“A dog frames a general concept of cats or sheep, and knows the
corresponding words as well as a philosopher. And the capacity to
understand is as good a proof of vocal intelligence, though in an
inferior degree, as the capacity to speak.”

Why the organs now used for speech should have been originally
perfected for this purpose, rather than any other organs, it is not
difficult to see. Ants have considerable powers of intercommunication
by means of their antennae, as shewn by Huber, who devotes a whole
chapter to their language. We might have used our fingers as efficient
instruments, for a person with practice can report to a deaf man every
word of a speech rapidly delivered at a public meeting; but the loss of
our hands, whilst thus employed, would have been a serious
inconvenience. As all the higher mammals possess vocal organs,
constructed on the same general plan as ours, and used as a means of
communication, it was obviously probable that these same organs would
be still further developed if the power of communication had to be
improved; and this has been effected by the aid of adjoining and well
adapted parts, namely the tongue and lips. (65. See some good remarks
to this effect by Dr. Maudsley, ‘The Physiology and Pathology of Mind,’
1868, p. 199.) The fact of the higher apes not using their vocal organs
for speech, no doubt depends on their intelligence not having been
sufficiently advanced. The possession by them of organs, which with
long-continued practice might have been used for speech, although not
thus used, is paralleled by the case of many birds which possess organs
fitted for singing, though they never sing. Thus, the nightingale and
crow have vocal organs similarly constructed, these being used by the
former for diversified song, and by the latter only for croaking. (66.
Macgillivray, ‘Hist. of British Birds,’ vol. ii. 1839, p. 29. An
excellent observer, Mr. Blackwall, remarks that the magpie learns to
pronounce single words, and even short sentences, more readily than
almost any other British bird; yet, as he adds, after long and closely
investigating its habits, he has never known it, in a state of nature,
display any unusual capacity for imitation. ‘Researches in Zoology,’
1834, p. 158.) If it be asked why apes have not had their intellects
developed to the same degree as that of man, general causes only can be
assigned in answer, and it is unreasonable to expect any thing more
definite, considering our ignorance with respect to the successive
stages of development through which each creature has passed.

The formation of different languages and of distinct species, and the
proofs that both have been developed through a gradual process, are
curiously parallel. (67. See the very interesting parallelism between
the development of species and languages, given by Sir C. Lyell in ‘The
Geological Evidences of the Antiquity of Man,’ 1863, chap. xxiii.) But
we can trace the formation of many words further back than that of
species, for we can perceive how they actually arose from the imitation
of various sounds. We find in distinct languages striking homologies
due to community of descent, and analogies due to a similar process of
formation. The manner in which certain letters or sounds change when
others change is very like correlated growth. We have in both cases the
reduplication of parts, the effects of long-continued use, and so
forth. The frequent presence of rudiments, both in languages and in
species, is still more remarkable. The letter m in the word am, means
I; so that in the expression I am, a superfluous and useless rudiment
has been retained. In the spelling also of words, letters often remain
as the rudiments of ancient forms of pronunciation. Languages, like
organic beings, can be classed in groups under groups; and they can be
classed either naturally according to descent, or artificially by other
characters. Dominant languages and dialects spread widely, and lead to
the gradual extinction of other tongues. A language, like a species,
when once extinct, never, as Sir C. Lyell remarks, reappears. The same
language never has two birth-places. Distinct languages may be crossed
or blended together. (68. See remarks to this effect by the Rev. F.W.
Farrar, in an interesting article, entitled ‘Philology and Darwinism,’
in ‘Nature,’ March 24th, 1870, p. 528.) We see variability in every
tongue, and new words are continually cropping up; but as there is a
limit to the powers of the memory, single words, like whole languages,
gradually become extinct. As Max Muller (69. ‘Nature,’ January 6th,
1870, p. 257.) has well remarked:—“A struggle for life is constantly
going on amongst the words and grammatical forms in each language. The
better, the shorter, the easier forms are constantly gaining the upper
hand, and they owe their success to their own inherent virtue.” To
these more important causes of the survival of certain words, mere
novelty and fashion may be added; for there is in the mind of man a
strong love for slight changes in all things. The survival or
preservation of certain favoured words in the struggle for existence is
natural selection.

The perfectly regular and wonderfully complex construction of the
languages of many barbarous nations has often been advanced as a proof,
either of the divine origin of these languages, or of the high art and
former civilisation of their founders. Thus F. von Schlegel writes: “In
those languages which appear to be at the lowest grade of intellectual
culture, we frequently observe a very high and elaborate degree of art
in their grammatical structure. This is especially the case with the
Basque and the Lapponian, and many of the American languages.” (70.
Quoted by C.S. Wake, ‘Chapters on Man,’ 1868, p. 101.) But it is
assuredly an error to speak of any language as an art, in the sense of
its having been elaborately and methodically formed. Philologists now
admit that conjugations, declensions, etc., originally existed as
distinct words, since joined together; and as such words express the
most obvious relations between objects and persons, it is not
surprising that they should have been used by the men of most races
during the earliest ages. With respect to perfection, the following
illustration will best shew how easily we may err: a Crinoid sometimes
consists of no less than 150,000 pieces of shell (71. Buckland,
‘Bridgewater Treatise,’ p. 411.), all arranged with perfect symmetry in
radiating lines; but a naturalist does not consider an animal of this
kind as more perfect than a bilateral one with comparatively few parts,
and with none of these parts alike, excepting on the opposite sides of
the body. He justly considers the differentiation and specialisation of
organs as the test of perfection. So with languages: the most
symmetrical and complex ought not to be ranked above irregular,
abbreviated, and bastardised languages, which have borrowed expressive
words and useful forms of construction from various conquering,
conquered, or immigrant races.

From these few and imperfect remarks I conclude that the extremely
complex and regular construction of many barbarous languages, is no
proof that they owe their origin to a special act of creation. (72. See
some good remarks on the simplification of languages, by Sir J.
Lubbock, ‘Origin of Civilisation,’ 1870, p. 278.) Nor, as we have seen,
does the faculty of articulate speech in itself offer any insuperable
objection to the belief that man has been developed from some lower
form.

SENSE OF BEAUTY.

This sense has been declared to be peculiar to man. I refer here only
to the pleasure given by certain colours, forms, and sounds, and which
may fairly be called a sense of the beautiful; with cultivated men such
sensations are, however, intimately associated with complex ideas and
trains of thought. When we behold a male bird elaborately displaying
his graceful plumes or splendid colours before the female, whilst other
birds, not thus decorated, make no such display, it is impossible to
doubt that she admires the beauty of her male partner. As women
everywhere deck themselves with these plumes, the beauty of such
ornaments cannot be disputed. As we shall see later, the nests of
humming-birds, and the playing passages of bower-birds are tastefully
ornamented with gaily-coloured objects; and this shews that they must
receive some kind of pleasure from the sight of such things. With the
great majority of animals, however, the taste for the beautiful is
confined, as far as we can judge, to the attractions of the opposite
sex. The sweet strains poured forth by many male birds during the
season of love, are certainly admired by the females, of which fact
evidence will hereafter be given. If female birds had been incapable of
appreciating the beautiful colours, the ornaments, and voices of their
male partners, all the labour and anxiety exhibited by the latter in
displaying their charms before the females would have been thrown away;
and this it is impossible to admit. Why certain bright colours should
excite pleasure cannot, I presume, be explained, any more than why
certain flavours and scents are agreeable; but habit has something to
do with the result, for that which is at first unpleasant to our
senses, ultimately becomes pleasant, and habits are inherited. With
respect to sounds, Helmholtz has explained to a certain extent on
physiological principles, why harmonies and certain cadences are
agreeable. But besides this, sounds frequently recurring at irregular
intervals are highly disagreeable, as every one will admit who has
listened at night to the irregular flapping of a rope on board ship.
The same principle seems to come into play with vision, as the eye
prefers symmetry or figures with some regular recurrence. Patterns of
this kind are employed by even the lowest savages as ornaments; and
they have been developed through sexual selection for the adornment of
some male animals. Whether we can or not give any reason for the
pleasure thus derived from vision and hearing, yet man and many of the
lower animals are alike pleased by the same colours, graceful shading
and forms, and the same sounds.

The taste for the beautiful, at least as far as female beauty is
concerned, is not of a special nature in the human mind; for it differs
widely in the different races of man, and is not quite the same even in
the different nations of the same race. Judging from the hideous
ornaments, and the equally hideous music admired by most savages, it
might be urged that their aesthetic faculty was not so highly developed
as in certain animals, for instance, as in birds. Obviously no animal
would be capable of admiring such scenes as the heavens at night, a
beautiful landscape, or refined music; but such high tastes are
acquired through culture, and depend on complex associations; they are
not enjoyed by barbarians or by uneducated persons.

Many of the faculties, which have been of inestimable service to man
for his progressive advancement, such as the powers of the imagination,
wonder, curiosity, an undefined sense of beauty, a tendency to
imitation, and the love of excitement or novelty, could hardly fail to
lead to capricious changes of customs and fashions. I have alluded to
this point, because a recent writer (73. ‘The Spectator,’ Dec. 4th,
1869, p. 1430.) has oddly fixed on Caprice “as one of the most
remarkable and typical differences between savages and brutes.” But not
only can we partially understand how it is that man is from various
conflicting influences rendered capricious, but that the lower animals
are, as we shall hereafter see, likewise capricious in their
affections, aversions, and sense of beauty. There is also reason to
suspect that they love novelty, for its own sake.

BELIEF IN GOD—RELIGION.

There is no evidence that man was aboriginally endowed with the
ennobling belief in the existence of an Omnipotent God. On the contrary
there is ample evidence, derived not from hasty travellers, but from
men who have long resided with savages, that numerous races have
existed, and still exist, who have no idea of one or more gods, and who
have no words in their languages to express such an idea. (74. See an
excellent article on this subject by the Rev. F.W. Farrar, in the
‘Anthropological Review,’ Aug. 1864, p. ccxvii. For further facts see
Sir J. Lubbock, ‘Prehistoric Times,’ 2nd edit., 1869, p. 564; and
especially the chapters on Religion in his ‘Origin of Civilisation,’
1870.) The question is of course wholly distinct from that higher one,
whether there exists a Creator and Ruler of the universe; and this has
been answered in the affirmative by some of the highest intellects that
have ever existed.

If, however, we include under the term “religion” the belief in unseen
or spiritual agencies, the case is wholly different; for this belief
seems to be universal with the less civilised races. Nor is it
difficult to comprehend how it arose. As soon as the important
faculties of the imagination, wonder, and curiosity, together with some
power of reasoning, had become partially developed, man would naturally
crave to understand what was passing around him, and would have vaguely
speculated on his own existence. As Mr. M’Lennan (75. ‘The Worship of
Animals and Plants,’ in the ‘Fortnightly Review,’ Oct. 1, 1869, p.
422.) has remarked, “Some explanation of the phenomena of life, a man
must feign for himself, and to judge from the universality of it, the
simplest hypothesis, and the first to occur to men, seems to have been
that natural phenomena are ascribable to the presence in animals,
plants, and things, and in the forces of nature, of such spirits
prompting to action as men are conscious they themselves possess.” It
is also probable, as Mr. Tylor has shewn, that dreams may have first
given rise to the notion of spirits; for savages do not readily
distinguish between subjective and objective impressions. When a savage
dreams, the figures which appear before him are believed to have come
from a distance, and to stand over him; or “the soul of the dreamer
goes out on its travels, and comes home with a remembrance of what it
has seen.” (76. Tylor, ‘Early History of Mankind,’ 1865, p. 6. See also
the three striking chapters on the ‘Development of Religion,’ in
Lubbock’s ‘Origin of Civilisation,’ 1870. In a like manner Mr. Herbert
Spencer, in his ingenious essay in the ‘Fortnightly Review’ (May 1st,
1870, p. 535), accounts for the earliest forms of religious belief
throughout the world, by man being led through dreams, shadows, and
other causes, to look at himself as a double essence, corporeal and
spiritual. As the spiritual being is supposed to exist after death and
to be powerful, it is propitiated by various gifts and ceremonies, and
its aid invoked. He then further shews that names or nicknames given
from some animal or other object, to the early progenitors or founders
of a tribe, are supposed after a long interval to represent the real
progenitor of the tribe; and such animal or object is then naturally
believed still to exist as a spirit, is held sacred, and worshipped as
a god. Nevertheless I cannot but suspect that there is a still earlier
and ruder stage, when anything which manifests power or movement is
thought to be endowed with some form of life, and with mental faculties
analogous to our own.) But until the faculties of imagination,
curiosity, reason, etc., had been fairly well developed in the mind of
man, his dreams would not have led him to believe in spirits, any more
than in the case of a dog.

The tendency in savages to imagine that natural objects and agencies
are animated by spiritual or living essences, is perhaps illustrated by
a little fact which I once noticed: my dog, a full-grown and very
sensible animal, was lying on the lawn during a hot and still day; but
at a little distance a slight breeze occasionally moved an open
parasol, which would have been wholly disregarded by the dog, had any
one stood near it. As it was, every time that the parasol slightly
moved, the dog growled fiercely and barked. He must, I think, have
reasoned to himself in a rapid and unconscious manner, that movement
without any apparent cause indicated the presence of some strange
living agent, and that no stranger had a right to be on his territory.

The belief in spiritual agencies would easily pass into the belief in
the existence of one or more gods. For savages would naturally
attribute to spirits the same passions, the same love of vengeance or
simplest form of justice, and the same affections which they themselves
feel. The Fuegians appear to be in this respect in an intermediate
condition, for when the surgeon on board the “Beagle” shot some young
ducklings as specimens, York Minster declared in the most solemn
manner, “Oh, Mr. Bynoe, much rain, much snow, blow much”; and this was
evidently a retributive punishment for wasting human food. So again he
related how, when his brother killed a “wild man,” storms long raged,
much rain and snow fell. Yet we could never discover that the Fuegians
believed in what we should call a God, or practised any religious
rites; and Jemmy Button, with justifiable pride, stoutly maintained
that there was no devil in his land. This latter assertion is the more
remarkable, as with savages the belief in bad spirits is far more
common than that in good ones.

The feeling of religious devotion is a highly complex one, consisting
of love, complete submission to an exalted and mysterious superior, a
strong sense of dependence (77. See an able article on the ‘Physical
Elements of Religion,’ by Mr. L. Owen Pike, in ‘Anthropological
Review,’ April 1870, p. lxiii.), fear, reverence, gratitude, hope for
the future, and perhaps other elements. No being could experience so
complex an emotion until advanced in his intellectual and moral
faculties to at least a moderately high level. Nevertheless, we see
some distant approach to this state of mind in the deep love of a dog
for his master, associated with complete submission, some fear, and
perhaps other feelings. The behaviour of a dog when returning to his
master after an absence, and, as I may add, of a monkey to his beloved
keeper, is widely different from that towards their fellows. In the
latter case the transports of joy appear to be somewhat less, and the
sense of equality is shewn in every action. Professor Braubach goes so
far as to maintain that a dog looks on his master as on a god. (78.
‘Religion, Moral, etc., der Darwin’schen Art-Lehre,’ 1869, s. 53. It is
said (Dr. W. Lauder Lindsay, ‘Journal of Mental Science,’ 1871, p. 43),
that Bacon long ago, and the poet Burns, held the same notion.)

The same high mental faculties which first led man to believe in unseen
spiritual agencies, then in fetishism, polytheism, and ultimately in
monotheism, would infallibly lead him, as long as his reasoning powers
remained poorly developed, to various strange superstitions and
customs. Many of these are terrible to think of—such as the sacrifice
of human beings to a blood-loving god; the trial of innocent persons by
the ordeal of poison or fire; witchcraft, etc.—yet it is well
occasionally to reflect on these superstitions, for they shew us what
an infinite debt of gratitude we owe to the improvement of our reason,
to science, and to our accumulated knowledge. As Sir J. Lubbock (79.
‘Prehistoric Times,’ 2nd edit., p. 571. In this work (p. 571) there
will be found an excellent account of the many strange and capricious
customs of savages.) has well observed, “it is not too much to say that
the horrible dread of unknown evil hangs like a thick cloud over savage
life, and embitters every pleasure.” These miserable and indirect
consequences of our highest faculties may be compared with the
incidental and occasional mistakes of the instincts of the lower
animals.




CHAPTER IV.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS—continued.


The moral sense—Fundamental proposition—The qualities of social
animals—Origin of sociability—Struggle between opposed instincts—Man a
social animal—The more enduring social instincts conquer other less
persistent instincts—The social virtues alone regarded by savages—The
self-regarding virtues acquired at a later stage of development—The
importance of the judgment of the members of the same community on
conduct—Transmission of moral tendencies—Summary.

I fully subscribe to the judgment of those writers (1. See, for
instance, on this subject, Quatrefages, ‘Unité de l’Espèce Humaine,’
1861, p. 21, etc.) who maintain that of all the differences between man
and the lower animals, the moral sense or conscience is by far the most
important. This sense, as Mackintosh (2. ‘Dissertation on Ethical
Philosophy,’ 1837, p. 231, etc.) remarks, “has a rightful supremacy
over every other principle of human action”; it is summed up in that
short but imperious word “ought,” so full of high significance. It is
the most noble of all the attributes of man, leading him without a
moment’s hesitation to risk his life for that of a fellow-creature; or
after due deliberation, impelled simply by the deep feeling of right or
duty, to sacrifice it in some great cause. Immanuel Kant exclaims,
“Duty! Wondrous thought, that workest neither by fond insinuation,
flattery, nor by any threat, but merely by holding up thy naked law in
the soul, and so extorting for thyself always reverence, if not always
obedience; before whom all appetites are dumb, however secretly they
rebel; whence thy original?” (3. ‘Metaphysics of Ethics,’ translated by
J.W. Semple, Edinburgh, 1836, p. 136.)

This great question has been discussed by many writers (4. Mr. Bain
gives a list (‘Mental and Moral Science,’ 1868, pp. 543-725) of
twenty-six British authors who have written on this subject, and whose
names are familiar to every reader; to these, Mr. Bain’s own name, and
those of Mr. Lecky, Mr. Shadworth Hodgson, Sir J. Lubbock, and others,
might be added.) of consummate ability; and my sole excuse for touching
on it, is the impossibility of here passing it over; and because, as
far as I know, no one has approached it exclusively from the side of
natural history. The investigation possesses, also, some independent
interest, as an attempt to see how far the study of the lower animals
throws light on one of the highest psychical faculties of man.

The following proposition seems to me in a high degree probable—namely,
that any animal whatever, endowed with well-marked social instincts (5.
Sir B. Brodie, after observing that man is a social animal
(‘Psychological Enquiries,’ 1854, p. 192), asks the pregnant question,
“ought not this to settle the disputed question as to the existence of
a moral sense?” Similar ideas have probably occurred to many persons,
as they did long ago to Marcus Aurelius. Mr. J.S. Mill speaks, in his
celebrated work, ‘Utilitarianism,’ (1864, pp. 45, 46), of the social
feelings as a “powerful natural sentiment,” and as “the natural basis
of sentiment for utilitarian morality.” Again he says, “Like the other
acquired capacities above referred to, the moral faculty, if not a part
of our nature, is a natural out-growth from it; capable, like them, in
a certain small degree of springing up spontaneously.” But in
opposition to all this, he also remarks, “if, as in my own belief, the
moral feelings are not innate, but acquired, they are not for that
reason less natural.” It is with hesitation that I venture to differ at
all from so profound a thinker, but it can hardly be disputed that the
social feelings are instinctive or innate in the lower animals; and why
should they not be so in man? Mr. Bain (see, for instance, ‘The
Emotions and the Will,’ 1865, p. 481) and others believe that the moral
sense is acquired by each individual during his lifetime. On the
general theory of evolution this is at least extremely improbable. The
ignoring of all transmitted mental qualities will, as it seems to me,
be hereafter judged as a most serious blemish in the works of Mr.
Mill.), the parental and filial affections being here included, would
inevitably acquire a moral sense or conscience, as soon as its
intellectual powers had become as well, or nearly as well developed, as
in man. For, FIRSTLY, the social instincts lead an animal to take
pleasure in the society of its fellows, to feel a certain amount of
sympathy with them, and to perform various services for them. The
services may be of a definite and evidently instinctive nature; or
there may be only a wish and readiness, as with most of the higher
social animals, to aid their fellows in certain general ways. But these
feelings and services are by no means extended to all the individuals
of the same species, only to those of the same association. SECONDLY,
as soon as the mental faculties had become highly developed, images of
all past actions and motives would be incessantly passing through the
brain of each individual: and that feeling of dissatisfaction, or even
misery, which invariably results, as we shall hereafter see, from any
unsatisfied instinct, would arise, as often as it was perceived that
the enduring and always present social instinct had yielded to some
other instinct, at the time stronger, but neither enduring in its
nature, nor leaving behind it a very vivid impression. It is clear that
many instinctive desires, such as that of hunger, are in their nature
of short duration; and after being satisfied, are not readily or
vividly recalled. THIRDLY, after the power of language had been
acquired, and the wishes of the community could be expressed, the
common opinion how each member ought to act for the public good, would
naturally become in a paramount degree the guide to action. But it
should be borne in mind that however great weight we may attribute to
public opinion, our regard for the approbation and disapprobation of
our fellows depends on sympathy, which, as we shall see, forms an
essential part of the social instinct, and is indeed its
foundation-stone. LASTLY, habit in the individual would ultimately play
a very important part in guiding the conduct of each member; for the
social instinct, together with sympathy, is, like any other instinct,
greatly strengthened by habit, and so consequently would be obedience
to the wishes and judgment of the community. These several subordinate
propositions must now be discussed, and some of them at considerable
length.

It may be well first to premise that I do not wish to maintain that any
strictly social animal, if its intellectual faculties were to become as
active and as highly developed as in man, would acquire exactly the
same moral sense as ours. In the same manner as various animals have
some sense of beauty, though they admire widely-different objects, so
they might have a sense of right and wrong, though led by it to follow
widely different lines of conduct. If, for instance, to take an extreme
case, men were reared under precisely the same conditions as hive-bees,
there can hardly be a doubt that our unmarried females would, like the
worker-bees, think it a sacred duty to kill their brothers, and mothers
would strive to kill their fertile daughters; and no one would think of
interfering. (6. Mr. H. Sidgwick remarks, in an able discussion on this
subject (the ‘Academy,’ June 15, 1872, p. 231), “a superior bee, we may
feel sure, would aspire to a milder solution of the population
question.” Judging, however, from the habits of many or most savages,
man solves the problem by female infanticide, polyandry and promiscuous
intercourse; therefore it may well be doubted whether it would be by a
milder method. Miss Cobbe, in commenting (‘Darwinism in Morals,’
‘Theological Review,’ April 1872, pp. 188-191) on the same
illustration, says, the PRINCIPLES of social duty would be thus
reversed; and by this, I presume, she means that the fulfilment of a
social duty would tend to the injury of individuals; but she overlooks
the fact, which she would doubtless admit, that the instincts of the
bee have been acquired for the good of the community. She goes so far
as to say that if the theory of ethics advocated in this chapter were
ever generally accepted, “I cannot but believe that in the hour of
their triumph would be sounded the knell of the virtue of mankind!” It
is to be hoped that the belief in the permanence of virtue on this
earth is not held by many persons on so weak a tenure.) Nevertheless,
the bee, or any other social animal, would gain in our supposed case,
as it appears to me, some feeling of right or wrong, or a conscience.
For each individual would have an inward sense of possessing certain
stronger or more enduring instincts, and others less strong or
enduring; so that there would often be a struggle as to which impulse
should be followed; and satisfaction, dissatisfaction, or even misery
would be felt, as past impressions were compared during their incessant
passage through the mind. In this case an inward monitor would tell the
animal that it would have been better to have followed the one impulse
rather than the other. The one course ought to have been followed, and
the other ought not; the one would have been right and the other wrong;
but to these terms I shall recur.

SOCIABILITY.

Animals of many kinds are social; we find even distinct species living
together; for example, some American monkeys; and united flocks of
rooks, jackdaws, and starlings. Man shews the same feeling in his
strong love for the dog, which the dog returns with interest. Every one
must have noticed how miserable horses, dogs, sheep, etc., are when
separated from their companions, and what strong mutual affection the
two former kinds, at least, shew on their reunion. It is curious to
speculate on the feelings of a dog, who will rest peacefully for hours
in a room with his master or any of the family, without the least
notice being taken of him; but if left for a short time by himself,
barks or howls dismally. We will confine our attention to the higher
social animals; and pass over insects, although some of these are
social, and aid one another in many important ways. The most common
mutual service in the higher animals is to warn one another of danger
by means of the united senses of all. Every sportsman knows, as Dr.
Jaeger remarks (7. ‘Die Darwin’sche Theorie,’ s. 101.), how difficult
it is to approach animals in a herd or troop. Wild horses and cattle do
not, I believe, make any danger-signal; but the attitude of any one of
them who first discovers an enemy, warns the others. Rabbits stamp
loudly on the ground with their hind-feet as a signal: sheep and
chamois do the same with their forefeet, uttering likewise a whistle.
Many birds, and some mammals, post sentinels, which in the case of
seals are said (8. Mr. R. Brown in ‘Proc. Zoolog. Soc.’ 1868, p. 409.)
generally to be the females. The leader of a troop of monkeys acts as
the sentinel, and utters cries expressive both of danger and of safety.
(9. Brehm, ‘Thierleben,’ B. i. 1864, s. 52, 79. For the case of the
monkeys extracting thorns from each other, see s. 54. With respect to
the Hamadryas turning over stones, the fact is given (s. 76), on the
evidence of Alvarez, whose observations Brehm thinks quite trustworthy.
For the cases of the old male baboons attacking the dogs, see s. 79;
and with respect to the eagle, s. 56.) Social animals perform many
little services for each other: horses nibble, and cows lick each
other, on any spot which itches: monkeys search each other for external
parasites; and Brehm states that after a troop of the Cercopithecus
griseo-viridis has rushed through a thorny brake, each monkey stretches
itself on a branch, and another monkey sitting by, “conscientiously”
examines its fur, and extracts every thorn or burr.

Animals also render more important services to one another: thus wolves
and some other beasts of prey hunt in packs, and aid one another in
attacking their victims. Pelicans fish in concert. The Hamadryas
baboons turn over stones to find insects, etc.; and when they come to a
large one, as many as can stand round, turn it over together and share
the booty. Social animals mutually defend each other. Bull bisons in N.
America, when there is danger, drive the cows and calves into the
middle of the herd, whilst they defend the outside. I shall also in a
future chapter give an account of two young wild bulls at Chillingham
attacking an old one in concert, and of two stallions together trying
to drive away a third stallion from a troop of mares. In Abyssinia,
Brehm encountered a great troop of baboons who were crossing a valley:
some had already ascended the opposite mountain, and some were still in
the valley; the latter were attacked by the dogs, but the old males
immediately hurried down from the rocks, and with mouths widely opened,
roared so fearfully, that the dogs quickly drew back. They were again
encouraged to the attack; but by this time all the baboons had
reascended the heights, excepting a young one, about six months old,
who, loudly calling for aid, climbed on a block of rock, and was
surrounded. Now one of the largest males, a true hero, came down again
from the mountain, slowly went to the young one, coaxed him, and
triumphantly led him away—the dogs being too much astonished to make an
attack. I cannot resist giving another scene which was witnessed by
this same naturalist; an eagle seized a young Cercopithecus, which, by
clinging to a branch, was not at once carried off; it cried loudly for
assistance, upon which the other members of the troop, with much
uproar, rushed to the rescue, surrounded the eagle, and pulled out so
many feathers, that he no longer thought of his prey, but only how to
escape. This eagle, as Brehm remarks, assuredly would never again
attack a single monkey of a troop. (10. Mr. Belt gives the case of a
spider-monkey (Ateles) in Nicaragua, which was heard screaming for
nearly two hours in the forest, and was found with an eagle perched
close by it. The bird apparently feared to attack as long as it
remained face to face; and Mr. Belt believes, from what he has seen of
the habits of these monkeys, that they protect themselves from eagles
by keeping two or three together. ‘The Naturalist in Nicaragua,’ 1874,
p. 118.)

It is certain that associated animals have a feeling of love for each
other, which is not felt by non-social adult animals. How far in most
cases they actually sympathise in the pains and pleasures of others, is
more doubtful, especially with respect to pleasures. Mr. Buxton,
however, who had excellent means of observation (11. ‘Annals and
Magazine of Natural History,’ November 1868, p. 382.), states that his
macaws, which lived free in Norfolk, took “an extravagant interest” in
a pair with a nest; and whenever the female left it, she was surrounded
by a troop “screaming horrible acclamations in her honour.” It is often
difficult to judge whether animals have any feeling for the sufferings
of others of their kind. Who can say what cows feel, when they surround
and stare intently on a dying or dead companion; apparently, however,
as Houzeau remarks, they feel no pity. That animals sometimes are far
from feeling any sympathy is too certain; for they will expel a wounded
animal from the herd, or gore or worry it to death. This is almost the
blackest fact in natural history, unless, indeed, the explanation which
has been suggested is true, that their instinct or reason leads them to
expel an injured companion, lest beasts of prey, including man, should
be tempted to follow the troop. In this case their conduct is not much
worse than that of the North American Indians, who leave their feeble
comrades to perish on the plains; or the Fijians, who, when their
parents get old, or fall ill, bury them alive. (12. Sir J. Lubbock,
‘Prehistoric Times,’ 2nd ed., p. 446.)

Many animals, however, certainly sympathise with each other’s distress
or danger. This is the case even with birds. Captain Stansbury (13. As
quoted by Mr. L.H. Morgan, ‘The American Beaver,’ 1868, p. 272. Capt.
Stansbury also gives an interesting account of the manner in which a
very young pelican, carried away by a strong stream, was guided and
encouraged in its attempts to reach the shore by half a dozen old
birds.) found on a salt lake in Utah an old and completely blind
pelican, which was very fat, and must have been well fed for a long
time by his companions. Mr. Blyth, as he informs me, saw Indian crows
feeding two or three of their companions which were blind; and I have
heard of an analogous case with the domestic cock. We may, if we
choose, call these actions instinctive; but such cases are much too
rare for the development of any special instinct. (14. As Mr. Bain
states, “effective aid to a sufferer springs from sympathy proper:”
‘Mental and Moral Science,’ 1868, p. 245.) I have myself seen a dog,
who never passed a cat who lay sick in a basket, and was a great friend
of his, without giving her a few licks with his tongue, the surest sign
of kind feeling in a dog.

It must be called sympathy that leads a courageous dog to fly at any
one who strikes his master, as he certainly will. I saw a person
pretending to beat a lady, who had a very timid little dog on her lap,
and the trial had never been made before; the little creature instantly
jumped away, but after the pretended beating was over, it was really
pathetic to see how perseveringly he tried to lick his mistress’s face,
and comfort her. Brehm (15. ‘Thierleben,’ B. i. s. 85.) states that
when a baboon in confinement was pursued to be punished, the others
tried to protect him. It must have been sympathy in the cases above
given which led the baboons and Cercopitheci to defend their young
comrades from the dogs and the eagle. I will give only one other
instance of sympathetic and heroic conduct, in the case of a little
American monkey. Several years ago a keeper at the Zoological Gardens
shewed me some deep and scarcely healed wounds on the nape of his own
neck, inflicted on him, whilst kneeling on the floor, by a fierce
baboon. The little American monkey, who was a warm friend of this
keeper, lived in the same large compartment, and was dreadfully afraid
of the great baboon. Nevertheless, as soon as he saw his friend in
peril, he rushed to the rescue, and by screams and bites so distracted
the baboon that the man was able to escape, after, as the surgeon
thought, running great risk of his life.

Besides love and sympathy, animals exhibit other qualities connected
with the social instincts, which in us would be called moral; and I
agree with Agassiz (16. ‘De l’Espèce et de la Classe,’ 1869, p. 97.)
that dogs possess something very like a conscience.

Dogs possess some power of self-command, and this does not appear to be
wholly the result of fear. As Braubach (17. ‘Die Darwin’sche
Art-Lehre,’ 1869, s. 54.) remarks, they will refrain from stealing food
in the absence of their master. They have long been accepted as the
very type of fidelity and obedience. But the elephant is likewise very
faithful to his driver or keeper, and probably considers him as the
leader of the herd. Dr. Hooker informs me that an elephant, which he
was riding in India, became so deeply bogged that he remained stuck
fast until the next day, when he was extricated by men with ropes.
Under such circumstances elephants will seize with their trunks any
object, dead or alive, to place under their knees, to prevent their
sinking deeper in the mud; and the driver was dreadfully afraid lest
the animal should have seized Dr. Hooker and crushed him to death. But
the driver himself, as Dr. Hooker was assured, ran no risk. This
forbearance under an emergency so dreadful for a heavy animal, is a
wonderful proof of noble fidelity. (18. See also Hooker’s ‘Himalayan
Journals,’ vol. ii. 1854, p. 333.)

All animals living in a body, which defend themselves or attack their
enemies in concert, must indeed be in some degree faithful to one
another; and those that follow a leader must be in some degree
obedient. When the baboons in Abyssinia (19. Brehm, ‘Thierleben,’ B. i.
s. 76.) plunder a garden, they silently follow their leader; and if an
imprudent young animal makes a noise, he receives a slap from the
others to teach him silence and obedience. Mr. Galton, who has had
excellent opportunities for observing the half-wild cattle in S.
Africa, says (20. See his extremely interesting paper on
‘Gregariousness in Cattle, and in Man,’ ‘Macmillan’s Magazine,’ Feb.
1871, p. 353.), that they cannot endure even a momentary separation
from the herd. They are essentially slavish, and accept the common
determination, seeking no better lot than to be led by any one ox who
has enough self-reliance to accept the position. The men who break in
these animals for harness, watch assiduously for those who, by grazing
apart, shew a self-reliant disposition, and these they train as
fore-oxen. Mr. Galton adds that such animals are rare and valuable; and
if many were born they would soon be eliminated, as lions are always on
the look-out for the individuals which wander from the herd.

With respect to the impulse which leads certain animals to associate
together, and to aid one another in many ways, we may infer that in
most cases they are impelled by the same sense of satisfaction or
pleasure which they experience in performing other instinctive actions;
or by the same sense of dissatisfaction as when other instinctive
actions are checked. We see this in innumerable instances, and it is
illustrated in a striking manner by the acquired instincts of our
domesticated animals; thus a young shepherd-dog delights in driving and
running round a flock of sheep, but not in worrying them; a young
fox-hound delights in hunting a fox, whilst some other kinds of dogs,
as I have witnessed, utterly disregard foxes. What a strong feeling of
inward satisfaction must impel a bird, so full of activity, to brood
day after day over her eggs. Migratory birds are quite miserable if
stopped from migrating; perhaps they enjoy starting on their long
flight; but it is hard to believe that the poor pinioned goose,
described by Audubon, which started on foot at the proper time for its
journey of probably more than a thousand miles, could have felt any joy
in doing so. Some instincts are determined solely by painful feelings,
as by fear, which leads to self-preservation, and is in some cases
directed towards special enemies. No one, I presume, can analyse the
sensations of pleasure or pain. In many instances, however, it is
probable that instincts are persistently followed from the mere force
of inheritance, without the stimulus of either pleasure or pain. A
young pointer, when it first scents game, apparently cannot help
pointing. A squirrel in a cage who pats the nuts which it cannot eat,
as if to bury them in the ground, can hardly be thought to act thus,
either from pleasure or pain. Hence the common assumption that men must
be impelled to every action by experiencing some pleasure or pain may
be erroneous. Although a habit may be blindly and implicitly followed,
independently of any pleasure or pain felt at the moment, yet if it be
forcibly and abruptly checked, a vague sense of dissatisfaction is
generally experienced.

It has often been assumed that animals were in the first place rendered
social, and that they feel as a consequence uncomfortable when
separated from each other, and comfortable whilst together; but it is a
more probable view that these sensations were first developed, in order
that those animals which would profit by living in society, should be
induced to live together, in the same manner as the sense of hunger and
the pleasure of eating were, no doubt, first acquired in order to
induce animals to eat. The feeling of pleasure from society is probably
an extension of the parental or filial affections, since the social
instinct seems to be developed by the young remaining for a long time
with their parents; and this extension may be attributed in part to
habit, but chiefly to natural selection. With those animals which were
benefited by living in close association, the individuals which took
the greatest pleasure in society would best escape various dangers,
whilst those that cared least for their comrades, and lived solitary,
would perish in greater numbers. With respect to the origin of the
parental and filial affections, which apparently lie at the base of the
social instincts, we know not the steps by which they have been gained;
but we may infer that it has been to a large extent through natural
selection. So it has almost certainly been with the unusual and
opposite feeling of hatred between the nearest relations, as with the
worker-bees which kill their brother drones, and with the queen-bees
which kill their daughter-queens; the desire to destroy their nearest
relations having been in this case of service to the community.
Parental affection, or some feeling which replaces it, has been
developed in certain animals extremely low in the scale, for example,
in star-fishes and spiders. It is also occasionally present in a few
members alone in a whole group of animals, as in the genus Forficula,
or earwigs.

The all-important emotion of sympathy is distinct from that of love. A
mother may passionately love her sleeping and passive infant, but she
can hardly at such times be said to feel sympathy for it. The love of a
man for his dog is distinct from sympathy, and so is that of a dog for
his master. Adam Smith formerly argued, as has Mr. Bain recently, that
the basis of sympathy lies in our strong retentiveness of former states
of pain or pleasure. Hence, “the sight of another person enduring
hunger, cold, fatigue, revives in us some recollection of these states,
which are painful even in idea.” We are thus impelled to relieve the
sufferings of another, in order that our own painful feelings may be at
the same time relieved. In like manner we are led to participate in the
pleasures of others. (21. See the first and striking chapter in Adam
Smith’s ‘Theory of Moral Sentiments.’ Also ‘Mr. Bain’s Mental and Moral
Science,’ 1868, pp. 244, and 275-282. Mr. Bain states, that, “sympathy
is, indirectly, a source of pleasure to the sympathiser”; and he
accounts for this through reciprocity. He remarks that “the person
benefited, or others in his stead, may make up, by sympathy and good
offices returned, for all the sacrifice.” But if, as appears to be the
case, sympathy is strictly an instinct, its exercise would give direct
pleasure, in the same manner as the exercise, as before remarked, of
almost every other instinct.) But I cannot see how this view explains
the fact that sympathy is excited, in an immeasurably stronger degree,
by a beloved, than by an indifferent person. The mere sight of
suffering, independently of love, would suffice to call up in us vivid
recollections and associations. The explanation may lie in the fact
that, with all animals, sympathy is directed solely towards the members
of the same community, and therefore towards known, and more or less
beloved members, but not to all the individuals of the same species.
This fact is not more surprising than that the fears of many animals
should be directed against special enemies. Species which are not
social, such as lions and tigers, no doubt feel sympathy for the
suffering of their own young, but not for that of any other animal.
With mankind, selfishness, experience, and imitation, probably add, as
Mr. Bain has shewn, to the power of sympathy; for we are led by the
hope of receiving good in return to perform acts of sympathetic
kindness to others; and sympathy is much strengthened by habit. In
however complex a manner this feeling may have originated, as it is one
of high importance to all those animals which aid and defend one
another, it will have been increased through natural selection; for
those communities, which included the greatest number of the most
sympathetic members, would flourish best, and rear the greatest number
of offspring.

It is, however, impossible to decide in many cases whether certain
social instincts have been acquired through natural selection, or are
the indirect result of other instincts and faculties, such as sympathy,
reason, experience, and a tendency to imitation; or again, whether they
are simply the result of long-continued habit. So remarkable an
instinct as the placing sentinels to warn the community of danger, can
hardly have been the indirect result of any of these faculties; it
must, therefore, have been directly acquired. On the other hand, the
habit followed by the males of some social animals of defending the
community, and of attacking their enemies or their prey in concert, may
perhaps have originated from mutual sympathy; but courage, and in most
cases strength, must have been previously acquired, probably through
natural selection.

Of the various instincts and habits, some are much stronger than
others; that is, some either give more pleasure in their performance,
and more distress in their prevention, than others; or, which is
probably quite as important, they are, through inheritance, more
persistently followed, without exciting any special feeling of pleasure
or pain. We are ourselves conscious that some habits are much more
difficult to cure or change than others. Hence a struggle may often be
observed in animals between different instincts, or between an instinct
and some habitual disposition; as when a dog rushes after a hare, is
rebuked, pauses, hesitates, pursues again, or returns ashamed to his
master; or as between the love of a female dog for her young puppies
and for her master,—for she may be seen to slink away to them, as if
half ashamed of not accompanying her master. But the most curious
instance known to me of one instinct getting the better of another, is
the migratory instinct conquering the maternal instinct. The former is
wonderfully strong; a confined bird will at the proper season beat her
breast against the wires of her cage, until it is bare and bloody. It
causes young salmon to leap out of the fresh water, in which they could
continue to exist, and thus unintentionally to commit suicide. Every
one knows how strong the maternal instinct is, leading even timid birds
to face great danger, though with hesitation, and in opposition to the
instinct of self-preservation. Nevertheless, the migratory instinct is
so powerful, that late in the autumn swallows, house-martins, and
swifts frequently desert their tender young, leaving them to perish
miserably in their nests. (22. This fact, the Rev. L. Jenyns states
(see his edition of ‘White’s Nat. Hist. of Selborne,’ 1853, p. 204) was
first recorded by the illustrious Jenner, in ‘Phil. Transact.’ 1824,
and has since been confirmed by several observers, especially by Mr.
Blackwall. This latter careful observer examined, late in the autumn,
during two years, thirty-six nests; he found that twelve contained
young dead birds, five contained eggs on the point of being hatched,
and three, eggs not nearly hatched. Many birds, not yet old enough for
a prolonged flight, are likewise deserted and left behind. See
Blackwall, ‘Researches in Zoology,’ 1834, pp. 108, 118. For some
additional evidence, although this is not wanted, see Leroy, ‘Lettres
Phil.’ 1802, p. 217. For Swifts, Gould’s ‘Introduction to the Birds of
Great Britain,’ 1823, p. 5. Similar cases have been observed in Canada
by Mr. Adams; ‘Pop. Science Review,’ July 1873, p. 283.)

We can perceive that an instinctive impulse, if it be in any way more
beneficial to a species than some other or opposed instinct, would be
rendered the more potent of the two through natural selection; for the
individuals which had it most strongly developed would survive in
larger numbers. Whether this is the case with the migratory in
comparison with the maternal instinct, may be doubted. The great
persistence, or steady action of the former at certain seasons of the
year during the whole day, may give it for a time paramount force.

MAN A SOCIAL ANIMAL.

Every one will admit that man is a social being. We see this in his
dislike of solitude, and in his wish for society beyond that of his own
family. Solitary confinement is one of the severest punishments which
can be inflicted. Some authors suppose that man primevally lived in
single families; but at the present day, though single families, or
only two or three together, roam the solitudes of some savage lands,
they always, as far as I can discover, hold friendly relations with
other families inhabiting the same district. Such families occasionally
meet in council, and unite for their common defence. It is no argument
against savage man being a social animal, that the tribes inhabiting
adjacent districts are almost always at war with each other; for the
social instincts never extend to all the individuals of the same
species. Judging from the analogy of the majority of the Quadrumana, it
is probable that the early ape-like progenitors of man were likewise
social; but this is not of much importance for us. Although man, as he
now exists, has few special instincts, having lost any which his early
progenitors may have possessed, this is no reason why he should not
have retained from an extremely remote period some degree of
instinctive love and sympathy for his fellows. We are indeed all
conscious that we do possess such sympathetic feelings (23. Hume
remarks (‘An Enquiry Concerning the Principles of Morals,’ edit. of
1751, p. 132), “There seems a necessity for confessing that the
happiness and misery of others are not spectacles altogether
indifferent to us, but that the view of the former...communicates a
secret joy; the appearance of the latter... throws a melancholy damp
over the imagination.”); but our consciousness does not tell us whether
they are instinctive, having originated long ago in the same manner as
with the lower animals, or whether they have been acquired by each of
us during our early years. As man is a social animal, it is almost
certain that he would inherit a tendency to be faithful to his
comrades, and obedient to the leader of his tribe; for these qualities
are common to most social animals. He would consequently possess some
capacity for self-command. He would from an inherited tendency be
willing to defend, in concert with others, his fellow-men; and would be
ready to aid them in any way, which did not too greatly interfere with
his own welfare or his own strong desires.

The social animals which stand at the bottom of the scale are guided
almost exclusively, and those which stand higher in the scale are
largely guided, by special instincts in the aid which they give to the
members of the same community; but they are likewise in part impelled
by mutual love and sympathy, assisted apparently by some amount of
reason. Although man, as just remarked, has no special instincts to
tell him how to aid his fellow-men, he still has the impulse, and with
his improved intellectual faculties would naturally be much guided in
this respect by reason and experience. Instinctive sympathy would also
cause him to value highly the approbation of his fellows; for, as Mr.
Bain has clearly shewn (24. ‘Mental and Moral Science,’ 1868, p. 254.),
the love of praise and the strong feeling of glory, and the still
stronger horror of scorn and infamy, “are due to the workings of
sympathy.” Consequently man would be influenced in the highest degree
by the wishes, approbation, and blame of his fellow-men, as expressed
by their gestures and language. Thus the social instincts, which must
have been acquired by man in a very rude state, and probably even by
his early ape-like progenitors, still give the impulse to some of his
best actions; but his actions are in a higher degree determined by the
expressed wishes and judgment of his fellow-men, and unfortunately very
often by his own strong selfish desires. But as love, sympathy and
self-command become strengthened by habit, and as the power of
reasoning becomes clearer, so that man can value justly the judgments
of his fellows, he will feel himself impelled, apart from any
transitory pleasure or pain, to certain lines of conduct. He might then
declare—not that any barbarian or uncultivated man could thus think—I
am the supreme judge of my own conduct, and in the words of Kant, I
will not in my own person violate the dignity of humanity.

THE MORE ENDURING SOCIAL INSTINCTS CONQUER THE LESS PERSISTENT
INSTINCTS.

We have not, however, as yet considered the main point, on which, from
our present point of view, the whole question of the moral sense turns.
Why should a man feel that he ought to obey one instinctive desire
rather than another? Why is he bitterly regretful, if he has yielded to
a strong sense of self-preservation, and has not risked his life to
save that of a fellow-creature? or why does he regret having stolen
food from hunger?

It is evident in the first place, that with mankind the instinctive
impulses have different degrees of strength; a savage will risk his own
life to save that of a member of the same community, but will be wholly
indifferent about a stranger: a young and timid mother urged by the
maternal instinct will, without a moment’s hesitation, run the greatest
danger for her own infant, but not for a mere fellow-creature.
Nevertheless many a civilised man, or even boy, who never before risked
his life for another, but full of courage and sympathy, has disregarded
the instinct of self-preservation, and plunged at once into a torrent
to save a drowning man, though a stranger. In this case man is impelled
by the same instinctive motive, which made the heroic little American
monkey, formerly described, save his keeper, by attacking the great and
dreaded baboon. Such actions as the above appear to be the simple
result of the greater strength of the social or maternal instincts
rather than that of any other instinct or motive; for they are
performed too instantaneously for reflection, or for pleasure or pain
to be felt at the time; though, if prevented by any cause, distress or
even misery might be felt. In a timid man, on the other hand, the
instinct of self-preservation might be so strong, that he would be
unable to force himself to run any such risk, perhaps not even for his
own child.

I am aware that some persons maintain that actions performed
impulsively, as in the above cases, do not come under the dominion of
the moral sense, and cannot be called moral. They confine this term to
actions done deliberately, after a victory over opposing desires, or
when prompted by some exalted motive. But it appears scarcely possible
to draw any clear line of distinction of this kind. (25. I refer here
to the distinction between what has been called MATERIAL and FORMAL
morality. I am glad to find that Professor Huxley (‘Critiques and
Addresses,’ 1873, p. 287) takes the same view on this subject as I do.
Mr. Leslie Stephen remarks (‘Essays on Freethinking and Plain
Speaking,’ 1873, p. 83), “the metaphysical distinction, between
material and formal morality is as irrelevant as other such
distinctions.”) As far as exalted motives are concerned, many instances
have been recorded of savages, destitute of any feeling of general
benevolence towards mankind, and not guided by any religious motive,
who have deliberately sacrificed their lives as prisoners(26. I have
given one such case, namely of three Patagonian Indians who preferred
being shot, one after the other, to betraying the plans of their
companions in war (‘Journal of Researches,’ 1845, p. 103).), rather
than betray their comrades; and surely their conduct ought to be
considered as moral. As far as deliberation, and the victory over
opposing motives are concerned, animals may be seen doubting between
opposed instincts, in rescuing their offspring or comrades from danger;
yet their actions, though done for the good of others, are not called
moral. Moreover, anything performed very often by us, will at last be
done without deliberation or hesitation, and can then hardly be
distinguished from an instinct; yet surely no one will pretend that
such an action ceases to be moral. On the contrary, we all feel that an
act cannot be considered as perfect, or as performed in the most noble
manner, unless it be done impulsively, without deliberation or effort,
in the same manner as by a man in whom the requisite qualities are
innate. He who is forced to overcome his fear or want of sympathy
before he acts, deserves, however, in one way higher credit than the
man whose innate disposition leads him to a good act without effort. As
we cannot distinguish between motives, we rank all actions of a certain
class as moral, if performed by a moral being. A moral being is one who
is capable of comparing his past and future actions or motives, and of
approving or disapproving of them. We have no reason to suppose that
any of the lower animals have this capacity; therefore, when a
Newfoundland dog drags a child out of the water, or a monkey faces
danger to rescue its comrade, or takes charge of an orphan monkey, we
do not call its conduct moral. But in the case of man, who alone can
with certainty be ranked as a moral being, actions of a certain class
are called moral, whether performed deliberately, after a struggle with
opposing motives, or impulsively through instinct, or from the effects
of slowly-gained habit.

But to return to our more immediate subject. Although some instincts
are more powerful than others, and thus lead to corresponding actions,
yet it is untenable, that in man the social instincts (including the
love of praise and fear of blame) possess greater strength, or have,
through long habit, acquired greater strength than the instincts of
self-preservation, hunger, lust, vengeance, etc. Why then does man
regret, even though trying to banish such regret, that he has followed
the one natural impulse rather than the other; and why does he further
feel that he ought to regret his conduct? Man in this respect differs
profoundly from the lower animals. Nevertheless we can, I think, see
with some degree of clearness the reason of this difference.

Man, from the activity of his mental faculties, cannot avoid
reflection: past impressions and images are incessantly and clearly
passing through his mind. Now with those animals which live permanently
in a body, the social instincts are ever present and persistent. Such
animals are always ready to utter the danger-signal, to defend the
community, and to give aid to their fellows in accordance with their
habits; they feel at all times, without the stimulus of any special
passion or desire, some degree of love and sympathy for them; they are
unhappy if long separated from them, and always happy to be again in
their company. So it is with ourselves. Even when we are quite alone,
how often do we think with pleasure or pain of what others think of
us,—of their imagined approbation or disapprobation; and this all
follows from sympathy, a fundamental element of the social instincts. A
man who possessed no trace of such instincts would be an unnatural
monster. On the other hand, the desire to satisfy hunger, or any
passion such as vengeance, is in its nature temporary, and can for a
time be fully satisfied. Nor is it easy, perhaps hardly possible, to
call up with complete vividness the feeling, for instance, of hunger;
nor indeed, as has often been remarked, of any suffering. The instinct
of self-preservation is not felt except in the presence of danger; and
many a coward has thought himself brave until he has met his enemy face
to face. The wish for another man’s property is perhaps as persistent a
desire as any that can be named; but even in this case the satisfaction
of actual possession is generally a weaker feeling than the desire:
many a thief, if not a habitual one, after success has wondered why he
stole some article. (27. Enmity or hatred seems also to be a highly
persistent feeling, perhaps more so than any other that can be named.
Envy is defined as hatred of another for some excellence or success;
and Bacon insists (Essay ix.), “Of all other affections envy is the
most importune and continual.” Dogs are very apt to hate both strange
men and strange dogs, especially if they live near at hand, but do not
belong to the same family, tribe, or clan; this feeling would thus seem
to be innate, and is certainly a most persistent one. It seems to be
the complement and converse of the true social instinct. From what we
hear of savages, it would appear that something of the same kind holds
good with them. If this be so, it would be a small step in any one to
transfer such feelings to any member of the same tribe if he had done
him an injury and had become his enemy. Nor is it probable that the
primitive conscience would reproach a man for injuring his enemy;
rather it would reproach him, if he had not revenged himself. To do
good in return for evil, to love your enemy, is a height of morality to
which it may be doubted whether the social instincts would, by
themselves, have ever led us. It is necessary that these instincts,
together with sympathy, should have been highly cultivated and extended
by the aid of reason, instruction, and the love or fear of God, before
any such golden rule would ever be thought of and obeyed.)

A man cannot prevent past impressions often repassing through his mind;
he will thus be driven to make a comparison between the impressions of
past hunger, vengeance satisfied, or danger shunned at other men’s
cost, with the almost ever-present instinct of sympathy, and with his
early knowledge of what others consider as praiseworthy or blameable.
This knowledge cannot be banished from his mind, and from instinctive
sympathy is esteemed of great moment. He will then feel as if he had
been baulked in following a present instinct or habit, and this with
all animals causes dissatisfaction, or even misery.

The above case of the swallow affords an illustration, though of a
reversed nature, of a temporary though for the time strongly persistent
instinct conquering another instinct, which is usually dominant over
all others. At the proper season these birds seem all day long to be
impressed with the desire to migrate; their habits change; they become
restless, are noisy and congregate in flocks. Whilst the mother-bird is
feeding, or brooding over her nestlings, the maternal instinct is
probably stronger than the migratory; but the instinct which is the
more persistent gains the victory, and at last, at a moment when her
young ones are not in sight, she takes flight and deserts them. When
arrived at the end of her long journey, and the migratory instinct has
ceased to act, what an agony of remorse the bird would feel, if, from
being endowed with great mental activity, she could not prevent the
image constantly passing through her mind, of her young ones perishing
in the bleak north from cold and hunger.

At the moment of action, man will no doubt be apt to follow the
stronger impulse; and though this may occasionally prompt him to the
noblest deeds, it will more commonly lead him to gratify his own
desires at the expense of other men. But after their gratification when
past and weaker impressions are judged by the ever-enduring social
instinct, and by his deep regard for the good opinion of his fellows,
retribution will surely come. He will then feel remorse, repentance,
regret, or shame; this latter feeling, however, relates almost
exclusively to the judgment of others. He will consequently resolve
more or less firmly to act differently for the future; and this is
conscience; for conscience looks backwards, and serves as a guide for
the future.

The nature and strength of the feelings which we call regret, shame,
repentance or remorse, depend apparently not only on the strength of
the violated instinct, but partly on the strength of the temptation,
and often still more on the judgment of our fellows. How far each man
values the appreciation of others, depends on the strength of his
innate or acquired feeling of sympathy; and on his own capacity for
reasoning out the remote consequences of his acts. Another element is
most important, although not necessary, the reverence or fear of the
Gods, or Spirits believed in by each man: and this applies especially
in cases of remorse. Several critics have objected that though some
slight regret or repentance may be explained by the view advocated in
this chapter, it is impossible thus to account for the soul-shaking
feeling of remorse. But I can see little force in this objection. My
critics do not define what they mean by remorse, and I can find no
definition implying more than an overwhelming sense of repentance.
Remorse seems to bear the same relation to repentance, as rage does to
anger, or agony to pain. It is far from strange that an instinct so
strong and so generally admired, as maternal love, should, if
disobeyed, lead to the deepest misery, as soon as the impression of the
past cause of disobedience is weakened. Even when an action is opposed
to no special instinct, merely to know that our friends and equals
despise us for it is enough to cause great misery. Who can doubt that
the refusal to fight a duel through fear has caused many men an agony
of shame? Many a Hindoo, it is said, has been stirred to the bottom of
his soul by having partaken of unclean food. Here is another case of
what must, I think, be called remorse. Dr. Landor acted as a magistrate
in West Australia, and relates (28. ‘Insanity in Relation to Law,’
Ontario, United States, 1871, p. 1.), that a native on his farm, after
losing one of his wives from disease, came and said that, “he was going
to a distant tribe to spear a woman, to satisfy his sense of duty to
his wife. I told him that if he did so, I would send him to prison for
life. He remained about the farm for some months, but got exceedingly
thin, and complained that he could not rest or eat, that his wife’s
spirit was haunting him, because he had not taken a life for hers. I
was inexorable, and assured him that nothing should save him if he
did.” Nevertheless the man disappeared for more than a year, and then
returned in high condition; and his other wife told Dr. Landor that her
husband had taken the life of a woman belonging to a distant tribe; but
it was impossible to obtain legal evidence of the act. The breach of a
rule held sacred by the tribe, will thus, as it seems, give rise to the
deepest feelings,—and this quite apart from the social instincts,
excepting in so far as the rule is grounded on the judgment of the
community. How so many strange superstitions have arisen throughout the
world we know not; nor can we tell how some real and great crimes, such
as incest, have come to be held in an abhorrence (which is not however
quite universal) by the lowest savages. It is even doubtful whether in
some tribes incest would be looked on with greater horror, than would
the marriage of a man with a woman bearing the same name, though not a
relation. “To violate this law is a crime which the Australians hold in
the greatest abhorrence, in this agreeing exactly with certain tribes
of North America. When the question is put in either district, is it
worse to kill a girl of a foreign tribe, or to marry a girl of one’s
own, an answer just opposite to ours would be given without
hesitation.” (29. E.B. Tylor, in ‘Contemporary Review,’ April 1873, p.
707.) We may, therefore, reject the belief, lately insisted on by some
writers, that the abhorrence of incest is due to our possessing a
special God-implanted conscience. On the whole it is intelligible, that
a man urged by so powerful a sentiment as remorse, though arising as
above explained, should be led to act in a manner, which he has been
taught to believe serves as an expiation, such as delivering himself up
to justice.

Man prompted by his conscience, will through long habit acquire such
perfect self-command, that his desires and passions will at last yield
instantly and without a struggle to his social sympathies and
instincts, including his feeling for the judgment of his fellows. The
still hungry, or the still revengeful man will not think of stealing
food, or of wreaking his vengeance. It is possible, or as we shall
hereafter see, even probable, that the habit of self-command may, like
other habits, be inherited. Thus at last man comes to feel, through
acquired and perhaps inherited habit, that it is best for him to obey
his more persistent impulses. The imperious word “ought” seems merely
to imply the consciousness of the existence of a rule of conduct,
however it may have originated. Formerly it must have been often
vehemently urged that an insulted gentleman OUGHT to fight a duel. We
even say that a pointer OUGHT to point, and a retriever to retrieve
game. If they fail to do so, they fail in their duty and act wrongly.

If any desire or instinct leading to an action opposed to the good of
others still appears, when recalled to mind, as strong as, or stronger
than, the social instinct, a man will feel no keen regret at having
followed it; but he will be conscious that if his conduct were known to
his fellows, it would meet with their disapprobation; and few are so
destitute of sympathy as not to feel discomfort when this is realised.
If he has no such sympathy, and if his desires leading to bad actions
are at the time strong, and when recalled are not over-mastered by the
persistent social instincts, and the judgment of others, then he is
essentially a bad man (30. Dr. Prosper Despine, in his Psychologie
Naturelle, 1868 (tom. i. p. 243; tom. ii. p. 169) gives many curious
cases of the worst criminals, who apparently have been entirely
destitute of conscience.); and the sole restraining motive left is the
fear of punishment, and the conviction that in the long run it would be
best for his own selfish interests to regard the good of others rather
than his own.

It is obvious that every one may with an easy conscience gratify his
own desires, if they do not interfere with his social instincts, that
is with the good of others; but in order to be quite free from
self-reproach, or at least of anxiety, it is almost necessary for him
to avoid the disapprobation, whether reasonable or not, of his
fellow-men. Nor must he break through the fixed habits of his life,
especially if these are supported by reason; for if he does, he will
assuredly feel dissatisfaction. He must likewise avoid the reprobation
of the one God or gods in whom, according to his knowledge or
superstition, he may believe; but in this case the additional fear of
divine punishment often supervenes.

THE STRICTLY SOCIAL VIRTUES AT FIRST ALONE REGARDED.

The above view of the origin and nature of the moral sense, which tells
us what we ought to do, and of the conscience which reproves us if we
disobey it, accords well with what we see of the early and undeveloped
condition of this faculty in mankind. The virtues which must be
practised, at least generally, by rude men, so that they may associate
in a body, are those which are still recognised as the most important.
But they are practised almost exclusively in relation to the men of the
same tribe; and their opposites are not regarded as crimes in relation
to the men of other tribes. No tribe could hold together if murder,
robbery, treachery, etc., were common; consequently such crimes within
the limits of the same tribe “are branded with everlasting infamy” (31.
See an able article in the ‘North British Review,’ 1867, p. 395. See
also Mr. W. Bagehot’s articles on the Importance of Obedience and
Coherence to Primitive Man, in the ‘Fortnightly Review,’ 1867, p. 529,
and 1868, p. 457, etc.); but excite no such sentiment beyond these
limits. A North-American Indian is well pleased with himself, and is
honoured by others, when he scalps a man of another tribe; and a Dyak
cuts off the head of an unoffending person, and dries it as a trophy.
The murder of infants has prevailed on the largest scale throughout the
world (32. The fullest account which I have met with is by Dr. Gerland,
in his ‘Ueber den Aussterben der Naturvölker,’ 1868; but I shall have
to recur to the subject of infanticide in a future chapter.), and has
met with no reproach; but infanticide, especially of females, has been
thought to be good for the tribe, or at least not injurious. Suicide
during former times was not generally considered as a crime (33. See
the very interesting discussion on suicide in Lecky’s ‘History of
European Morals,’ vol. i. 1869, p. 223. With respect to savages, Mr.
Winwood Reade informs me that the negroes of West Africa often commit
suicide. It is well known how common it was amongst the miserable
aborigines of South America after the Spanish conquest. For New
Zealand, see the voyage of the Novara, and for the Aleutian Islands,
Müller, as quoted by Houzeau, ‘Les Facultés Mentales,’ etc., tom. ii.
p. 136.), but rather, from the courage displayed, as an honourable act;
and it is still practised by some semi-civilised and savage nations
without reproach, for it does not obviously concern others of the
tribe. It has been recorded that an Indian Thug conscientiously
regretted that he had not robbed and strangled as many travellers as
did his father before him. In a rude state of civilisation the robbery
of strangers is, indeed, generally considered as honourable.

Slavery, although in some ways beneficial during ancient times (34. See
Mr. Bagehot, ‘Physics and Politics,’ 1872, p. 72.), is a great crime;
yet it was not so regarded until quite recently, even by the most
civilised nations. And this was especially the case, because the slaves
belonged in general to a race different from that of their masters. As
barbarians do not regard the opinion of their women, wives are commonly
treated like slaves. Most savages are utterly indifferent to the
sufferings of strangers, or even delight in witnessing them. It is well
known that the women and children of the North-American Indians aided
in torturing their enemies. Some savages take a horrid pleasure in
cruelty to animals (35. See, for instance, Mr. Hamilton’s account of
the Kaffirs, ‘Anthropological Review,’ 1870, p. xv.), and humanity is
an unknown virtue. Nevertheless, besides the family affections,
kindness is common, especially during sickness, between the members of
the same tribe, and is sometimes extended beyond these limits. Mungo
Park’s touching account of the kindness of the negro women of the
interior to him is well known. Many instances could be given of the
noble fidelity of savages towards each other, but not to strangers;
common experience justifies the maxim of the Spaniard, “Never, never
trust an Indian.” There cannot be fidelity without truth; and this
fundamental virtue is not rare between the members of the same tribe:
thus Mungo Park heard the negro women teaching their young children to
love the truth. This, again, is one of the virtues which becomes so
deeply rooted in the mind, that it is sometimes practised by savages,
even at a high cost, towards strangers; but to lie to your enemy has
rarely been thought a sin, as the history of modern diplomacy too
plainly shews. As soon as a tribe has a recognised leader, disobedience
becomes a crime, and even abject submission is looked at as a sacred
virtue.

As during rude times no man can be useful or faithful to his tribe
without courage, this quality has universally been placed in the
highest rank; and although in civilised countries a good yet timid man
may be far more useful to the community than a brave one, we cannot
help instinctively honouring the latter above a coward, however
benevolent. Prudence, on the other hand, which does not concern the
welfare of others, though a very useful virtue, has never been highly
esteemed. As no man can practise the virtues necessary for the welfare
of his tribe without self-sacrifice, self-command, and the power of
endurance, these qualities have been at all times highly and most
justly valued. The American savage voluntarily submits to the most
horrid tortures without a groan, to prove and strengthen his fortitude
and courage; and we cannot help admiring him, or even an Indian Fakir,
who, from a foolish religious motive, swings suspended by a hook buried
in his flesh.

The other so-called self-regarding virtues, which do not obviously,
though they may really, affect the welfare of the tribe, have never
been esteemed by savages, though now highly appreciated by civilised
nations. The greatest intemperance is no reproach with savages. Utter
licentiousness, and unnatural crimes, prevail to an astounding extent.
(36. Mr. M’Lennan has given (‘Primitive Marriage,’ 1865, p. 176) a good
collection of facts on this head.) As soon, however, as marriage,
whether polygamous, or monogamous, becomes common, jealousy will lead
to the inculcation of female virtue; and this, being honoured, will
tend to spread to the unmarried females. How slowly it spreads to the
male sex, we see at the present day. Chastity eminently requires
self-command; therefore it has been honoured from a very early period
in the moral history of civilised man. As a consequence of this, the
senseless practice of celibacy has been ranked from a remote period as
a virtue. (38. Lecky, ‘History of European Morals,’ vol. i. 1869, p.
109.) The hatred of indecency, which appears to us so natural as to be
thought innate, and which is so valuable an aid to chastity, is a
modern virtue, appertaining exclusively, as Sir G. Staunton remarks
(38. ‘Embassy to China,’ vol. ii. p. 348.), to civilised life. This is
shewn by the ancient religious rites of various nations, by the
drawings on the walls of Pompeii, and by the practices of many savages.

We have now seen that actions are regarded by savages, and were
probably so regarded by primeval man, as good or bad, solely as they
obviously affect the welfare of the tribe,—not that of the species, nor
that of an individual member of the tribe. This conclusion agrees well
with the belief that the so-called moral sense is aboriginally derived
from the social instincts, for both relate at first exclusively to the
community.

The chief causes of the low morality of savages, as judged by our
standard, are, firstly, the confinement of sympathy to the same tribe.
Secondly, powers of reasoning insufficient to recognise the bearing of
many virtues, especially of the self-regarding virtues, on the general
welfare of the tribe. Savages, for instance, fail to trace the
multiplied evils consequent on a want of temperance, chastity, etc.
And, thirdly, weak power of self-command; for this power has not been
strengthened through long-continued, perhaps inherited, habit,
instruction and religion.

I have entered into the above details on the immorality of savages (39.
See on this subject copious evidence in Chap. vii. of Sir J. Lubbock,
‘Origin of Civilisation,’ 1870.), because some authors have recently
taken a high view of their moral nature, or have attributed most of
their crimes to mistaken benevolence. (40. For instance Lecky, ‘History
of European Morals,’ vol. i. p. 124.) These authors appear to rest
their conclusion on savages possessing those virtues which are
serviceable, or even necessary, for the existence of the family and of
the tribe,—qualities which they undoubtedly do possess, and often in a
high degree.

CONCLUDING REMARKS.

It was assumed formerly by philosophers of the derivative (41. This
term is used in an able article in the ‘Westminster Review,’ Oct. 1869,
p. 498. For the “Greatest happiness principle,” see J.S. Mill,
‘Utilitarianism,’ p. 17.) school of morals that the foundation of
morality lay in a form of Selfishness; but more recently the “Greatest
happiness principle” has been brought prominently forward. It is,
however, more correct to speak of the latter principle as the standard,
and not as the motive of conduct. Nevertheless, all the authors whose
works I have consulted, with a few exceptions (42. Mill recognises
(‘System of Logic,’ vol. ii. p. 422) in the clearest manner, that
actions may be performed through habit without the anticipation of
pleasure. Mr. H. Sidgwick also, in his Essay on Pleasure and Desire
(‘The Contemporary Review,’ April 1872, p. 671), remarks: “To sum up,
in contravention of the doctrine that our conscious active impulses are
always directed towards the production of agreeable sensations in
ourselves, I would maintain that we find everywhere in consciousness
extra-regarding impulse, directed towards something that is not
pleasure; that in many cases the impulse is so far incompatible with
the self-regarding that the two do not easily co-exist in the same
moment of consciousness.” A dim feeling that our impulses do not by any
means always arise from any contemporaneous or anticipated pleasure,
has, I cannot but think, been one chief cause of the acceptance of the
intuitive theory of morality, and of the rejection of the utilitarian
or “Greatest happiness” theory. With respect to the latter theory the
standard and the motive of conduct have no doubt often been confused,
but they are really in some degree blended.), write as if there must be
a distinct motive for every action, and that this must be associated
with some pleasure or displeasure. But man seems often to act
impulsively, that is from instinct or long habit, without any
consciousness of pleasure, in the same manner as does probably a bee or
ant, when it blindly follows its instincts. Under circumstances of
extreme peril, as during a fire, when a man endeavours to save a
fellow-creature without a moment’s hesitation, he can hardly feel
pleasure; and still less has he time to reflect on the dissatisfaction
which he might subsequently experience if he did not make the attempt.
Should he afterwards reflect over his own conduct, he would feel that
there lies within him an impulsive power widely different from a search
after pleasure or happiness; and this seems to be the deeply planted
social instinct.

In the case of the lower animals it seems much more appropriate to
speak of their social instincts, as having been developed for the
general good rather than for the general happiness of the species. The
term, general good, may be defined as the rearing of the greatest
number of individuals in full vigour and health, with all their
faculties perfect, under the conditions to which they are subjected. As
the social instincts both of man and the lower animals have no doubt
been developed by nearly the same steps, it would be advisable, if
found practicable, to use the same definition in both cases, and to
take as the standard of morality, the general good or welfare of the
community, rather than the general happiness; but this definition would
perhaps require some limitation on account of political ethics.

When a man risks his life to save that of a fellow-creature, it seems
also more correct to say that he acts for the general good, rather than
for the general happiness of mankind. No doubt the welfare and the
happiness of the individual usually coincide; and a contented, happy
tribe will flourish better than one that is discontented and unhappy.
We have seen that even at an early period in the history of man, the
expressed wishes of the community will have naturally influenced to a
large extent the conduct of each member; and as all wish for happiness,
the “greatest happiness principle” will have become a most important
secondary guide and object; the social instinct, however, together with
sympathy (which leads to our regarding the approbation and
disapprobation of others), having served as the primary impulse and
guide. Thus the reproach is removed of laying the foundation of the
noblest part of our nature in the base principle of selfishness;
unless, indeed, the satisfaction which every animal feels, when it
follows its proper instincts, and the dissatisfaction felt when
prevented, be called selfish.

The wishes and opinions of the members of the same community, expressed
at first orally, but later by writing also, either form the sole guides
of our conduct, or greatly reinforce the social instincts; such
opinions, however, have sometimes a tendency directly opposed to these
instincts. This latter fact is well exemplified by the LAW OF HONOUR,
that is, the law of the opinion of our equals, and not of all our
countrymen. The breach of this law, even when the breach is known to be
strictly accordant with true morality, has caused many a man more agony
than a real crime. We recognise the same influence in the burning sense
of shame which most of us have felt, even after the interval of years,
when calling to mind some accidental breach of a trifling, though
fixed, rule of etiquette. The judgment of the community will generally
be guided by some rude experience of what is best in the long run for
all the members; but this judgment will not rarely err from ignorance
and weak powers of reasoning. Hence the strangest customs and
superstitions, in complete opposition to the true welfare and happiness
of mankind, have become all-powerful throughout the world. We see this
in the horror felt by a Hindoo who breaks his caste, and in many other
such cases. It would be difficult to distinguish between the remorse
felt by a Hindoo who has yielded to the temptation of eating unclean
food, from that felt after committing a theft; but the former would
probably be the more severe.

How so many absurd rules of conduct, as well as so many absurd
religious beliefs, have originated, we do not know; nor how it is that
they have become, in all quarters of the world, so deeply impressed on
the mind of men; but it is worthy of remark that a belief constantly
inculcated during the early years of life, whilst the brain is
impressible, appears to acquire almost the nature of an instinct; and
the very essence of an instinct is that it is followed independently of
reason. Neither can we say why certain admirable virtues, such as the
love of truth, are much more highly appreciated by some savage tribes
than by others (43. Good instances are given by Mr. Wallace in
‘Scientific Opinion,’ Sept. 15, 1869; and more fully in his
‘Contributions to the Theory of Natural Selection,’ 1870, p. 353.);
nor, again, why similar differences prevail even amongst highly
civilised nations. Knowing how firmly fixed many strange customs and
superstitions have become, we need feel no surprise that the
self-regarding virtues, supported as they are by reason, should now
appear to us so natural as to be thought innate, although they were not
valued by man in his early condition.

Not withstanding many sources of doubt, man can generally and readily
distinguish between the higher and lower moral rules. The higher are
founded on the social instincts, and relate to the welfare of others.
They are supported by the approbation of our fellow-men and by reason.
The lower rules, though some of them when implying self-sacrifice
hardly deserve to be called lower, relate chiefly to self, and arise
from public opinion, matured by experience and cultivation; for they
are not practised by rude tribes.

As man advances in civilisation, and small tribes are united into
larger communities, the simplest reason would tell each individual that
he ought to extend his social instincts and sympathies to all the
members of the same nation, though personally unknown to him. This
point being once reached, there is only an artificial barrier to
prevent his sympathies extending to the men of all nations and races.
If, indeed, such men are separated from him by great differences in
appearance or habits, experience unfortunately shews us how long it is,
before we look at them as our fellow-creatures. Sympathy beyond the
confines of man, that is, humanity to the lower animals, seems to be
one of the latest moral acquisitions. It is apparently unfelt by
savages, except towards their pets. How little the old Romans knew of
it is shewn by their abhorrent gladiatorial exhibitions. The very idea
of humanity, as far as I could observe, was new to most of the Gauchos
of the Pampas. This virtue, one of the noblest with which man is
endowed, seems to arise incidentally from our sympathies becoming more
tender and more widely diffused, until they are extended to all
sentient beings. As soon as this virtue is honoured and practised by
some few men, it spreads through instruction and example to the young,
and eventually becomes incorporated in public opinion.

The highest possible stage in moral culture is when we recognise that
we ought to control our thoughts, and “not even in inmost thought to
think again the sins that made the past so pleasant to us.” (44.
Tennyson, Idylls of the King, p. 244.) Whatever makes any bad action
familiar to the mind, renders its performance by so much the easier. As
Marcus Aurelius long ago said, “Such as are thy habitual thoughts, such
also will be the character of thy mind; for the soul is dyed by the
thoughts.” (45. ‘The Thoughts of the Emperor M. Aurelius Antoninus,’
English translation, 2nd edit., 1869. p. 112. Marcus Aurelius was born
A.D. 121.)

Our great philosopher, Herbert Spencer, has recently explained his
views on the moral sense. He says (46. Letter to Mr. Mill in Bain’s
‘Mental and Moral Science,’ 1868, p. 722.), “I believe that the
experiences of utility organised and consolidated through all past
generations of the human race, have been producing corresponding
modifications, which, by continued transmission and accumulation, have
become in us certain faculties of moral intuition—certain emotions
responding to right and wrong conduct, which have no apparent basis in
the individual experiences of utility.” There is not the least inherent
improbability, as it seems to me, in virtuous tendencies being more or
less strongly inherited; for, not to mention the various dispositions
and habits transmitted by many of our domestic animals to their
offspring, I have heard of authentic cases in which a desire to steal
and a tendency to lie appeared to run in families of the upper ranks;
and as stealing is a rare crime in the wealthy classes, we can hardly
account by accidental coincidence for the tendency occurring in two or
three members of the same family. If bad tendencies are transmitted, it
is probable that good ones are likewise transmitted. That the state of
the body by affecting the brain, has great influence on the moral
tendencies is known to most of those who have suffered from chronic
derangements of the digestion or liver. The same fact is likewise shewn
by the “perversion or destruction of the moral sense being often one of
the earliest symptoms of mental derangement” (47. Maudsley, ‘Body and
Mind,’ 1870, p. 60.); and insanity is notoriously often inherited.
Except through the principle of the transmission of moral tendencies,
we cannot understand the differences believed to exist in this respect
between the various races of mankind.

Even the partial transmission of virtuous tendencies would be an
immense assistance to the primary impulse derived directly and
indirectly from the social instincts. Admitting for a moment that
virtuous tendencies are inherited, it appears probable, at least in
such cases as chastity, temperance, humanity to animals, etc., that
they become first impressed on the mental organization through habit,
instruction and example, continued during several generations in the
same family, and in a quite subordinate degree, or not at all, by the
individuals possessing such virtues having succeeded best in the
struggle for life. My chief source of doubt with respect to any such
inheritance, is that senseless customs, superstitions, and tastes, such
as the horror of a Hindoo for unclean food, ought on the same principle
to be transmitted. I have not met with any evidence in support of the
transmission of superstitious customs or senseless habits, although in
itself it is perhaps not less probable than that animals should acquire
inherited tastes for certain kinds of food or fear of certain foes.

Finally the social instincts, which no doubt were acquired by man as by
the lower animals for the good of the community, will from the first
have given to him some wish to aid his fellows, some feeling of
sympathy, and have compelled him to regard their approbation and
disapprobation. Such impulses will have served him at a very early
period as a rude rule of right and wrong. But as man gradually advanced
in intellectual power, and was enabled to trace the more remote
consequences of his actions; as he acquired sufficient knowledge to
reject baneful customs and superstitions; as he regarded more and more,
not only the welfare, but the happiness of his fellow-men; as from
habit, following on beneficial experience, instruction and example, his
sympathies became more tender and widely diffused, extending to men of
all races, to the imbecile, maimed, and other useless members of
society, and finally to the lower animals,—so would the standard of his
morality rise higher and higher. And it is admitted by moralists of the
derivative school and by some intuitionists, that the standard of
morality has risen since an early period in the history of man. (48. A
writer in the ‘North British Review’ (July 1869, p. 531), well capable
of forming a sound judgment, expresses himself strongly in favour of
this conclusion. Mr. Lecky (‘History of Morals,’ vol. i. p. 143) seems
to a certain extent to coincide therein.)

As a struggle may sometimes be seen going on between the various
instincts of the lower animals, it is not surprising that there should
be a struggle in man between his social instincts, with their derived
virtues, and his lower, though momentarily stronger impulses or
desires. This, as Mr. Galton (49. See his remarkable work on
‘Hereditary Genius,’ 1869, p. 349. The Duke of Argyll (‘Primeval Man,’
1869, p. 188) has some good remarks on the contest in man’s nature
between right and wrong.) has remarked, is all the less surprising, as
man has emerged from a state of barbarism within a comparatively recent
period. After having yielded to some temptation we feel a sense of
dissatisfaction, shame, repentance, or remorse, analogous to the
feelings caused by other powerful instincts or desires, when left
unsatisfied or baulked. We compare the weakened impression of a past
temptation with the ever present social instincts, or with habits,
gained in early youth and strengthened during our whole lives, until
they have become almost as strong as instincts. If with the temptation
still before us we do not yield, it is because either the social
instinct or some custom is at the moment predominant, or because we
have learnt that it will appear to us hereafter the stronger, when
compared with the weakened impression of the temptation, and we realise
that its violation would cause us suffering. Looking to future
generations, there is no cause to fear that the social instincts will
grow weaker, and we may expect that virtuous habits will grow stronger,
becoming perhaps fixed by inheritance. In this case the struggle
between our higher and lower impulses will be less severe, and virtue
will be triumphant.

A SUMMARY OF THE LAST TWO CHAPTERS.

There can be no doubt that the difference between the mind of the
lowest man and that of the highest animal is immense. An
anthropomorphous ape, if he could take a dispassionate view of his own
case, would admit that though he could form an artful plan to plunder a
garden—though he could use stones for fighting or for breaking open
nuts, yet that the thought of fashioning a stone into a tool was quite
beyond his scope. Still less, as he would admit, could he follow out a
train of metaphysical reasoning, or solve a mathematical problem, or
reflect on God, or admire a grand natural scene. Some apes, however,
would probably declare that they could and did admire the beauty of the
coloured skin and fur of their partners in marriage. They would admit,
that though they could make other apes understand by cries some of
their perceptions and simpler wants, the notion of expressing definite
ideas by definite sounds had never crossed their minds. They might
insist that they were ready to aid their fellow-apes of the same troop
in many ways, to risk their lives for them, and to take charge of their
orphans; but they would be forced to acknowledge that disinterested
love for all living creatures, the most noble attribute of man, was
quite beyond their comprehension.

Nevertheless the difference in mind between man and the higher animals,
great as it is, certainly is one of degree and not of kind. We have
seen that the senses and intuitions, the various emotions and
faculties, such as love, memory, attention, curiosity, imitation,
reason, etc., of which man boasts, may be found in an incipient, or
even sometimes in a well-developed condition, in the lower animals.
They are also capable of some inherited improvement, as we see in the
domestic dog compared with the wolf or jackal. If it could be proved
that certain high mental powers, such as the formation of general
concepts, self-consciousness, etc., were absolutely peculiar to man,
which seems extremely doubtful, it is not improbable that these
qualities are merely the incidental results of other highly-advanced
intellectual faculties; and these again mainly the result of the
continued use of a perfect language. At what age does the new-born
infant possess the power of abstraction, or become self-conscious, and
reflect on its own existence? We cannot answer; nor can we answer in
regard to the ascending organic scale. The half-art, half-instinct of
language still bears the stamp of its gradual evolution. The ennobling
belief in God is not universal with man; and the belief in spiritual
agencies naturally follows from other mental powers. The moral sense
perhaps affords the best and highest distinction between man and the
lower animals; but I need say nothing on this head, as I have so lately
endeavoured to shew that the social instincts,—the prime principle of
man’s moral constitution (50. ‘The Thoughts of Marcus Aurelius,’ etc.,
p. 139.)—with the aid of active intellectual powers and the effects of
habit, naturally lead to the golden rule, “As ye would that men should
do to you, do ye to them likewise;” and this lies at the foundation of
morality.

In the next chapter I shall make some few remarks on the probable steps
and means by which the several mental and moral faculties of man have
been gradually evolved. That such evolution is at least possible, ought
not to be denied, for we daily see these faculties developing in every
infant; and we may trace a perfect gradation from the mind of an utter
idiot, lower than that of an animal low in the scale, to the mind of a
Newton.




CHAPTER V.
ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FACULTIES DURING
PRIMEVAL AND CIVILISED TIMES.


Advancement of the intellectual powers through natural
selection—Importance of imitation—Social and moral faculties—Their
development within the limits of the same tribe—Natural selection as
affecting civilised nations—Evidence that civilised nations were once
barbarous.

The subjects to be discussed in this chapter are of the highest
interest, but are treated by me in an imperfect and fragmentary manner.
Mr. Wallace, in an admirable paper before referred to (1.
Anthropological Review, May 1864, p. clviii.), argues that man, after
he had partially acquired those intellectual and moral faculties which
distinguish him from the lower animals, would have been but little
liable to bodily modifications through natural selection or any other
means. For man is enabled through his mental faculties “to keep with an
unchanged body in harmony with the changing universe.” He has great
power of adapting his habits to new conditions of life. He invents
weapons, tools, and various stratagems to procure food and to defend
himself. When he migrates into a colder climate he uses clothes, builds
sheds, and makes fires; and by the aid of fire cooks food otherwise
indigestible. He aids his fellow-men in many ways, and anticipates
future events. Even at a remote period he practised some division of
labour.

The lower animals, on the other hand, must have their bodily structure
modified in order to survive under greatly changed conditions. They
must be rendered stronger, or acquire more effective teeth or claws,
for defence against new enemies; or they must be reduced in size, so as
to escape detection and danger. When they migrate into a colder
climate, they must become clothed with thicker fur, or have their
constitutions altered. If they fail to be thus modified, they will
cease to exist.

The case, however, is widely different, as Mr. Wallace has with justice
insisted, in relation to the intellectual and moral faculties of man.
These faculties are variable; and we have every reason to believe that
the variations tend to be inherited. Therefore, if they were formerly
of high importance to primeval man and to his ape-like progenitors,
they would have been perfected or advanced through natural selection.
Of the high importance of the intellectual faculties there can be no
doubt, for man mainly owes to them his predominant position in the
world. We can see, that in the rudest state of society, the individuals
who were the most sagacious, who invented and used the best weapons or
traps, and who were best able to defend themselves, would rear the
greatest number of offspring. The tribes, which included the largest
number of men thus endowed, would increase in number and supplant other
tribes. Numbers depend primarily on the means of subsistence, and this
depends partly on the physical nature of the country, but in a much
higher degree on the arts which are there practised. As a tribe
increases and is victorious, it is often still further increased by the
absorption of other tribes. (2. After a time the members or tribes
which are absorbed into another tribe assume, as Sir Henry Maine
remarks (‘Ancient Law,’ 1861, p. 131), that they are the co-descendants
of the same ancestors.) The stature and strength of the men of a tribe
are likewise of some importance for its success, and these depend in
part on the nature and amount of the food which can be obtained. In
Europe the men of the Bronze period were supplanted by a race more
powerful, and, judging from their sword-handles, with larger hands (3.
Morlot, ‘Soc. Vaud. Sc. Nat.’ 1860, p. 294.); but their success was
probably still more due to their superiority in the arts.

All that we know about savages, or may infer from their traditions and
from old monuments, the history of which is quite forgotten by the
present inhabitants, shew that from the remotest times successful
tribes have supplanted other tribes. Relics of extinct or forgotten
tribes have been discovered throughout the civilised regions of the
earth, on the wild plains of America, and on the isolated islands in
the Pacific Ocean. At the present day civilised nations are everywhere
supplanting barbarous nations, excepting where the climate opposes a
deadly barrier; and they succeed mainly, though not exclusively,
through their arts, which are the products of the intellect. It is,
therefore, highly probable that with mankind the intellectual faculties
have been mainly and gradually perfected through natural selection; and
this conclusion is sufficient for our purpose. Undoubtedly it would be
interesting to trace the development of each separate faculty from the
state in which it exists in the lower animals to that in which it
exists in man; but neither my ability nor knowledge permits the
attempt.

It deserves notice that, as soon as the progenitors of man became
social (and this probably occurred at a very early period), the
principle of imitation, and reason, and experience would have
increased, and much modified the intellectual powers in a way, of which
we see only traces in the lower animals. Apes are much given to
imitation, as are the lowest savages; and the simple fact previously
referred to, that after a time no animal can be caught in the same
place by the same sort of trap, shews that animals learn by experience,
and imitate the caution of others. Now, if some one man in a tribe,
more sagacious than the others, invented a new snare or weapon, or
other means of attack or defence, the plainest self-interest, without
the assistance of much reasoning power, would prompt the other members
to imitate him; and all would thus profit. The habitual practice of
each new art must likewise in some slight degree strengthen the
intellect. If the new invention were an important one, the tribe would
increase in number, spread, and supplant other tribes. In a tribe thus
rendered more numerous there would always be a rather greater chance of
the birth of other superior and inventive members. If such men left
children to inherit their mental superiority, the chance of the birth
of still more ingenious members would be somewhat better, and in a very
small tribe decidedly better. Even if they left no children, the tribe
would still include their blood-relations; and it has been ascertained
by agriculturists (4. I have given instances in my Variation of Animals
under Domestication, vol. ii. p. 196.) that by preserving and breeding
from the family of an animal, which when slaughtered was found to be
valuable, the desired character has been obtained.

Turning now to the social and moral faculties. In order that primeval
men, or the ape-like progenitors of man, should become social, they
must have acquired the same instinctive feelings, which impel other
animals to live in a body; and they no doubt exhibited the same general
disposition. They would have felt uneasy when separated from their
comrades, for whom they would have felt some degree of love; they would
have warned each other of danger, and have given mutual aid in attack
or defence. All this implies some degree of sympathy, fidelity, and
courage. Such social qualities, the paramount importance of which to
the lower animals is disputed by no one, were no doubt acquired by the
progenitors of man in a similar manner, namely, through natural
selection, aided by inherited habit. When two tribes of primeval man,
living in the same country, came into competition, if (other
circumstances being equal) the one tribe included a great number of
courageous, sympathetic and faithful members, who were always ready to
warn each other of danger, to aid and defend each other, this tribe
would succeed better and conquer the other. Let it be borne in mind how
all-important in the never-ceasing wars of savages, fidelity and
courage must be. The advantage which disciplined soldiers have over
undisciplined hordes follows chiefly from the confidence which each man
feels in his comrades. Obedience, as Mr. Bagehot has well shewn (5. See
a remarkable series of articles on ‘Physics and Politics,’ in the
‘Fortnightly Review,’ Nov. 1867; April 1, 1868; July 1, 1869, since
separately published.), is of the highest value, for any form of
government is better than none. Selfish and contentious people will not
cohere, and without coherence nothing can be effected. A tribe rich in
the above qualities would spread and be victorious over other tribes:
but in the course of time it would, judging from all past history, be
in its turn overcome by some other tribe still more highly endowed.
Thus the social and moral qualities would tend slowly to advance and be
diffused throughout the world.

But it may be asked, how within the limits of the same tribe did a
large number of members first become endowed with these social and
moral qualities, and how was the standard of excellence raised? It is
extremely doubtful whether the offspring of the more sympathetic and
benevolent parents, or of those who were the most faithful to their
comrades, would be reared in greater numbers than the children of
selfish and treacherous parents belonging to the same tribe. He who was
ready to sacrifice his life, as many a savage has been, rather than
betray his comrades, would often leave no offspring to inherit his
noble nature. The bravest men, who were always willing to come to the
front in war, and who freely risked their lives for others, would on an
average perish in larger numbers than other men. Therefore, it hardly
seems probable, that the number of men gifted with such virtues, or
that the standard of their excellence, could be increased through
natural selection, that is, by the survival of the fittest; for we are
not here speaking of one tribe being victorious over another.

Although the circumstances, leading to an increase in the number of
those thus endowed within the same tribe, are too complex to be clearly
followed out, we can trace some of the probable steps. In the first
place, as the reasoning powers and foresight of the members became
improved, each man would soon learn that if he aided his fellow-men, he
would commonly receive aid in return. From this low motive he might
acquire the habit of aiding his fellows; and the habit of performing
benevolent actions certainly strengthens the feeling of sympathy which
gives the first impulse to benevolent actions. Habits, moreover,
followed during many generations probably tend to be inherited.

But another and much more powerful stimulus to the development of the
social virtues, is afforded by the praise and the blame of our
fellow-men. To the instinct of sympathy, as we have already seen, it is
primarily due, that we habitually bestow both praise and blame on
others, whilst we love the former and dread the latter when applied to
ourselves; and this instinct no doubt was originally acquired, like all
the other social instincts, through natural selection. At how early a
period the progenitors of man in the course of their development,
became capable of feeling and being impelled by, the praise or blame of
their fellow-creatures, we cannot of course say. But it appears that
even dogs appreciate encouragement, praise, and blame. The rudest
savages feel the sentiment of glory, as they clearly shew by preserving
the trophies of their prowess, by their habit of excessive boasting,
and even by the extreme care which they take of their personal
appearance and decorations; for unless they regarded the opinion of
their comrades, such habits would be senseless.

They certainly feel shame at the breach of some of their lesser rules,
and apparently remorse, as shewn by the case of the Australian who grew
thin and could not rest from having delayed to murder some other woman,
so as to propitiate his dead wife’s spirit. Though I have not met with
any other recorded case, it is scarcely credible that a savage, who
will sacrifice his life rather than betray his tribe, or one who will
deliver himself up as a prisoner rather than break his parole (6. Mr.
Wallace gives cases in his ‘Contributions to the Theory of Natural
Selection,’ 1870, p. 354.), would not feel remorse in his inmost soul,
if he had failed in a duty, which he held sacred.

We may therefore conclude that primeval man, at a very remote period,
was influenced by the praise and blame of his fellows. It is obvious,
that the members of the same tribe would approve of conduct which
appeared to them to be for the general good, and would reprobate that
which appeared evil. To do good unto others—to do unto others as ye
would they should do unto you—is the foundation-stone of morality. It
is, therefore, hardly possible to exaggerate the importance during rude
times of the love of praise and the dread of blame. A man who was not
impelled by any deep, instinctive feeling, to sacrifice his life for
the good of others, yet was roused to such actions by a sense of glory,
would by his example excite the same wish for glory in other men, and
would strengthen by exercise the noble feeling of admiration. He might
thus do far more good to his tribe than by begetting offspring with a
tendency to inherit his own high character.

With increased experience and reason, man perceives the more remote
consequences of his actions, and the self-regarding virtues, such as
temperance, chastity, etc., which during early times are, as we have
before seen, utterly disregarded, come to be highly esteemed or even
held sacred. I need not, however, repeat what I have said on this head
in the fourth chapter. Ultimately our moral sense or conscience becomes
a highly complex sentiment—originating in the social instincts, largely
guided by the approbation of our fellow-men, ruled by reason,
self-interest, and in later times by deep religious feelings, and
confirmed by instruction and habit.

It must not be forgotten that although a high standard of morality
gives but a slight or no advantage to each individual man and his
children over the other men of the same tribe, yet that an increase in
the number of well-endowed men and an advancement in the standard of
morality will certainly give an immense advantage to one tribe over
another. A tribe including many members who, from possessing in a high
degree the spirit of patriotism, fidelity, obedience, courage, and
sympathy, were always ready to aid one another, and to sacrifice
themselves for the common good, would be victorious over most other
tribes; and this would be natural selection. At all times throughout
the world tribes have supplanted other tribes; and as morality is one
important element in their success, the standard of morality and the
number of well-endowed men will thus everywhere tend to rise and
increase.

It is, however, very difficult to form any judgment why one particular
tribe and not another has been successful and has risen in the scale of
civilisation. Many savages are in the same condition as when first
discovered several centuries ago. As Mr. Bagehot has remarked, we are
apt to look at progress as normal in human society; but history refutes
this. The ancients did not even entertain the idea, nor do the Oriental
nations at the present day. According to another high authority, Sir
Henry Maine (7. ‘Ancient Law,’ 1861, p. 22. For Mr. Bagehot’s remarks,
‘Fortnightly Review,’ April 1, 1868, p. 452.), “the greatest part of
mankind has never shewn a particle of desire that its civil
institutions should be improved.” Progress seems to depend on many
concurrent favourable conditions, far too complex to be followed out.
But it has often been remarked, that a cool climate, from leading to
industry and to the various arts, has been highly favourable thereto.
The Esquimaux, pressed by hard necessity, have succeeded in many
ingenious inventions, but their climate has been too severe for
continued progress. Nomadic habits, whether over wide plains, or
through the dense forests of the tropics, or along the shores of the
sea, have in every case been highly detrimental. Whilst observing the
barbarous inhabitants of Tierra del Fuego, it struck me that the
possession of some property, a fixed abode, and the union of many
families under a chief, were the indispensable requisites for
civilisation. Such habits almost necessitate the cultivation of the
ground; and the first steps in cultivation would probably result, as I
have elsewhere shewn (8. ‘The Variation of Animals and Plants under
Domestication,’ vol. i. p. 309.), from some such accident as the seeds
of a fruit-tree falling on a heap of refuse, and producing an unusually
fine variety. The problem, however, of the first advance of savages
towards civilisation is at present much too difficult to be solved.

NATURAL SELECTION AS AFFECTING CIVILISED NATIONS.

I have hitherto only considered the advancement of man from a
semi-human condition to that of the modern savage. But some remarks on
the action of natural selection on civilised nations may be worth
adding. This subject has been ably discussed by Mr. W.R. Greg (9.
‘Fraser’s Magazine,’ Sept. 1868, p. 353. This article seems to have
struck many persons, and has given rise to two remarkable essays and a
rejoinder in the ‘Spectator,’ Oct. 3rd and 17th, 1868. It has also been
discussed in the ‘Quarterly Journal of Science,’ 1869, p. 152, and by
Mr. Lawson Tait in the ‘Dublin Quarterly Journal of Medical Science,’
Feb. 1869, and by Mr. E. Ray Lankester in his ‘Comparative Longevity,’
1870, p. 128. Similar views appeared previously in the ‘Australasian,’
July 13, 1867. I have borrowed ideas from several of these writers.),
and previously by Mr. Wallace and Mr. Galton. (10. For Mr. Wallace, see
‘Anthropological Review,’ as before cited. Mr. Galton in ‘Macmillan’s
Magazine,’ Aug. 1865, p. 318; also his great work, ‘Hereditary Genius,’
1870.) Most of my remarks are taken from these three authors. With
savages, the weak in body or mind are soon eliminated; and those that
survive commonly exhibit a vigorous state of health. We civilised men,
on the other hand, do our utmost to check the process of elimination;
we build asylums for the imbecile, the maimed, and the sick; we
institute poor-laws; and our medical men exert their utmost skill to
save the life of every one to the last moment. There is reason to
believe that vaccination has preserved thousands, who from a weak
constitution would formerly have succumbed to small-pox. Thus the weak
members of civilised societies propagate their kind. No one who has
attended to the breeding of domestic animals will doubt that this must
be highly injurious to the race of man. It is surprising how soon a
want of care, or care wrongly directed, leads to the degeneration of a
domestic race; but excepting in the case of man himself, hardly any one
is so ignorant as to allow his worst animals to breed.

The aid which we feel impelled to give to the helpless is mainly an
incidental result of the instinct of sympathy, which was originally
acquired as part of the social instincts, but subsequently rendered, in
the manner previously indicated, more tender and more widely diffused.
Nor could we check our sympathy, even at the urging of hard reason,
without deterioration in the noblest part of our nature. The surgeon
may harden himself whilst performing an operation, for he knows that he
is acting for the good of his patient; but if we were intentionally to
neglect the weak and helpless, it could only be for a contingent
benefit, with an overwhelming present evil. We must therefore bear the
undoubtedly bad effects of the weak surviving and propagating their
kind; but there appears to be at least one check in steady action,
namely that the weaker and inferior members of society do not marry so
freely as the sound; and this check might be indefinitely increased by
the weak in body or mind refraining from marriage, though this is more
to be hoped for than expected.

In every country in which a large standing army is kept up, the finest
young men are taken by the conscription or are enlisted. They are thus
exposed to early death during war, are often tempted into vice, and are
prevented from marrying during the prime of life. On the other hand the
shorter and feebler men, with poor constitutions, are left at home, and
consequently have a much better chance of marrying and propagating
their kind. (11. Prof. H. Fick (‘Einfluss der Naturwissenschaft auf das
Recht,’ June 1872) has some good remarks on this head, and on other
such points.)

Man accumulates property and bequeaths it to his children, so that the
children of the rich have an advantage over the poor in the race for
success, independently of bodily or mental superiority. On the other
hand, the children of parents who are short-lived, and are therefore on
an average deficient in health and vigour, come into their property
sooner than other children, and will be likely to marry earlier, and
leave a larger number of offspring to inherit their inferior
constitutions. But the inheritance of property by itself is very far
from an evil; for without the accumulation of capital the arts could
not progress; and it is chiefly through their power that the civilised
races have extended, and are now everywhere extending their range, so
as to take the place of the lower races. Nor does the moderate
accumulation of wealth interfere with the process of selection. When a
poor man becomes moderately rich, his children enter trades or
professions in which there is struggle enough, so that the able in body
and mind succeed best. The presence of a body of well-instructed men,
who have not to labour for their daily bread, is important to a degree
which cannot be over-estimated; as all high intellectual work is
carried on by them, and on such work, material progress of all kinds
mainly depends, not to mention other and higher advantages. No doubt
wealth when very great tends to convert men into useless drones, but
their number is never large; and some degree of elimination here
occurs, for we daily see rich men, who happen to be fools or
profligate, squandering away their wealth.

Primogeniture with entailed estates is a more direct evil, though it
may formerly have been a great advantage by the creation of a dominant
class, and any government is better than none. Most eldest sons, though
they may be weak in body or mind, marry, whilst the younger sons,
however superior in these respects, do not so generally marry. Nor can
worthless eldest sons with entailed estates squander their wealth. But
here, as elsewhere, the relations of civilised life are so complex that
some compensatory checks intervene. The men who are rich through
primogeniture are able to select generation after generation the more
beautiful and charming women; and these must generally be healthy in
body and active in mind. The evil consequences, such as they may be, of
the continued preservation of the same line of descent, without any
selection, are checked by men of rank always wishing to increase their
wealth and power; and this they effect by marrying heiresses. But the
daughters of parents who have produced single children, are themselves,
as Mr. Galton (12. ‘Hereditary Genius,’ 1870, pp. 132-140.) has shewn,
apt to be sterile; and thus noble families are continually cut off in
the direct line, and their wealth flows into some side channel; but
unfortunately this channel is not determined by superiority of any
kind.

Although civilisation thus checks in many ways the action of natural
selection, it apparently favours the better development of the body, by
means of good food and the freedom from occasional hardships. This may
be inferred from civilised men having been found, wherever compared, to
be physically stronger than savages. (13. Quatrefages, ‘Revue des Cours
Scientifiques,’ 1867-68, p. 659.) They appear also to have equal powers
of endurance, as has been proved in many adventurous expeditions. Even
the great luxury of the rich can be but little detrimental; for the
expectation of life of our aristocracy, at all ages and of both sexes,
is very little inferior to that of healthy English lives in the lower
classes. (14. See the fifth and sixth columns, compiled from good
authorities, in the table given in Mr. E.R. Lankester’s ‘Comparative
Longevity,’ 1870, p. 115.)

We will now look to the intellectual faculties. If in each grade of
society the members were divided into two equal bodies, the one
including the intellectually superior and the other the inferior, there
can be little doubt that the former would succeed best in all
occupations, and rear a greater number of children. Even in the lowest
walks of life, skill and ability must be of some advantage; though in
many occupations, owing to the great division of labour, a very small
one. Hence in civilised nations there will be some tendency to an
increase both in the number and in the standard of the intellectually
able. But I do not wish to assert that this tendency may not be more
than counterbalanced in other ways, as by the multiplication of the
reckless and improvident; but even to such as these, ability must be
some advantage.

It has often been objected to views like the foregoing, that the most
eminent men who have ever lived have left no offspring to inherit their
great intellect. Mr. Galton says, “I regret I am unable to solve the
simple question whether, and how far, men and women who are prodigies
of genius are infertile. I have, however, shewn that men of eminence
are by no means so.” (15. ‘Hereditary Genius,’ 1870, p. 330.) Great
lawgivers, the founders of beneficent religions, great philosophers and
discoverers in science, aid the progress of mankind in a far higher
degree by their works than by leaving a numerous progeny. In the case
of corporeal structures, it is the selection of the slightly
better-endowed and the elimination of the slightly less well-endowed
individuals, and not the preservation of strongly-marked and rare
anomalies, that leads to the advancement of a species. (16. ‘Origin of
Species’ (fifth edition, 1869), p. 104.) So it will be with the
intellectual faculties, since the somewhat abler men in each grade of
society succeed rather better than the less able, and consequently
increase in number, if not otherwise prevented. When in any nation the
standard of intellect and the number of intellectual men have
increased, we may expect from the law of the deviation from an average,
that prodigies of genius will, as shewn by Mr. Galton, appear somewhat
more frequently than before.

In regard to the moral qualities, some elimination of the worst
dispositions is always in progress even in the most civilised nations.
Malefactors are executed, or imprisoned for long periods, so that they
cannot freely transmit their bad qualities. Melancholic and insane
persons are confined, or commit suicide. Violent and quarrelsome men
often come to a bloody end. The restless who will not follow any steady
occupation—and this relic of barbarism is a great check to civilisation
(17. ‘Hereditary Genius,’ 1870, p. 347.)—emigrate to newly-settled
countries; where they prove useful pioneers. Intemperance is so highly
destructive, that the expectation of life of the intemperate, at the
age of thirty for instance, is only 13.8 years; whilst for the rural
labourers of England at the same age it is 40.59 years. (18. E. Ray
Lankester, ‘Comparative Longevity,’ 1870, p. 115. The table of the
intemperate is from Neison’s ‘Vital Statistics.’ In regard to
profligacy, see Dr. Farr, ‘Influence of Marriage on Mortality,’ ‘Nat.
Assoc. for the Promotion of Social Science,’ 1858.) Profligate women
bear few children, and profligate men rarely marry; both suffer from
disease. In the breeding of domestic animals, the elimination of those
individuals, though few in number, which are in any marked manner
inferior, is by no means an unimportant element towards success. This
especially holds good with injurious characters which tend to reappear
through reversion, such as blackness in sheep; and with mankind some of
the worst dispositions, which occasionally without any assignable cause
make their appearance in families, may perhaps be reversions to a
savage state, from which we are not removed by very many generations.
This view seems indeed recognised in the common expression that such
men are the black sheep of the family.

With civilised nations, as far as an advanced standard of morality, and
an increased number of fairly good men are concerned, natural selection
apparently effects but little; though the fundamental social instincts
were originally thus gained. But I have already said enough, whilst
treating of the lower races, on the causes which lead to the advance of
morality, namely, the approbation of our fellow-men—the strengthening
of our sympathies by habit—example and imitation—reason—experience, and
even self-interest—instruction during youth, and religious feelings.

A most important obstacle in civilised countries to an increase in the
number of men of a superior class has been strongly insisted on by Mr.
Greg and Mr. Galton (19. ‘Fraser’s Magazine,’ Sept. 1868, p. 353.
‘Macmillan’s Magazine,’ Aug. 1865, p. 318. The Rev. F.W. Farrar
(‘Fraser’s Magazine,’ Aug. 1870, p. 264) takes a different view.),
namely, the fact that the very poor and reckless, who are often
degraded by vice, almost invariably marry early, whilst the careful and
frugal, who are generally otherwise virtuous, marry late in life, so
that they may be able to support themselves and their children in
comfort. Those who marry early produce within a given period not only a
greater number of generations, but, as shewn by Dr. Duncan (20. ‘On the
Laws of the Fertility of Women,’ in ‘Transactions of the Royal
Society,’ Edinburgh, vol. xxiv. p. 287; now published separately under
the title of ‘Fecundity, Fertility, and Sterility,’ 1871. See, also,
Mr. Galton, ‘Hereditary Genius,’ pp. 352-357, for observations to the
above effect.), they produce many more children. The children,
moreover, that are borne by mothers during the prime of life are
heavier and larger, and therefore probably more vigorous, than those
born at other periods. Thus the reckless, degraded, and often vicious
members of society, tend to increase at a quicker rate than the
provident and generally virtuous members. Or as Mr. Greg puts the case:
“The careless, squalid, unaspiring Irishman multiplies like rabbits:
the frugal, foreseeing, self-respecting, ambitious Scot, stern in his
morality, spiritual in his faith, sagacious and disciplined in his
intelligence, passes his best years in struggle and in celibacy,
marries late, and leaves few behind him. Given a land originally
peopled by a thousand Saxons and a thousand Celts—and in a dozen
generations five-sixths of the population would be Celts, but
five-sixths of the property, of the power, of the intellect, would
belong to the one-sixth of Saxons that remained. In the eternal
‘struggle for existence,’ it would be the inferior and LESS favoured
race that had prevailed—and prevailed by virtue not of its good
qualities but of its faults.”

There are, however, some checks to this downward tendency. We have seen
that the intemperate suffer from a high rate of mortality, and the
extremely profligate leave few offspring. The poorest classes crowd
into towns, and it has been proved by Dr. Stark from the statistics of
ten years in Scotland (21. ‘Tenth Annual Report of Births, Deaths,
etc., in Scotland,’ 1867, p. xxix.), that at all ages the death-rate is
higher in towns than in rural districts, “and during the first five
years of life the town death-rate is almost exactly double that of the
rural districts.” As these returns include both the rich and the poor,
no doubt more than twice the number of births would be requisite to
keep up the number of the very poor inhabitants in the towns,
relatively to those in the country. With women, marriage at too early
an age is highly injurious; for it has been found in France that,
“Twice as many wives under twenty die in the year, as died out of the
same number of the unmarried.” The mortality, also, of husbands under
twenty is “excessively high” (22. These quotations are taken from our
highest authority on such questions, namely, Dr. Farr, in his paper ‘On
the Influence of Marriage on the Mortality of the French People,’ read
before the Nat. Assoc. for the Promotion of Social Science, 1858.), but
what the cause of this may be, seems doubtful. Lastly, if the men who
prudently delay marrying until they can bring up their families in
comfort, were to select, as they often do, women in the prime of life,
the rate of increase in the better class would be only slightly
lessened.

It was established from an enormous body of statistics, taken during
1853, that the unmarried men throughout France, between the ages of
twenty and eighty, die in a much larger proportion than the married:
for instance, out of every 1000 unmarried men, between the ages of
twenty and thirty, 11.3 annually died, whilst of the married, only 6.5
died. (23. Dr. Farr, ibid. The quotations given below are extracted
from the same striking paper.) A similar law was proved to hold good,
during the years 1863 and 1864, with the entire population above the
age of twenty in Scotland: for instance, out of every 1000 unmarried
men, between the ages of twenty and thirty, 14.97 annually died, whilst
of the married only 7.24 died, that is less than half. (24. I have
taken the mean of the quinquennial means, given in ‘The Tenth Annual
Report of Births, Deaths, etc., in Scotland,’ 1867. The quotation from
Dr. Stark is copied from an article in the ‘Daily News,’ Oct. 17, 1868,
which Dr. Farr considers very carefully written.) Dr. Stark remarks on
this, “Bachelorhood is more destructive to life than the most
unwholesome trades, or than residence in an unwholesome house or
district where there has never been the most distant attempt at
sanitary improvement.” He considers that the lessened mortality is the
direct result of “marriage, and the more regular domestic habits which
attend that state.” He admits, however, that the intemperate,
profligate, and criminal classes, whose duration of life is low, do not
commonly marry; and it must likewise be admitted that men with a weak
constitution, ill health, or any great infirmity in body or mind, will
often not wish to marry, or will be rejected. Dr. Stark seems to have
come to the conclusion that marriage in itself is a main cause of
prolonged life, from finding that aged married men still have a
considerable advantage in this respect over the unmarried of the same
advanced age; but every one must have known instances of men, who with
weak health during youth did not marry, and yet have survived to old
age, though remaining weak, and therefore always with a lessened chance
of life or of marrying. There is another remarkable circumstance which
seems to support Dr. Stark’s conclusion, namely, that widows and
widowers in France suffer in comparison with the married a very heavy
rate of mortality; but Dr. Farr attributes this to the poverty and evil
habits consequent on the disruption of the family, and to grief. On the
whole we may conclude with Dr. Farr that the lesser mortality of
married than of unmarried men, which seems to be a general law, “is
mainly due to the constant elimination of imperfect types, and to the
skilful selection of the finest individuals out of each successive
generation;” the selection relating only to the marriage state, and
acting on all corporeal, intellectual, and moral qualities. (25. Dr.
Duncan remarks (‘Fecundity, Fertility, etc.’ 1871, p. 334) on this
subject: “At every age the healthy and beautiful go over from the
unmarried side to the married, leaving the unmarried columns crowded
with the sickly and unfortunate.”) We may, therefore, infer that sound
and good men who out of prudence remain for a time unmarried, do not
suffer a high rate of mortality.

If the various checks specified in the two last paragraphs, and perhaps
others as yet unknown, do not prevent the reckless, the vicious and
otherwise inferior members of society from increasing at a quicker rate
than the better class of men, the nation will retrograde, as has too
often occurred in the history of the world. We must remember that
progress is no invariable rule. It is very difficult to say why one
civilised nation rises, becomes more powerful, and spreads more widely,
than another; or why the same nation progresses more quickly at one
time than at another. We can only say that it depends on an increase in
the actual number of the population, on the number of men endowed with
high intellectual and moral faculties, as well as on their standard of
excellence. Corporeal structure appears to have little influence,
except so far as vigour of body leads to vigour of mind.

It has been urged by several writers that as high intellectual powers
are advantageous to a nation, the old Greeks, who stood some grades
higher in intellect than any race that has ever existed (26. See the
ingenious and original argument on this subject by Mr. Galton,
‘Hereditary Genius,’ pp. 340-342.), ought, if the power of natural
selection were real, to have risen still higher in the scale, increased
in number, and stocked the whole of Europe. Here we have the tacit
assumption, so often made with respect to corporeal structures, that
there is some innate tendency towards continued development in mind and
body. But development of all kinds depends on many concurrent
favourable circumstances. Natural selection acts only tentatively.
Individuals and races may have acquired certain indisputable
advantages, and yet have perished from failing in other characters. The
Greeks may have retrograded from a want of coherence between the many
small states, from the small size of their whole country, from the
practice of slavery, or from extreme sensuality; for they did not
succumb until “they were enervated and corrupt to the very core.” (27.
Mr. Greg, ‘Fraser’s Magazine,’ Sept. 1868, p. 357.) The western nations
of Europe, who now so immeasurably surpass their former savage
progenitors, and stand at the summit of civilisation, owe little or
none of their superiority to direct inheritance from the old Greeks,
though they owe much to the written works of that wonderful people.

Who can positively say why the Spanish nation, so dominant at one time,
has been distanced in the race. The awakening of the nations of Europe
from the dark ages is a still more perplexing problem. At that early
period, as Mr. Galton has remarked, almost all the men of a gentle
nature, those given to meditation or culture of the mind, had no refuge
except in the bosom of a Church which demanded celibacy (28.
‘Hereditary Genius,’ 1870, pp. 357-359. The Rev. F.W. Farrar (‘Fraser’s
Magazine,’ Aug. 1870, p. 257) advances arguments on the other side. Sir
C. Lyell had already (‘Principles of Geology,’ vol. ii. 1868, p. 489),
in a striking passage called attention to the evil influence of the
Holy Inquisition in having, through selection, lowered the general
standard of intelligence in Europe.); and this could hardly fail to
have had a deteriorating influence on each successive generation.
During this same period the Holy Inquisition selected with extreme care
the freest and boldest men in order to burn or imprison them. In Spain
alone some of the best men—those who doubted and questioned, and
without doubting there can be no progress—were eliminated during three
centuries at the rate of a thousand a year. The evil which the Catholic
Church has thus effected is incalculable, though no doubt
counterbalanced to a certain, perhaps to a large, extent in other ways;
nevertheless, Europe has progressed at an unparalleled rate.

The remarkable success of the English as colonists, compared to other
European nations, has been ascribed to their “daring and persistent
energy”; a result which is well illustrated by comparing the progress
of the Canadians of English and French extraction; but who can say how
the English gained their energy? There is apparently much truth in the
belief that the wonderful progress of the United States, as well as the
character of the people, are the results of natural selection; for the
more energetic, restless, and courageous men from all parts of Europe
have emigrated during the last ten or twelve generations to that great
country, and have there succeeded best. (29. Mr. Galton, ‘Macmillan’s
Magazine,’ August 1865, p. 325. See also, ‘Nature,’ ‘On Darwinism and
National Life,’ Dec. 1869, p. 184.) Looking to the distant future, I do
not think that the Rev. Mr. Zincke takes an exaggerated view when he
says (30. ‘Last Winter in the United States,’ 1868, p. 29.): “All other
series of events—as that which resulted in the culture of mind in
Greece, and that which resulted in the empire of Rome—only appear to
have purpose and value when viewed in connection with, or rather as
subsidiary to...the great stream of Anglo-Saxon emigration to the
west.” Obscure as is the problem of the advance of civilisation, we can
at least see that a nation which produced during a lengthened period
the greatest number of highly intellectual, energetic, brave,
patriotic, and benevolent men, would generally prevail over less
favoured nations.

Natural selection follows from the struggle for existence; and this
from a rapid rate of increase. It is impossible not to regret bitterly,
but whether wisely is another question, the rate at which man tends to
increase; for this leads in barbarous tribes to infanticide and many
other evils, and in civilised nations to abject poverty, celibacy, and
to the late marriages of the prudent. But as man suffers from the same
physical evils as the lower animals, he has no right to expect an
immunity from the evils consequent on the struggle for existence. Had
he not been subjected during primeval times to natural selection,
assuredly he would never have attained to his present rank. Since we
see in many parts of the world enormous areas of the most fertile land
capable of supporting numerous happy homes, but peopled only by a few
wandering savages, it might be argued that the struggle for existence
had not been sufficiently severe to force man upwards to his highest
standard. Judging from all that we know of man and the lower animals,
there has always been sufficient variability in their intellectual and
moral faculties, for a steady advance through natural selection. No
doubt such advance demands many favourable concurrent circumstances;
but it may well be doubted whether the most favourable would have
sufficed, had not the rate of increase been rapid, and the consequent
struggle for existence extremely severe. It even appears from what we
see, for instance, in parts of S. America, that a people which may be
called civilised, such as the Spanish settlers, is liable to become
indolent and to retrograde, when the conditions of life are very easy.
With highly civilised nations continued progress depends in a
subordinate degree on natural selection; for such nations do not
supplant and exterminate one another as do savage tribes. Nevertheless
the more intelligent members within the same community will succeed
better in the long run than the inferior, and leave a more numerous
progeny, and this is a form of natural selection. The more efficient
causes of progress seem to consist of a good education during youth
whilst the brain is impressible, and of a high standard of excellence,
inculcated by the ablest and best men, embodied in the laws, customs
and traditions of the nation, and enforced by public opinion. It
should, however, be borne in mind, that the enforcement of public
opinion depends on our appreciation of the approbation and
disapprobation of others; and this appreciation is founded on our
sympathy, which it can hardly be doubted was originally developed
through natural selection as one of the most important elements of the
social instincts. (31. I am much indebted to Mr. John Morley for some
good criticisms on this subject: see, also Broca, ‘Les Selections,’
‘Revue d’Anthropologie,’ 1872.)

ON THE EVIDENCE THAT ALL CIVILISED NATIONS WERE ONCE BARBAROUS.

The present subject has been treated in so full and admirable a manner
by Sir J. Lubbock (32. ‘On the Origin of Civilisation,’ ‘Proceedings of
the Ethnological Society,’ Nov. 26, 1867.), Mr. Tylor, Mr. M’Lennan,
and others, that I need here give only the briefest summary of their
results. The arguments recently advanced by the Duke of Argyll (33.
‘Primeval Man,’ 1869.) and formerly by Archbishop Whately, in favour of
the belief that man came into the world as a civilised being, and that
all savages have since undergone degradation, seem to me weak in
comparison with those advanced on the other side. Many nations, no
doubt, have fallen away in civilisation, and some may have lapsed into
utter barbarism, though on this latter head I have met with no
evidence. The Fuegians were probably compelled by other conquering
hordes to settle in their inhospitable country, and they may have
become in consequence somewhat more degraded; but it would be difficult
to prove that they have fallen much below the Botocudos, who inhabit
the finest parts of Brazil.

The evidence that all civilised nations are the descendants of
barbarians, consists, on the one side, of clear traces of their former
low condition in still-existing customs, beliefs, language, etc.; and
on the other side, of proofs that savages are independently able to
raise themselves a few steps in the scale of civilisation, and have
actually thus risen. The evidence on the first head is extremely
curious, but cannot be here given: I refer to such cases as that of the
art of enumeration, which, as Mr. Tylor clearly shews by reference to
the words still used in some places, originated in counting the
fingers, first of one hand and then of the other, and lastly of the
toes. We have traces of this in our own decimal system, and in the
Roman numerals, where, after the V, which is supposed to be an
abbreviated picture of a human hand, we pass on to VI, etc., when the
other hand no doubt was used. So again, “when we speak of three-score
and ten, we are counting by the vigesimal system, each score thus
ideally made, standing for 20—for ‘one man’ as a Mexican or Carib would
put it.” (34. ‘Royal Institution of Great Britain,’ March 15, 1867.
Also, ‘Researches into the Early History of Mankind,’ 1865.) According
to a large and increasing school of philologists, every language bears
the marks of its slow and gradual evolution. So it is with the art of
writing, for letters are rudiments of pictorial representations. It is
hardly possible to read Mr. M’Lennan’s work (35. ‘Primitive Marriage,’
1865. See, likewise, an excellent article, evidently by the same
author, in the ‘North British Review,’ July 1869. Also, Mr. L.H.
Morgan, ‘A Conjectural Solution of the Origin of the Class. System of
Relationship,’ in ‘Proc. American Acad. of Sciences,’ vol. vii. Feb.
1868. Prof. Schaaffhausen (‘Anthropolog. Review,’ Oct. 1869, p. 373)
remarks on “the vestiges of human sacrifices found both in Homer and
the Old Testament.”) and not admit that almost all civilised nations
still retain traces of such rude habits as the forcible capture of
wives. What ancient nation, as the same author asks, can be named that
was originally monogamous? The primitive idea of justice, as shewn by
the law of battle and other customs of which vestiges still remain, was
likewise most rude. Many existing superstitions are the remnants of
former false religious beliefs. The highest form of religion—the grand
idea of God hating sin and loving righteousness—was unknown during
primeval times.

Turning to the other kind of evidence: Sir J. Lubbock has shewn that
some savages have recently improved a little in some of their simpler
arts. From the extremely curious account which he gives of the weapons,
tools, and arts, in use amongst savages in various parts of the world,
it cannot be doubted that these have nearly all been independent
discoveries, excepting perhaps the art of making fire. (36. Sir J.
Lubbock, ‘Prehistoric Times,’ 2nd edit. 1869, chaps. xv. and xvi. et
passim. See also the excellent 9th Chapter in Tylor’s ‘Early History of
Mankind,’ 2nd edit., 1870.) The Australian boomerang is a good instance
of one such independent discovery. The Tahitians when first visited had
advanced in many respects beyond the inhabitants of most of the other
Polynesian islands. There are no just grounds for the belief that the
high culture of the native Peruvians and Mexicans was derived from
abroad (37. Dr. F. Müller has made some good remarks to this effect in
the ‘Reise der Novara: Anthropolog. Theil,’ Abtheil. iii. 1868, s.
127.); many native plants were there cultivated, and a few native
animals domesticated. We should bear in mind that, judging from the
small influence of most missionaries, a wandering crew from some
semi-civilised land, if washed to the shores of America, would not have
produced any marked effect on the natives, unless they had already
become somewhat advanced. Looking to a very remote period in the
history of the world, we find, to use Sir J. Lubbock’s well-known
terms, a paleolithic and neolithic period; and no one will pretend that
the art of grinding rough flint tools was a borrowed one. In all parts
of Europe, as far east as Greece, in Palestine, India, Japan, New
Zealand, and Africa, including Egypt, flint tools have been discovered
in abundance; and of their use the existing inhabitants retain no
tradition. There is also indirect evidence of their former use by the
Chinese and ancient Jews. Hence there can hardly be a doubt that the
inhabitants of these countries, which include nearly the whole
civilised world, were once in a barbarous condition. To believe that
man was aboriginally civilised and then suffered utter degradation in
so many regions, is to take a pitiably low view of human nature. It is
apparently a truer and more cheerful view that progress has been much
more general than retrogression; that man has risen, though by slow and
interrupted steps, from a lowly condition to the highest standard as
yet attained by him in knowledge, morals and religion.




CHAPTER VI.
ON THE AFFINITIES AND GENEALOGY OF MAN.


Position of man in the animal series—The natural system
genealogical—Adaptive characters of slight value—Various small points
of resemblance between man and the Quadrumana—Rank of man in the
natural system—Birthplace and antiquity of man—Absence of fossil
connecting links—Lower stages in the genealogy of man, as inferred,
firstly from his affinities and secondly from his structure—Early
androgynous condition of the Vertebrata—Conclusion.

Even if it be granted that the difference between man and his nearest
allies is as great in corporeal structure as some naturalists maintain,
and although we must grant that the difference between them is immense
in mental power, yet the facts given in the earlier chapters appear to
declare, in the plainest manner, that man is descended from some lower
form, notwithstanding that connecting-links have not hitherto been
discovered.

Man is liable to numerous, slight, and diversified variations, which
are induced by the same general causes, are governed and transmitted in
accordance with the same general laws, as in the lower animals. Man has
multiplied so rapidly, that he has necessarily been exposed to struggle
for existence, and consequently to natural selection. He has given rise
to many races, some of which differ so much from each other, that they
have often been ranked by naturalists as distinct species. His body is
constructed on the same homological plan as that of other mammals. He
passes through the same phases of embryological development. He retains
many rudimentary and useless structures, which no doubt were once
serviceable. Characters occasionally make their re-appearance in him,
which we have reason to believe were possessed by his early
progenitors. If the origin of man had been wholly different from that
of all other animals, these various appearances would be mere empty
deceptions; but such an admission is incredible. These appearances, on
the other hand, are intelligible, at least to a large extent, if man is
the co-descendant with other mammals of some unknown and lower form.

Some naturalists, from being deeply impressed with the mental and
spiritual powers of man, have divided the whole organic world into
three kingdoms, the Human, the Animal, and the Vegetable, thus giving
to man a separate kingdom. (1. Isidore Geoffroy St.-Hilaire gives a
detailed account of the position assigned to man by various naturalists
in their classifications: ‘Hist. Nat. Gen.’ tom. ii. 1859, pp.
170-189.) Spiritual powers cannot be compared or classed by the
naturalist: but he may endeavour to shew, as I have done, that the
mental faculties of man and the lower animals do not differ in kind,
although immensely in degree. A difference in degree, however great,
does not justify us in placing man in a distinct kingdom, as will
perhaps be best illustrated by comparing the mental powers of two
insects, namely, a coccus or scale-insect and an ant, which undoubtedly
belong to the same class. The difference is here greater than, though
of a somewhat different kind from, that between man and the highest
mammal. The female coccus, whilst young, attaches itself by its
proboscis to a plant; sucks the sap, but never moves again; is
fertilised and lays eggs; and this is its whole history. On the other
hand, to describe the habits and mental powers of worker-ants, would
require, as Pierre Huber has shewn, a large volume; I may, however,
briefly specify a few points. Ants certainly communicate information to
each other, and several unite for the same work, or for games of play.
They recognise their fellow-ants after months of absence, and feel
sympathy for each other. They build great edifices, keep them clean,
close the doors in the evening, and post sentries. They make roads as
well as tunnels under rivers, and temporary bridges over them, by
clinging together. They collect food for the community, and when an
object, too large for entrance, is brought to the nest, they enlarge
the door, and afterwards build it up again. They store up seeds, of
which they prevent the germination, and which, if damp, are brought up
to the surface to dry. They keep aphides and other insects as
milch-cows. They go out to battle in regular bands, and freely
sacrifice their lives for the common weal. They emigrate according to a
preconcerted plan. They capture slaves. They move the eggs of their
aphides, as well as their own eggs and cocoons, into warm parts of the
nest, in order that they may be quickly hatched; and endless similar
facts could be given. (2. Some of the most interesting facts ever
published on the habits of ants are given by Mr. Belt, in his
‘Naturalist in Nicaragua,’ 1874. See also Mr. Moggridge’s admirable
work, ‘Harvesting Ants,’ etc., 1873, also ‘L’Instinct chez les
Insectes,’ by M. George Pouchet, ‘Revue des Deux Mondes,’ Feb. 1870, p.
682.) On the whole, the difference in mental power between an ant and a
coccus is immense; yet no one has ever dreamed of placing these insects
in distinct classes, much less in distinct kingdoms. No doubt the
difference is bridged over by other insects; and this is not the case
with man and the higher apes. But we have every reason to believe that
the breaks in the series are simply the results of many forms having
become extinct.

Professor Owen, relying chiefly on the structure of the brain, has
divided the mammalian series into four sub-classes. One of these he
devotes to man; in another he places both the marsupials and the
Monotremata; so that he makes man as distinct from all other mammals as
are these two latter groups conjoined. This view has not been accepted,
as far as I am aware, by any naturalist capable of forming an
independent judgment, and therefore need not here be further
considered.

We can understand why a classification founded on any single character
or organ—even an organ so wonderfully complex and important as the
brain—or on the high development of the mental faculties, is almost
sure to prove unsatisfactory. This principle has indeed been tried with
hymenopterous insects; but when thus classed by their habits or
instincts, the arrangement proved thoroughly artificial. (3. Westwood,
‘Modern Classification of Insects,’ vol. ii. 1840, p. 87.)
Classifications may, of course, be based on any character whatever, as
on size, colour, or the element inhabited; but naturalists have long
felt a profound conviction that there is a natural system. This system,
it is now generally admitted, must be, as far as possible, genealogical
in arrangement,—that is, the co-descendants of the same form must be
kept together in one group, apart from the co-descendants of any other
form; but if the parent-forms are related, so will be their
descendants, and the two groups together will form a larger group. The
amount of difference between the several groups—that is the amount of
modification which each has undergone—is expressed by such terms as
genera, families, orders, and classes. As we have no record of the
lines of descent, the pedigree can be discovered only by observing the
degrees of resemblance between the beings which are to be classed. For
this object numerous points of resemblance are of much more importance
than the amount of similarity or dissimilarity in a few points. If two
languages were found to resemble each other in a multitude of words and
points of construction, they would be universally recognised as having
sprung from a common source, notwithstanding that they differed greatly
in some few words or points of construction. But with organic beings
the points of resemblance must not consist of adaptations to similar
habits of life: two animals may, for instance, have had their whole
frames modified for living in the water, and yet they will not be
brought any nearer to each other in the natural system. Hence we can
see how it is that resemblances in several unimportant structures, in
useless and rudimentary organs, or not now functionally active, or in
an embryological condition, are by far the most serviceable for
classification; for they can hardly be due to adaptations within a late
period; and thus they reveal the old lines of descent or of true
affinity.

We can further see why a great amount of modification in some one
character ought not to lead us to separate widely any two organisms. A
part which already differs much from the same part in other allied
forms has already, according to the theory of evolution, varied much;
consequently it would (as long as the organism remained exposed to the
same exciting conditions) be liable to further variations of the same
kind; and these, if beneficial, would be preserved, and thus be
continually augmented. In many cases the continued development of a
part, for instance, of the beak of a bird, or of the teeth of a mammal,
would not aid the species in gaining its food, or for any other object;
but with man we can see no definite limit to the continued development
of the brain and mental faculties, as far as advantage is concerned.
Therefore in determining the position of man in the natural or
genealogical system, the extreme development of his brain ought not to
outweigh a multitude of resemblances in other less important or quite
unimportant points.

The greater number of naturalists who have taken into consideration the
whole structure of man, including his mental faculties, have followed
Blumenbach and Cuvier, and have placed man in a separate Order, under
the title of the Bimana, and therefore on an equality with the orders
of the Quadrumana, Carnivora, etc. Recently many of our best
naturalists have recurred to the view first propounded by Linnaeus, so
remarkable for his sagacity, and have placed man in the same Order with
the Quadrumana, under the title of the Primates. The justice of this
conclusion will be admitted: for in the first place, we must bear in
mind the comparative insignificance for classification of the great
development of the brain in man, and that the strongly-marked
differences between the skulls of man and the Quadrumana (lately
insisted upon by Bischoff, Aeby, and others) apparently follow from
their differently developed brains. In the second place, we must
remember that nearly all the other and more important differences
between man and the Quadrumana are manifestly adaptive in their nature,
and relate chiefly to the erect position of man; such as the structure
of his hand, foot, and pelvis, the curvature of his spine, and the
position of his head. The family of Seals offers a good illustration of
the small importance of adaptive characters for classification. These
animals differ from all other Carnivora in the form of their bodies and
in the structure of their limbs, far more than does man from the higher
apes; yet in most systems, from that of Cuvier to the most recent one
by Mr. Flower (4. ‘Proceedings Zoological Society,’ 1863, p. 4.), seals
are ranked as a mere family in the Order of the Carnivora. If man had
not been his own classifier, he would never have thought of founding a
separate order for his own reception.

It would be beyond my limits, and quite beyond my knowledge, even to
name the innumerable points of structure in which man agrees with the
other Primates. Our great anatomist and philosopher, Prof. Huxley, has
fully discussed this subject (5. ‘Evidence as to Man’s Place in
Nature,’ 1863, p. 70, et passim.), and concludes that man in all parts
of his organization differs less from the higher apes, than these do
from the lower members of the same group. Consequently there “is no
justification for placing man in a distinct order.”

In an early part of this work I brought forward various facts, shewing
how closely man agrees in constitution with the higher mammals; and
this agreement must depend on our close similarity in minute structure
and chemical composition. I gave, as instances, our liability to the
same diseases, and to the attacks of allied parasites; our tastes in
common for the same stimulants, and the similar effects produced by
them, as well as by various drugs, and other such facts.

As small unimportant points of resemblance between man and the
Quadrumana are not commonly noticed in systematic works, and as, when
numerous, they clearly reveal our relationship, I will specify a few
such points. The relative position of our features is manifestly the
same; and the various emotions are displayed by nearly similar
movements of the muscles and skin, chiefly above the eyebrows and round
the mouth. Some few expressions are, indeed, almost the same, as in the
weeping of certain kinds of monkeys and in the laughing noise made by
others, during which the corners of the mouth are drawn backwards, and
the lower eyelids wrinkled. The external ears are curiously alike. In
man the nose is much more prominent than in most monkeys; but we may
trace the commencement of an aquiline curvature in the nose of the
Hoolock Gibbon; and this in the Semnopithecus nasica is carried to a
ridiculous extreme.

The faces of many monkeys are ornamented with beards, whiskers, or
moustaches. The hair on the head grows to a great length in some
species of Semnopithecus (6. Isidore Geoffroy St.-Hilaire, ‘Hist. Nat.
Gen.’ tom. ii. 1859, p. 217.); and in the Bonnet monkey (Macacus
radiatus) it radiates from a point on the crown, with a parting down
the middle. It is commonly said that the forehead gives to man his
noble and intellectual appearance; but the thick hair on the head of
the Bonnet monkey terminates downwards abruptly, and is succeeded by
hair so short and fine that at a little distance the forehead, with the
exception of the eyebrows, appears quite naked. It has been erroneously
asserted that eyebrows are not present in any monkey. In the species
just named the degree of nakedness of the forehead differs in different
individuals; and Eschricht states (7. ‘Über die Richtung der Haare,’
etc., Müller’s ‘Archiv fur Anat. und Phys.’ 1837, s. 51.) that in our
children the limit between the hairy scalp and the naked forehead is
sometimes not well defined; so that here we seem to have a trifling
case of reversion to a progenitor, in whom the forehead had not as yet
become quite naked.

It is well known that the hair on our arms tends to converge from above
and below to a point at the elbow. This curious arrangement, so unlike
that in most of the lower mammals, is common to the gorilla,
chimpanzee, orang, some species of Hylobates, and even to some few
American monkeys. But in Hylobates agilis the hair on the fore-arm is
directed downwards or towards the wrist in the ordinary manner; and in
H. lar it is nearly erect, with only a very slight forward inclination;
so that in this latter species it is in a transitional state. It can
hardly be doubted that with most mammals the thickness of the hair on
the back and its direction, is adapted to throw off the rain; even the
transverse hairs on the fore-legs of a dog may serve for this end when
he is coiled up asleep. Mr. Wallace, who has carefully studied the
habits of the orang, remarks that the convergence of the hair towards
the elbow on the arms of the orang may be explained as serving to throw
off the rain, for this animal during rainy weather sits with its arms
bent, and with the hands clasped round a branch or over its head.
According to Livingstone, the gorilla also “sits in pelting rain with
his hands over his head.” (8. Quoted by Reade, ‘The African Sketch
Book,’ vol i. 1873, p. 152.) If the above explanation is correct, as
seems probable, the direction of the hair on our own arms offers a
curious record of our former state; for no one supposes that it is now
of any use in throwing off the rain; nor, in our present erect
condition, is it properly directed for this purpose.

It would, however, be rash to trust too much to the principle of
adaptation in regard to the direction of the hair in man or his early
progenitors; for it is impossible to study the figures given by
Eschricht of the arrangement of the hair on the human foetus (this
being the same as in the adult) and not agree with this excellent
observer that other and more complex causes have intervened. The points
of convergence seem to stand in some relation to those points in the
embryo which are last closed in during development. There appears,
also, to exist some relation between the arrangement of the hair on the
limbs, and the course of the medullary arteries. (9. On the hair in
Hylobates, see ‘Natural History of Mammals,’ by C.L. Martin, 1841, p.
415. Also, Isidore Geoffroy on the American monkeys and other kinds,
‘Hist. Nat. Gen.’ vol. ii. 1859, pp. 216, 243. Eschricht, ibid. s. 46,
55, 61. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 619. Wallace,
‘Contributions to the Theory of Natural Selection,’ 1870, p. 344.)

It must not be supposed that the resemblances between man and certain
apes in the above and in many other points—such as in having a naked
forehead, long tresses on the head, etc.,—are all necessarily the
result of unbroken inheritance from a common progenitor, or of
subsequent reversion. Many of these resemblances are more probably due
to analogous variation, which follows, as I have elsewhere attempted to
shew (10. ‘Origin of Species,’ 5th edit. 1869, p.194. ‘The Variation of
Animals and Plants under Domestication,’ vol. ii. 1868, p. 348.), from
co-descended organisms having a similar constitution, and having been
acted on by like causes inducing similar modifications. With respect to
the similar direction of the hair on the fore-arms of man and certain
monkeys, as this character is common to almost all the anthropomorphous
apes, it may probably be attributed to inheritance; but this is not
certain, as some very distinct American monkeys are thus characterised.

Although, as we have now seen, man has no just right to form a separate
Order for his own reception, he may perhaps claim a distinct Sub-order
or Family. Prof. Huxley, in his last work (11. ‘An Introduction to the
Classification of Animals,’ 1869, p. 99.), divides the primates into
three Sub-orders; namely, the Anthropidae with man alone, the Simiadae
including monkeys of all kinds, and the Lemuridae with the diversified
genera of lemurs. As far as differences in certain important points of
structure are concerned, man may no doubt rightly claim the rank of a
Sub-order; and this rank is too low, if we look chiefly to his mental
faculties. Nevertheless, from a genealogical point of view it appears
that this rank is too high, and that man ought to form merely a Family,
or possibly even only a Sub-family. If we imagine three lines of
descent proceeding from a common stock, it is quite conceivable that
two of them might after the lapse of ages be so slightly changed as
still to remain as species of the same genus, whilst the third line
might become so greatly modified as to deserve to rank as a distinct
Sub-family, Family, or even Order. But in this case it is almost
certain that the third line would still retain through inheritance
numerous small points of resemblance with the other two. Here, then,
would occur the difficulty, at present insoluble, how much weight we
ought to assign in our classifications to strongly-marked differences
in some few points,—that is, to the amount of modification undergone;
and how much to close resemblance in numerous unimportant points, as
indicating the lines of descent or genealogy. To attach much weight to
the few but strong differences is the most obvious and perhaps the
safest course, though it appears more correct to pay great attention to
the many small resemblances, as giving a truly natural classification.

In forming a judgment on this head with reference to man, we must
glance at the classification of the Simiadae. This family is divided by
almost all naturalists into the Catarrhine group, or Old World monkeys,
all of which are characterised (as their name expresses) by the
peculiar structure of their nostrils, and by having four premolars in
each jaw; and into the Platyrrhine group or New World monkeys
(including two very distinct sub-groups), all of which are
characterised by differently constructed nostrils, and by having six
premolars in each jaw. Some other small differences might be mentioned.
Now man unquestionably belongs in his dentition, in the structure of
his nostrils, and some other respects, to the Catarrhine or Old World
division; nor does he resemble the Platyrrhines more closely than the
Catarrhines in any characters, excepting in a few of not much
importance and apparently of an adaptive nature. It is therefore
against all probability that some New World species should have
formerly varied and produced a man-like creature, with all the
distinctive characters proper to the Old World division; losing at the
same time all its own distinctive characters. There can, consequently,
hardly be a doubt that man is an off-shoot from the Old World Simian
stem; and that under a genealogical point of view he must be classed
with the Catarrhine division. (12. This is nearly the same
classification as that provisionally adopted by Mr. St. George Mivart,
(‘Transactions, Philosophical Society,” 1867, p. 300), who, after
separating the Lemuridae, divides the remainder of the Primates into
the Hominidae, the Simiadae which answer to the Catarrhines, the
Cebidae, and the Hapalidae,—these two latter groups answering to the
Platyrrhines. Mr. Mivart still abides by the same view; see ‘Nature,’
1871, p. 481.)

The anthropomorphous apes, namely the gorilla, chimpanzee, orang, and
hylobates, are by most naturalists separated from the other Old World
monkeys, as a distinct sub-group. I am aware that Gratiolet, relying on
the structure of the brain, does not admit the existence of this
sub-group, and no doubt it is a broken one. Thus the orang, as Mr. St.
G. Mivart remarks, “is one of the most peculiar and aberrant forms to
be found in the Order.” (13. ‘Transactions, Zoolog. Soc.’ vol. vi.
1867, p. 214.) The remaining non-anthropomorphous Old World monkeys,
are again divided by some naturalists into two or three smaller
sub-groups; the genus Semnopithecus, with its peculiar sacculated
stomach, being the type of one sub-group. But it appears from M.
Gaudry’s wonderful discoveries in Attica, that during the Miocene
period a form existed there, which connected Semnopithecus and Macacus;
and this probably illustrates the manner in which the other and higher
groups were once blended together.

If the anthropomorphous apes be admitted to form a natural sub-group,
then as man agrees with them, not only in all those characters which he
possesses in common with the whole Catarrhine group, but in other
peculiar characters, such as the absence of a tail and of callosities,
and in general appearance, we may infer that some ancient member of the
anthropomorphous sub-group gave birth to man. It is not probable that,
through the law of analogous variation, a member of one of the other
lower sub-groups should have given rise to a man-like creature,
resembling the higher anthropomorphous apes in so many respects. No
doubt man, in comparison with most of his allies, has undergone an
extraordinary amount of modification, chiefly in consequence of the
great development of his brain and his erect position; nevertheless, we
should bear in mind that he “is but one of several exceptional forms of
Primates.” (14. Mr. St. G. Mivart, ‘Transactions of the Philosophical
Society,’ 1867, p. 410.)

Every naturalist, who believes in the principle of evolution, will
grant that the two main divisions of the Simiadae, namely the
Catarrhine and Platyrrhine monkeys, with their sub-groups, have all
proceeded from some one extremely ancient progenitor. The early
descendants of this progenitor, before they had diverged to any
considerable extent from each other, would still have formed a single
natural group; but some of the species or incipient genera would have
already begun to indicate by their diverging characters the future
distinctive marks of the Catarrhine and Platyrrhine divisions. Hence
the members of this supposed ancient group would not have been so
uniform in their dentition, or in the structure of their nostrils, as
are the existing Catarrhine monkeys in one way and the Platyrrhines in
another way, but would have resembled in this respect the allied
Lemuridae, which differ greatly from each other in the form of their
muzzles (15. Messrs. Murie and Mivart on the Lemuroidea, ‘Transactions,
Zoological Society,’ vol. vii, 1869, p. 5.), and to an extraordinary
degree in their dentition.

The Catarrhine and Platyrrhine monkeys agree in a multitude of
characters, as is shewn by their unquestionably belonging to one and
the same Order. The many characters which they possess in common can
hardly have been independently acquired by so many distinct species; so
that these characters must have been inherited. But a naturalist would
undoubtedly have ranked as an ape or a monkey, an ancient form which
possessed many characters common to the Catarrhine and Platyrrhine
monkeys, other characters in an intermediate condition, and some few,
perhaps, distinct from those now found in either group. And as man from
a genealogical point of view belongs to the Catarrhine or Old World
stock, we must conclude, however much the conclusion may revolt our
pride, that our early progenitors would have been properly thus
designated. (16. Haeckel has come to this same conclusion. See ‘Über
die Entstehung des Menschengeschlechts,’ in Virchow’s ‘Sammlung.
gemein. wissen. Vorträge,’ 1868, s. 61. Also his ‘Natürliche
Schöpfungsgeschichte,’ 1868, in which he gives in detail his views on
the genealogy of man.) But we must not fall into the error of supposing
that the early progenitor of the whole Simian stock, including man, was
identical with, or even closely resembled, any existing ape or monkey.

ON THE BIRTHPLACE AND ANTIQUITY OF MAN.

We are naturally led to enquire, where was the birthplace of man at
that stage of descent when our progenitors diverged from the Catarrhine
stock? The fact that they belonged to this stock clearly shews that
they inhabited the Old World; but not Australia nor any oceanic island,
as we may infer from the laws of geographical distribution. In each
great region of the world the living mammals are closely related to the
extinct species of the same region. It is therefore probable that
Africa was formerly inhabited by extinct apes closely allied to the
gorilla and chimpanzee; and as these two species are now man’s nearest
allies, it is somewhat more probable that our early progenitors lived
on the African continent than elsewhere. But it is useless to speculate
on this subject; for two or three anthropomorphous apes, one the
Dryopithecus (17. Dr. C. Forsyth Major, ‘Sur les Singes fossiles
trouvés en Italie:’ ‘Soc. Ital. des Sc. Nat.’ tom. xv. 1872.) of
Lartet, nearly as large as a man, and closely allied to Hylobates,
existed in Europe during the Miocene age; and since so remote a period
the earth has certainly undergone many great revolutions, and there has
been ample time for migration on the largest scale.

At the period and place, whenever and wherever it was, when man first
lost his hairy covering, he probably inhabited a hot country; a
circumstance favourable for the frugiferous diet on which, judging from
analogy, he subsisted. We are far from knowing how long ago it was when
man first diverged from the Catarrhine stock; but it may have occurred
at an epoch as remote as the Eocene period; for that the higher apes
had diverged from the lower apes as early as the Upper Miocene period
is shewn by the existence of the Dryopithecus. We are also quite
ignorant at how rapid a rate organisms, whether high or low in the
scale, may be modified under favourable circumstances; we know,
however, that some have retained the same form during an enormous lapse
of time. From what we see going on under domestication, we learn that
some of the co-descendants of the same species may be not at all, some
a little, and some greatly changed, all within the same period. Thus it
may have been with man, who has undergone a great amount of
modification in certain characters in comparison with the higher apes.

The great break in the organic chain between man and his nearest
allies, which cannot be bridged over by any extinct or living species,
has often been advanced as a grave objection to the belief that man is
descended from some lower form; but this objection will not appear of
much weight to those who, from general reasons, believe in the general
principle of evolution. Breaks often occur in all parts of the series,
some being wide, sharp and defined, others less so in various degrees;
as between the orang and its nearest allies—between the Tarsius and the
other Lemuridae—between the elephant, and in a more striking manner
between the Ornithorhynchus or Echidna, and all other mammals. But
these breaks depend merely on the number of related forms which have
become extinct. At some future period, not very distant as measured by
centuries, the civilised races of man will almost certainly
exterminate, and replace, the savage races throughout the world. At the
same time the anthropomorphous apes, as Professor Schaaffhausen has
remarked (18. ‘Anthropological Review,’ April 1867, p. 236.), will no
doubt be exterminated. The break between man and his nearest allies
will then be wider, for it will intervene between man in a more
civilised state, as we may hope, even than the Caucasian, and some ape
as low as a baboon, instead of as now between the negro or Australian
and the gorilla.

With respect to the absence of fossil remains, serving to connect man
with his ape-like progenitors, no one will lay much stress on this fact
who reads Sir C. Lyell’s discussion (19. ‘Elements of Geology,’ 1865,
pp. 583-585. ‘Antiquity of Man,’ 1863, p. 145.), where he shews that in
all the vertebrate classes the discovery of fossil remains has been a
very slow and fortuitous process. Nor should it be forgotten that those
regions which are the most likely to afford remains connecting man with
some extinct ape-like creature, have not as yet been searched by
geologists.

LOWER STAGES IN THE GENEALOGY OF MAN.

We have seen that man appears to have diverged from the Catarrhine or
Old World division of the Simiadae, after these had diverged from the
New World division. We will now endeavour to follow the remote traces
of his genealogy, trusting principally to the mutual affinities between
the various classes and orders, with some slight reference to the
periods, as far as ascertained, of their successive appearance on the
earth. The Lemuridae stand below and near to the Simiadae, and
constitute a very distinct family of the primates, or, according to
Haeckel and others, a distinct Order. This group is diversified and
broken to an extraordinary degree, and includes many aberrant forms. It
has, therefore, probably suffered much extinction. Most of the remnants
survive on islands, such as Madagascar and the Malayan archipelago,
where they have not been exposed to so severe a competition as they
would have been on well-stocked continents. This group likewise
presents many gradations, leading, as Huxley remarks (20. ‘Man’s Place
in Nature,’ p. 105.), “insensibly from the crown and summit of the
animal creation down to creatures from which there is but a step, as it
seems, to the lowest, smallest, and least intelligent of the placental
mammalia.” From these various considerations it is probable that the
Simiadae were originally developed from the progenitors of the existing
Lemuridae; and these in their turn from forms standing very low in the
mammalian series.

The Marsupials stand in many important characters below the placental
mammals. They appeared at an earlier geological period, and their range
was formerly much more extensive than at present. Hence the Placentata
are generally supposed to have been derived from the Implacentata or
Marsupials; not, however, from forms closely resembling the existing
Marsupials, but from their early progenitors. The Monotremata are
plainly allied to the Marsupials, forming a third and still lower
division in the great mammalian series. They are represented at the
present day solely by the Ornithorhynchus and Echidna; and these two
forms may be safely considered as relics of a much larger group,
representatives of which have been preserved in Australia through some
favourable concurrence of circumstances. The Monotremata are eminently
interesting, as leading in several important points of structure
towards the class of reptiles.

In attempting to trace the genealogy of the Mammalia, and therefore of
man, lower down in the series, we become involved in greater and
greater obscurity; but as a most capable judge, Mr. Parker, has
remarked, we have good reason to believe, that no true bird or reptile
intervenes in the direct line of descent. He who wishes to see what
ingenuity and knowledge can effect, may consult Prof. Haeckel’s works.
(21. Elaborate tables are given in his ‘Generelle Morphologie’ (B. ii.
s. cliii. and s. 425); and with more especial reference to man in his
‘Natürliche Schöpfungsgeschichte,’ 1868. Prof. Huxley, in reviewing
this latter work (‘The Academy,’ 1869, p. 42) says, that he considers
the phylum or lines of descent of the Vertebrata to be admirably
discussed by Haeckel, although he differs on some points. He expresses,
also, his high estimate of the general tenor and spirit of the whole
work.) I will content myself with a few general remarks. Every
evolutionist will admit that the five great vertebrate classes, namely,
mammals, birds, reptiles, amphibians, and fishes, are descended from
some one prototype; for they have much in common, especially during
their embryonic state. As the class of fishes is the most lowly
organised, and appeared before the others, we may conclude that all the
members of the vertebrate kingdom are derived from some fishlike
animal. The belief that animals so distinct as a monkey, an elephant, a
humming-bird, a snake, a frog, and a fish, etc., could all have sprung
from the same parents, will appear monstrous to those who have not
attended to the recent progress of natural history. For this belief
implies the former existence of links binding closely together all
these forms, now so utterly unlike.

Nevertheless, it is certain that groups of animals have existed, or do
now exist, which serve to connect several of the great vertebrate
classes more or less closely. We have seen that the Ornithorhynchus
graduates towards reptiles; and Prof. Huxley has discovered, and is
confirmed by Mr. Cope and others, that the Dinosaurians are in many
important characters intermediate between certain reptiles and certain
birds—the birds referred to being the ostrich-tribe (itself evidently a
widely-diffused remnant of a larger group) and the Archeopteryx, that
strange Secondary bird, with a long lizard-like tail. Again, according
to Prof. Owen (22. ‘Palaeontology’ 1860, p. 199.), the
Ichthyosaurians—great sea-lizards furnished with paddles—present many
affinities with fishes, or rather, according to Huxley, with
amphibians; a class which, including in its highest division frogs and
toads, is plainly allied to the Ganoid fishes. These latter fishes
swarmed during the earlier geological periods, and were constructed on
what is called a generalised type, that is, they presented diversified
affinities with other groups of organisms. The Lepidosiren is also so
closely allied to amphibians and fishes, that naturalists long disputed
in which of these two classes to rank it; it, and also some few Ganoid
fishes, have been preserved from utter extinction by inhabiting rivers,
which are harbours of refuge, and are related to the great waters of
the ocean in the same way that islands are to continents.

Lastly, one single member of the immense and diversified class of
fishes, namely, the lancelet or amphioxus, is so different from all
other fishes, that Haeckel maintains that it ought to form a distinct
class in the vertebrate kingdom. This fish is remarkable for its
negative characters; it can hardly be said to possess a brain,
vertebral column, or heart, etc.; so that it was classed by the older
naturalists amongst the worms. Many years ago Prof. Goodsir perceived
that the lancelet presented some affinities with the Ascidians, which
are invertebrate, hermaphrodite, marine creatures permanently attached
to a support. They hardly appear like animals, and consist of a simple,
tough, leathery sack, with two small projecting orifices. They belong
to the Mulluscoida of Huxley—a lower division of the great kingdom of
the Mollusca; but they have recently been placed by some naturalists
amongst the Vermes or worms. Their larvae somewhat resemble tadpoles in
shape (23. At the Falkland Islands I had the satisfaction of seeing, in
April, 1833, and therefore some years before any other naturalist, the
locomotive larvae of a compound Ascidian, closely allied to Synoicum,
but apparently generically distinct from it. The tail was about five
times as long as the oblong head, and terminated in a very fine
filament. It was, as sketched by me under a simple microscope, plainly
divided by transverse opaque partitions, which I presume represent the
great cells figured by Kovalevsky. At an early stage of development the
tail was closely coiled round the head of the larva.), and have the
power of swimming freely about. Mr. Kovalevsky (24. ‘Memoires de
l’Acad. des Sciences de St. Petersbourg,’ tom. x. No. 15, 1866.) has
lately observed that the larvae of Ascidians are related to the
Vertebrata, in their manner of development, in the relative position of
the nervous system, and in possessing a structure closely like the
chorda dorsalis of vertebrate animals; and in this he has been since
confirmed by Prof. Kupffer. M. Kovalevsky writes to me from Naples,
that he has now carried these observations yet further, and should his
results be well established, the whole will form a discovery of the
very greatest value. Thus, if we may rely on embryology, ever the
safest guide in classification, it seems that we have at last gained a
clue to the source whence the Vertebrata were derived. (25. But I am
bound to add that some competent judges dispute this conclusion; for
instance, M. Giard, in a series of papers in the ‘Archives de Zoologie
Experimentale,’ for 1872. Nevertheless, this naturalist remarks, p.
281, “L’organisation de la larve ascidienne en dehors de toute
hypothèse et de toute théorie, nous montre comment la nature peut
produire la disposition fondamentale du type vertébré (l’existence
d’une corde dorsale) chez un invertébré par la seule condition vitale
de l’adaptation, et cette simple possibilité du passage supprime
l’abîme entre les deux sous-règnes, encore bien qu’en ignore par où le
passage s’est fait en realité.”) We should then be justified in
believing that at an extremely remote period a group of animals
existed, resembling in many respects the larvae of our present
Ascidians, which diverged into two great branches—the one retrograding
in development and producing the present class of Ascidians, the other
rising to the crown and summit of the animal kingdom by giving birth to
the Vertebrata.

We have thus far endeavoured rudely to trace the genealogy of the
Vertebrata by the aid of their mutual affinities. We will now look to
man as he exists; and we shall, I think, be able partially to restore
the structure of our early progenitors, during successive periods, but
not in due order of time. This can be effected by means of the
rudiments which man still retains, by the characters which occasionally
make their appearance in him through reversion, and by the aid of the
principles of morphology and embryology. The various facts, to which I
shall here allude, have been given in the previous chapters.

The early progenitors of man must have been once covered with hair,
both sexes having beards; their ears were probably pointed, and capable
of movement; and their bodies were provided with a tail, having the
proper muscles. Their limbs and bodies were also acted on by many
muscles which now only occasionally reappear, but are normally present
in the Quadrumana. At this or some earlier period, the great artery and
nerve of the humerus ran through a supra-condyloid foramen. The
intestine gave forth a much larger diverticulum or caecum than that now
existing. The foot was then prehensile, judging from the condition of
the great toe in the foetus; and our progenitors, no doubt, were
arboreal in their habits, and frequented some warm, forest-clad land.
The males had great canine teeth, which served them as formidable
weapons. At a much earlier period the uterus was double; the excreta
were voided through a cloaca; and the eye was protected by a third
eyelid or nictitating membrane. At a still earlier period the
progenitors of man must have been aquatic in their habits; for
morphology plainly tells us that our lungs consist of a modified
swim-bladder, which once served as a float. The clefts on the neck in
the embryo of man shew where the branchiae once existed. In the lunar
or weekly recurrent periods of some of our functions we apparently
still retain traces of our primordial birthplace, a shore washed by the
tides. At about this same early period the true kidneys were replaced
by the corpora wolffiana. The heart existed as a simple pulsating
vessel; and the chorda dorsalis took the place of a vertebral column.
These early ancestors of man, thus seen in the dim recesses of time,
must have been as simply, or even still more simply organised than the
lancelet or amphioxus.

There is one other point deserving a fuller notice. It has long been
known that in the vertebrate kingdom one sex bears rudiments of various
accessory parts, appertaining to the reproductive system, which
properly belong to the opposite sex; and it has now been ascertained
that at a very early embryonic period both sexes possess true male and
female glands. Hence some remote progenitor of the whole vertebrate
kingdom appears to have been hermaphrodite or androgynous. (26. This is
the conclusion of Prof. Gegenbaur, one of the highest authorities in
comparative anatomy: see ‘Grundzüge der vergleich. Anat.’ 1870, s. 876.
The result has been arrived at chiefly from the study of the Amphibia;
but it appears from the researches of Waldeyer (as quoted in ‘Journal
of Anat. and Phys.’ 1869, p. 161), that the sexual organs of even “the
higher vertebrata are, in their early condition, hermaphrodite.”
Similar views have long been held by some authors, though until
recently without a firm basis.) But here we encounter a singular
difficulty. In the mammalian class the males possess rudiments of a
uterus with the adjacent passage, in their vesiculae prostaticae; they
bear also rudiments of mammae, and some male Marsupials have traces of
a marsupial sack. (27. The male Thylacinus offers the best instance.
Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 771.) Other analogous
facts could be added. Are we, then, to suppose that some extremely
ancient mammal continued androgynous, after it had acquired the chief
distinctions of its class, and therefore after it had diverged from the
lower classes of the vertebrate kingdom? This seems very improbable,
for we have to look to fishes, the lowest of all the classes, to find
any still existent androgynous forms. (28. Hermaphroditism has been
observed in several species of Serranus, as well as in some other
fishes, where it is either normal and symmetrical, or abnormal and
unilateral. Dr. Zouteveen has given me references on this subject, more
especially to a paper by Prof. Halbertsma, in the ‘Transact. of the
Dutch Acad. of Sciences,’ vol. xvi. Dr. Gunther doubts the fact, but it
has now been recorded by too many good observers to be any longer
disputed. Dr. M. Lessona writes to me, that he has verified the
observations made by Cavolini on Serranus. Prof. Ercolani has recently
shewn (‘Accad. delle Scienze,’ Bologna, Dec. 28, 1871) that eels are
androgynous.) That various accessory parts, proper to each sex, are
found in a rudimentary condition in the opposite sex, may be explained
by such organs having been gradually acquired by the one sex, and then
transmitted in a more or less imperfect state to the other. When we
treat of sexual selection, we shall meet with innumerable instances of
this form of transmission,—as in the case of the spurs, plumes, and
brilliant colours, acquired for battle or ornament by male birds, and
inherited by the females in an imperfect or rudimentary condition.

The possession by male mammals of functionally imperfect mammary organs
is, in some respects, especially curious. The Monotremata have the
proper milk-secreting glands with orifices, but no nipples; and as
these animals stand at the very base of the mammalian series, it is
probable that the progenitors of the class also had milk-secreting
glands, but no nipples. This conclusion is supported by what is known
of their manner of development; for Professor Turner informs me, on the
authority of Kolliker and Langer, that in the embryo the mammary glands
can be distinctly traced before the nipples are in the least visible;
and the development of successive parts in the individual generally
represents and accords with the development of successive beings in the
same line of descent. The Marsupials differ from the Monotremata by
possessing nipples; so that probably these organs were first acquired
by the Marsupials, after they had diverged from, and risen above, the
Monotremata, and were then transmitted to the placental mammals. (29.
Prof. Gegenbaur has shewn (‘Jenäische Zeitschrift,’ Bd. vii. p. 212)
that two distinct types of nipples prevail throughout the several
mammalian orders, but that it is quite intelligible how both could have
been derived from the nipples of the Marsupials, and the latter from
those of the Monotremata. See, also, a memoir by Dr. Max Huss, on the
mammary glands, ibid. B. viii. p. 176.) No one will suppose that the
marsupials still remained androgynous, after they had approximately
acquired their present structure. How then are we to account for male
mammals possessing mammae? It is possible that they were first
developed in the females and then transferred to the males, but from
what follows this is hardly probable.

It may be suggested, as another view, that long after the progenitors
of the whole mammalian class had ceased to be androgynous, both sexes
yielded milk, and thus nourished their young; and in the case of the
Marsupials, that both sexes carried their young in marsupial sacks.
This will not appear altogether improbable, if we reflect that the
males of existing syngnathous fishes receive the eggs of the females in
their abdominal pouches, hatch them, and afterwards, as some believe,
nourish the young (30. Mr. Lockwood believes (as quoted in ‘Quart.
Journal of Science,’ April 1868, p. 269), from what he has observed of
the development of Hippocampus, that the walls of the abdominal pouch
of the male in some way afford nourishment. On male fishes hatching the
ova in their mouths, see a very interesting paper by Prof. Wyman, in
‘Proc. Boston Soc. of Nat. Hist.’ Sept. 15, 1857; also Prof. Turner, in
‘Journal of Anatomy and Physiology,’ Nov. 1, 1866, p. 78. Dr. Gunther
has likewise described similar cases.);—that certain other male fishes
hatch the eggs within their mouths or branchial cavities;—that certain
male toads take the chaplets of eggs from the females, and wind them
round their own thighs, keeping them there until the tadpoles are
born;—that certain male birds undertake the whole duty of incubation,
and that male pigeons, as well as the females, feed their nestlings
with a secretion from their crops. But the above suggestion first
occurred to me from mammary glands of male mammals being so much more
perfectly developed than the rudiments of the other accessory
reproductive parts, which are found in the one sex though proper to the
other. The mammary glands and nipples, as they exist in male mammals,
can indeed hardly be called rudimentary; they are merely not fully
developed, and not functionally active. They are sympathetically
affected under the influence of certain diseases, like the same organs
in the female. They often secrete a few drops of milk at birth and at
puberty: this latter fact occurred in the curious case, before referred
to, where a young man possessed two pairs of mammae. In man and some
other male mammals these organs have been known occasionally to become
so well developed during maturity as to yield a fair supply of milk.
Now if we suppose that during a former prolonged period male mammals
aided the females in nursing their offspring (31. Mlle. C. Royer has
suggested a similar view in her ‘Origine de l’homme,’ etc., 1870.), and
that afterwards from some cause (as from the production of a smaller
number of young) the males ceased to give this aid, disuse of the
organs during maturity would lead to their becoming inactive; and from
two well-known principles of inheritance, this state of inactivity
would probably be transmitted to the males at the corresponding age of
maturity. But at an earlier age these organs would be left unaffected,
so that they would be almost equally well developed in the young of
both sexes.

—CONCLUSION—

Von Baer has defined advancement or progress in the organic scale
better than any one else, as resting on the amount of differentiation
and specialisation of the several parts of a being,—when arrived at
maturity, as I should be inclined to add. Now as organisms have become
slowly adapted to diversified lines of life by means of natural
selection, their parts will have become more and more differentiated
and specialised for various functions from the advantage gained by the
division of physiological labour. The same part appears often to have
been modified first for one purpose, and then long afterwards for some
other and quite distinct purpose; and thus all the parts are rendered
more and more complex. But each organism still retains the general type
of structure of the progenitor from which it was aboriginally derived.
In accordance with this view it seems, if we turn to geological
evidence, that organisation on the whole has advanced throughout the
world by slow and interrupted steps. In the great kingdom of the
Vertebrata it has culminated in man. It must not, however, be supposed
that groups of organic beings are always supplanted, and disappear as
soon as they have given birth to other and more perfect groups. The
latter, though victorious over their predecessors, may not have become
better adapted for all places in the economy of nature. Some old forms
appear to have survived from inhabiting protected sites, where they
have not been exposed to very severe competition; and these often aid
us in constructing our genealogies, by giving us a fair idea of former
and lost populations. But we must not fall into the error of looking at
the existing members of any lowly-organised group as perfect
representatives of their ancient predecessors.

The most ancient progenitors in the kingdom of the Vertebrata, at which
we are able to obtain an obscure glance, apparently consisted of a
group of marine animals (32. The inhabitants of the seashore must be
greatly affected by the tides; animals living either about the MEAN
high-water mark, or about the MEAN low-water mark, pass through a
complete cycle of tidal changes in a fortnight. Consequently, their
food supply will undergo marked changes week by week. The vital
functions of such animals, living under these conditions for many
generations, can hardly fail to run their course in regular weekly
periods. Now it is a mysterious fact that in the higher and now
terrestrial Vertebrata, as well as in other classes, many normal and
abnormal processes have one or more whole weeks as their periods; this
would be rendered intelligible if the Vertebrata are descended from an
animal allied to the existing tidal Ascidians. Many instances of such
periodic processes might be given, as the gestation of mammals, the
duration of fevers, etc. The hatching of eggs affords also a good
example, for, according to Mr. Bartlett (‘Land and Water,’ Jan. 7,
1871), the eggs of the pigeon are hatched in two weeks; those of the
fowl in three; those of the duck in four; those of the goose in five;
and those of the ostrich in seven weeks. As far as we can judge, a
recurrent period, if approximately of the right duration for any
process or function, would not, when once gained, be liable to change;
consequently it might be thus transmitted through almost any number of
generations. But if the function changed, the period would have to
change, and would be apt to change almost abruptly by a whole week.
This conclusion, if sound, is highly remarkable; for the period of
gestation in each mammal, and the hatching of each bird’s eggs, and
many other vital processes, thus betray to us the primordial birthplace
of these animals.), resembling the larvae of existing Ascidians. These
animals probably gave rise to a group of fishes, as lowly organised as
the lancelet; and from these the Ganoids, and other fishes like the
Lepidosiren, must have been developed. From such fish a very small
advance would carry us on to the Amphibians. We have seen that birds
and reptiles were once intimately connected together; and the
Monotremata now connect mammals with reptiles in a slight degree. But
no one can at present say by what line of descent the three higher and
related classes, namely, mammals, birds, and reptiles, were derived
from the two lower vertebrate classes, namely, amphibians and fishes.
In the class of mammals the steps are not difficult to conceive which
led from the ancient Monotremata to the ancient Marsupials; and from
these to the early progenitors of the placental mammals. We may thus
ascend to the Lemuridae; and the interval is not very wide from these
to the Simiadae. The Simiadae then branched off into two great stems,
the New World and Old World monkeys; and from the latter, at a remote
period, Man, the wonder and glory of the Universe, proceeded.

Thus we have given to man a pedigree of prodigious length, but not, it
may be said, of noble quality. The world, it has often been remarked,
appears as if it had long been preparing for the advent of man: and
this, in one sense is strictly true, for he owes his birth to a long
line of progenitors. If any single link in this chain had never
existed, man would not have been exactly what he now is. Unless we
wilfully close our eyes, we may, with our present knowledge,
approximately recognise our parentage; nor need we feel ashamed of it.
The most humble organism is something much higher than the inorganic
dust under our feet; and no one with an unbiassed mind can study any
living creature, however humble, without being struck with enthusiasm
at its marvellous structure and properties.




CHAPTER VII.
ON THE RACES OF MAN.


The nature and value of specific characters—Application to the races of
man—Arguments in favour of, and opposed to, ranking the so-called races
of man as distinct species—Sub-species—Monogenists and
polygenists—Convergence of character—Numerous points of resemblance in
body and mind between the most distinct races of man—The state of man
when he first spread over the earth—Each race not descended from a
single pair—The extinction of races—The formation of races—The effects
of crossing—Slight influence of the direct action of the conditions of
life—Slight or no influence of natural selection—Sexual selection.

It is not my intention here to describe the several so-called races of
men; but I am about to enquire what is the value of the differences
between them under a classificatory point of view, and how they have
originated. In determining whether two or more allied forms ought to be
ranked as species or varieties, naturalists are practically guided by
the following considerations; namely, the amount of difference between
them, and whether such differences relate to few or many points of
structure, and whether they are of physiological importance; but more
especially whether they are constant. Constancy of character is what is
chiefly valued and sought for by naturalists. Whenever it can be shewn,
or rendered probable, that the forms in question have remained distinct
for a long period, this becomes an argument of much weight in favour of
treating them as species. Even a slight degree of sterility between any
two forms when first crossed, or in their offspring, is generally
considered as a decisive test of their specific distinctness; and their
continued persistence without blending within the same area, is usually
accepted as sufficient evidence, either of some degree of mutual
sterility, or in the case of animals of some mutual repugnance to
pairing.

Independently of fusion from intercrossing, the complete absence, in a
well-investigated region, of varieties linking together any two
closely-allied forms, is probably the most important of all the
criterions of their specific distinctness; and this is a somewhat
different consideration from mere constancy of character, for two forms
may be highly variable and yet not yield intermediate varieties.
Geographical distribution is often brought into play unconsciously and
sometimes consciously; so that forms living in two widely separated
areas, in which most of the other inhabitants are specifically
distinct, are themselves usually looked at as distinct; but in truth
this affords no aid in distinguishing geographical races from so-called
good or true species.

Now let us apply these generally-admitted principles to the races of
man, viewing him in the same spirit as a naturalist would any other
animal. In regard to the amount of difference between the races, we
must make some allowance for our nice powers of discrimination gained
by the long habit of observing ourselves. In India, as Elphinstone
remarks, although a newly-arrived European cannot at first distinguish
the various native races, yet they soon appear to him extremely
dissimilar (1. ‘History of India,’ 1841, vol. i. p. 323. Father Ripa
makes exactly the same remark with respect to the Chinese.); and the
Hindoo cannot at first perceive any difference between the several
European nations. Even the most distinct races of man are much more
like each other in form than would at first be supposed; certain negro
tribes must be excepted, whilst others, as Dr. Rohlfs writes to me, and
as I have myself seen, have Caucasian features. This general similarity
is well shewn by the French photographs in the Collection
Anthropologique du Museum de Paris of the men belonging to various
races, the greater number of which might pass for Europeans, as many
persons to whom I have shewn them have remarked. Nevertheless, these
men, if seen alive, would undoubtedly appear very distinct, so that we
are clearly much influenced in our judgment by the mere colour of the
skin and hair, by slight differences in the features, and by
expression.

There is, however, no doubt that the various races, when carefully
compared and measured, differ much from each other,—as in the texture
of the hair, the relative proportions of all parts of the body (2. A
vast number of measurements of Whites, Blacks, and Indians, are given
in the ‘Investigations in the Military and Anthropolog. Statistics of
American Soldiers,’ by B.A. Gould, 1869, pp. 298-358; ‘On the capacity
of the lungs,’ p. 471. See also the numerous and valuable tables, by
Dr. Weisbach, from the observations of Dr. Scherzer and Dr. Schwarz, in
the ‘Reise der Novara: Anthropolog. Theil,’ 1867.), the capacity of the
lungs, the form and capacity of the skull, and even in the convolutions
of the brain. (3. See, for instance, Mr. Marshall’s account of the
brain of a Bushwoman, in ‘Philosophical Transactions,’ 1864, p. 519.)
But it would be an endless task to specify the numerous points of
difference. The races differ also in constitution, in acclimatisation
and in liability to certain diseases. Their mental characteristics are
likewise very distinct; chiefly as it would appear in their emotional,
but partly in their intellectual faculties. Every one who has had the
opportunity of comparison, must have been struck with the contrast
between the taciturn, even morose, aborigines of S. America and the
light-hearted, talkative negroes. There is a nearly similar contrast
between the Malays and the Papuans (4. Wallace, ‘The Malay
Archipelago,’ vol. ii. 1869, p. 178.), who live under the same physical
conditions, and are separated from each other only by a narrow space of
sea.

We will first consider the arguments which may be advanced in favour of
classing the races of man as distinct species, and then the arguments
on the other side. If a naturalist, who had never before seen a Negro,
Hottentot, Australian, or Mongolian, were to compare them, he would at
once perceive that they differed in a multitude of characters, some of
slight and some of considerable importance. On enquiry he would find
that they were adapted to live under widely different climates, and
that they differed somewhat in bodily constitution and mental
disposition. If he were then told that hundreds of similar specimens
could be brought from the same countries, he would assuredly declare
that they were as good species as many to which he had been in the
habit of affixing specific names. This conclusion would be greatly
strengthened as soon as he had ascertained that these forms had all
retained the same character for many centuries; and that negroes,
apparently identical with existing negroes, had lived at least 4000
years ago. (5. With respect to the figures in the famous Egyptian caves
of Abou-Simbel, M. Pouchet says (‘The Plurality of the Human Races,’
Eng. translat., 1864, p. 50), that he was far from finding recognisable
representations of the dozen or more nations which some authors believe
that they can recognise. Even some of the most strongly-marked races
cannot be identified with that degree of unanimity which might have
been expected from what has been written on the subject. Thus Messrs.
Nott and Gliddon (‘Types of Mankind,’ p. 148), state that Rameses II.,
or the Great, has features superbly European; whereas Knox, another
firm believer in the specific distinctness of the races of man (‘Races
of Man,’ 1850, p. 201), speaking of young Memnon (the same as Rameses
II., as I am informed by Mr. Birch), insists in the strongest manner
that he is identical in character with the Jews of Antwerp. Again, when
I looked at the statue of Amunoph III., I agreed with two officers of
the establishment, both competent judges, that he had a strongly-marked
negro type of features; but Messrs. Nott and Gliddon (ibid. p. 146,
fig. 53), describe him as a hybrid, but not of “negro intermixture.”)
He would also hear, on the authority of an excellent observer, Dr. Lund
(6. As quoted by Nott and Gliddon, ‘Types of Mankind,’ 1854, p. 439.
They give also corroborative evidence; but C. Vogt thinks that the
subject requires further investigation.), that the human skulls found
in the caves of Brazil, entombed with many extinct mammals, belonged to
the same type as that now prevailing throughout the American Continent.

Our naturalist would then perhaps turn to geographical distribution,
and he would probably declare that those forms must be distinct
species, which differ not only in appearance, but are fitted for hot,
as well as damp or dry countries, and for the Arctic regions. He might
appeal to the fact that no species in the group next to man—namely, the
Quadrumana, can resist a low temperature, or any considerable change of
climate; and that the species which come nearest to man have never been
reared to maturity, even under the temperate climate of Europe. He
would be deeply impressed with the fact, first noticed by Agassiz (7.
‘Diversity of Origin of the Human Races,’ in the ‘Christian Examiner,’
July 1850.), that the different races of man are distributed over the
world in the same zoological provinces, as those inhabited by
undoubtedly distinct species and genera of mammals. This is manifestly
the case with the Australian, Mongolian, and Negro races of man; in a
less well-marked manner with the Hottentots; but plainly with the
Papuans and Malays, who are separated, as Mr. Wallace has shewn, by
nearly the same line which divides the great Malayan and Australian
zoological provinces. The Aborigines of America range throughout the
Continent; and this at first appears opposed to the above rule, for
most of the productions of the Southern and Northern halves differ
widely: yet some few living forms, as the opossum, range from the one
into the other, as did formerly some of the gigantic Edentata. The
Esquimaux, like other Arctic animals, extend round the whole polar
regions. It should be observed that the amount of difference between
the mammals of the several zoological provinces does not correspond
with the degree of separation between the latter; so that it can hardly
be considered as an anomaly that the Negro differs more, and the
American much less from the other races of man, than do the mammals of
the African and American continents from the mammals of the other
provinces. Man, it may be added, does not appear to have aboriginally
inhabited any oceanic island; and in this respect, he resembles the
other members of his class.

In determining whether the supposed varieties of the same kind of
domestic animal should be ranked as such, or as specifically distinct,
that is, whether any of them are descended from distinct wild species,
every naturalist would lay much stress on the fact of their external
parasites being specifically distinct. All the more stress would be
laid on this fact, as it would be an exceptional one; for I am informed
by Mr. Denny that the most different kinds of dogs, fowls, and pigeons,
in England, are infested by the same species of Pediculi or lice. Now
Mr. A. Murray has carefully examined the Pediculi collected in
different countries from the different races of man (8. ‘Transactions
of the Royal Society of Edinburgh,’ vol. xxii, 1861, p. 567.); and he
finds that they differ, not only in colour, but in the structure of
their claws and limbs. In every case in which many specimens were
obtained the differences were constant. The surgeon of a whaling ship
in the Pacific assured me that when the Pediculi, with which some
Sandwich Islanders on board swarmed, strayed on to the bodies of the
English sailors, they died in the course of three or four days. These
Pediculi were darker coloured, and appeared different from those proper
to the natives of Chiloe in South America, of which he gave me
specimens. These, again, appeared larger and much softer than European
lice. Mr. Murray procured four kinds from Africa, namely, from the
Negroes of the Eastern and Western coasts, from the Hottentots and
Kaffirs; two kinds from the natives of Australia; two from North and
two from South America. In these latter cases it may be presumed that
the Pediculi came from natives inhabiting different districts. With
insects slight structural differences, if constant, are generally
esteemed of specific value: and the fact of the races of man being
infested by parasites, which appear to be specifically distinct, might
fairly be urged as an argument that the races themselves ought to be
classed as distinct species.

Our supposed naturalist having proceeded thus far in his investigation,
would next enquire whether the races of men, when crossed, were in any
degree sterile. He might consult the work (9. ‘On the Phenomena of
Hybridity in the Genus Homo,’ Eng. translat., 1864.) of Professor
Broca, a cautious and philosophical observer, and in this he would find
good evidence that some races were quite fertile together, but evidence
of an opposite nature in regard to other races. Thus it has been
asserted that the native women of Australia and Tasmania rarely produce
children to European men; the evidence, however, on this head has now
been shewn to be almost valueless. The half-castes are killed by the
pure blacks: and an account has lately been published of eleven
half-caste youths murdered and burnt at the same time, whose remains
were found by the police. (10. See the interesting letter by Mr. T.A.
Murray, in the ‘Anthropological Review,’ April 1868, p. liii. In this
letter Count Strzelecki’s statement that Australian women who have
borne children to a white man, are afterwards sterile with their own
race, is disproved. M. A. de Quatrefages has also collected (Revue des
Cours Scientifiques, March, 1869, p. 239), much evidence that
Australians and Europeans are not sterile when crossed.) Again, it has
often been said that when mulattoes intermarry, they produce few
children; on the other hand, Dr. Bachman, of Charleston (11. ‘An
Examination of Prof. Agassiz’s Sketch of the Nat. Provinces of the
Animal World,’ Charleston, 1855, p. 44.), positively asserts that he
has known mulatto families which have intermarried for several
generations, and have continued on an average as fertile as either pure
whites or pure blacks. Enquiries formerly made by Sir C. Lyell on this
subject led him, as he informs me, to the same conclusion. (12. Dr.
Rohlfs writes to me that he found the mixed races in the Great Sahara,
derived from Arabs, Berbers, and Negroes of three tribes,
extraordinarily fertile. On the other hand, Mr. Winwood Reade informs
me that the Negroes on the Gold Coast, though admiring white men and
mulattoes, have a maxim that mulattoes should not intermarry, as the
children are few and sickly. This belief, as Mr. Reade remarks,
deserves attention, as white men have visited and resided on the Gold
Coast for four hundred years, so that the natives have had ample time
to gain knowledge through experience.) In the United States the census
for the year 1854 included, according to Dr. Bachman, 405,751
mulattoes; and this number, considering all the circumstances of the
case, seems small; but it may partly be accounted for by the degraded
and anomalous position of the class, and by the profligacy of the
women. A certain amount of absorption of mulattoes into negroes must
always be in progress; and this would lead to an apparent diminution of
the former. The inferior vitality of mulattoes is spoken of in a
trustworthy work (13. ‘Military and Anthropological Statistics of
American Soldiers,’ by B.A. Gould, 1869, p. 319.) as a well-known
phenomenon; and this, although a different consideration from their
lessened fertility, may perhaps be advanced as a proof of the specific
distinctness of the parent races. No doubt both animal and vegetable
hybrids, when produced from extremely distinct species, are liable to
premature death; but the parents of mulattoes cannot be put under the
category of extremely distinct species. The common Mule, so notorious
for long life and vigour, and yet so sterile, shews how little
necessary connection there is in hybrids between lessened fertility and
vitality; other analogous cases could be cited.

Even if it should hereafter be proved that all the races of men were
perfectly fertile together, he who was inclined from other reasons to
rank them as distinct species, might with justice argue that fertility
and sterility are not safe criterions of specific distinctness. We know
that these qualities are easily affected by changed conditions of life,
or by close inter-breeding, and that they are governed by highly
complex laws, for instance, that of the unequal fertility of converse
crosses between the same two species. With forms which must be ranked
as undoubted species, a perfect series exists from those which are
absolutely sterile when crossed, to those which are almost or
completely fertile. The degrees of sterility do not coincide strictly
with the degrees of difference between the parents in external
structure or habits of life. Man in many respects may be compared with
those animals which have long been domesticated, and a large body of
evidence can be advanced in favour of the Pallasian doctrine (14. The
‘Variation of Animals and Plants under Domestication,’ vol. ii. p. 109.
I may here remind the reader that the sterility of species when crossed
is not a specially-acquired quality, but, like the incapacity of
certain trees to be grafted together, is incidental on other acquired
differences. The nature of these differences is unknown, but they
relate more especially to the reproductive system, and much less so to
external structure or to ordinary differences in constitution. One
important element in the sterility of crossed species apparently lies
in one or both having been long habituated to fixed conditions; for we
know that changed conditions have a special influence on the
reproductive system, and we have good reason to believe (as before
remarked) that the fluctuating conditions of domestication tend to
eliminate that sterility which is so general with species, in a natural
state, when crossed. It has elsewhere been shewn by me (ibid. vol. ii.
p. 185, and ‘Origin of Species,’ 5th edit. p. 317), that the sterility
of crossed species has not been acquired through natural selection: we
can see that when two forms have already been rendered very sterile, it
is scarcely possible that their sterility should be augmented by the
preservation or survival of the more and more sterile individuals; for,
as the sterility increases, fewer and fewer offspring will be produced
from which to breed, and at last only single individuals will be
produced at the rarest intervals. But there is even a higher grade of
sterility than this. Both Gartner and Kolreuter have proved that in
genera of plants, including many species, a series can be formed from
species which, when crossed, yield fewer and fewer seeds, to species
which never produce a single seed, but yet are affected by the pollen
of the other species, as shewn by the swelling of the germen. It is
here manifestly impossible to select the more sterile individuals,
which have already ceased to yield seeds; so that the acme of
sterility, when the germen alone is affected, cannot have been gained
through selection. This acme, and no doubt the other grades of
sterility, are the incidental results of certain unknown differences in
the constitution of the reproductive system of the species which are
crossed.), that domestication tends to eliminate the sterility which is
so general a result of the crossing of species in a state of nature.
From these several considerations, it may be justly urged that the
perfect fertility of the intercrossed races of man, if established,
would not absolutely preclude us from ranking them as distinct species.

Independently of fertility, the characters presented by the offspring
from a cross have been thought to indicate whether or not the
parent-forms ought to be ranked as species or varieties; but after
carefully studying the evidence, I have come to the conclusion that no
general rules of this kind can be trusted. The ordinary result of a
cross is the production of a blended or intermediate form; but in
certain cases some of the offspring take closely after one parent-form,
and some after the other. This is especially apt to occur when the
parents differ in characters which first appeared as sudden variations
or monstrosities. (15. ‘The Variation of Animals,’ etc., vol. ii. p.
92.) I refer to this point, because Dr. Rohlfs informs me that he has
frequently seen in Africa the offspring of negroes crossed with members
of other races, either completely black or completely white, or rarely
piebald. On the other hand, it is notorious that in America mulattoes
commonly present an intermediate appearance.

We have now seen that a naturalist might feel himself fully justified
in ranking the races of man as distinct species; for he has found that
they are distinguished by many differences in structure and
constitution, some being of importance. These differences have, also,
remained nearly constant for very long periods of time. Our naturalist
will have been in some degree influenced by the enormous range of man,
which is a great anomaly in the class of mammals, if mankind be viewed
as a single species. He will have been struck with the distribution of
the several so-called races, which accords with that of other
undoubtedly distinct species of mammals. Finally, he might urge that
the mutual fertility of all the races has not as yet been fully proved,
and even if proved would not be an absolute proof of their specific
identity.

On the other side of the question, if our supposed naturalist were to
enquire whether the forms of man keep distinct like ordinary species,
when mingled together in large numbers in the same country, he would
immediately discover that this was by no means the case. In Brazil he
would behold an immense mongrel population of Negroes and Portuguese;
in Chiloe, and other parts of South America, he would behold the whole
population consisting of Indians and Spaniards blended in various
degrees. (16. M. de Quatrefages has given (‘Anthropological Review,’
Jan. 1869, p. 22), an interesting account of the success and energy of
the Paulistas in Brazil, who are a much crossed race of Portuguese and
Indians, with a mixture of the blood of other races.) In many parts of
the same continent he would meet with the most complex crosses between
Negroes, Indians, and Europeans; and judging from the vegetable
kingdom, such triple crosses afford the severest test of the mutual
fertility of the parent forms. In one island of the Pacific he would
find a small population of mingled Polynesian and English blood; and in
the Fiji Archipelago a population of Polynesian and Negritos crossed in
all degrees. Many analogous cases could be added; for instance, in
Africa. Hence the races of man are not sufficiently distinct to inhabit
the same country without fusion; and the absence of fusion affords the
usual and best test of specific distinctness.

Our naturalist would likewise be much disturbed as soon as he perceived
that the distinctive characters of all the races were highly variable.
This fact strikes every one on first beholding the negro slaves in
Brazil, who have been imported from all parts of Africa. The same
remark holds good with the Polynesians, and with many other races. It
may be doubted whether any character can be named which is distinctive
of a race and is constant. Savages, even within the limits of the same
tribe, are not nearly so uniform in character, as has been often
asserted. Hottentot women offer certain peculiarities, more strongly
marked than those occurring in any other race, but these are known not
to be of constant occurrence. In the several American tribes, colour
and hairiness differ considerably; as does colour to a certain degree,
and the shape of the features greatly, in the Negroes of Africa. The
shape of the skull varies much in some races (17. For instance, with
the aborigines of America and Australia, Prof. Huxley says (‘Transact.
Internat. Congress of Prehist. Arch.’ 1868, p. 105), that the skulls of
many South Germans and Swiss are “as short and as broad as those of the
Tartars,” etc.); and so it is with every other character. Now all
naturalists have learnt by dearly bought experience, how rash it is to
attempt to define species by the aid of inconstant characters.

But the most weighty of all the arguments against treating the races of
man as distinct species, is that they graduate into each other,
independently in many cases, as far as we can judge, of their having
intercrossed. Man has been studied more carefully than any other
animal, and yet there is the greatest possible diversity amongst
capable judges whether he should be classed as a single species or
race, or as two (Virey), as three (Jacquinot), as four (Kant), five
(Blumenbach), six (Buffon), seven (Hunter), eight (Agassiz), eleven
(Pickering), fifteen (Bory St. Vincent), sixteen (Desmoulins),
twenty-two (Morton), sixty (Crawfurd), or as sixty-three, according to
Burke. (18. See a good discussion on this subject in Waitz,
‘Introduction to Anthropology,’ Eng. translat., 1863, pp. 198-208, 227.
I have taken some of the above statements from H. Tuttle’s ‘Origin and
Antiquity of Physical Man,’ Boston, 1866, p. 35.) This diversity of
judgment does not prove that the races ought not to be ranked as
species, but it shews that they graduate into each other, and that it
is hardly possible to discover clear distinctive characters between
them.

Every naturalist who has had the misfortune to undertake the
description of a group of highly varying organisms, has encountered
cases (I speak after experience) precisely like that of man; and if of
a cautious disposition, he will end by uniting all the forms which
graduate into each other, under a single species; for he will say to
himself that he has no right to give names to objects which he cannot
define. Cases of this kind occur in the Order which includes man,
namely in certain genera of monkeys; whilst in other genera, as in
Cercopithecus, most of the species can be determined with certainty. In
the American genus Cebus, the various forms are ranked by some
naturalists as species, by others as mere geographical races. Now if
numerous specimens of Cebus were collected from all parts of South
America, and those forms which at present appear to be specifically
distinct, were found to graduate into each other by close steps, they
would usually be ranked as mere varieties or races; and this course has
been followed by most naturalists with respect to the races of man.
Nevertheless, it must be confessed that there are forms, at least in
the vegetable kingdom (19. Prof. Nageli has carefully described several
striking cases in his ‘Botanische Mittheilungen,’ B. ii. 1866, ss.
294-369. Prof. Asa Gray has made analogous remarks on some intermediate
forms in the Compositae of N. America.), which we cannot avoid naming
as species, but which are connected together by numberless gradations,
independently of intercrossing.

Some naturalists have lately employed the term “sub-species” to
designate forms which possess many of the characteristics of true
species, but which hardly deserve so high a rank. Now if we reflect on
the weighty arguments above given, for raising the races of man to the
dignity of species, and the insuperable difficulties on the other side
in defining them, it seems that the term “sub-species” might here be
used with propriety. But from long habit the term “race” will perhaps
always be employed. The choice of terms is only so far important in
that it is desirable to use, as far as possible, the same terms for the
same degrees of difference. Unfortunately this can rarely be done: for
the larger genera generally include closely-allied forms, which can be
distinguished only with much difficulty, whilst the smaller genera
within the same family include forms that are perfectly distinct; yet
all must be ranked equally as species. So again, species within the
same large genus by no means resemble each other to the same degree: on
the contrary, some of them can generally be arranged in little groups
round other species, like satellites round planets. (20. ‘Origin of
Species,’ 5th edit. p. 68.)

The question whether mankind consists of one or several species has of
late years been much discussed by anthropologists, who are divided into
the two schools of monogenists and polygenists. Those who do not admit
the principle of evolution, must look at species as separate creations,
or in some manner as distinct entities; and they must decide what forms
of man they will consider as species by the analogy of the method
commonly pursued in ranking other organic beings as species. But it is
a hopeless endeavour to decide this point, until some definition of the
term “species” is generally accepted; and the definition must not
include an indeterminate element such as an act of creation. We might
as well attempt without any definition to decide whether a certain
number of houses should be called a village, town, or city. We have a
practical illustration of the difficulty in the never-ending doubts
whether many closely-allied mammals, birds, insects, and plants, which
represent each other respectively in North America and Europe, should
be ranked as species or geographical races; and the like holds true of
the productions of many islands situated at some little distance from
the nearest continent.

Those naturalists, on the other hand, who admit the principle of
evolution, and this is now admitted by the majority of rising men, will
feel no doubt that all the races of man are descended from a single
primitive stock; whether or not they may think fit to designate the
races as distinct species, for the sake of expressing their amount of
difference. (21. See Prof. Huxley to this effect in the ‘Fortnightly
Review,’ 1865, p. 275.) With our domestic animals the question whether
the various races have arisen from one or more species is somewhat
different. Although it may be admitted that all the races, as well as
all the natural species within the same genus, have sprung from the
same primitive stock, yet it is a fit subject for discussion, whether
all the domestic races of the dog, for instance, have acquired their
present amount of difference since some one species was first
domesticated by man; or whether they owe some of their characters to
inheritance from distinct species, which had already been
differentiated in a state of nature. With man no such question can
arise, for he cannot be said to have been domesticated at any
particular period.

During an early stage in the divergence of the races of man from a
common stock, the differences between the races and their number must
have been small; consequently as far as their distinguishing characters
are concerned, they then had less claim to rank as distinct species
than the existing so-called races. Nevertheless, so arbitrary is the
term of species, that such early races would perhaps have been ranked
by some naturalists as distinct species, if their differences, although
extremely slight, had been more constant than they are at present, and
had not graduated into each other.

It is however possible, though far from probable, that the early
progenitors of man might formerly have diverged much in character,
until they became more unlike each other than any now existing races;
but that subsequently, as suggested by Vogt (22. ‘Lectures on Man,’
Eng. translat., 1864, p. 468.), they converged in character. When man
selects the offspring of two distinct species for the same object, he
sometimes induces a considerable amount of convergence, as far as
general appearance is concerned. This is the case, as shewn by von
Nathusius (23. ‘Die Rassen des Schweines,’ 1860, s. 46. ‘Vorstudien für
Geschichte,’ etc., Schweinesschädel, 1864, s. 104. With respect to
cattle, see M. de Quatrefages, ‘Unité de l’Espèce Humaine,’ 1861, p.
119.), with the improved breeds of the pig, which are descended from
two distinct species; and in a less marked manner with the improved
breeds of cattle. A great anatomist, Gratiolet, maintains that the
anthropomorphous apes do not form a natural sub-group; but that the
orang is a highly developed gibbon or semnopithecus, the chimpanzee a
highly developed macacus, and the gorilla a highly developed mandrill.
If this conclusion, which rests almost exclusively on brain-characters,
be admitted, we should have a case of convergence at least in external
characters, for the anthropomorphous apes are certainly more like each
other in many points, than they are to other apes. All analogical
resemblances, as of a whale to a fish, may indeed be said to be cases
of convergence; but this term has never been applied to superficial and
adaptive resemblances. It would, however, be extremely rash to
attribute to convergence close similarity of character in many points
of structure amongst the modified descendants of widely distinct
beings. The form of a crystal is determined solely by the molecular
forces, and it is not surprising that dissimilar substances should
sometimes assume the same form; but with organic beings we should bear
in mind that the form of each depends on an infinity of complex
relations, namely on variations, due to causes far too intricate to be
followed,—on the nature of the variations preserved, these depending on
the physical conditions, and still more on the surrounding organisms
which compete with each,—and lastly, on inheritance (in itself a
fluctuating element) from innumerable progenitors, all of which have
had their forms determined through equally complex relations. It
appears incredible that the modified descendants of two organisms, if
these differed from each other in a marked manner, should ever
afterwards converge so closely as to lead to a near approach to
identity throughout their whole organisation. In the case of the
convergent races of pigs above referred to, evidence of their descent
from two primitive stocks is, according to von Nathusius, still plainly
retained, in certain bones of their skulls. If the races of man had
descended, as is supposed by some naturalists, from two or more
species, which differed from each other as much, or nearly as much, as
does the orang from the gorilla, it can hardly be doubted that marked
differences in the structure of certain bones would still be
discoverable in man as he now exists.

Although the existing races of man differ in many respects, as in
colour, hair, shape of skull, proportions of the body, etc., yet if
their whole structure be taken into consideration they are found to
resemble each other closely in a multitude of points. Many of these are
of so unimportant or of so singular a nature, that it is extremely
improbable that they should have been independently acquired by
aboriginally distinct species or races. The same remark holds good with
equal or greater force with respect to the numerous points of mental
similarity between the most distinct races of man. The American
aborigines, Negroes and Europeans are as different from each other in
mind as any three races that can be named; yet I was incessantly
struck, whilst living with the Fuegians on board the “Beagle,” with the
many little traits of character, shewing how similar their minds were
to ours; and so it was with a full-blooded negro with whom I happened
once to be intimate.

He who will read Mr. Tylor’s and Sir J. Lubbock’s interesting works
(24. Tylor’s ‘Early History of Mankind,’ 1865: with respect to
gesture-language, see p. 54. Lubbock’s ‘Prehistoric Times,’ 2nd edit.
1869.) can hardly fail to be deeply impressed with the close similarity
between the men of all races in tastes, dispositions and habits. This
is shewn by the pleasure which they all take in dancing, rude music,
acting, painting, tattooing, and otherwise decorating themselves; in
their mutual comprehension of gesture-language, by the same expression
in their features, and by the same inarticulate cries, when excited by
the same emotions. This similarity, or rather identity, is striking,
when contrasted with the different expressions and cries made by
distinct species of monkeys. There is good evidence that the art of
shooting with bows and arrows has not been handed down from any common
progenitor of mankind, yet as Westropp and Nilsson have remarked (25.
‘On Analogous Forms of Implements,’ in ‘Memoirs of Anthropological
Society’ by H.M. Westropp. ‘The Primitive Inhabitants of Scandinavia,’
Eng. translat., edited by Sir J. Lubbock, 1868, p. 104.), the stone
arrow-heads, brought from the most distant parts of the world, and
manufactured at the most remote periods, are almost identical; and this
fact can only be accounted for by the various races having similar
inventive or mental powers. The same observation has been made by
archaeologists (26. Westropp ‘On Cromlechs,’ etc., ‘Journal of
Ethnological Soc.’ as given in ‘Scientific Opinion,’ June 2nd, 1869, p.
3.) with respect to certain widely-prevalent ornaments, such as
zig-zags, etc.; and with respect to various simple beliefs and customs,
such as the burying of the dead under megalithic structures. I remember
observing in South America (27. ‘Journal of Researches: Voyage of the
“Beagle,”’ p. 46.), that there, as in so many other parts of the world,
men have generally chosen the summits of lofty hills, to throw up piles
of stones, either as a record of some remarkable event, or for burying
their dead.

Now when naturalists observe a close agreement in numerous small
details of habits, tastes, and dispositions between two or more
domestic races, or between nearly-allied natural forms, they use this
fact as an argument that they are descended from a common progenitor
who was thus endowed; and consequently that all should be classed under
the same species. The same argument may be applied with much force to
the races of man.

As it is improbable that the numerous and unimportant points of
resemblance between the several races of man in bodily structure and
mental faculties (I do not here refer to similar customs) should all
have been independently acquired, they must have been inherited from
progenitors who had these same characters. We thus gain some insight
into the early state of man, before he had spread step by step over the
face of the earth. The spreading of man to regions widely separated by
the sea, no doubt, preceded any great amount of divergence of character
in the several races; for otherwise we should sometimes meet with the
same race in distinct continents; and this is never the case. Sir J.
Lubbock, after comparing the arts now practised by savages in all parts
of the world, specifies those which man could not have known, when he
first wandered from his original birthplace; for if once learnt they
would never have been forgotten. (28. ‘Prehistoric Times,’ 1869, p.
574.) He thus shews that “the spear, which is but a development of the
knife-point, and the club, which is but a long hammer, are the only
things left.” He admits, however, that the art of making fire probably
had been already discovered, for it is common to all the races now
existing, and was known to the ancient cave-inhabitants of Europe.
Perhaps the art of making rude canoes or rafts was likewise known; but
as man existed at a remote epoch, when the land in many places stood at
a very different level to what it does now, he would have been able,
without the aid of canoes, to have spread widely. Sir J. Lubbock
further remarks how improbable it is that our earliest ancestors could
have “counted as high as ten, considering that so many races now in
existence cannot get beyond four.” Nevertheless, at this early period,
the intellectual and social faculties of man could hardly have been
inferior in any extreme degree to those possessed at present by the
lowest savages; otherwise primeval man could not have been so eminently
successful in the struggle for life, as proved by his early and wide
diffusion.

From the fundamental differences between certain languages, some
philologists have inferred that when man first became widely diffused,
he was not a speaking animal; but it may be suspected that languages,
far less perfect than any now spoken, aided by gestures, might have
been used, and yet have left no traces on subsequent and more
highly-developed tongues. Without the use of some language, however
imperfect, it appears doubtful whether man’s intellect could have risen
to the standard implied by his dominant position at an early period.

Whether primeval man, when he possessed but few arts, and those of the
rudest kind, and when his power of language was extremely imperfect,
would have deserved to be called man, must depend on the definition
which we employ. In a series of forms graduating insensibly from some
ape-like creature to man as he now exists, it would be impossible to
fix on any definite point where the term “man” ought to be used. But
this is a matter of very little importance. So again, it is almost a
matter of indifference whether the so-called races of man are thus
designated, or are ranked as species or sub-species; but the latter
term appears the more appropriate. Finally, we may conclude that when
the principle of evolution is generally accepted, as it surely will be
before long, the dispute between the monogenists and the polygenists
will die a silent and unobserved death.

One other question ought not to be passed over without notice, namely,
whether, as is sometimes assumed, each sub-species or race of man has
sprung from a single pair of progenitors. With our domestic animals a
new race can readily be formed by carefully matching the varying
offspring from a single pair, or even from a single individual
possessing some new character; but most of our races have been formed,
not intentionally from a selected pair, but unconsciously by the
preservation of many individuals which have varied, however slightly,
in some useful or desired manner. If in one country stronger and
heavier horses, and in another country lighter and fleeter ones, were
habitually preferred, we may feel sure that two distinct sub-breeds
would be produced in the course of time, without any one pair having
been separated and bred from, in either country. Many races have been
thus formed, and their manner of formation is closely analogous to that
of natural species. We know, also, that the horses taken to the
Falkland Islands have, during successive generations, become smaller
and weaker, whilst those which have run wild on the Pampas have
acquired larger and coarser heads; and such changes are manifestly due,
not to any one pair, but to all the individuals having been subjected
to the same conditions, aided, perhaps, by the principle of reversion.
The new sub-breeds in such cases are not descended from any single
pair, but from many individuals which have varied in different degrees,
but in the same general manner; and we may conclude that the races of
man have been similarly produced, the modifications being either the
direct result of exposure to different conditions, or the indirect
result of some form of selection. But to this latter subject we shall
presently return.

ON THE EXTINCTION OF THE RACES OF MAN.

The partial or complete extinction of many races and sub-races of man
is historically known. Humboldt saw in South America a parrot which was
the sole living creature that could speak a word of the language of a
lost tribe. Ancient monuments and stone implements found in all parts
of the world, about which no tradition has been preserved by the
present inhabitants, indicate much extinction. Some small and broken
tribes, remnants of former races, still survive in isolated and
generally mountainous districts. In Europe the ancient races were all,
according to Shaaffhausen (29. Translation in ‘Anthropological Review,’
Oct. 1868, p. 431.), “lower in the scale than the rudest living
savages”; they must therefore have differed, to a certain extent, from
any existing race. The remains described by Professor Broca from Les
Eyzies, though they unfortunately appear to have belonged to a single
family, indicate a race with a most singular combination of low or
simious, and of high characteristics. This race is “entirely different
from any other, ancient or modern, that we have heard of.” (30.
‘Transactions, International Congress of Prehistoric Archaeology’ 1868,
pp. 172-175. See also Broca (tr.) in ‘Anthropological Review,’ Oct.
1868, p. 410.) It differed, therefore, from the quaternary race of the
caverns of Belgium.

Man can long resist conditions which appear extremely unfavourable for
his existence. (31. Dr. Gerland, ‘Ueber das Aussterben der
Naturvölker,’ 1868, s. 82.) He has long lived in the extreme regions of
the North, with no wood for his canoes or implements, and with only
blubber as fuel, and melted snow as drink. In the southern extremity of
America the Fuegians survive without the protection of clothes, or of
any building worthy to be called a hovel. In South Africa the
aborigines wander over arid plains, where dangerous beasts abound. Man
can withstand the deadly influence of the Terai at the foot of the
Himalaya, and the pestilential shores of tropical Africa.

Extinction follows chiefly from the competition of tribe with tribe,
and race with race. Various checks are always in action, serving to
keep down the numbers of each savage tribe,—such as periodical famines,
nomadic habits and the consequent deaths of infants, prolonged
suckling, wars, accidents, sickness, licentiousness, the stealing of
women, infanticide, and especially lessened fertility. If any one of
these checks increases in power, even slightly, the tribe thus affected
tends to decrease; and when of two adjoining tribes one becomes less
numerous and less powerful than the other, the contest is soon settled
by war, slaughter, cannibalism, slavery, and absorption. Even when a
weaker tribe is not thus abruptly swept away, if it once begins to
decrease, it generally goes on decreasing until it becomes extinct.
(32. Gerland (ibid. s. 12) gives facts in support of this statement.)

When civilised nations come into contact with barbarians the struggle
is short, except where a deadly climate gives its aid to the native
race. Of the causes which lead to the victory of civilised nations,
some are plain and simple, others complex and obscure. We can see that
the cultivation of the land will be fatal in many ways to savages, for
they cannot, or will not, change their habits. New diseases and vices
have in some cases proved highly destructive; and it appears that a new
disease often causes much death, until those who are most susceptible
to its destructive influence are gradually weeded out (33. See remarks
to this effect in Sir H. Holland’s ‘Medical Notes and Reflections,’
1839, p. 390.); and so it may be with the evil effects from spirituous
liquors, as well as with the unconquerably strong taste for them shewn
by so many savages. It further appears, mysterious as is the fact, that
the first meeting of distinct and separated people generates disease.
(34. I have collected (‘Journal of Researches: Voyage of the “Beagle,”’
p. 435) a good many cases bearing on this subject; see also Gerland,
ibid. s. 8. Poeppig speaks of the “breath of civilisation as poisonous
to savages.”) Mr. Sproat, who in Vancouver Island closely attended to
the subject of extinction, believed that changed habits of life,
consequent on the advent of Europeans, induces much ill health. He
lays, also, great stress on the apparently trifling cause that the
natives become “bewildered and dull by the new life around them; they
lose the motives for exertion, and get no new ones in their place.”
(35. Sproat, ‘Scenes and Studies of Savage Life,’ 1868, p. 284.)

The grade of their civilisation seems to be a most important element in
the success of competing nations. A few centuries ago Europe feared the
inroads of Eastern barbarians; now any such fear would be ridiculous.
It is a more curious fact, as Mr. Bagehot has remarked, that savages
did not formerly waste away before the classical nations, as they now
do before modern civilised nations; had they done so, the old moralists
would have mused over the event; but there is no lament in any writer
of that period over the perishing barbarians. (36. Bagehot, ‘Physics
and Politics,’ ‘Fortnightly Review,’ April 1, 1868, p. 455.) The most
potent of all the causes of extinction, appears in many cases to be
lessened fertility and ill-health, especially amongst the children,
arising from changed conditions of life, notwithstanding that the new
conditions may not be injurious in themselves. I am much indebted to
Mr. H.H. Howorth for having called my attention to this subject, and
for having given me information respecting it. I have collected the
following cases.

When Tasmania was first colonised the natives were roughly estimated by
some at 7000 and by others at 20,000. Their number was soon greatly
reduced, chiefly by fighting with the English and with each other.
After the famous hunt by all the colonists, when the remaining natives
delivered themselves up to the government, they consisted only of 120
individuals (37. All the statements here given are taken from ‘The Last
of the Tasmanians,’ by J. Bonwick, 1870.), who were in 1832 transported
to Flinders Island. This island, situated between Tasmania and
Australia, is forty miles long, and from twelve to eighteen miles
broad: it seems healthy, and the natives were well treated.
Nevertheless, they suffered greatly in health. In 1834 they consisted
(Bonwick, p. 250) of forty-seven adult males, forty-eight adult
females, and sixteen children, or in all of 111 souls. In 1835 only one
hundred were left. As they continued rapidly to decrease, and as they
themselves thought that they should not perish so quickly elsewhere,
they were removed in 1847 to Oyster Cove in the southern part of
Tasmania. They then consisted (Dec. 20th, 1847) of fourteen men,
twenty-two women and ten children. (38. This is the statement of the
Governor of Tasmania, Sir W. Denison, ‘Varieties of Vice-Regal Life,’
1870, vol. i. p. 67.) But the change of site did no good. Disease and
death still pursued them, and in 1864 one man (who died in 1869), and
three elderly women alone survived. The infertility of the women is
even a more remarkable fact than the liability of all to ill-health and
death. At the time when only nine women were left at Oyster Cove, they
told Mr. Bonwick (p. 386), that only two had ever borne children: and
these two had together produced only three children!

With respect to the cause of this extraordinary state of things, Dr.
Story remarks that death followed the attempts to civilise the natives.
“If left to themselves to roam as they were wont and undisturbed, they
would have reared more children, and there would have been less
mortality.” Another careful observer of the natives, Mr. Davis,
remarks, “The births have been few and the deaths numerous. This may
have been in a great measure owing to their change of living and food;
but more so to their banishment from the mainland of Van Diemen’s Land,
and consequent depression of spirits” (Bonwick, pp. 388, 390).

Similar facts have been observed in two widely different parts of
Australia. The celebrated explorer, Mr. Gregory, told Mr. Bonwick, that
in Queensland “the want of reproduction was being already felt with the
blacks, even in the most recently settled parts, and that decay would
set in.” Of thirteen aborigines from Shark’s Bay who visited Murchison
River, twelve died of consumption within three months. (39. For these
cases, see Bonwick’s ‘Daily Life of the Tasmanians,’ 1870, p. 90: and
the ‘Last of the Tasmanians,’ 1870, p. 386.)

The decrease of the Maories of New Zealand has been carefully
investigated by Mr. Fenton, in an admirable Report, from which all the
following statements, with one exception, are taken. (40. ‘Observations
on the Aboriginal Inhabitants of New Zealand,’ published by the
Government, 1859.) The decrease in number since 1830 is admitted by
every one, including the natives themselves, and is still steadily
progressing. Although it has hitherto been found impossible to take an
actual census of the natives, their numbers were carefully estimated by
residents in many districts. The result seems trustworthy, and shows
that during the fourteen years, previous to 1858, the decrease was
19.42 per cent. Some of the tribes, thus carefully examined, lived
above a hundred miles apart, some on the coast, some inland; and their
means of subsistence and habits differed to a certain extent (p. 28).
The total number in 1858 was believed to be 53,700, and in 1872, after
a second interval of fourteen years, another census was taken, and the
number is given as only 36,359, shewing a decrease of 32.29 per cent!
(41. ‘New Zealand,’ by Alex. Kennedy, 1873, p. 47.) Mr. Fenton, after
shewing in detail the insufficiency of the various causes, usually
assigned in explanation of this extraordinary decrease, such as new
diseases, the profligacy of the women, drunkenness, wars, etc.,
concludes on weighty grounds that it depends chiefly on the
unproductiveness of the women, and on the extraordinary mortality of
the young children (pp. 31, 34). In proof of this he shews (p. 33) that
in 1844 there was one non-adult for every 2.57 adults; whereas in 1858
there was only one non-adult for every 3.27 adults. The mortality of
the adults is also great. He adduces as a further cause of the decrease
the inequality of the sexes; for fewer females are born than males. To
this latter point, depending perhaps on a widely distinct cause, I
shall return in a future chapter. Mr. Fenton contrasts with
astonishment the decrease in New Zealand with the increase in Ireland;
countries not very dissimilar in climate, and where the inhabitants now
follow nearly similar habits. The Maories themselves (p. 35) “attribute
their decadence, in some measure, to the introduction of new food and
clothing, and the attendant change of habits”; and it will be seen,
when we consider the influence of changed conditions on fertility, that
they are probably right. The diminution began between the years 1830
and 1840; and Mr. Fenton shews (p. 40) that about 1830, the art of
manufacturing putrid corn (maize), by long steeping in water, was
discovered and largely practised; and this proves that a change of
habits was beginning amongst the natives, even when New Zealand was
only thinly inhabited by Europeans. When I visited the Bay of Islands
in 1835, the dress and food of the inhabitants had already been much
modified: they raised potatoes, maize, and other agricultural produce,
and exchanged them for English manufactured goods and tobacco.

It is evident from many statements in the life of Bishop Patteson (42.
‘Life of J.C. Patteson,’ by C.M. Younge, 1874; see more especially vol.
i. p. 530.), that the Melanesians of the New Hebrides and neighbouring
archipelagoes, suffered to an extraordinary degree in health, and
perished in large numbers, when they were removed to New Zealand,
Norfolk Island, and other salubrious places, in order to be educated as
missionaries.

The decrease of the native population of the Sandwich Islands is as
notorious as that of New Zealand. It has been roughly estimated by those
best capable of judging, that when Cook discovered the Islands in 1779, the
population amounted to about 300,000. According to a loose census in 1823,
the numbers then were 142,050. In 1832, and at several subsequent periods,
an accurate census was officially taken, but I have been able to obtain
only the following returns:
                Native Population          Annual rate of decrease
                                           per cent., assuming it to
              (Except during 1832 and      have been uniform between
              1836, when the few           the successive censuses;
              foreigners in the islands    these censuses being taken
  Year        were included.)              at irregular intervals.

  1832              130,313
                                                   4.46
  1836              108,579
                                                   2.47
  1853               71,019
                                                   0.81
  1860               67,084
                                                   2.18
  1866               58,765
                                                   2.17
  1872               51,531

We here see that in the interval of forty years, between 1832 and 1872,
the population has decreased no less than sixty-eight per cent.! This
has been attributed by most writers to the profligacy of the women, to
former bloody wars, and to the severe labour imposed on conquered
tribes and to newly introduced diseases, which have been on several
occasions extremely destructive. No doubt these and other such causes
have been highly efficient, and may account for the extraordinary rate
of decrease between the years 1832 and 1836; but the most potent of all
the causes seems to be lessened fertility. According to Dr.
Ruschenberger of the U.S. Navy, who visited these islands between 1835
and 1837, in one district of Hawaii, only twenty-five men out of 1134,
and in another district only ten out of 637, had a family with as many
as three children. Of eighty married women, only thirty-nine had ever
borne children; and “the official report gives an average of half a
child to each married couple in the whole island.” This is almost
exactly the same average as with the Tasmanians at Oyster Cove. Jarves,
who published his History in 1843, says that “families who have three
children are freed from all taxes; those having more, are rewarded by
gifts of land and other encouragements.” This unparalleled enactment by
the government well shews how infertile the race had become. The Rev.
A. Bishop stated in the Hawaiian ‘Spectator’ in 1839, that a large
proportion of the children die at early ages, and Bishop Staley informs
me that this is still the case, just as in New Zealand. This has been
attributed to the neglect of the children by the women, but it is
probably in large part due to innate weakness of constitution in the
children, in relation to the lessened fertility of their parents. There
is, moreover, a further resemblance to the case of New Zealand, in the
fact that there is a large excess of male over female births: the
census of 1872 gives 31,650 males to 25,247 females of all ages, that
is 125.36 males for every 100 females; whereas in all civilised
countries the females exceed the males. No doubt the profligacy of the
women may in part account for their small fertility; but their changed
habits of life is a much more probable cause, and which will at the
same time account for the increased mortality, especially of the
children. The islands were visited by Cook in 1779, Vancouver in 1794,
and often subsequently by whalers. In 1819 missionaries arrived, and
found that idolatry had been already abolished, and other changes
effected by the king. After this period there was a rapid change in
almost all the habits of life of the natives, and they soon became “the
most civilised of the Pacific Islanders.” One of my informants, Mr.
Coan, who was born on the islands, remarks that the natives have
undergone a greater change in their habits of life in the course of
fifty years than Englishmen during a thousand years. From information
received from Bishop Staley, it does not appear that the poorer classes
have ever much changed their diet, although many new kinds of fruit
have been introduced, and the sugar-cane is in universal use. Owing,
however, to their passion for imitating Europeans, they altered their
manner of dressing at an early period, and the use of alcoholic drinks
became very general. Although these changes appear inconsiderable, I
can well believe, from what is known with respect to animals, that they
might suffice to lessen the fertility of the natives. (43. The
foregoing statements are taken chiefly from the following works:
Jarves’ ‘History of the Hawaiian Islands,’ 1843, pp. 400-407. Cheever,
‘Life in the Sandwich Islands,’ 1851, p. 277. Ruschenberger is quoted
by Bonwick, ‘Last of the Tasmanians,’ 1870, p. 378. Bishop is quoted by
Sir E. Belcher, ‘Voyage Round the World,’ 1843, vol. i. p. 272. I owe
the census of the several years to the kindness of Mr. Coan, at the
request of Dr. Youmans of New York; and in most cases I have compared
the Youmans figures with those given in several of the above-named
works. I have omitted the census for 1850, as I have seen two widely
different numbers given.)

Lastly, Mr. Macnamara states (44. ‘The Indian Medical Gazette,’ Nov. 1,
1871, p. 240.) that the low and degraded inhabitants of the Andaman
Islands, on the eastern side of the Gulf of Bengal, are “eminently
susceptible to any change of climate: in fact, take them away from
their island homes, and they are almost certain to die, and that
independently of diet or extraneous influences.” He further states that
the inhabitants of the Valley of Nepal, which is extremely hot in
summer, and also the various hill-tribes of India, suffer from
dysentery and fever when on the plains; and they die if they attempt to
pass the whole year there.

We thus see that many of the wilder races of man are apt to suffer much
in health when subjected to changed conditions or habits of life, and
not exclusively from being transported to a new climate. Mere
alterations in habits, which do not appear injurious in themselves,
seem to have this same effect; and in several cases the children are
particularly liable to suffer. It has often been said, as Mr. Macnamara
remarks, that man can resist with impunity the greatest diversities of
climate and other changes; but this is true only of the civilised
races. Man in his wild condition seems to be in this respect almost as
susceptible as his nearest allies, the anthropoid apes, which have
never yet survived long, when removed from their native country.

Lessened fertility from changed conditions, as in the case of the
Tasmanians, Maories, Sandwich Islanders, and apparently the
Australians, is still more interesting than their liability to
ill-health and death; for even a slight degree of infertility, combined
with those other causes which tend to check the increase of every
population, would sooner or later lead to extinction. The diminution of
fertility may be explained in some cases by the profligacy of the women
(as until lately with the Tahitians), but Mr. Fenton has shewn that
this explanation by no means suffices with the New Zealanders, nor does
it with the Tasmanians.

In the paper above quoted, Mr. Macnamara gives reasons for believing
that the inhabitants of districts subject to malaria are apt to be
sterile; but this cannot apply in several of the above cases. Some
writers have suggested that the aborigines of islands have suffered in
fertility and health from long continued inter-breeding; but in the
above cases infertility has coincided too closely with the arrival of
Europeans for us to admit this explanation. Nor have we at present any
reason to believe that man is highly sensitive to the evil effects of
inter-breeding, especially in areas so large as New Zealand, and the
Sandwich archipelago with its diversified stations. On the contrary, it
is known that the present inhabitants of Norfolk Island are nearly all
cousins or near relations, as are the Todas in India, and the
inhabitants of some of the Western Islands of Scotland; and yet they
seem not to have suffered in fertility. (45. On the close relationship
of the Norfolk Islanders, Sir W. Denison, ‘Varieties of Vice-Regal
Life,’ vol. i. 1870, p. 410. For the Todas, see Col. Marshall’s work
1873, p. 110. For the Western Islands of Scotland, Dr. Mitchell,
‘Edinburgh Medical Journal,’ March to June, 1865.)

A much more probable view is suggested by the analogy of the lower
animals. The reproductive system can be shewn to be susceptible to an
extraordinary degree (though why we know not) to changed conditions of
life; and this susceptibility leads both to beneficial and to evil
results. A large collection of facts on this subject is given in chap.
xviii. of vol. ii. of my ‘Variation of Animals and Plants under
Domestication.’ I can here give only the briefest abstract; and every
one interested in the subject may consult the above work. Very slight
changes increase the health, vigour, and fertility of most or all
organic beings, whilst other changes are known to render a large number
of animals sterile. One of the most familiar cases, is that of tamed
elephants not breeding in India; though they often breed in Ava, where
the females are allowed to roam about the forests to some extent, and
are thus placed under more natural conditions. The case of various
American monkeys, both sexes of which have been kept for many years
together in their own countries, and yet have very rarely or never
bred, is a more apposite instance, because of their relationship to
man. It is remarkable how slight a change in the conditions often
induces sterility in a wild animal when captured; and this is the more
strange as all our domesticated animals have become more fertile than
they were in a state of nature; and some of them can resist the most
unnatural conditions with undiminished fertility. (46. For the evidence
on this head, see ‘Variation of Animals,’ etc., vol. ii. p. 111.)
Certain groups of animals are much more liable than others to be
affected by captivity; and generally all the species of the same group
are affected in the same manner. But sometimes a single species in a
group is rendered sterile, whilst the others are not so; on the other
hand, a single species may retain its fertility whilst most of the
others fail to breed. The males and females of some species when
confined, or when allowed to live almost, but not quite free, in their
native country, never unite; others thus circumstanced frequently unite
but never produce offspring; others again produce some offspring, but
fewer than in a state of nature; and as bearing on the above cases of
man, it is important to remark that the young are apt to be weak and
sickly, or malformed, and to perish at an early age.

Seeing how general is this law of the susceptibility of the
reproductive system to changed conditions of life, and that it holds
good with our nearest allies, the Quadrumana, I can hardly doubt that
it applies to man in his primeval state. Hence if savages of any race
are induced suddenly to change their habits of life, they become more
or less sterile, and their young offspring suffer in health, in the
same manner and from the same cause, as do the elephant and
hunting-leopard in India, many monkeys in America, and a host of
animals of all kinds, on removal from their natural conditions.

We can see why it is that aborigines, who have long inhabited islands,
and who must have been long exposed to nearly uniform conditions,
should be specially affected by any change in their habits, as seems to
be the case. Civilised races can certainly resist changes of all kinds
far better than savages; and in this respect they resemble domesticated
animals, for though the latter sometimes suffer in health (for instance
European dogs in India), yet they are rarely rendered sterile, though a
few such instances have been recorded. (47. ‘Variation of Animals,’
etc., vol. ii. p. 16.) The immunity of civilised races and domesticated
animals is probably due to their having been subjected to a greater
extent, and therefore having grown somewhat more accustomed, to
diversified or varying conditions, than the majority of wild animals;
and to their having formerly immigrated or been carried from country to
country, and to different families or sub-races having inter-crossed.
It appears that a cross with civilised races at once gives to an
aboriginal race an immunity from the evil consequences of changed
conditions. Thus the crossed offspring from the Tahitians and English,
when settled in Pitcairn Island, increased so rapidly that the island
was soon overstocked; and in June 1856 they were removed to Norfolk
Island. They then consisted of 60 married persons and 134 children,
making a total of 194. Here they likewise increased so rapidly, that
although sixteen of them returned to Pitcairn Island in 1859, they
numbered in January 1868, 300 souls; the males and females being in
exactly equal numbers. What a contrast does this case present with that
of the Tasmanians; the Norfolk Islanders INCREASED in only twelve and a
half years from 194 to 300; whereas the Tasmanians DECREASED during
fifteen years from 120 to 46, of which latter number only ten were
children. (48. These details are taken from ‘The Mutineers of the
“Bounty,”’ by Lady Belcher, 1870; and from ‘Pitcairn Island,’ ordered
to be printed by the House of Commons, May 29, 1863. The following
statements about the Sandwich Islanders are from the ‘Honolulu
Gazette,’ and from Mr. Coan.)

So again in the interval between the census of 1866 and 1872 the
natives of full blood in the Sandwich Islands decreased by 8081, whilst
the half-castes, who are believed to be healthier, increased by 847;
but I do not know whether the latter number includes the offspring from
the half-castes, or only the half-castes of the first generation.

The cases which I have here given all relate to aborigines, who have
been subjected to new conditions as the result of the immigration of
civilised men. But sterility and ill-health would probably follow, if
savages were compelled by any cause, such as the inroad of a conquering
tribe, to desert their homes and to change their habits. It is an
interesting circumstance that the chief check to wild animals becoming
domesticated, which implies the power of their breeding freely when
first captured, and one chief check to wild men, when brought into
contact with civilisation, surviving to form a civilised race, is the
same, namely, sterility from changed conditions of life.

Finally, although the gradual decrease and ultimate extinction of the
races of man is a highly complex problem, depending on many causes
which differ in different places and at different times; it is the same
problem as that presented by the extinction of one of the higher
animals—of the fossil horse, for instance, which disappeared from South
America, soon afterwards to be replaced, within the same districts, by
countless troups of the Spanish horse. The New Zealander seems
conscious of this parallelism, for he compares his future fate with
that of the native rat now almost exterminated by the European rat.
Though the difficulty is great to our imagination, and really great, if
we wish to ascertain the precise causes and their manner of action, it
ought not to be so to our reason, as long as we keep steadily in mind
that the increase of each species and each race is constantly checked
in various ways; so that if any new check, even a slight one, be
superadded, the race will surely decrease in number; and decreasing
numbers will sooner or later lead to extinction; the end, in most
cases, being promptly determined by the inroads of conquering tribes.

ON THE FORMATION OF THE RACES OF MAN.

In some cases the crossing of distinct races has led to the formation
of a new race. The singular fact that the Europeans and Hindoos, who
belong to the same Aryan stock, and speak a language fundamentally the
same, differ widely in appearance, whilst Europeans differ but little
from Jews, who belong to the Semitic stock, and speak quite another
language, has been accounted for by Broca (49. ‘On Anthropology,’
translation, ‘Anthropological Review,’ Jan. 1868, p. 38.), through
certain Aryan branches having been largely crossed by indigenous tribes
during their wide diffusion. When two races in close contact cross, the
first result is a heterogeneous mixture: thus Mr. Hunter, in describing
the Santali or hill-tribes of India, says that hundreds of
imperceptible gradations may be traced “from the black, squat tribes of
the mountains to the tall olive-coloured Brahman, with his intellectual
brow, calm eyes, and high but narrow head”; so that it is necessary in
courts of justice to ask the witnesses whether they are Santalis or
Hindoos. (50. ‘The Annals of Rural Bengal,’ 1868, p. 134.) Whether a
heterogeneous people, such as the inhabitants of some of the Polynesian
islands, formed by the crossing of two distinct races, with few or no
pure members left, would ever become homogeneous, is not known from
direct evidence. But as with our domesticated animals, a cross-breed
can certainly be fixed and made uniform by careful selection (51. ‘The
Variation of Animals and Plants under Domestication,’ vol. ii. p. 95.)
in the course of a few generations, we may infer that the free
intercrossing of a heterogeneous mixture during a long descent would
supply the place of selection, and overcome any tendency to reversion;
so that the crossed race would ultimately become homogeneous, though it
might not partake in an equal degree of the characters of the two
parent-races.

Of all the differences between the races of man, the colour of the skin
is the most conspicuous and one of the best marked. It was formerly
thought that differences of this kind could be accounted for by long
exposure to different climates; but Pallas first shewed that this is
not tenable, and he has since been followed by almost all
anthropologists. (52. Pallas, ‘Act. Acad. St. Petersburg,’ 1780, part
ii. p. 69. He was followed by Rudolphi, in his ‘Beytrage zur
Anthropologie,’ 1812. An excellent summary of the evidence is given by
Godron, ‘De l’Espèce,’ 1859, vol. ii. p. 246, etc.) This view has been
rejected chiefly because the distribution of the variously coloured
races, most of whom must have long inhabited their present homes, does
not coincide with corresponding differences of climate. Some little
weight may be given to such cases as that of the Dutch families, who,
as we hear on excellent authority (53. Sir Andrew Smith, as quoted by
Knox, ‘Races of Man,’ 1850, p. 473.), have not undergone the least
change of colour after residing for three centuries in South Africa. An
argument on the same side may likewise be drawn from the uniform
appearance in various parts of the world of gipsies and Jews, though
the uniformity of the latter has been somewhat exaggerated. (54. See De
Quatrefages on this head, ‘Revue des Cours Scientifiques,’ Oct. 17,
1868, p. 731.) A very damp or a very dry atmosphere has been supposed
to be more influential in modifying the colour of the skin than mere
heat; but as D’Orbigny in South America, and Livingstone in Africa,
arrived at diametrically opposite conclusions with respect to dampness
and dryness, any conclusion on this head must be considered as very
doubtful. (55. Livingstone’s ‘Travels and Researches in S. Africa,’
1857, pp. 338, 339. D’Orbigny, as quoted by Godron, ‘De l’Espece,’ vol.
ii. p. 266.)

Various facts, which I have given elsewhere, prove that the colour of
the skin and hair is sometimes correlated in a surprising manner with a
complete immunity from the action of certain vegetable poisons, and
from the attacks of certain parasites. Hence it occurred to me, that
negroes and other dark races might have acquired their dark tints by
the darker individuals escaping from the deadly influence of the miasma
of their native countries, during a long series of generations.

I afterwards found that this same idea had long ago occurred to Dr.
Wells. (56. See a paper read before the Royal Soc. in 1813, and
published in his Essays in 1818. I have given an account of Dr. Wells’
views in the Historical Sketch (p. xvi.) to my ‘Origin of Species.’
Various cases of colour correlated with constitutional peculiarities
are given in my ‘Variation of Animals and Plants under Domestication,’
vol. ii. pp. 227, 335.) It has long been known that negroes, and even
mulattoes, are almost completely exempt from the yellow-fever, so
destructive in tropical America. (57. See, for instance, Nott and
Gliddon, ‘Types of Mankind,’ p. 68.) They likewise escape to a large
extent the fatal intermittent fevers, that prevail along at least 2600
miles of the shores of Africa, and which annually cause one-fifth of
the white settlers to die, and another fifth to return home invalided.
(58. Major Tulloch, in a paper read before the Statistical Society,
April 20, 1840, and given in the ‘Athenaeum,’ 1840, p. 353.) This
immunity in the negro seems to be partly inherent, depending on some
unknown peculiarity of constitution, and partly the result of
acclimatisation. Pouchet (59. ‘The Plurality of the Human Race’
(translat.), 1864, p. 60.) states that the negro regiments recruited
near the Soudan, and borrowed from the Viceroy of Egypt for the Mexican
war, escaped the yellow-fever almost equally with the negroes
originally brought from various parts of Africa and accustomed to the
climate of the West Indies. That acclimatisation plays a part, is shewn
by the many cases in which negroes have become somewhat liable to
tropical fevers, after having resided for some time in a colder
climate. (60. Quatrefages, ‘Unité de l’Espèce Humaine,’ 1861, p. 205.
Waitz, ‘Introduction to Anthropology,’ translat., vol. i. 1863, p. 124.
Livingstone gives analogous cases in his ‘Travels.’) The nature of the
climate under which the white races have long resided, likewise has
some influence on them; for during the fearful epidemic of yellow fever
in Demerara during 1837, Dr. Blair found that the death-rate of the
immigrants was proportional to the latitude of the country whence they
had come. With the negro the immunity, as far as it is the result of
acclimatisation, implies exposure during a prodigious length of time;
for the aborigines of tropical America who have resided there from time
immemorial, are not exempt from yellow fever; and the Rev. H.B.
Tristram states, that there are districts in Northern Africa which the
native inhabitants are compelled annually to leave, though the negroes
can remain with safety.

That the immunity of the negro is in any degree correlated with the
colour of his skin is a mere conjecture: it may be correlated with some
difference in his blood, nervous system, or other tissues.
Nevertheless, from the facts above alluded to, and from some connection
apparently existing between complexion and a tendency to consumption,
the conjecture seemed to me not improbable. Consequently I endeavoured,
with but little success (61. In the spring of 1862 I obtained
permission from the Director-General of the Medical department of the
Army, to transmit to the surgeons of the various regiments on foreign
service a blank table, with the following appended remarks, but I have
received no returns. “As several well-marked cases have been recorded
with our domestic animals of a relation between the colour of the
dermal appendages and the constitution; and it being notorious that
there is some limited degree of relation between the colour of the
races of man and the climate inhabited by them; the following
investigation seems worth consideration. Namely, whether there is any
relation in Europeans between the colour of their hair, and their
liability to the diseases of tropical countries. If the surgeons of the
several regiments, when stationed in unhealthy tropical districts,
would be so good as first to count, as a standard of comparison, how
many men, in the force whence the sick are drawn, have dark and
light-coloured hair, and hair of intermediate or doubtful tints; and if
a similar account were kept by the same medical gentlemen, of all the
men who suffered from malarious and yellow fevers, or from dysentery,
it would soon be apparent, after some thousand cases had been
tabulated, whether there exists any relation between the colour of the
hair and constitutional liability to tropical diseases. Perhaps no such
relation would be discovered, but the investigation is well worth
making. In case any positive result were obtained, it might be of some
practical use in selecting men for any particular service.
Theoretically the result would be of high interest, as indicating one
means by which a race of men inhabiting from a remote period an
unhealthy tropical climate, might have become dark-coloured by the
better preservation of dark-haired or dark-complexioned individuals
during a long succession of generations.”), to ascertain how far it
holds good. The late Dr. Daniell, who had long lived on the West Coast
of Africa, told me that he did not believe in any such relation. He was
himself unusually fair, and had withstood the climate in a wonderful
manner. When he first arrived as a boy on the coast, an old and
experienced negro chief predicted from his appearance that this would
prove the case. Dr. Nicholson, of Antigua, after having attended to
this subject, writes to me that dark-coloured Europeans escape the
yellow fever more than those that are light-coloured. Mr. J.M. Harris
altogether denies that Europeans with dark hair withstand a hot climate
better than other men: on the contrary, experience has taught him in
making a selection of men for service on the coast of Africa, to choose
those with red hair. (62. ‘Anthropological Review,’ Jan. 1866, p. xxi.
Dr. Sharpe also says, with respect to India (‘Man a Special Creation,’
1873, p. 118), “that it has been noticed by some medical officers that
Europeans with light hair and florid complexions suffer less from
diseases of tropical countries than persons with dark hair and sallow
complexions; and, so far as I know, there appear to be good grounds for
this remark.” On the other hand, Mr. Heddle, of Sierra Leone, “who has
had more clerks killed under him than any other man,” by the climate of
the West African Coast (W. Reade, ‘African Sketch Book,’ vol. ii. p.
522), holds a directly opposite view, as does Capt. Burton.) As far,
therefore, as these slight indications go, there seems no foundation
for the hypothesis, that blackness has resulted from the darker and
darker individuals having survived better during long exposure to
fever-generating miasma.

Dr. Sharpe remarks (63. ‘Man a Special Creation,’ 1873, p. 119.), that
a tropical sun, which burns and blisters a white skin, does not injure
a black one at all; and, as he adds, this is not due to habit in the
individual, for children only six or eight months old are often carried
about naked, and are not affected. I have been assured by a medical
man, that some years ago during each summer, but not during the winter,
his hands became marked with light brown patches, like, although larger
than freckles, and that these patches were never affected by
sun-burning, whilst the white parts of his skin have on several
occasions been much inflamed and blistered. With the lower animals
there is, also, a constitutional difference in liability to the action
of the sun between those parts of the skin clothed with white hair and
other parts. (64. ‘Variation of Animals and Plants under
Domestication,’ vol. ii. pp. 336, 337.) Whether the saving of the skin
from being thus burnt is of sufficient importance to account for a dark
tint having been gradually acquired by man through natural selection, I
am unable to judge. If it be so, we should have to assume that the
natives of tropical America have lived there for a much shorter time
than the Negroes in Africa, or the Papuans in the southern parts of the
Malay archipelago, just as the lighter-coloured Hindoos have resided in
India for a shorter time than the darker aborigines of the central and
southern parts of the peninsula.

Although with our present knowledge we cannot account for the
differences of colour in the races of man, through any advantage thus
gained, or from the direct action of climate; yet we must not quite
ignore the latter agency, for there is good reason to believe that some
inherited effect is thus produced. (65. See, for instance, Quatrefages
(‘Revue des Cours Scientifiques,’ Oct. 10, 1868, p. 724) on the effects
of residence in Abyssinia and Arabia, and other analogous cases. Dr.
Rolle (‘Der Mensch, seine Abstammung,’ etc., 1865, s. 99) states, on
the authority of Khanikof, that the greater number of German families
settled in Georgia, have acquired in the course of two generations dark
hair and eyes. Mr. D. Forbes informs me that the Quichuas in the Andes
vary greatly in colour, according to the position of the valleys
inhabited by them.)

We have seen in the second chapter that the conditions of life affect
the development of the bodily frame in a direct manner, and that the
effects are transmitted. Thus, as is generally admitted, the European
settlers in the United States undergo a slight but extraordinary rapid
change of appearance. Their bodies and limbs become elongated; and I
hear from Col. Bernys that during the late war in the United States,
good evidence was afforded of this fact by the ridiculous appearance
presented by the German regiments, when dressed in ready-made clothes
manufactured for the American market, and which were much too long for
the men in every way. There is, also, a considerable body of evidence
shewing that in the Southern States the house-slaves of the third
generation present a markedly different appearance from the
field-slaves. (66. Harlan, ‘Medical Researches,’ p. 532. Quatrefages
(‘Unité de l’Espèce Humaine,’ 1861, p. 128) has collected much evidence
on this head.)

If, however, we look to the races of man as distributed over the world,
we must infer that their characteristic differences cannot be accounted
for by the direct action of different conditions of life, even after
exposure to them for an enormous period of time. The Esquimaux live
exclusively on animal food; they are clothed in thick fur, and are
exposed to intense cold and to prolonged darkness; yet they do not
differ in any extreme degree from the inhabitants of Southern China,
who live entirely on vegetable food, and are exposed almost naked to a
hot, glaring climate. The unclothed Fuegians live on the marine
productions of their inhospitable shores; the Botocudos of Brazil
wander about the hot forests of the interior and live chiefly on
vegetable productions; yet these tribes resemble each other so closely
that the Fuegians on board the “Beagle” were mistaken by some
Brazilians for Botocudos. The Botocudos again, as well as the other
inhabitants of tropical America, are wholly different from the Negroes
who inhabit the opposite shores of the Atlantic, are exposed to a
nearly similar climate, and follow nearly the same habits of life.

Nor can the differences between the races of man be accounted for by
the inherited effects of the increased or decreased use of parts,
except to a quite insignificant degree. Men who habitually live in
canoes, may have their legs somewhat stunted; those who inhabit lofty
regions may have their chests enlarged; and those who constantly use
certain sense-organs may have the cavities in which they are lodged
somewhat increased in size, and their features consequently a little
modified. With civilised nations, the reduced size of the jaws from
lessened use—the habitual play of different muscles serving to express
different emotions—and the increased size of the brain from greater
intellectual activity, have together produced a considerable effect on
their general appearance when compared with savages. (67. See Prof.
Schaaffhausen, translat., in ‘Anthropological Review,’ Oct. 1868, p.
429.) Increased bodily stature, without any corresponding increase in
the size of the brain, may (judging from the previously adduced case of
rabbits), have given to some races an elongated skull of the
dolichocephalic type.

Lastly, the little-understood principle of correlated development has
sometimes come into action, as in the case of great muscular
development and strongly projecting supra-orbital ridges. The colour of
the skin and hair are plainly correlated, as is the texture of the hair
with its colour in the Mandans of North America. (68. Mr. Catlin states
(‘N. American Indians,’ 3rd ed., 1842, vol. i. p. 49) that in the whole
tribe of the Mandans, about one in ten or twelve of the members, of all
ages and both sexes, have bright silvery grey hair, which is
hereditary. Now this hair is as coarse and harsh as that of a horse’s
mane, whilst the hair of other colours is fine and soft.) The colour
also of the skin, and the odour emitted by it, are likewise in some
manner connected. With the breeds of sheep the number of hairs within a
given space and the number of excretory pores are related. (69. On the
odour of the skin, Godron, ‘Sur l’Espèce,’ tom. ii. p. 217. On the
pores in the skin, Dr. Wilckens, ‘Die Aufgaben der Landwirth.
Zootechnik,’ 1869, s. 7.) If we may judge from the analogy of our
domesticated animals, many modifications of structure in man probably
come under this principle of correlated development.

We have now seen that the external characteristic differences between
the races of man cannot be accounted for in a satisfactory manner by
the direct action of the conditions of life, nor by the effects of the
continued use of parts, nor through the principle of correlation. We
are therefore led to enquire whether slight individual differences, to
which man is eminently liable, may not have been preserved and
augmented during a long series of generations through natural
selection. But here we are at once met by the objection that beneficial
variations alone can be thus preserved; and as far as we are enabled to
judge, although always liable to err on this head, none of the
differences between the races of man are of any direct or special
service to him. The intellectual and moral or social faculties must of
course be excepted from this remark. The great variability of all the
external differences between the races of man, likewise indicates that
they cannot be of much importance; for if important, they would long
ago have been either fixed and preserved, or eliminated. In this
respect man resembles those forms, called by naturalists protean or
polymorphic, which have remained extremely variable, owing, as it
seems, to such variations being of an indifferent nature, and to their
having thus escaped the action of natural selection.

We have thus far been baffled in all our attempts to account for the
differences between the races of man; but there remains one important
agency, namely Sexual Selection, which appears to have acted powerfully
on man, as on many other animals. I do not intend to assert that sexual
selection will account for all the differences between the races. An
unexplained residuum is left, about which we can only say, in our
ignorance, that as individuals are continually born with, for instance,
heads a little rounder or narrower, and with noses a little longer or
shorter, such slight differences might become fixed and uniform, if the
unknown agencies which induced them were to act in a more constant
manner, aided by long-continued intercrossing. Such variations come
under the provisional class, alluded to in our second chapter, which
for want of a better term are often called spontaneous. Nor do I
pretend that the effects of sexual selection can be indicated with
scientific precision; but it can be shewn that it would be an
inexplicable fact if man had not been modified by this agency, which
appears to have acted powerfully on innumerable animals. It can further
be shewn that the differences between the races of man, as in colour,
hairiness, form of features, etc., are of a kind which might have been
expected to come under the influence of sexual selection. But in order
to treat this subject properly, I have found it necessary to pass the
whole animal kingdom in review. I have therefore devoted to it the
Second Part of this work. At the close I shall return to man, and,
after attempting to shew how far he has been modified through sexual
selection, will give a brief summary of the chapters in this First
Part.

NOTE ON THE RESEMBLANCES AND DIFFERENCES IN THE STRUCTURE AND THE
DEVELOPMENT OF THE BRAIN IN MAN AND APES BY PROFESSOR HUXLEY, F.R.S.

The controversy respecting the nature and the extent of the differences
in the structure of the brain in man and the apes, which arose some
fifteen years ago, has not yet come to an end, though the subject
matter of the dispute is, at present, totally different from what it
was formerly. It was originally asserted and re-asserted, with singular
pertinacity, that the brain of all the apes, even the highest, differs
from that of man, in the absence of such conspicuous structures as the
posterior lobes of the cerebral hemispheres, with the posterior cornu
of the lateral ventricle and the hippocampus minor, contained in those
lobes, which are so obvious in man.

But the truth that the three structures in question are as well
developed in apes’ as in human brains, or even better; and that it is
characteristic of all the Primates (if we exclude the Lemurs) to have
these parts well developed, stands at present on as secure a basis as
any proposition in comparative anatomy. Moreover, it is admitted by
every one of the long series of anatomists who, of late years, have
paid special attention to the arrangement of the complicated sulci and
gyri which appear upon the surface of the cerebral hemispheres in man
and the higher apes, that they are disposed after the very same pattern
in him, as in them. Every principal gyrus and sulcus of a chimpanzee’s
brain is clearly represented in that of a man, so that the terminology
which applies to the one answers for the other. On this point there is
no difference of opinion. Some years since, Professor Bischoff
published a memoir (70. ‘Die Grosshirn-Windungen des Menschen;’
‘Abhandlungen der K. Bayerischen Akademie,’ B. x. 1868.) on the
cerebral convolutions of man and apes; and as the purpose of my learned
colleague was certainly not to diminish the value of the differences
between apes and men in this respect, I am glad to make a citation from
him.

“That the apes, and especially the orang, chimpanzee and gorilla, come
very close to man in their organisation, much nearer than to any other
animal, is a well known fact, disputed by nobody. Looking at the matter
from the point of view of organisation alone, no one probably would
ever have disputed the view of Linnaeus, that man should be placed,
merely as a peculiar species, at the head of the mammalia and of those
apes. Both shew, in all their organs, so close an affinity, that the
most exact anatomical investigation is needed in order to demonstrate
those differences which really exist. So it is with the brains. The
brains of man, the orang, the chimpanzee, the gorilla, in spite of all
the important differences which they present, come very close to one
another” (loc. cit. p. 101).

There remains, then, no dispute as to the resemblance in fundamental
characters, between the ape’s brain and man’s: nor any as to the
wonderfully close similarity between the chimpanzee, orang and man, in
even the details of the arrangement of the gyri and sulci of the
cerebral hemispheres. Nor, turning to the differences between the
brains of the highest apes and that of man, is there any serious
question as to the nature and extent of these differences. It is
admitted that the man’s cerebral hemispheres are absolutely and
relatively larger than those of the orang and chimpanzee; that his
frontal lobes are less excavated by the upward protrusion of the roof
of the orbits; that his gyri and sulci are, as a rule, less
symmetrically disposed, and present a greater number of secondary
plications. And it is admitted that, as a rule, in man, the
temporo-occipital or “external perpendicular” fissure, which is usually
so strongly marked a feature of the ape’s brain is but faintly marked.
But it is also clear, that none of these differences constitutes a
sharp demarcation between the man’s and the ape’s brain. In respect to
the external perpendicular fissure of Gratiolet, in the human brain for
instance, Professor Turner remarks: (71. ‘Convolutions of the Human
Cerebrum Topographically Considered,’ 1866, p. 12.)

“In some brains it appears simply as an indentation of the margin of
the hemisphere, but, in others, it extends for some distance more or
less transversely outwards. I saw it in the right hemisphere of a
female brain pass more than two inches outwards; and on another
specimen, also the right hemisphere, it proceeded for four-tenths of an
inch outwards, and then extended downwards, as far as the lower margin
of the outer surface of the hemisphere. The imperfect definition of
this fissure in the majority of human brains, as compared with its
remarkable distinctness in the brain of most Quadrumana, is owing to
the presence, in the former, of certain superficial, well marked,
secondary convolutions which bridge it over and connect the parietal
with the occipital lobe. The closer the first of these bridging gyri
lies to the longitudinal fissure, the shorter is the external
parieto-occipital fissure” (loc. cit. p. 12).

The obliteration of the external perpendicular fissure of Gratiolet,
therefore, is not a constant character of the human brain. On the other
hand, its full development is not a constant character of the higher
ape’s brain. For, in the chimpanzee, the more or less extensive
obliteration of the external perpendicular sulcus by “bridging
convolutions,” on one side or the other, has been noted over and over
again by Prof. Rolleston, Mr. Marshall, M. Broca and Professor Turner.
At the conclusion of a special paper on this subject the latter writes:
(72. Notes more especially on the bridging convolutions in the Brain of
the Chimpanzee, ‘Proceedings of the Royal Society of Edinburgh,’
1865-6.)

“The three specimens of the brain of a chimpanzee, just described,
prove, that the generalisation which Gratiolet has attempted to draw of
the complete absence of the first connecting convolution and the
concealment of the second, as essentially characteristic features in
the brain of this animal, is by no means universally applicable. In
only one specimen did the brain, in these particulars, follow the law
which Gratiolet has expressed. As regards the presence of the superior
bridging convolution, I am inclined to think that it has existed in one
hemisphere, at least, in a majority of the brains of this animal which
have, up to this time, been figured or described. The superficial
position of the second bridging convolution is evidently less frequent,
and has as yet, I believe, only been seen in the brain (A) recorded in
this communication. The asymmetrical arrangement in the convolutions of
the two hemispheres, which previous observers have referred to in their
descriptions, is also well illustrated in these specimens” (pp. 8, 9).

Even were the presence of the temporo-occipital, or external
perpendicular, sulcus, a mark of distinction between the higher apes
and man, the value of such a distinctive character would be rendered
very doubtful by the structure of the brain in the Platyrrhine apes. In
fact, while the temporo-occipital is one of the most constant of sulci
in the Catarrhine, or Old World, apes, it is never very strongly
developed in the New World apes; it is absent in the smaller
Platyrrhini; rudimentary in Pithecia (73. Flower, ‘On the Anatomy of
Pithecia Monachus,’ ‘Proceedings of the Zoological Society,’ 1862.);
and more or less obliterated by bridging convolutions in Ateles.

A character which is thus variable within the limits of a single group
can have no great taxonomic value.

It is further established, that the degree of asymmetry of the
convolution of the two sides in the human brain is subject to much
individual variation; and that, in those individuals of the Bushman
race who have been examined, the gyri and sulci of the two hemispheres
are considerably less complicated and more symmetrical than in the
European brain, while, in some individuals of the chimpanzee, their
complexity and asymmetry become notable. This is particularly the case
in the brain of a young male chimpanzee figured by M. Broca. (‘L’ordre
des Primates,’ p. 165, fig. 11.)

Again, as respects the question of absolute size, it is established
that the difference between the largest and the smallest healthy human
brain is greater than the difference between the smallest healthy human
brain and the largest chimpanzee’s or orang’s brain.

Moreover, there is one circumstance in which the orang’s and
chimpanzee’s brains resemble man’s, but in which they differ from the
lower apes, and that is the presence of two corpora candicantia—the
Cynomorpha having but one.

In view of these facts I do not hesitate in this year 1874, to repeat
and insist upon the proposition which I enunciated in 1863: (74. ‘Man’s
Place in Nature,’ p. 102.)

“So far as cerebral structure goes, therefore, it is clear that man
differs less from the chimpanzee or the orang, than these do even from
the monkeys, and that the difference between the brain of the
chimpanzee and of man is almost insignificant when compared with that
between the chimpanzee brain and that of a Lemur.”

In the paper to which I have referred, Professor Bischoff does not deny
the second part of this statement, but he first makes the irrelevant
remark that it is not wonderful if the brains of an orang and a Lemur
are very different; and secondly, goes on to assert that, “If we
successively compare the brain of a man with that of an orang; the
brain of this with that of a chimpanzee; of this with that of a
gorilla, and so on of a Hylobates, Semnopithecus, Cynocephalus,
Cercopithecus, Macacus, Cebus, Callithrix, Lemur, Stenops, Hapale, we
shall not meet with a greater, or even as great a, break in the degree
of development of the convolutions, as we find between the brain of a
man and that of an orang or chimpanzee.”

To which I reply, firstly, that whether this assertion be true or
false, it has nothing whatever to do with the proposition enunciated in
‘Man’s Place in Nature,’ which refers not to the development of the
convolutions alone, but to the structure of the whole brain. If
Professor Bischoff had taken the trouble to refer to p. 96 of the work
he criticises, in fact, he would have found the following passage: “And
it is a remarkable circumstance that though, so far as our present
knowledge extends, there IS one true structural break in the series of
forms of Simian brains, this hiatus does not lie between man and the
manlike apes, but between the lower and the lowest Simians, or in other
words, between the Old and New World apes and monkeys and the Lemurs.
Every Lemur which has yet been examined, in fact, has its cerebellum
partially visible from above; and its posterior lobe, with the
contained posterior cornu and hippocampus minor, more or less
rudimentary. Every marmoset, American monkey, Old World monkey, baboon
or manlike ape, on the contrary, has its cerebellum entirely hidden,
posteriorly, by the cerebral lobes, and possesses a large posterior
cornu with a well-developed hippocampus minor.”

This statement was a strictly accurate account of what was known when
it was made; and it does not appear to me to be more than apparently
weakened by the subsequent discovery of the relatively small
development of the posterior lobes in the Siamang and in the Howling
monkey. Notwithstanding the exceptional brevity of the posterior lobes
in these two species, no one will pretend that their brains, in the
slightest degree, approach those of the Lemurs. And if, instead of
putting Hapale out of its natural place, as Professor Bischoff most
unaccountably does, we write the series of animals he has chosen to
mention as follows: Homo, Pithecus, Troglodytes, Hylobates,
Semnopithecus, Cynocephalus, Cercopithecus, Macacus, Cebus, Callithrix,
Hapale, Lemur, Stenops, I venture to reaffirm that the great break in
this series lies between Hapale and Lemur, and that this break is
considerably greater than that between any other two terms of that
series. Professor Bischoff ignores the fact that long before he wrote,
Gratiolet had suggested the separation of the Lemurs from the other
Primates on the very ground of the difference in their cerebral
characters; and that Professor Flower had made the following
observations in the course of his description of the brain of the Javan
Loris: (75. ‘Transactions of the Zoological Society,’ vol. v. 1862.)

“And it is especially remarkable that, in the development of the
posterior lobes, there is no approximation to the Lemurine, short
hemisphered brain, in those monkeys which are commonly supposed to
approach this family in other respects, viz. the lower members of the
Platyrrhine group.”

So far as the structure of the adult brain is concerned, then, the very
considerable additions to our knowledge, which have been made by the
researches of so many investigators, during the past ten years, fully
justify the statement which I made in 1863. But it has been said, that,
admitting the similarity between the adult brains of man and apes, they
are nevertheless, in reality, widely different, because they exhibit
fundamental differences in the mode of their development. No one would
be more ready than I to admit the force of this argument, if such
fundamental differences of development really exist. But I deny that
they do exist. On the contrary, there is a fundamental agreement in the
development of the brain in men and apes.

Gratiolet originated the statement that there is a fundamental
difference in the development of the brains of apes and that of
man—consisting in this; that, in the apes, the sulci which first make
their appearance are situated on the posterior region of the cerebral
hemispheres, while, in the human foetus, the sulci first become visible
on the frontal lobes. (76. Chez tous les singes, les plis postérieurs
se developpent les premiers; les plis antérieurs se developpent plus
tard, aussi la vertèbre occipitale et la parietale sont-elles
relativement tres-grandes chez le foetus. L’Homme présente une
exception remarquable quant a l’époque de l’apparition des plis
frontaux, qui sont les premiers indiqués; mais le développement general
du lobe frontal, envisagé seulement par rapport a son volume, suit les
mêmes lois que dans les singes: Gratiolet, ‘Mémoire sur les plis
cérèbres de l’Homme et des Primateaux,’ p. 39, Tab. iv, fig. 3.)

This general statement is based upon two observations, the one of a
Gibbon almost ready to be born, in which the posterior gyri were “well
developed,” while those of the frontal lobes were “hardly indicated”
(77. Gratiolet’s words are (loc. cit. p. 39): “Dans le foetus dont il
s’agit les plis cérébraux posterieurs sont bien developpés, tandis que
les plis du lobe frontal sont a peine indiqués.” The figure, however
(Pl. iv, fig. 3), shews the fissure of Rolando, and one of the frontal
sulci plainly enough. Nevertheless, M. Alix, in his ‘Notice sur les
travaux anthropologiques de Gratiolet’ (‘Mem. de la Societé
d’Anthropologie de Paris,’ 1868, page 32), writes thus: “Gratiolet a eu
entre les mains le cerveau d’un foetus de Gibbon, singe eminemment
supérieur, et tellement rapproché de l’orang, que des naturalistes
tres-compétents l’ont rangé parmi les anthropoides. M. Huxley, par
exemple, n’hesite pas sur ce point. Eh bien, c’est sur le cerveau d’un
foetus de Gibbon que Gratiolet a vu LES CIRCONVOLUTIONS DU LOBE
TEMPORO-SPHENOIDAL DÉJÀ DEVELOPPÉES LORSQU’IL N’EXISTENT PAS ENCORE DE
PLIS SUR LE LOBE FRONTAL. Il etait donc bien autorisé a dire que, chez
l’homme les circonvolutions apparaissent d’a en w, tandis que chez les
singes elles se developpent d’w en a.”), and the other of a human
foetus at the 22nd or 23rd week of uterogestation, in which Gratiolet
notes that the insula was uncovered, but that nevertheless “des
incisures sement de lobe anterieur, une scissure peu profonde indique
la separation du lobe occipital, tres-reduit, d’ailleurs dès cette
époque. Le reste de la surface cérébrale est encore absolument lisse.”

Three views of this brain are given in Plate II, figs. 1, 2, 3, of the
work cited, shewing the upper, lateral and inferior views of the
hemispheres, but not the inner view. It is worthy of note that the
figure by no means bears out Gratiolet’s description, inasmuch as the
fissure (antero-temporal) on the posterior half of the face of the
hemisphere is more marked than any of those vaguely indicated in the
anterior half. If the figure is correct, it in no way justifies
Gratiolet’s conclusion: “Il y a donc entre ces cerveaux [those of a
Callithrix and of a Gibbon] et celui du foetus humain une différence
fondamental. Chez celui-ci, longtemps avant que les plis temporaux
apparaissent, les plis frontaux, ESSAYENT d’exister.”

Since Gratiolet’s time, however, the development of the gyri and sulci
of the brain has been made the subject of renewed investigation by
Schmidt, Bischoff, Pansch (78. ‘Ueber die typische Anordnung der
Furchen und Windungen auf den Grosshirn-Hemisphären des Menschen und
der Affen,’ ‘Archiv für Anthropologie,’ iii. 1868.), and more
particularly by Ecker (79. ‘Zur Entwicklungs Geschichte der Furchen und
Windungen der Grosshirn-Hemisphären im Foetus des Menschen,’ ‘Archiv
für Anthropologie,’ iii. 1868.), whose work is not only the latest, but
by far the most complete, memoir on the subject.

The final results of their inquiries may be summed up as follows:— 1.
In the human foetus, the sylvian fissure is formed in the course of the
third month of uterogestation. In this, and in the fourth month, the
cerebral hemispheres are smooth and rounded (with the exception of the
sylvian depression), and they project backwards far beyond the
cerebellum.

2. The sulci, properly so called, begin to appear in the interval
between the end of the fourth and the beginning of the sixth month of
foetal life, but Ecker is careful to point out that, not only the time,
but the order, of their appearance is subject to considerable
individual variation. In no case, however, are either the frontal or
the temporal sulci the earliest.

The first which appears, in fact, lies on the inner face of the
hemisphere (whence doubtless Gratiolet, who does not seem to have
examined that face in his foetus, overlooked it), and is either the
internal perpendicular (occipito-parietal), or the calcarine sulcus,
these two being close together and eventually running into one another.
As a rule the occipito-parietal is the earlier of the two.

3. At the latter part of this period, another sulcus, the
“posterio-parietal,” or “Fissure of Rolando” is developed, and it is
followed, in the course of the sixth month, by the other principal
sulci of the frontal, parietal, temporal and occipital lobes. There is,
however, no clear evidence that one of these constantly appears before
the other; and it is remarkable that, in the brain at the period
described and figured by Ecker (loc. cit. pp. 212-213, Taf. II, figs.
1, 2, 3, 4), the antero-temporal sulcus (scissure parallele) so
characteristic of the ape’s brain, is as well, if not better developed
than the fissure of Rolando, and is much more marked than the proper
frontal sulci.

Taking the facts as they now stand, it appears to me that the order of
the appearance of the sulci and gyri in the foetal human brain is in
perfect harmony with the general doctrine of evolution, and with the
view that man has been evolved from some ape-like form; though there
can be no doubt that form was, in many respects, different from any
member of the Primates now living.

Von Baer taught us, half a century ago, that, in the course of their
development, allied animals put on at first, the characters of the
greater groups to which they belong, and, by degrees, assume those
which restrict them within the limits of their family, genus, and
species; and he proved, at the same time, that no developmental stage
of a higher animal is precisely similar to the adult condition of any
lower animal. It is quite correct to say that a frog passes through the
condition of a fish, inasmuch as at one period of its life the tadpole
has all the characters of a fish, and if it went no further, would have
to be grouped among fishes. But it is equally true that a tadpole is
very different from any known fish.

In like manner, the brain of a human foetus, at the fifth month, may
correctly be said to be, not only the brain of an ape, but that of an
Arctopithecine or marmoset-like ape; for its hemispheres, with their
great posterior lobster, and with no sulci but the sylvian and the
calcarine, present the characteristics found only in the group of the
Arctopithecine Primates. But it is equally true, as Gratiolet remarks,
that, in its widely open sylvian fissure, it differs from the brain of
any actual marmoset. No doubt it would be much more similar to the
brain of an advanced foetus of a marmoset. But we know nothing whatever
of the development of the brain in the marmosets. In the Platyrrhini
proper, the only observation with which I am acquainted is due to
Pansch, who found in the brain of a foetal Cebus Apella, in addition to
the sylvian fissure and the deep calcarine fissure, only a very shallow
antero-temporal fissure (scissure parallele of Gratiolet).

Now this fact, taken together with the circumstance that the
antero-temporal sulcus is present in such Platyrrhini as the Saimiri,
which present mere traces of sulci on the anterior half of the exterior
of the cerebral hemispheres, or none at all, undoubtedly, so far as it
goes, affords fair evidence in favour of Gratiolet’s hypothesis, that
the posterior sulci appear before the anterior, in the brains of the
Platyrrhini. But, it by no means follows, that the rule which may hold
good for the Platyrrhini extends to the Catarrhini. We have no
information whatever respecting the development of the brain in the
Cynomorpha; and, as regards the Anthropomorpha, nothing but the account
of the brain of the Gibbon, near birth, already referred to. At the
present moment there is not a shadow of evidence to shew that the sulci
of a chimpanzee’s, or orang’s, brain do not appear in the same order as
a man’s.

Gratiolet opens his preface with the aphorism: “Il est dangereux dans
les sciences de conclure trop vite.” I fear he must have forgotten this
sound maxim by the time he had reached the discussion of the
differences between men and apes, in the body of his work. No doubt,
the excellent author of one of the most remarkable contributions to the
just understanding of the mammalian brain which has ever been made,
would have been the first to admit the insufficiency of his data had he
lived to profit by the advance of inquiry. The misfortune is that his
conclusions have been employed by persons incompetent to appreciate
their foundation, as arguments in favour of obscurantism. (80. For
example, M. l’Abbe Lecomte in his terrible pamphlet, ‘Le Darwinisme et
l’origine de l’Homme,’ 1873.)

But it is important to remark that, whether Gratiolet was right or
wrong in his hypothesis respecting the relative order of appearance of
the temporal and frontal sulci, the fact remains; that before either
temporal or frontal sulci, appear, the foetal brain of man presents
characters which are found only in the lowest group of the Primates
(leaving out the Lemurs); and that this is exactly what we should
expect to be the case, if man has resulted from the gradual
modification of the same form as that from which the other Primates
have sprung.




PART II.
SEXUAL SELECTION.




CHAPTER VIII.
PRINCIPLES OF SEXUAL SELECTION.


Secondary sexual characters—Sexual selection—Manner of action—Excess of
males—Polygamy—The male alone generally modified through sexual
selection—Eagerness of the male—Variability of the male—Choice exerted
by the female—Sexual compared with natural selection—Inheritance, at
corresponding periods of life, at corresponding seasons of the year,
and as limited by sex—Relations between the several forms of
inheritance—Causes why one sex and the young are not modified through
sexual selection—Supplement on the proportional numbers of the two
sexes throughout the animal kingdom—The proportion of the sexes in
relation to natural selection.

With animals which have their sexes separated, the males necessarily
differ from the females in their organs of reproduction; and these are
the primary sexual characters. But the sexes often differ in what
Hunter has called secondary sexual characters, which are not directly
connected with the act of reproduction; for instance, the male
possesses certain organs of sense or locomotion, of which the female is
quite destitute, or has them more highly-developed, in order that he
may readily find or reach her; or again the male has special organs of
prehension for holding her securely. These latter organs, of infinitely
diversified kinds, graduate into those which are commonly ranked as
primary, and in some cases can hardly be distinguished from them; we
see instances of this in the complex appendages at the apex of the
abdomen in male insects. Unless indeed we confine the term “primary” to
the reproductive glands, it is scarcely possible to decide which ought
to be called primary and which secondary.

The female often differs from the male in having organs for the
nourishment or protection of her young, such as the mammary glands of
mammals, and the abdominal sacks of the marsupials. In some few cases
also the male possesses similar organs, which are wanting in the
female, such as the receptacles for the ova in certain male fishes, and
those temporarily developed in certain male frogs. The females of most
bees are provided with a special apparatus for collecting and carrying
pollen, and their ovipositor is modified into a sting for the defence
of the larvae and the community. Many similar cases could be given, but
they do not here concern us. There are, however, other sexual
differences quite unconnected with the primary reproductive organs, and
it is with these that we are more especially concerned—such as the
greater size, strength, and pugnacity of the male, his weapons of
offence or means of defence against rivals, his gaudy colouring and
various ornaments, his power of song, and other such characters.

Besides the primary and secondary sexual differences, such as the
foregoing, the males and females of some animals differ in structures
related to different habits of life, and not at all, or only
indirectly, to the reproductive functions. Thus the females of certain
flies (Culicidae and Tabanidae) are blood-suckers, whilst the males,
living on flowers, have mouths destitute of mandibles. (1. Westwood,
‘Modern Classification of Insects,’ vol. ii. 1840, p. 541. For the
statement about Tanais, mentioned below, I am indebted to Fritz
Muller.) The males of certain moths and of some crustaceans (e.g.
Tanais) have imperfect, closed mouths, and cannot feed. The
complemental males of certain Cirripedes live like epiphytic plants
either on the female or the hermaphrodite form, and are destitute of a
mouth and of prehensile limbs. In these cases it is the male which has
been modified, and has lost certain important organs, which the females
possess. In other cases it is the female which has lost such parts; for
instance, the female glow-worm is destitute of wings, as also are many
female moths, some of which never leave their cocoons. Many female
parasitic crustaceans have lost their natatory legs. In some
weevil-beetles (Curculionidae) there is a great difference between the
male and female in the length of the rostrum or snout (2. Kirby and
Spence, ‘Introduction to Entomology,’ vol. iii. 1826, p. 309.); but the
meaning of this and of many analogous differences, is not at all
understood. Differences of structure between the two sexes in relation
to different habits of life are generally confined to the lower
animals; but with some few birds the beak of the male differs from that
of the female. In the Huia of New Zealand the difference is wonderfully
great, and we hear from Dr. Buller (3. ‘Birds of New Zealand,’ 1872, p.
66.) that the male uses his strong beak in chiselling the larvae of
insects out of decayed wood, whilst the female probes the softer parts
with her far longer, much curved and pliant beak: and thus they
mutually aid each other. In most cases, differences of structure
between the sexes are more or less directly connected with the
propagation of the species: thus a female, which has to nourish a
multitude of ova, requires more food than the male, and consequently
requires special means for procuring it. A male animal, which lives for
a very short time, might lose its organs for procuring food through
disuse, without detriment; but he would retain his locomotive organs in
a perfect state, so that he might reach the female. The female, on the
other hand, might safely lose her organs for flying, swimming, or
walking, if she gradually acquired habits which rendered such powers
useless.

We are, however, here concerned only with sexual selection. This
depends on the advantage which certain individuals have over others of
the same sex and species solely in respect of reproduction. When, as in
the cases above mentioned, the two sexes differ in structure in
relation to different habits of life, they have no doubt been modified
through natural selection, and by inheritance limited to one and the
same sex. So again the primary sexual organs, and those for nourishing
or protecting the young, come under the same influence; for those
individuals which generated or nourished their offspring best, would
leave, ceteris paribus, the greatest number to inherit their
superiority; whilst those which generated or nourished their offspring
badly, would leave but few to inherit their weaker powers. As the male
has to find the female, he requires organs of sense and locomotion, but
if these organs are necessary for the other purposes of life, as is
generally the case, they will have been developed through natural
selection. When the male has found the female, he sometimes absolutely
requires prehensile organs to hold her; thus Dr. Wallace informs me
that the males of certain moths cannot unite with the females if their
tarsi or feet are broken. The males of many oceanic crustaceans, when
adult, have their legs and antennae modified in an extraordinary manner
for the prehension of the female; hence we may suspect that it is
because these animals are washed about by the waves of the open sea,
that they require these organs in order to propagate their kind, and if
so, their development has been the result of ordinary or natural
selection. Some animals extremely low in the scale have been modified
for this same purpose; thus the males of certain parasitic worms, when
fully grown, have the lower surface of the terminal part of their
bodies roughened like a rasp, and with this they coil round and
permanently hold the females. (4. M. Perrier advances this case (‘Revue
Scientifique,’ Feb. 1, 1873, p. 865) as one fatal to the belief in
sexual election, inasmuch as he supposes that I attribute all the
differences between the sexes to sexual selection. This distinguished
naturalist, therefore, like so many other Frenchmen, has not taken the
trouble to understand even the first principles of sexual selection. An
English naturalist insists that the claspers of certain male animals
could not have been developed through the choice of the female! Had I
not met with this remark, I should not have thought it possible for any
one to have read this chapter and to have imagined that I maintain that
the choice of the female had anything to do with the development of the
prehensile organs in the male.)

When the two sexes follow exactly the same habits of life, and the male
has the sensory or locomotive organs more highly developed than those
of the female, it may be that the perfection of these is indispensable
to the male for finding the female; but in the vast majority of cases,
they serve only to give one male an advantage over another, for with
sufficient time, the less well-endowed males would succeed in pairing
with the females; and judging from the structure of the female, they
would be in all other respects equally well adapted for their ordinary
habits of life. Since in such cases the males have acquired their
present structure, not from being better fitted to survive in the
struggle for existence, but from having gained an advantage over other
males, and from having transmitted this advantage to their male
offspring alone, sexual selection must here have come into action. It
was the importance of this distinction which led me to designate this
form of selection as Sexual Selection. So again, if the chief service
rendered to the male by his prehensile organs is to prevent the escape
of the female before the arrival of other males, or when assaulted by
them, these organs will have been perfected through sexual selection,
that is by the advantage acquired by certain individuals over their
rivals. But in most cases of this kind it is impossible to distinguish
between the effects of natural and sexual selection. Whole chapters
could be filled with details on the differences between the sexes in
their sensory, locomotive, and prehensile organs. As, however, these
structures are not more interesting than others adapted for the
ordinary purposes of life I shall pass them over almost entirely,
giving only a few instances under each class.

There are many other structures and instincts which must have been
developed through sexual selection—such as the weapons of offence and
the means of defence of the males for fighting with and driving away
their rivals—their courage and pugnacity—their various ornaments—their
contrivances for producing vocal or instrumental music—and their glands
for emitting odours, most of these latter structures serving only to
allure or excite the female. It is clear that these characters are the
result of sexual and not of ordinary selection, since unarmed,
unornamented, or unattractive males would succeed equally well in the
battle for life and in leaving a numerous progeny, but for the presence
of better endowed males. We may infer that this would be the case,
because the females, which are unarmed and unornamented, are able to
survive and procreate their kind. Secondary sexual characters of the
kind just referred to, will be fully discussed in the following
chapters, as being in many respects interesting, but especially as
depending on the will, choice, and rivalry of the individuals of either
sex. When we behold two males fighting for the possession of the
female, or several male birds displaying their gorgeous plumage, and
performing strange antics before an assembled body of females, we
cannot doubt that, though led by instinct, they know what they are
about, and consciously exert their mental and bodily powers.

Just as man can improve the breeds of his game-cocks by the selection
of those birds which are victorious in the cockpit, so it appears that
the strongest and most vigorous males, or those provided with the best
weapons, have prevailed under nature, and have led to the improvement
of the natural breed or species. A slight degree of variability leading
to some advantage, however slight, in reiterated deadly contests would
suffice for the work of sexual selection; and it is certain that
secondary sexual characters are eminently variable. Just as man can
give beauty, according to his standard of taste, to his male poultry,
or more strictly can modify the beauty originally acquired by the
parent species, can give to the Sebright bantam a new and elegant
plumage, an erect and peculiar carriage—so it appears that female birds
in a state of nature, have by a long selection of the more attractive
males, added to their beauty or other attractive qualities. No doubt
this implies powers of discrimination and taste on the part of the
female which will at first appear extremely improbable; but by the
facts to be adduced hereafter, I hope to be able to shew that the
females actually have these powers. When, however, it is said that the
lower animals have a sense of beauty, it must not be supposed that such
sense is comparable with that of a cultivated man, with his multiform
and complex associated ideas. A more just comparison would be between
the taste for the beautiful in animals, and that in the lowest savages,
who admire and deck themselves with any brilliant, glittering, or
curious object.

From our ignorance on several points, the precise manner in which
sexual selection acts is somewhat uncertain. Nevertheless if those
naturalists who already believe in the mutability of species, will read
the following chapters, they will, I think, agree with me, that sexual
selection has played an important part in the history of the organic
world. It is certain that amongst almost all animals there is a
struggle between the males for the possession of the female. This fact
is so notorious that it would be superfluous to give instances. Hence
the females have the opportunity of selecting one out of several males,
on the supposition that their mental capacity suffices for the exertion
of a choice. In many cases special circumstances tend to make the
struggle between the males particularly severe. Thus the males of our
migratory birds generally arrive at their places of breeding before the
females, so that many males are ready to contend for each female. I am
informed by Mr. Jenner Weir, that the bird-catchers assert that this is
invariably the case with the nightingale and blackcap, and with respect
to the latter he can himself confirm the statement.

Mr. Swaysland of Brighton has been in the habit, during the last forty
years, of catching our migratory birds on their first arrival, and he
has never known the females of any species to arrive before their
males. During one spring he shot thirty-nine males of Ray’s wagtail
(Budytes Raii) before he saw a single female. Mr. Gould has ascertained
by the dissection of those snipes which arrive the first in this
country, that the males come before the females. And the like holds
good with most of the migratory birds of the United States. (5. J.A.
Allen, on the ‘Mammals and Winter Birds of Florida,’ Bulletin of
Comparative Zoology, Harvard College, p. 268.) The majority of the male
salmon in our rivers, on coming up from the sea, are ready to breed
before the females. So it appears to be with frogs and toads.
Throughout the great class of insects the males almost always are the
first to emerge from the pupal state, so that they generally abound for
a time before any females can be seen. (6. Even with those plants in
which the sexes are separate, the male flowers are generally mature
before the female. As first shewn by C.K. Sprengel, many hermaphrodite
plants are dichogamous; that is, their male and female organs are not
ready at the same time, so that they cannot be self-fertilised. Now in
such flowers, the pollen is in general matured before the stigma,
though there are exceptional cases in which the female organs are
beforehand.) The cause of this difference between the males and females
in their periods of arrival and maturity is sufficiently obvious. Those
males which annually first migrated into any country, or which in the
spring were first ready to breed, or were the most eager, would leave
the largest number of offspring; and these would tend to inherit
similar instincts and constitutions. It must be borne in mind that it
would have been impossible to change very materially the time of sexual
maturity in the females, without at the same time interfering with the
period of the production of the young—a period which must be determined
by the seasons of the year. On the whole there can be no doubt that
with almost all animals, in which the sexes are separate, there is a
constantly recurrent struggle between the males for the possession of
the females.

Our difficulty in regard to sexual selection lies in understanding how
it is that the males which conquer other males, or those which prove
the most attractive to the females, leave a greater number of offspring
to inherit their superiority than their beaten and less attractive
rivals. Unless this result does follow, the characters which give to
certain males an advantage over others, could not be perfected and
augmented through sexual selection. When the sexes exist in exactly
equal numbers, the worst-endowed males will (except where polygamy
prevails), ultimately find females, and leave as many offspring, as
well fitted for their general habits of life, as the best-endowed
males. From various facts and considerations, I formerly inferred that
with most animals, in which secondary sexual characters are well
developed, the males considerably exceeded the females in number; but
this is not by any means always true. If the males were to the females
as two to one, or as three to two, or even in a somewhat lower ratio,
the whole affair would be simple; for the better-armed or more
attractive males would leave the largest number of offspring. But after
investigating, as far as possible, the numerical proportion of the
sexes, I do not believe that any great inequality in number commonly
exists. In most cases sexual selection appears to have been effective
in the following manner.

Let us take any species, a bird for instance, and divide the females
inhabiting a district into two equal bodies, the one consisting of the
more vigorous and better-nourished individuals, and the other of the
less vigorous and healthy. The former, there can be little doubt, would
be ready to breed in the spring before the others; and this is the
opinion of Mr. Jenner Weir, who has carefully attended to the habits of
birds during many years. There can also be no doubt that the most
vigorous, best-nourished and earliest breeders would on an average
succeed in rearing the largest number of fine offspring. (7. Here is
excellent evidence on the character of the offspring from an
experienced ornithologist. Mr. J.A. Allen, in speaking (‘Mammals and
Winter Birds of E. Florida,’ p. 229) of the later broods, after the
accidental destruction of the first, says, that these “are found to be
smaller and paler-coloured than those hatched earlier in the season. In
cases where several broods are reared each year, as a general rule the
birds of the earlier broods seem in all respects the most perfect and
vigorous.”) The males, as we have seen, are generally ready to breed
before the females; the strongest, and with some species the best armed
of the males, drive away the weaker; and the former would then unite
with the more vigorous and better-nourished females, because they are
the first to breed. (8. Hermann Müller has come to this same conclusion
with respect to those female bees which are the first to emerge from
the pupa each year. See his remarkable essay, ‘Anwendung der
Darwin’schen Lehre auf Bienen,’ ‘Verh. d. V. Jahrg.’ xxix. p. 45.) Such
vigorous pairs would surely rear a larger number of offspring than the
retarded females, which would be compelled to unite with the conquered
and less powerful males, supposing the sexes to be numerically equal;
and this is all that is wanted to add, in the course of successive
generations, to the size, strength and courage of the males, or to
improve their weapons.

But in very many cases the males which conquer their rivals, do not
obtain possession of the females, independently of the choice of the
latter. The courtship of animals is by no means so simple and short an
affair as might be thought. The females are most excited by, or prefer
pairing with, the more ornamented males, or those which are the best
songsters, or play the best antics; but it is obviously probable that
they would at the same time prefer the more vigorous and lively males,
and this has in some cases been confirmed by actual observation. (9.
With respect to poultry, I have received information, hereafter to be
given, to this effect. Even with birds, such as pigeons, which pair for
life, the female, as I hear from Mr. Jenner Weir, will desert her mate
if he is injured or grows weak.) Thus the more vigorous females, which
are the first to breed, will have the choice of many males; and though
they may not always select the strongest or best armed, they will
select those which are vigorous and well armed, and in other respects
the most attractive. Both sexes, therefore, of such early pairs would
as above explained, have an advantage over others in rearing offspring;
and this apparently has sufficed during a long course of generations to
add not only to the strength and fighting powers of the males, but
likewise to their various ornaments or other attractions.

In the converse and much rarer case of the males selecting particular
females, it is plain that those which were the most vigorous and had
conquered others, would have the freest choice; and it is almost
certain that they would select vigorous as well as attractive females.
Such pairs would have an advantage in rearing offspring, more
especially if the male had the power to defend the female during the
pairing-season as occurs with some of the higher animals, or aided her
in providing for the young. The same principles would apply if each sex
preferred and selected certain individuals of the opposite sex;
supposing that they selected not only the more attractive, but likewise
the more vigorous individuals.

NUMERICAL PROPORTION OF THE TWO SEXES.

I have remarked that sexual selection would be a simple affair if the
males were considerably more numerous than the females. Hence I was led
to investigate, as far as I could, the proportions between the two
sexes of as many animals as possible; but the materials are scanty. I
will here give only a brief abstract of the results, retaining the
details for a supplementary discussion, so as not to interfere with the
course of my argument. Domesticated animals alone afford the means of
ascertaining the proportional numbers at birth; but no records have
been specially kept for this purpose. By indirect means, however, I
have collected a considerable body of statistics, from which it appears
that with most of our domestic animals the sexes are nearly equal at
birth. Thus 25,560 births of race-horses have been recorded during
twenty-one years, and the male births were to the female births as 99.7
to 100. In greyhounds the inequality is greater than with any other
animal, for out of 6878 births during twelve years, the male births
were to the female as 110.1 to 100. It is, however, in some degree
doubtful whether it is safe to infer that the proportion would be the
same under natural conditions as under domestication; for slight and
unknown differences in the conditions affect the proportion of the
sexes. Thus with mankind, the male births in England are as 104.5, in
Russia as 108.9, and with the Jews of Livonia as 120, to 100 female
births. But I shall recur to this curious point of the excess of male
births in the supplement to this chapter. At the Cape of Good Hope,
however, male children of European extraction have been born during
several years in the proportion of between 90 and 99 to 100 female
children.

For our present purpose we are concerned with the proportions of the
sexes, not only at birth, but also at maturity, and this adds another
element of doubt; for it is a well-ascertained fact that with man the
number of males dying before or during birth, and during the first two
years of infancy, is considerably larger than that of females. So it
almost certainly is with male lambs, and probably with some other
animals. The males of some species kill one another by fighting; or
they drive one another about until they become greatly emaciated. They
must also be often exposed to various dangers, whilst wandering about
in eager search for the females. In many kinds of fish the males are
much smaller than the females, and they are believed often to be
devoured by the latter, or by other fishes. The females of some birds
appear to die earlier than the males; they are also liable to be
destroyed on their nests, or whilst in charge of their young. With
insects the female larvae are often larger than those of the males, and
would consequently be more likely to be devoured. In some cases the
mature females are less active and less rapid in their movements than
the males, and could not escape so well from danger. Hence, with
animals in a state of nature, we must rely on mere estimation, in order
to judge of the proportions of the sexes at maturity; and this is but
little trustworthy, except when the inequality is strongly marked.
Nevertheless, as far as a judgment can be formed, we may conclude from
the facts given in the supplement, that the males of some few mammals,
of many birds, of some fish and insects, are considerably more numerous
than the females.

The proportion between the sexes fluctuates slightly during successive
years: thus with race-horses, for every 100 mares born the stallions
varied from 107.1 in one year to 92.6 in another year, and with
greyhounds from 116.3 to 95.3. But had larger numbers been tabulated
throughout an area more extensive than England, these fluctuations
would probably have disappeared; and such as they are, would hardly
suffice to lead to effective sexual selection in a state of nature.
Nevertheless, in the cases of some few wild animals, as shewn in the
supplement, the proportions seem to fluctuate either during different
seasons or in different localities in a sufficient degree to lead to
such selection. For it should be observed that any advantage, gained
during certain years or in certain localities by those males which were
able to conquer their rivals, or were the most attractive to the
females, would probably be transmitted to the offspring, and would not
subsequently be eliminated. During the succeeding seasons, when, from
the equality of the sexes, every male was able to procure a female, the
stronger or more attractive males previously produced would still have
at least as good a chance of leaving offspring as the weaker or less
attractive.

POLYGAMY.

The practice of polygamy leads to the same results as would follow from
an actual inequality in the number of the sexes; for if each male
secures two or more females, many males cannot pair; and the latter
assuredly will be the weaker or less attractive individuals. Many
mammals and some few birds are polygamous, but with animals belonging
to the lower classes I have found no evidence of this habit. The
intellectual powers of such animals are, perhaps, not sufficient to
lead them to collect and guard a harem of females. That some relation
exists between polygamy and the development of secondary sexual
characters, appears nearly certain; and this supports the view that a
numerical preponderance of males would be eminently favourable to the
action of sexual selection. Nevertheless many animals, which are
strictly monogamous, especially birds, display strongly-marked
secondary sexual characters; whilst some few animals, which are
polygamous, do not have such characters.

We will first briefly run through the mammals, and then turn to birds.
The gorilla seems to be polygamous, and the male differs considerably
from the female; so it is with some baboons, which live in herds
containing twice as many adult females as males. In South America the
Mycetes caraya presents well-marked sexual differences, in colour,
beard, and vocal organs; and the male generally lives with two or three
wives: the male of the Cebus capucinus differs somewhat from the
female, and appears to be polygamous. (10. On the Gorilla, Savage and
Wyman, ‘Boston Journal of Natural History,’ vol. v. 1845-47, p. 423. On
Cynocephalus, Brehm, ‘Thierleben,’ B. i. 1864, s. 77. On Mycetes,
Rengger, ‘Naturgeschichte der Säugethiere von Paraguay,’ 1830, ss. 14,
20. On Cebus, Brehm, ibid. s. 108.) Little is known on this head with
respect to most other monkeys, but some species are strictly
monogamous. The ruminants are eminently polygamous, and they present
sexual differences more frequently than almost any other group of
mammals; this holds good, especially in their weapons, but also in
other characters. Most deer, cattle, and sheep are polygamous; as are
most antelopes, though some are monogamous. Sir Andrew Smith, in
speaking of the antelopes of South Africa, says that in herds of about
a dozen there was rarely more than one mature male. The Asiatic
Antilope saiga appears to be the most inordinate polygamist in the
world; for Pallas (11. Pallas, ‘Spicilegia Zoolog., Fasc.’ xii. 1777,
p. 29. Sir Andrew Smith, ‘Illustrations of the Zoology of S. Africa,’
1849, pl. 29, on the Kobus. Owen, in his ‘Anatomy of Vertebrates’ (vol.
iii. 1868, p. 633) gives a table shewing incidentally which species of
antelopes are gregarious.) states that the male drives away all rivals,
and collects a herd of about a hundred females and kids together; the
female is hornless and has softer hair, but does not otherwise differ
much from the male. The wild horse of the Falkland Islands and of the
Western States of N. America is polygamous, but, except in his greater
size and in the proportions of his body, differs but little from the
mare. The wild boar presents well-marked sexual characters, in his
great tusks and some other points. In Europe and in India he leads a
solitary life, except during the breeding-season; but as is believed by
Sir W. Elliot, who has had many opportunities in India of observing
this animal, he consorts at this season with several females. Whether
this holds good in Europe is doubtful, but it is supported by some
evidence. The adult male Indian elephant, like the boar, passes much of
his time in solitude; but as Dr. Campbell states, when with others, “It
is rare to find more than one male with a whole herd of females”; the
larger males expelling or killing the smaller and weaker ones. The male
differs from the female in his immense tusks, greater size, strength,
and endurance; so great is the difference in these respects that the
males when caught are valued at one-fifth more than the females. (12.
Dr. Campbell, in ‘Proc. Zoolog. Soc.’ 1869, p. 138. See also an
interesting paper by Lieut. Johnstone, in ‘Proceedings, Asiatic Society
of Bengal,’ May 1868.) The sexes of other pachydermatous animals differ
very little or not at all, and, as far as known, they are not
polygamists. Nor have I heard of any species in the Orders of
Cheiroptera, Edentata, Insectivora and Rodents being polygamous,
excepting that amongst the Rodents, the common rat, according to some
rat-catchers, lives with several females. Nevertheless the two sexes of
some sloths (Edentata) differ in the character and colour of certain
patches of hair on their shoulders. (13. Dr. Gray, in ‘Annals and
Magazine of Natural History,’ 1871, p. 302.) And many kinds of bats
(Cheiroptera) present well-marked sexual differences, chiefly in the
males possessing odoriferous glands and pouches, and by their being of
a lighter colour. (14. See Dr. Dobson’s excellent paper in ‘Proceedings
of the Zoological Society,’ 1873, p. 241.) In the great order of
Rodents, as far as I can learn, the sexes rarely differ, and when they
do so, it is but slightly in the tint of the fur.

As I hear from Sir Andrew Smith, the lion in South Africa sometimes
lives with a single female, but generally with more, and, in one case,
was found with as many as five females; so that he is polygamous. As
far as I can discover, he is the only polygamist amongst all the
terrestrial Carnivora, and he alone presents well-marked sexual
characters. If, however, we turn to the marine Carnivora, as we shall
hereafter see, the case is widely different; for many species of seals
offer extraordinary sexual differences, and they are eminently
polygamous. Thus, according to Peron, the male sea-elephant of the
Southern Ocean always possesses several females, and the sea-lion of
Forster is said to be surrounded by from twenty to thirty females. In
the North, the male sea-bear of Steller is accompanied by even a
greater number of females. It is an interesting fact, as Dr. Gill
remarks (15. ‘The Eared Seals,’ American Naturalist, vol. iv. Jan.
1871.), that in the monogamous species, “or those living in small
communities, there is little difference in size between the males and
females; in the social species, or rather those of which the males have
harems, the males are vastly larger than the females.”

Amongst birds, many species, the sexes of which differ greatly from
each other, are certainly monogamous. In Great Britain we see
well-marked sexual differences, for instance, in the wild-duck which
pairs with a single female, the common blackbird, and the bullfinch
which is said to pair for life. I am informed by Mr. Wallace that the
like is true of the Chatterers or Cotingidae of South America, and of
many other birds. In several groups I have not been able to discover
whether the species are polygamous or monogamous. Lesson says that
birds of paradise, so remarkable for their sexual differences, are
polygamous, but Mr. Wallace doubts whether he had sufficient evidence.
Mr. Salvin tells me he has been led to believe that humming-birds are
polygamous. The male widow-bird, remarkable for his caudal plumes,
certainly seems to be a polygamist. (16. ‘The Ibis,’ vol. iii. 1861, p.
133, on the Progne Widow-bird. See also on the Vidua axillaris, ibid.
vol. ii. 1860, p. 211. On the polygamy of the Capercailzie and Great
Bustard, see L. Lloyd, ‘Game Birds of Sweden,’ 1867, pp. 19, and 182.
Montagu and Selby speak of the Black Grouse as polygamous and of the
Red Grouse as monogamous.) I have been assured by Mr. Jenner Weir and
by others, that it is somewhat common for three starlings to frequent
the same nest; but whether this is a case of polygamy or polyandry has
not been ascertained.

The Gallinaceae exhibit almost as strongly marked sexual differences as
birds of paradise or humming-birds, and many of the species are, as is
well known, polygamous; others being strictly monogamous. What a
contrast is presented between the sexes of the polygamous peacock or
pheasant, and the monogamous guinea-fowl or partridge! Many similar
cases could be given, as in the grouse tribe, in which the males of the
polygamous capercailzie and black-cock differ greatly from the females;
whilst the sexes of the monogamous red grouse and ptarmigan differ very
little. In the Cursores, except amongst the bustards, few species offer
strongly-marked sexual differences, and the great bustard (Otis tarda)
is said to be polygamous. With the Grallatores, extremely few species
differ sexually, but the ruff (Machetes pugnax) affords a marked
exception, and this species is believed by Montagu to be a polygamist.
Hence it appears that amongst birds there often exists a close relation
between polygamy and the development of strongly-marked sexual
differences. I asked Mr. Bartlett, of the Zoological Gardens, who has
had very large experience with birds, whether the male tragopan (one of
the Gallinaceae) was polygamous, and I was struck by his answering, “I
do not know, but should think so from his splendid colours.”

It deserves notice that the instinct of pairing with a single female is
easily lost under domestication. The wild-duck is strictly monogamous,
the domestic-duck highly polygamous. The Rev. W.D. Fox informs me that
out of some half-tamed wild-ducks, on a large pond in his
neighbourhood, so many mallards were shot by the gamekeeper that only
one was left for every seven or eight females; yet unusually large
broods were reared. The guinea-fowl is strictly monogamous; but Mr. Fox
finds that his birds succeed best when he keeps one cock to two or
three hens. Canary-birds pair in a state of nature, but the breeders in
England successfully put one male to four or five females. I have
noticed these cases, as rendering it probable that wild monogamous
species might readily become either temporarily or permanently
polygamous.

Too little is known of the habits of reptiles and fishes to enable us
to speak of their marriage arrangements. The stickle-back
(Gasterosteus), however, is said to be a polygamist (17. Noel
Humphreys, ‘River Gardens,’ 1857.); and the male during the
breeding-season differs conspicuously from the female.

To sum up on the means through which, as far as we can judge, sexual
selection has led to the development of secondary sexual characters. It
has been shewn that the largest number of vigorous offspring will be
reared from the pairing of the strongest and best-armed males,
victorious in contests over other males, with the most vigorous and
best-nourished females, which are the first to breed in the spring. If
such females select the more attractive, and at the same time vigorous
males, they will rear a larger number of offspring than the retarded
females, which must pair with the less vigorous and less attractive
males. So it will be if the more vigorous males select the more
attractive and at the same time healthy and vigorous females; and this
will especially hold good if the male defends the female, and aids in
providing food for the young. The advantage thus gained by the more
vigorous pairs in rearing a larger number of offspring has apparently
sufficed to render sexual selection efficient. But a large numerical
preponderance of males over females will be still more efficient;
whether the preponderance is only occasional and local, or permanent;
whether it occurs at birth, or afterwards from the greater destruction
of the females; or whether it indirectly follows from the practice of
polygamy.

THE MALE GENERALLY MORE MODIFIED THAN THE FEMALE.

Throughout the animal kingdom, when the sexes differ in external
appearance, it is, with rare exceptions, the male which has been the
more modified; for, generally, the female retains a closer resemblance
to the young of her own species, and to other adult members of the same
group. The cause of this seems to lie in the males of almost all
animals having stronger passions than the females. Hence it is the
males that fight together and sedulously display their charms before
the females; and the victors transmit their superiority to their male
offspring. Why both sexes do not thus acquire the characters of their
fathers, will be considered hereafter. That the males of all mammals
eagerly pursue the females is notorious to every one. So it is with
birds; but many cock birds do not so much pursue the hen, as display
their plumage, perform strange antics, and pour forth their song in her
presence. The male in the few fish observed seems much more eager than
the female; and the same is true of alligators, and apparently of
Batrachians. Throughout the enormous class of insects, as Kirby
remarks, “the law is that the male shall seek the female.” (18. Kirby
and Spence, ‘Introduction to Entomology,’ vol. iii. 1826, p. 342.) Two
good authorities, Mr. Blackwall and Mr. C. Spence Bate, tell me that
the males of spiders and crustaceans are more active and more erratic
in their habits than the females. When the organs of sense or
locomotion are present in the one sex of insects and crustaceans and
absent in the other, or when, as is frequently the case, they are more
highly developed in the one than in the other, it is, as far as I can
discover, almost invariably the male which retains such organs, or has
them most developed; and this shews that the male is the more active
member in the courtship of the sexes. (19. One parasitic Hymenopterous
insect (Westwood, ‘Modern Class. of Insects,’ vol. ii. p. 160) forms an
exception to the rule, as the male has rudimentary wings, and never
quits the cell in which it is born, whilst the female has
well-developed wings. Audouin believes that the females of this species
are impregnated by the males which are born in the same cells with
them; but it is much more probable that the females visit other cells,
so that close inter-breeding is thus avoided. We shall hereafter meet
in various classes, with a few exceptional cases, in which the female,
instead of the male, is the seeker and wooer.)

The female, on the other hand, with the rarest exceptions, is less
eager than the male. As the illustrious Hunter (20. ‘Essays and
Observations,’ edited by Owen, vol. i. 1861, p. 194.) long ago
observed, she generally “requires to be courted;” she is coy, and may
often be seen endeavouring for a long time to escape from the male.
Every observer of the habits of animals will be able to call to mind
instances of this kind. It is shewn by various facts, given hereafter,
and by the results fairly attributable to sexual selection, that the
female, though comparatively passive, generally exerts some choice and
accepts one male in preference to others. Or she may accept, as
appearances would sometimes lead us to believe, not the male which is
the most attractive to her, but the one which is the least distasteful.
The exertion of some choice on the part of the female seems a law
almost as general as the eagerness of the male.

We are naturally led to enquire why the male, in so many and such
distinct classes, has become more eager than the female, so that he
searches for her, and plays the more active part in courtship. It would
be no advantage and some loss of power if each sex searched for the
other; but why should the male almost always be the seeker? The ovules
of plants after fertilisation have to be nourished for a time; hence
the pollen is necessarily brought to the female organs—being placed on
the stigma, by means of insects or the wind, or by the spontaneous
movements of the stamens; and in the Algae, etc., by the locomotive
power of the antherozooids. With lowly-organised aquatic animals,
permanently affixed to the same spot and having their sexes separate,
the male element is invariably brought to the female; and of this we
can see the reason, for even if the ova were detached before
fertilisation, and did not require subsequent nourishment or
protection, there would yet be greater difficulty in transporting them
than the male element, because, being larger than the latter, they are
produced in far smaller numbers. So that many of the lower animals are,
in this respect, analogous with plants. (21. Prof. Sachs (‘Lehrbuch der
Botanik,’ 1870, S. 633) in speaking of the male and female reproductive
cells, remarks, “verhält sich die eine bei der Vereinigung activ,...die
andere erscheint bei der Vereinigung passiv.”) The males of affixed and
aquatic animals having been led to emit their fertilising element in
this way, it is natural that any of their descendants, which rose in
the scale and became locomotive, should retain the same habit; and they
would approach the female as closely as possible, in order not to risk
the loss of the fertilising element in a long passage of it through the
water. With some few of the lower animals, the females alone are fixed,
and the males of these must be the seekers. But it is difficult to
understand why the males of species, of which the progenitors were
primordially free, should invariably have acquired the habit of
approaching the females, instead of being approached by them. But in
all cases, in order that the males should seek efficiently, it would be
necessary that they should be endowed with strong passions; and the
acquirement of such passions would naturally follow from the more eager
leaving a larger number of offspring than the less eager.

The great eagerness of the males has thus indirectly led to their much
more frequently developing secondary sexual characters than the
females. But the development of such characters would be much aided, if
the males were more liable to vary than the females—as I concluded they
were—after a long study of domesticated animals. Von Nathusius, who has
had very wide experience, is strongly of the same opinion. (22.
‘Vorträge uber Viehzucht,’ 1872, p. 63.) Good evidence also in favour
of this conclusion can be produced by a comparison of the two sexes in
mankind. During the Novara Expedition (23. ‘Reise der Novara:
Anthropolog. Theil,’ 1867, ss. 216-269. The results were calculated by
Dr. Weisbach from measurements made by Drs. K. Scherzer and Schwarz. On
the greater variability of the males of domesticated animals, see my
‘Variation of Animals and Plants under Domestication,’ vol. ii. 1868,
p. 75.) a vast number of measurements was made of various parts of the
body in different races, and the men were found in almost every case to
present a greater range of variation than the women; but I shall have
to recur to this subject in a future chapter. Mr. J. Wood (24.
‘Proceedings of the Royal Society,’ vol. xvi. July 1868, pp. 519 and
524.), who has carefully attended to the variation of the muscles in
man, puts in italics the conclusion that “the greatest number of
abnormalities in each subject is found in the males.” He had previously
remarked that “altogether in 102 subjects, the varieties of redundancy
were found to be half as many again as in females, contrasting widely
with the greater frequency of deficiency in females before described.”
Professor Macalister likewise remarks (25. ‘Proc. Royal Irish Academy,’
vol. x. 1868, p. 123.) that variations in the muscles “are probably
more common in males than females.” Certain muscles which are not
normally present in mankind are also more frequently developed in the
male than in the female sex, although exceptions to this rule are said
to occur. Dr. Burt Wilder (26. ‘Massachusetts Medical Society,’ vol.
ii. No. 3, 1868, p. 9.) has tabulated the cases of 152 individuals with
supernumerary digits, of which 86 were males, and 39, or less than
half, females, the remaining 27 being of unknown sex. It should not,
however, be overlooked that women would more frequently endeavour to
conceal a deformity of this kind than men. Again, Dr. L. Meyer asserts
that the ears of man are more variable in form than those of a woman.
(27. ‘Archiv fur Path. Anat. und Phys.’ 1871, p. 488.) Lastly the
temperature is more variable in man than in woman. (28. The conclusions
recently arrived at by Dr. J. Stockton Hough, on the temperature of
man, are given in the ‘Pop. Sci. Review,’ Jan. 1st, 1874, p. 97.)

The cause of the greater general variability in the male sex, than in
the female is unknown, except in so far as secondary sexual characters
are extraordinarily variable, and are usually confined to the males;
and, as we shall presently see, this fact is, to a certain extent,
intelligible. Through the action of sexual and natural selection male
animals have been rendered in very many instances widely different from
their females; but independently of selection the two sexes, from
differing constitutionally, tend to vary in a somewhat different
manner. The female has to expend much organic matter in the formation
of her ova, whereas the male expends much force in fierce contests with
his rivals, in wandering about in search of the female, in exerting his
voice, pouring out odoriferous secretions, etc.: and this expenditure
is generally concentrated within a short period. The great vigour of
the male during the season of love seems often to intensify his
colours, independently of any marked difference from the female. (29.
Prof. Mantegazza is inclined to believe (‘Lettera a Carlo Darwin,’
‘Archivio per l’Anthropologia,’ 1871, p. 306) that the bright colours,
common in so many male animals, are due to the presence and retention
by them of the spermatic fluid; but this can hardly be the case; for
many male birds, for instance young pheasants, become brightly coloured
in the autumn of their first year.) In mankind, and even as low down in
the organic scale as in the Lepidoptera, the temperature of the body is
higher in the male than in the female, accompanied in the case of man
by a slower pulse. (30. For mankind, see Dr. J. Stockton Hough, whose
conclusions are given in the ‘Popular Science Review,’ 1874, p. 97. See
Girard’s observations on the Lepidoptera, as given in the ‘Zoological
Record,’ 1869, p. 347.) On the whole the expenditure of matter and
force by the two sexes is probably nearly equal, though effected in
very different ways and at different rates.

From the causes just specified the two sexes can hardly fail to differ
somewhat in constitution, at least during the breeding-season; and,
although they may be subjected to exactly the same conditions, they
will tend to vary in a different manner. If such variations are of no
service to either sex, they will not be accumulated and increased by
sexual or natural selection. Nevertheless, they may become permanent if
the exciting cause acts permanently; and in accordance with a frequent
form of inheritance they may be transmitted to that sex alone in which
they first appeared. In this case the two sexes will come to present
permanent, yet unimportant, differences of character. For instance, Mr.
Allen shews that with a large number of birds inhabiting the northern
and southern United States, the specimens from the south are
darker-coloured than those from the north; and this seems to be the
direct result of the difference in temperature, light, etc., between
the two regions. Now, in some few cases, the two sexes of the same
species appear to have been differently affected; in the Agelaeus
phoeniceus the males have had their colours greatly intensified in the
south; whereas with Cardinalis virginianus it is the females which have
been thus affected; with Quiscalus major the females have been rendered
extremely variable in tint, whilst the males remain nearly uniform.
(31. ‘Mammals and Birds of E. Florida,’ pp. 234, 280, 295.)

A few exceptional cases occur in various classes of animals, in which
the females instead of the males have acquired well pronounced
secondary sexual characters, such as brighter colours, greater size,
strength, or pugnacity. With birds there has sometimes been a complete
transposition of the ordinary characters proper to each sex; the
females having become the more eager in courtship, the males remaining
comparatively passive, but apparently selecting the more attractive
females, as we may infer from the results. Certain hen birds have thus
been rendered more highly coloured or otherwise ornamented, as well as
more powerful and pugnacious than the cocks; these characters being
transmitted to the female offspring alone.

It may be suggested that in some cases a double process of selection
has been carried on; that the males have selected the more attractive
females, and the latter the more attractive males. This process,
however, though it might lead to the modification of both sexes, would
not make the one sex different from the other, unless indeed their
tastes for the beautiful differed; but this is a supposition too
improbable to be worth considering in the case of any animal, excepting
man. There are, however, many animals in which the sexes resemble each
other, both being furnished with the same ornaments, which analogy
would lead us to attribute to the agency of sexual selection. In such
cases it may be suggested with more plausibility, that there has been a
double or mutual process of sexual selection; the more vigorous and
precocious females selecting the more attractive and vigorous males,
the latter rejecting all except the more attractive females. But from
what we know of the habits of animals, this view is hardly probable,
for the male is generally eager to pair with any female. It is more
probable that the ornaments common to both sexes were acquired by one
sex, generally the male, and then transmitted to the offspring of both
sexes. If, indeed, during a lengthened period the males of any species
were greatly to exceed the females in number, and then during another
lengthened period, but under different conditions, the reverse were to
occur, a double, but not simultaneous, process of sexual selection
might easily be carried on, by which the two sexes might be rendered
widely different.

We shall hereafter see that many animals exist, of which neither sex is
brilliantly coloured or provided with special ornaments, and yet the
members of both sexes or of one alone have probably acquired simple
colours, such as white or black, through sexual selection. The absence
of bright tints or other ornaments may be the result of variations of
the right kind never having occurred, or of the animals themselves
having preferred plain black or white. Obscure tints have often been
developed through natural selection for the sake of protection, and the
acquirement through sexual selection of conspicuous colours, appears to
have been sometimes checked from the danger thus incurred. But in other
cases the males during long ages may have struggled together for the
possession of the females, and yet no effect will have been produced,
unless a larger number of offspring were left by the more successful
males to inherit their superiority, than by the less successful: and
this, as previously shewn, depends on many complex contingencies.

Sexual selection acts in a less rigorous manner than natural selection.
The latter produces its effects by the life or death at all ages of the
more or less successful individuals. Death, indeed, not rarely ensues
from the conflicts of rival males. But generally the less successful
male merely fails to obtain a female, or obtains a retarded and less
vigorous female later in the season, or, if polygamous, obtains fewer
females; so that they leave fewer, less vigorous, or no offspring. In
regard to structures acquired through ordinary or natural selection,
there is in most cases, as long as the conditions of life remain the
same, a limit to the amount of advantageous modification in relation to
certain special purposes; but in regard to structures adapted to make
one male victorious over another, either in fighting or in charming the
female, there is no definite limit to the amount of advantageous
modification; so that as long as the proper variations arise the work
of sexual selection will go on. This circumstance may partly account
for the frequent and extraordinary amount of variability presented by
secondary sexual characters. Nevertheless, natural selection will
determine that such characters shall not be acquired by the victorious
males, if they would be highly injurious, either by expending too much
of their vital powers, or by exposing them to any great danger. The
development, however, of certain structures—of the horns, for instance,
in certain stags—has been carried to a wonderful extreme; and in some
cases to an extreme which, as far as the general conditions of life are
concerned, must be slightly injurious to the male. From this fact we
learn that the advantages which favoured males derive from conquering
other males in battle or courtship, and thus leaving a numerous
progeny, are in the long run greater than those derived from rather
more perfect adaptation to their conditions of life. We shall further
see, and it could never have been anticipated, that the power to charm
the female has sometimes been more important than the power to conquer
other males in battle.

LAWS OF INHERITANCE.

In order to understand how sexual selection has acted on many animals
of many classes, and in the course of ages has produced a conspicuous
result, it is necessary to bear in mind the laws of inheritance, as far
as they are known. Two distinct elements are included under the term
“inheritance”—the transmission, and the development of characters; but
as these generally go together, the distinction is often overlooked. We
see this distinction in those characters which are transmitted through
the early years of life, but are developed only at maturity or during
old age. We see the same distinction more clearly with secondary sexual
characters, for these are transmitted through both sexes, though
developed in one alone. That they are present in both sexes, is
manifest when two species, having strongly-marked sexual characters,
are crossed, for each transmits the characters proper to its own male
and female sex to the hybrid offspring of either sex. The same fact is
likewise manifest, when characters proper to the male are occasionally
developed in the female when she grows old or becomes diseased, as, for
instance, when the common hen assumes the flowing tail-feathers,
hackles, comb, spurs, voice, and even pugnacity of the cock.
Conversely, the same thing is evident, more or less plainly, with
castrated males. Again, independently of old age or disease, characters
are occasionally transferred from the male to the female, as when, in
certain breeds of the fowl, spurs regularly appear in the young and
healthy females. But in truth they are simply developed in the female;
for in every breed each detail in the structure of the spur is
transmitted through the female to her male offspring. Many cases will
hereafter be given, where the female exhibits, more or less perfectly,
characters proper to the male, in whom they must have been first
developed, and then transferred to the female. The converse case of the
first development of characters in the female and of transference to
the male, is less frequent; it will therefore be well to give one
striking instance. With bees the pollen-collecting apparatus is used by
the female alone for gathering pollen for the larvae, yet in most of
the species it is partially developed in the males to whom it is quite
useless, and it is perfectly developed in the males of Bombus or the
humble-bee. (32. H. Muller, ‘Anwendung der Darwin’schen Lehre,’ etc.,
Verh. d. n. V. Jahrg., xxix. p. 42.) As not a single other
Hymenopterous insect, not even the wasp, which is closely allied to the
bee, is provided with a pollen-collecting apparatus, we have no grounds
for supposing that male bees primordially collected pollen as well as
the females; although we have some reason to suspect that male mammals
primordially suckled their young as well as the females. Lastly, in all
cases of reversion, characters are transmitted through two, three, or
many more generations, and are then developed under certain unknown
favourable conditions. This important distinction between transmission
and development will be best kept in mind by the aid of the hypothesis
of pangenesis. According to this hypothesis, every unit or cell of the
body throws off gemmules or undeveloped atoms, which are transmitted to
the offspring of both sexes, and are multiplied by self-division. They
may remain undeveloped during the early years of life or during
successive generations; and their development into units or cells, like
those from which they were derived, depends on their affinity for, and
union with other units or cells previously developed in the due order
of growth.

INHERITANCE AT CORRESPONDING PERIODS OF LIFE.

This tendency is well established. A new character, appearing in a
young animal, whether it lasts throughout life or is only transient,
will, in general, reappear in the offspring at the same age and last
for the same time. If, on the other hand, a new character appears at
maturity, or even during old age, it tends to reappear in the offspring
at the same advanced age. When deviations from this rule occur, the
transmitted characters much oftener appear before, than after the
corresponding age. As I have dwelt on this subject sufficiently in
another work (33. The ‘Variation of Animals and Plants under
Domestication,’ vol. ii. 1868, p. 75. In the last chapter but one, the
provisional hypothesis of pangenesis, above alluded to, is fully
explained.), I will here merely give two or three instances, for the
sake of recalling the subject to the reader’s mind. In several breeds
of the Fowl, the down-covered chickens, the young birds in their first
true plumage, and the adults differ greatly from one another, as well
as from their common parent-form, the Gallus bankiva; and these
characters are faithfully transmitted by each breed to their offspring
at the corresponding periods of life. For instance, the chickens of
spangled Hamburgs, whilst covered with down, have a few dark spots on
the head and rump, but are not striped longitudinally, as in many other
breeds; in their first true plumage, “they are beautifully pencilled,”
that is each feather is transversely marked by numerous dark bars; but
in their second plumage the feathers all become spangled or tipped with
a dark round spot. (34. These facts are given on the high authority of
a great breeder, Mr. Teebay; see Tegetmeier’s ‘Poultry Book,’ 1868, p.
158. On the characters of chickens of different breeds, and on the
breeds of the pigeon, alluded to in the following paragraph, see
‘Variation of Animals,’ etc., vol. i. pp. 160, 249; vol. ii. p. 77.)
Hence in this breed variations have occurred at, and been transmitted
to, three distinct periods of life. The Pigeon offers a more remarkable
case, because the aboriginal parent species does not undergo any change
of plumage with advancing age, excepting that at maturity the breast
becomes more iridescent; yet there are breeds which do not acquire
their characteristic colours until they have moulted two, three, or
four times; and these modifications of plumage are regularly
transmitted.

INHERITANCE AT CORRESPONDING SEASONS OF THE YEAR.

With animals in a state of nature, innumerable instances occur of
characters appearing periodically at different seasons. We see this in
the horns of the stag, and in the fur of Arctic animals which becomes
thick and white during the winter. Many birds acquire bright colours
and other decorations during the breeding-season alone. Pallas states
(35. ‘Novae species Quadrupedum e Glirium ordine,’ 1778, p. 7. On the
transmission of colour by the horse, see ‘Variation of Animals and
Plants under Domestication,’ vol. i. p. 51. Also vol. ii. p. 71, for a
general discussion on ‘Inheritance as limited by Sex.’), that in
Siberia domestic cattle and horses become lighter-coloured during the
winter; and I have myself observed, and heard of similar strongly
marked changes of colour, that is, from brownish cream-colour or
reddish-brown to a perfect white, in several ponies in England.
Although I do not know that this tendency to change the colour of the
coat during different seasons is transmitted, yet it probably is so, as
all shades of colour are strongly inherited by the horse. Nor is this
form of inheritance, as limited by the seasons, more remarkable than
its limitation by age or sex.

INHERITANCE AS LIMITED BY SEX. — The equal transmission of characters
to both sexes is the commonest form of inheritance, at least with those
animals which do not present strongly-marked sexual differences, and
indeed with many of these. But characters are somewhat commonly
transferred exclusively to that sex, in which they first appear. Ample
evidence on this head has been advanced in my work on ‘Variation under
Domestication,’ but a few instances may here be given. There are breeds
of the sheep and goat, in which the horns of the male differ greatly in
shape from those of the female; and these differences, acquired under
domestication, are regularly transmitted to the same sex. As a rule, it
is the females alone in cats which are tortoise-shell, the
corresponding colour in the males being rusty-red. With most breeds of
the fowl, the characters proper to each sex are transmitted to the same
sex alone. So general is this form of transmission that it is an
anomaly when variations in certain breeds are transmitted equally to
both sexes. There are also certain sub-breeds of the fowl in which the
males can hardly be distinguished from one another, whilst the females
differ considerably in colour. The sexes of the pigeon in the
parent-species do not differ in any external character; nevertheless,
in certain domesticated breeds the male is coloured differently from
the female. (36. Dr. Chapuis, ‘Le Pigeon Voyageur Belge,’ 1865, p. 87.
Boitard et Corbie, ‘Les Pigeons de Volière,’ etc., 1824, p. 173. See,
also, on similar differences in certain breeds at Modena, ‘Le
variazioni dei Colombi domestici,’ del Paolo Bonizzi, 1873.) The wattle
in the English Carrier pigeon, and the crop in the Pouter, are more
highly developed in the male than in the female; and although these
characters have been gained through long-continued selection by man,
the slight differences between the sexes are wholly due to the form of
inheritance which has prevailed; for they have arisen, not from, but
rather in opposition to, the wish of the breeder.

Most of our domestic races have been formed by the accumulation of many
slight variations; and as some of the successive steps have been
transmitted to one sex alone, and some to both sexes, we find in the
different breeds of the same species all gradations between great
sexual dissimilarity and complete similarity. Instances have already
been given with the breeds of the fowl and pigeon, and under nature
analogous cases are common. With animals under domestication, but
whether in nature I will not venture to say, one sex may lose
characters proper to it, and may thus come somewhat to resemble the
opposite sex; for instance, the males of some breeds of the fowl have
lost their masculine tail-plumes and hackles. On the other hand, the
differences between the sexes may be increased under domestication, as
with merino sheep, in which the ewes have lost their horns. Again,
characters proper to one sex may suddenly appear in the other sex; as
in those sub-breeds of the fowl in which the hens acquire spurs whilst
young; or, as in certain Polish sub-breeds, in which the females, as
there is reason to believe, originally acquired a crest, and
subsequently transferred it to the males. All these cases are
intelligible on the hypothesis of pangenesis; for they depend on the
gemmules of certain parts, although present in both sexes, becoming,
through the influence of domestication, either dormant or developed in
either sex.

There is one difficult question which it will be convenient to defer to
a future chapter; namely, whether a character at first developed in
both sexes, could through selection be limited in its development to
one sex alone. If, for instance, a breeder observed that some of his
pigeons (of which the characters are usually transferred in an equal
degree to both sexes) varied into pale blue, could he by long-continued
selection make a breed, in which the males alone should be of this
tint, whilst the females remained unchanged? I will here only say, that
this, though perhaps not impossible, would be extremely difficult; for
the natural result of breeding from the pale-blue males would be to
change the whole stock of both sexes to this tint. If, however,
variations of the desired tint appeared, which were from the first
limited in their development to the male sex, there would not be the
least difficulty in making a breed with the two sexes of a different
colour, as indeed has been effected with a Belgian breed, in which the
males alone are streaked with black. In a similar manner, if any
variation appeared in a female pigeon, which was from the first
sexually limited in its development to the females, it would be easy to
make a breed with the females alone thus characterised; but if the
variation was not thus originally limited, the process would be
extremely difficult, perhaps impossible. (37. Since the publication of
the first edition of this work, it has been highly satisfactory to me
to find the following remarks (the ‘Field,’ Sept. 1872) from so
experienced a breeder as Mr. Tegetmeier. After describing some curious
cases in pigeons, of the transmission of colour by one sex alone, and
the formation of a sub-breed with this character, he says: “It is a
singular circumstance that Mr. Darwin should have suggested the
possibility of modifying the sexual colours of birds by a course of
artificial selection. When he did so, he was in ignorance of these
facts that I have related; but it is remarkable how very closely he
suggested the right method of procedure.”)

ON THE RELATION BETWEEN THE PERIOD OF DEVELOPMENT OF A CHARACTER AND
ITS TRANSMISSION TO ONE SEX OR TO BOTH SEXES.

Why certain characters should be inherited by both sexes, and other
characters by one sex alone, namely by that sex in which the character
first appeared, is in most cases quite unknown. We cannot even
conjecture why with certain sub-breeds of the pigeon, black striae,
though transmitted through the female, should be developed in the male
alone, whilst every other character is equally transferred to both
sexes. Why, again, with cats, the tortoise-shell colour should, with
rare exceptions, be developed in the female alone. The very same
character, such as deficient or supernumerary digits, colour-blindness,
etc., may with mankind be inherited by the males alone of one family,
and in another family by the females alone, though in both cases
transmitted through the opposite as well as through the same sex. (38.
References are given in my ‘Variation of Animals and Plants under
Domestication,’ vol. ii. p. 72.) Although we are thus ignorant, the two
following rules seem often to hold good—that variations which first
appear in either sex at a late period of life, tend to be developed in
the same sex alone; whilst variations which first appear early in life
in either sex tend to be developed in both sexes. I am, however, far
from supposing that this is the sole determining cause. As I have not
elsewhere discussed this subject, and it has an important bearing on
sexual selection, I must here enter into lengthy and somewhat intricate
details.

It is in itself probable that any character appearing at an early age
would tend to be inherited equally by both sexes, for the sexes do not
differ much in constitution before the power of reproduction is gained.
On the other hand, after this power has been gained and the sexes have
come to differ in constitution, the gemmules (if I may again use the
language of pangenesis) which are cast off from each varying part in
the one sex would be much more likely to possess the proper affinities
for uniting with the tissues of the same sex, and thus becoming
developed, than with those of the opposite sex.

I was first led to infer that a relation of this kind exists, from the
fact that whenever and in whatever manner the adult male differs from
the adult female, he differs in the same manner from the young of both
sexes. The generality of this fact is quite remarkable: it holds good
with almost all mammals, birds, amphibians, and fishes; also with many
crustaceans, spiders, and some few insects, such as certain orthoptera
and libellulae. In all these cases the variations, through the
accumulation of which the male acquired his proper masculine
characters, must have occurred at a somewhat late period of life;
otherwise the young males would have been similarly characterised; and
conformably with our rule, the variations are transmitted to and
developed in the adult males alone. When, on the other hand, the adult
male closely resembles the young of both sexes (these, with rare
exceptions, being alike), he generally resembles the adult female; and
in most of these cases the variations through which the young and old
acquired their present characters, probably occurred, according to our
rule, during youth. But there is here room for doubt, for characters
are sometimes transferred to the offspring at an earlier age than that
at which they first appeared in the parents, so that the parents may
have varied when adult, and have transferred their characters to their
offspring whilst young. There are, moreover, many animals, in which the
two sexes closely resemble each other, and yet both differ from their
young: and here the characters of the adults must have been acquired
late in life; nevertheless, these characters, in apparent contradiction
to our rule, are transferred to both sexes. We must not however,
overlook the possibility or even probability of successive variations
of the same nature occurring, under exposure to similar conditions,
simultaneously in both sexes at a rather late period of life; and in
this case the variations would be transferred to the offspring of both
sexes at a corresponding late age; and there would then be no real
contradiction to the rule that variations occurring late in life are
transferred exclusively to the sex in which they first appeared. This
latter rule seems to hold true more generally than the second one,
namely, that variations which occur in either sex early in life tend to
be transferred to both sexes. As it was obviously impossible even to
estimate in how large a number of cases throughout the animal kingdom
these two propositions held good, it occurred to me to investigate some
striking or crucial instances, and to rely on the result.

An excellent case for investigation is afforded by the Deer family. In
all the species, but one, the horns are developed only in the males,
though certainly transmitted through the females, and capable of
abnormal development in them. In the reindeer, on the other hand, the
female is provided with horns; so that in this species, the horns
ought, according to our rule, to appear early in life, long before the
two sexes are mature and have come to differ much in constitution. In
all the other species the horns ought to appear later in life, which
would lead to their development in that sex alone, in which they first
appeared in the progenitor of the whole Family. Now in seven species,
belonging to distinct sections of the family and inhabiting different
regions, in which the stags alone bear horns, I find that the horns
first appear at periods, varying from nine months after birth in the
roebuck, to ten, twelve or even more months in the stags of the six
other and larger species. (39. I am much obliged to Mr. Cupples for
having made enquiries for me in regard to the Roebuck and Red Deer of
Scotland from Mr. Robertson, the experienced head-forester to the
Marquis of Breadalbane. In regard to Fallow-deer, I have to thank Mr.
Eyton and others for information. For the Cervus alces of N. America,
see ‘Land and Water,’ 1868, pp. 221 and 254; and for the C. Virginianus
and strongyloceros of the same continent, see J.D. Caton, in ‘Ottawa
Acad. of Nat. Sc.’ 1868, p. 13. For Cervus Eldi of Pegu, see Lieut.
Beaven, ‘Proccedings of the Zoological Society,’ 1867, p. 762.) But
with the reindeer the case is widely different; for, as I hear from
Prof. Nilsson, who kindly made special enquiries for me in Lapland, the
horns appear in the young animals within four or five weeks after
birth, and at the same time in both sexes. So that here we have a
structure, developed at a most unusually early age in one species of
the family, and likewise common to both sexes in this one species
alone.

In several kinds of antelopes, only the males are provided with horns,
whilst in the greater number both sexes bear horns. With respect to the
period of development, Mr. Blyth informs me that there was at one time
in the Zoological Gardens a young koodoo (Ant. strepsiceros), of which
the males alone are horned, and also the young of a closely-allied
species, the eland (Ant. oreas), in which both sexes are horned. Now it
is in strict conformity with our rule, that in the young male koodoo,
although ten months old, the horns were remarkably small, considering
the size ultimately attained by them; whilst in the young male eland,
although only three months old, the horns were already very much larger
than in the koodoo. It is also a noticeable fact that in the
prong-horned antelope (40. Antilocapra Americana. I have to thank Dr.
Canfield for information with respect to the horns of the female: see
also his paper in ‘Proceedings of the Zoological Society,’ 1866, p.
109. Also Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 627), only a few
of the females, about one in five, have horns, and these are in a
rudimentary state, though sometimes above four inches long: so that as
far as concerns the possession of horns by the males alone, this
species is in an intermediate condition, and the horns do not appear
until about five or six months after birth. Therefore in comparison
with what little we know of the development of the horns in other
antelopes, and from what we do know with respect to the horns of deer,
cattle, etc., those of the prong-horned antelope appear at an
intermediate period of life,—that is, not very early, as in cattle and
sheep, nor very late, as in the larger deer and antelopes. The horns of
sheep, goats, and cattle, which are well developed in both sexes,
though not quite equal in size, can be felt, or even seen, at birth or
soon afterwards. (41. I have been assured that the horns of the sheep
in North Wales can always be felt, and are sometimes even an inch in
length, at birth. Youatt says (‘Cattle,’ 1834, p. 277), that the
prominence of the frontal bone in cattle penetrates the cutis at birth,
and that the horny matter is soon formed over it.) Our rule, however,
seems to fail in some breeds of sheep, for instance merinos, in which
the rams alone are horned; for I cannot find on enquiry (42. I am
greatly indebted to Prof. Victor Carus for having made enquiries for
me, from the highest authorities, with respect to the merino sheep of
Saxony. On the Guinea coast of Africa there is, however, a breed of
sheep in which, as with merinos, the rams alone bear horns; and Mr.
Winwood Reade informs me that in one case observed by him, a young ram,
born on Feb. 10th, first shewed horns on March 6th, so that in this
instance, in conformity with rule, the development of the horns
occurred at a later period of life than in Welsh sheep, in which both
sexes are horned.), that the horns are developed later in life in this
breed than in ordinary sheep in which both sexes are horned. But with
domesticated sheep the presence or absence of horns is not a firmly
fixed character; for a certain proportion of the merino ewes bear small
horns, and some of the rams are hornless; and in most breeds hornless
ewes are occasionally produced.

Dr. W. Marshall has lately made a special study of the protuberances so
common on the heads of birds (43. ‘Über die knochernen Schädelhöcker
der Vögel,’ in the ‘Niederland. Archiv fur Zoologie,’ B.i. Heft 2,
1872.), and he comes to the following conclusion:—that with those
species in which they are confined to the males, they are developed
late in life; whereas with those species in which they are common to
the two sexes, they are developed at a very early period. This is
certainly a striking confirmation of my two laws of inheritance.

In most of the species of the splendid family of the Pheasants, the
males differ conspicuously from the females, and they acquire their
ornaments at a rather late period of life. The eared pheasant
(Crossoptilon auritum), however, offers a remarkable exception, for
both sexes possess the fine caudal plumes, the large ear-tufts and the
crimson velvet about the head; I find that all these characters appear
very early in life in accordance with rule. The adult male can,
however, be distinguished from the adult female by the presence of
spurs; and conformably with our rule, these do not begin to be
developed before the age of six months, as I am assured by Mr.
Bartlett, and even at this age, the two sexes can hardly be
distinguished. (44. In the common peacock (Pavo cristatus) the male
alone possesses spurs, whilst both sexes of the Java Peacock (P.
muticus) offer the unusual case of being furnished with spurs. Hence I
fully expected that in the latter species they would have been
developed earlier in life than in the common peacock; but M. Hegt of
Amsterdam informs me, that with young birds of the previous year, of
both species, compared on April 23rd, 1869, there was no difference in
the development of the spurs. The spurs, however, were as yet
represented merely by slight knobs or elevations. I presume that I
should have been informed if any difference in the rate of development
had been observed subsequently.) The male and female Peacock differ
conspicuously from each other in almost every part of their plumage,
except in the elegant head-crest, which is common to both sexes; and
this is developed very early in life, long before the other ornaments,
which are confined to the male. The wild-duck offers an analogous case,
for the beautiful green speculum on the wings is common to both sexes,
though duller and somewhat smaller in the female, and it is developed
early in life, whilst the curled tail-feathers and other ornaments of
the male are developed later. (45. In some other species of the Duck
family the speculum differs in a greater degree in the two sexes; but I
have not been able to discover whether its full development occurs
later in life in the males of such species, than in the male of the
common duck, as ought to be the case according to our rule. With the
allied Mergus cucullatus we have, however, a case of this kind: the two
sexes differ conspicuously in general plumage, and to a considerable
degree in the speculum, which is pure white in the male and
greyish-white in the female. Now the young males at first entirely
resemble the females, and have a greyish-white speculum, which becomes
pure white at an earlier age than that at which the adult male acquires
his other and more strongly-marked sexual differences: see Audubon,
‘Ornithological Biography,’ vol. iii. 1835, pp. 249-250.) Between such
extreme cases of close sexual resemblance and wide dissimilarity, as
those of the Crossoptilon and peacock, many intermediate ones could be
given, in which the characters follow our two rules in their order of
development.

As most insects emerge from the pupal state in a mature condition, it
is doubtful whether the period of development can determine the
transference of their characters to one or to both sexes. But we do not
know that the coloured scales, for instance, in two species of
butterflies, in one of which the sexes differ in colour, whilst in the
other they are alike, are developed at the same relative age in the
cocoon. Nor do we know whether all the scales are simultaneously
developed on the wings of the same species of butterfly, in which
certain coloured marks are confined to one sex, whilst others are
common to both sexes. A difference of this kind in the period of
development is not so improbable as it may at first appear; for with
the Orthoptera, which assume their adult state, not by a single
metamorphosis, but by a succession of moults, the young males of some
species at first resemble the females, and acquire their distinctive
masculine characters only at a later moult. Strictly analogous cases
occur at the successive moults of certain male crustaceans.

We have as yet considered the transference of characters, relatively to
their period of development, only in species in a natural state; we
will now turn to domesticated animals, and first touch on monstrosities
and diseases. The presence of supernumerary digits, and the absence of
certain phalanges, must be determined at an early embryonic period—the
tendency to profuse bleeding is at least congenital, as is probably
colour-blindness—yet these peculiarities, and other similar ones, are
often limited in their transmission to one sex; so that the rule that
characters, developed at an early period, tend to be transmitted to
both sexes, here wholly fails. But this rule, as before remarked, does
not appear to be nearly so general as the converse one, namely, that
characters which appear late in life in one sex are transmitted
exclusively to the same sex. From the fact of the above abnormal
peculiarities becoming attached to one sex, long before the sexual
functions are active, we may infer that there must be some difference
between the sexes at an extremely early age. With respect to
sexually-limited diseases, we know too little of the period at which
they originate, to draw any safe conclusion. Gout, however, seems to
fall under our rule, for it is generally caused by intemperance during
manhood, and is transmitted from the father to his sons in a much more
marked manner than to his daughters.

In the various domestic breeds of sheep, goats, and cattle, the males
differ from their respective females in the shape or development of
their horns, forehead, mane, dewlap, tail, and hump on the shoulders;
and these peculiarities, in accordance with our rule, are not fully
developed until a rather late period of life. The sexes of dogs do not
differ, except that in certain breeds, especially in the Scotch
deer-hound, the male is much larger and heavier than the female; and,
as we shall see in a future chapter, the male goes on increasing in
size to an unusually late period of life, which, according to rule,
will account for his increased size being transmitted to his male
offspring alone. On the other hand, the tortoise-shell colour, which is
confined to female cats, is quite distinct at birth, and this case
violates the rule. There is a breed of pigeons in which the males alone
are streaked with black, and the streaks can be detected even in the
nestlings; but they become more conspicuous at each successive moult,
so that this case partly opposes and partly supports the rule. With the
English Carrier and Pouter pigeons, the full development of the wattle
and the crop occurs rather late in life, and conformably with the rule,
these characters are transmitted in full perfection to the males alone.
The following cases perhaps come within the class previously alluded
to, in which both sexes have varied in the same manner at a rather late
period of life, and have consequently transferred their new characters
to both sexes at a corresponding late period; and if so, these cases
are not opposed to our rule:—there exist sub-breeds of the pigeon,
described by Neumeister (46. ‘Das Ganze der Taubenzucht,’ 1837, ss. 21,
24. For the case of the streaked pigeons, see Dr. Chapuis, ‘Le pigeon
voyageur Belge,’ 1865, p. 87.), in which both sexes change their colour
during two or three moults (as is likewise the case with the Almond
Tumbler); nevertheless, these changes, though occurring rather late in
life, are common to both sexes. One variety of the Canary-bird, namely
the London Prize, offers a nearly analogous case.

With the breeds of the Fowl the inheritance of various characters by
one or both sexes, seems generally determined by the period at which
such characters are developed. Thus in all the many breeds in which the
adult male differs greatly in colour from the female, as well as from
the wild parent-species, he differs also from the young male, so that
the newly-acquired characters must have appeared at a rather late
period of life. On the other hand, in most of the breeds in which the
two sexes resemble each other, the young are coloured in nearly the
same manner as their parents, and this renders it probable that their
colours first appeared early in life. We have instances of this fact in
all black and white breeds, in which the young and old of both sexes
are alike; nor can it be maintained that there is something peculiar in
a black or white plumage, which leads to its transference to both
sexes; for the males alone of many natural species are either black or
white, the females being differently coloured. With the so-called
Cuckoo sub-breeds of the fowl, in which the feathers are transversely
pencilled with dark stripes, both sexes and the chickens are coloured
in nearly the same manner. The laced plumage of the Sebright bantam is
the same in both sexes, and in the young chickens the wing-feathers are
distinctly, though imperfectly laced. Spangled Hamburgs, however, offer
a partial exception; for the two sexes, though not quite alike,
resemble each other more closely than do the sexes of the aboriginal
parent-species; yet they acquire their characteristic plumage late in
life, for the chickens are distinctly pencilled. With respect to other
characters besides colour, in the wild-parent species and in most of
the domestic breeds, the males alone possess a well-developed comb; but
in the young of the Spanish fowl it is largely developed at a very
early age, and, in accordance with this early development in the male,
it is of unusual size in the adult female. In the Game breeds pugnacity
is developed at a wonderfully early age, of which curious proofs could
be given; and this character is transmitted to both sexes, so that the
hens, from their extreme pugnacity, are now generally exhibited in
separate pens. With the Polish breeds the bony protuberance of the
skull which supports the crest is partially developed even before the
chickens are hatched, and the crest itself soon begins to grow, though
at first feebly (47. For full particulars and references on all these
points respecting the several breeds of the Fowl, see ‘Variation of
Animals and Plants under Domestication,’ vol. i. pp. 250, 256. In
regard to the higher animals, the sexual differences which have arisen
under domestication are described in the same work under the head of
each species.); and in this breed the adults of both sexes are
characterised by a great bony protuberance and an immense crest.

Finally, from what we have now seen of the relation which exists in
many natural species and domesticated races, between the period of the
development of their characters and the manner of their
transmission—for example, the striking fact of the early growth of the
horns in the reindeer, in which both sexes bear horns, in comparison
with their much later growth in the other species in which the male
alone bears horns—we may conclude that one, though not the sole cause
of characters being exclusively inherited by one sex, is their
development at a late age. And secondly, that one, though apparently a
less efficient cause of characters being inherited by both sexes, is
their development at an early age, whilst the sexes differ but little
in constitution. It appears, however, that some difference must exist
between the sexes even during a very early embryonic period, for
characters developed at this age not rarely become attached to one sex.

A SUMMARY AND CONCLUDING REMARKS.

From the foregoing discussion on the various laws of inheritance, we
learn that the characters of the parents often, or even generally, tend
to become developed in the offspring of the same sex, at the same age,
and periodically at the same season of the year, in which they first
appeared in the parents. But these rules, owing to unknown causes, are
far from being fixed. Hence during the modification of a species, the
successive changes may readily be transmitted in different ways; some
to one sex, and some to both; some to the offspring at one age, and
some to the offspring at all ages. Not only are the laws of inheritance
extremely complex, but so are the causes which induce and govern
variability. The variations thus induced are preserved and accumulated
by sexual selection, which is in itself an extremely complex affair,
depending, as it does, on the ardour in love, the courage, and the
rivalry of the males, as well as on the powers of perception, the
taste, and will of the female. Sexual selection will also be largely
dominated by natural selection tending towards the general welfare of
the species. Hence the manner in which the individuals of either or
both sexes have been affected through sexual selection cannot fail to
be complex in the highest degree.

When variations occur late in life in one sex, and are transmitted to
the same sex at the same age, the other sex and the young are left
unmodified. When they occur late in life, but are transmitted to both
sexes at the same age, the young alone are left unmodified. Variations,
however, may occur at any period of life in one sex or in both, and be
transmitted to both sexes at all ages, and then all the individuals of
the species are similarly modified. In the following chapters it will
be seen that all these cases frequently occur in nature.

Sexual selection can never act on any animal before the age for
reproduction arrives. From the great eagerness of the male it has
generally acted on this sex and not on the females. The males have thus
become provided with weapons for fighting with their rivals, with
organs for discovering and securely holding the female, and for
exciting or charming her. When the sexes differ in these respects, it
is also, as we have seen, an extremely general law that the adult male
differs more or less from the young male; and we may conclude from this
fact that the successive variations, by which the adult male became
modified, did not generally occur much before the age for reproduction.
Whenever some or many of the variations occurred early in life, the
young males would partake more or less of the characters of the adult
males; and differences of this kind between the old and young males may
be observed in many species of animals.

It is probable that young male animals have often tended to vary in a
manner which would not only have been of no use to them at an early
age, but would have been actually injurious—as by acquiring bright
colours, which would render them conspicuous to their enemies, or by
acquiring structures, such as great horns, which would expend much
vital force in their development. Variations of this kind occurring in
the young males would almost certainly be eliminated through natural
selection. With the adult and experienced males, on the other hand, the
advantages derived from the acquisition of such characters, would more
than counterbalance some exposure to danger, and some loss of vital
force.

As variations which give to the male a better chance of conquering
other males, or of finding, securing, or charming the opposite sex,
would, if they happened to arise in the female, be of no service to
her, they would not be preserved in her through sexual selection. We
have also good evidence with domesticated animals, that variations of
all kinds are, if not carefully selected, soon lost through
intercrossing and accidental deaths. Consequently in a state of nature,
if variations of the above kind chanced to arise in the female line,
and to be transmitted exclusively in this line, they would be extremely
liable to be lost. If, however, the females varied and transmitted
their newly acquired characters to their offspring of both sexes, the
characters which were advantageous to the males would be preserved by
them through sexual selection, and the two sexes would in consequence
be modified in the same manner, although such characters were of no use
to the females: but I shall hereafter have to recur to these more
intricate contingencies. Lastly, the females may acquire, and
apparently have often acquired by transference, characters from the
male sex.

As variations occurring later in life, and transmitted to one sex
alone, have incessantly been taken advantage of and accumulated through
sexual selection in relation to the reproduction of the species;
therefore it appears, at first sight, an unaccountable fact that
similar variations have not frequently been accumulated through natural
selection, in relation to the ordinary habits of life. If this had
occurred, the two sexes would often have been differently modified, for
the sake, for instance, of capturing prey or of escaping from danger.
Differences of this kind between the two sexes do occasionally occur,
especially in the lower classes. But this implies that the two sexes
follow different habits in their struggles for existence, which is a
rare circumstance with the higher animals. The case, however, is widely
different with the reproductive functions, in which respect the sexes
necessarily differ. For variations in structure which are related to
these functions, have often proved of value to one sex, and from having
arisen at a late period of life, have been transmitted to one sex
alone; and such variations, thus preserved and transmitted, have given
rise to secondary sexual characters.

In the following chapters, I shall treat of the secondary sexual
characters in animals of all classes, and shall endeavour in each case
to apply the principles explained in the present chapter. The lowest
classes will detain us for a very short time, but the higher animals,
especially birds, must be treated at considerable length. It should be
borne in mind that for reasons already assigned, I intend to give only
a few illustrative instances of the innumerable structures by the aid
of which the male finds the female, or, when found, holds her. On the
other hand, all structures and instincts by the aid of which the male
conquers other males, and by which he allures or excites the female,
will be fully discussed, as these are in many ways the most
interesting.

SUPPLEMENT ON THE PROPORTIONAL NUMBERS OF THE TWO SEXES IN ANIMALS
BELONGING TO VARIOUS CLASSES.

As no one, as far as I can discover, has paid attention to the relative
numbers of the two sexes throughout the animal kingdom, I will here
give such materials as I have been able to collect, although they are
extremely imperfect. They consist in only a few instances of actual
enumeration, and the numbers are not very large. As the proportions are
known with certainty only in mankind, I will first give them as a
standard of comparison.

MAN.

In England during ten years (from 1857 to 1866) the average number of
children born alive yearly was 707,120, in the proportion of 104.5
males to 100 females. But in 1857 the male births throughout England
were as 105.2, and in 1865 as 104.0 to 100. Looking to separate
districts, in Buckinghamshire (where about 5000 children are annually
born) the MEAN proportion of male to female births, during the whole
period of the above ten years, was as 102.8 to 100; whilst in N. Wales
(where the average annual births are 12,873) it was as high as 106.2 to
100. Taking a still smaller district, viz., Rutlandshire (where the
annual births average only 739), in 1864 the male births were as 114.6,
and in 1862 as only 97.0 to 100; but even in this small district the
average of the 7385 births during the whole ten years, was as 104.5 to
100: that is in the same ratio as throughout England. (48.
‘Twenty-ninth Annual Report of the Registrar-General for 1866.’ In this
report (p. xii.) a special decennial table is given.) The proportions
are sometimes slightly disturbed by unknown causes; thus Prof. Faye
states “that in some districts of Norway there has been during a
decennial period a steady deficiency of boys, whilst in others the
opposite condition has existed.” In France during forty-four years the
male to the female births have been as 106.2 to 100; but during this
period it has occurred five times in one department, and six times in
another, that the female births have exceeded the males. In Russia the
average proportion is as high as 108.9, and in Philadelphia in the
United States as 110.5 to 100. (49. For Norway and Russia, see abstract
of Prof. Faye’s researches, in ‘British and Foreign Medico-Chirurg.
Review,’ April 1867, pp. 343, 345. For France, the ‘Annuaire pour l’An
1867,’ p. 213. For Philadelphia, Dr. Stockton Hough, ‘Social Science
Assoc.’ 1874. For the Cape of Good Hope, Quetelet as quoted by Dr. H.H.
Zouteveen, in the Dutch Translation of this work (vol. i. p. 417),
where much information is given on the proportion of the sexes.) The
average for Europe, deduced by Bickes from about seventy million
births, is 106 males to 100 females. On the other hand, with white
children born at the Cape of Good Hope, the proportion of males is so
low as to fluctuate during successive years between 90 and 99 males for
every 100 females. It is a singular fact that with Jews the proportion
of male births is decidedly larger than with Christians: thus in
Prussia the proportion is as 113, in Breslau as 114, and in Livonia as
120 to 100; the Christian births in these countries being the same as
usual, for instance, in Livonia as 104 to 100. (50. In regard to the
Jews, see M. Thury, ‘La Loi de Production des Sexes,’ 1863, p. 25.)

Prof. Faye remarks that “a still greater preponderance of males would
be met with, if death struck both sexes in equal proportion in the womb
and during birth. But the fact is, that for every 100 still-born
females, we have in several countries from 134.6 to 144.9 still-born
males. During the first four or five years of life, also, more male
children die than females, for example in England, during the first
year, 126 boys die for every 100 girls—a proportion which in France is
still more unfavourable.” (51. ‘British and Foreign Medico-Chirurg.
Review,’ April 1867, p. 343. Dr. Stark also remarks (‘Tenth Annual
Report of Births, Deaths, etc., in Scotland,’ 1867, p. xxviii.) that
“These examples may suffice to show that, at almost every stage of
life, the males in Scotland have a greater liability to death and a
higher death-rate than the females. The fact, however, of this
peculiarity being most strongly developed at that infantile period of
life when the dress, food, and general treatment of both sexes are
alike, seems to prove that the higher male death-rate is an impressed,
natural, and constitutional peculiarity due to sex alone.”) Dr.
Stockton Hough accounts for these facts in part by the more frequent
defective development of males than of females. We have before seen
that the male sex is more variable in structure than the female; and
variations in important organs would generally be injurious. But the
size of the body, and especially of the head, being greater in male
than female infants is another cause: for the males are thus more
liable to be injured during parturition. Consequently the still-born
males are more numerous; and, as a highly competent judge, Dr. Crichton
Browne (52. ‘West Riding Lunatic Asylum Reports,’ vol. i. 1871, p. 8.
Sir J. Simpson has proved that the head of the male infant exceeds that
of the female by 3/8ths of an inch in circumference, and by 1/8th in
transverse diameter. Quetelet has shewn that woman is born smaller than
man; see Dr. Duncan, ‘Fecundity, Fertility, and Sterility,’ 1871, p.
382.), believes, male infants often suffer in health for some years
after birth. Owing to this excess in the death-rate of male children,
both at birth and for some time subsequently, and owing to the exposure
of grown men to various dangers, and to their tendency to emigrate, the
females in all old-settled countries, where statistical records have
been kept, are found to preponderate considerably over the males. (53.
With the savage Guaranys of Paraguay, according to the accurate Azara
(‘Voyages dans l’Amerique merid.’ tom. ii. 1809, pp. 60, 179), the
women are to the men in the proportion of 14 to 13.)

It seems at first sight a mysterious fact that in different nations,
under different conditions and climates, in Naples, Prussia,
Westphalia, Holland, France, England and the United States, the excess
of male over female births is less when they are illegitimate than when
legitimate. (54. Babbage, ‘Edinburgh Journal of Science,’ 1829, vol. i.
p. 88; also p. 90, on still-born children. On illegitimate children in
England, see ‘Report of Registrar-General for 1866,’ p. xv.) This has
been explained by different writers in many different ways, as from the
mothers being generally young, from the large proportion of first
pregnancies, etc. But we have seen that male infants, from the large
size of their heads, suffer more than female infants during
parturition; and as the mothers of illegitimate children must be more
liable than other women to undergo bad labours, from various causes,
such as attempts at concealment by tight lacing, hard work, distress of
mind, etc., their male infants would proportionably suffer. And this
probably is the most efficient of all the causes of the proportion of
males to females born alive being less amongst illegitimate children
than amongst the legitimate. With most animals the greater size of the
adult male than of the female, is due to the stronger males having
conquered the weaker in their struggles for the possession of the
females, and no doubt it is owing to this fact that the two sexes of at
least some animals differ in size at birth. Thus we have the curious
fact that we may attribute the more frequent deaths of male than female
infants, especially amongst the illegitimate, at least in part to
sexual selection.

It has often been supposed that the relative age of the two parents
determine the sex of the offspring; and Prof. Leuckart (55. Leuckart,
in Wagner ‘Handwörterbuch der Phys.’ B. iv. 1853, s. 774.) has advanced
what he considers sufficient evidence, with respect to man and certain
domesticated animals, that this is one important though not the sole
factor in the result. So again the period of impregnation relatively to
the state of the female has been thought by some to be the efficient
cause; but recent observations discountenance this belief. According to
Dr. Stockton Hough (56. ‘Social Science Association of Philadelphia,’
1874.), the season of the year, the poverty or wealth of the parents,
residence in the country or in cities, the crossing of foreign
immigrants, etc., all influence the proportion of the sexes. With
mankind, polygamy has also been supposed to lead to the birth of a
greater proportion of female infants; but Dr. J. Campbell (57.
‘Anthropological Review,’ April 1870, p. cviii.) carefully attended to
this subject in the harems of Siam, and concludes that the proportion
of male to female births is the same as from monogamous unions. Hardly
any animal has been rendered so highly polygamous as the English
race-horse, and we shall immediately see that his male and female
offspring are almost exactly equal in number. I will now give the facts
which I have collected with respect to the proportional numbers of the
sexes of various animals; and will then briefly discuss how far
selection has come into play in determining the result.

HORSES.

Mr. Tegetmeier has been so kind as to tabulate for me from the ‘Racing
Calendar’ the births of race-horses during a period of twenty-one
years, viz., from 1846 to 1867; 1849 being omitted, as no returns were
that year published. The total births were 25,560 (58. During eleven
years a record was kept of the number of mares which proved barren or
prematurely slipped their foals; and it deserves notice, as shewing how
infertile these highly-nurtured and rather closely-interbred animals
have become, that not far from one-third of the mares failed to produce
living foals. Thus during 1866, 809 male colts and 816 female colts
were born, and 743 mares failed to produce offspring. During 1867, 836
males and 902 females were born, and 794 mares failed.), consisting of
12,763 males and 12,797 females, or in the proportion of 99.7 males to
100 females. As these numbers are tolerably large, and as they are
drawn from all parts of England, during several years, we may with much
confidence conclude that with the domestic horse, or at least with the
race-horse, the two sexes are produced in almost equal numbers. The
fluctuations in the proportions during successive years are closely
like those which occur with mankind, when a small and thinly-populated
area is considered; thus in 1856 the male horses were as 107.1, and in
1867 as only 92.6 to 100 females. In the tabulated returns the
proportions vary in cycles, for the males exceeded the females during
six successive years; and the females exceeded the males during two
periods each of four years; this, however, may be accidental; at least
I can detect nothing of the kind with man in the decennial table in the
Registrar’s Report for 1866.

DOGS.

During a period of twelve years, from 1857 to 1868, the births of a
large number of greyhounds, throughout England, were sent to the
‘Field’ newspaper; and I am again indebted to Mr. Tegetmeier for
carefully tabulating the results. The recorded births were 6878,
consisting of 3605 males and 3273 females, that is, in the proportion
of 110.1 males to 100 females. The greatest fluctuations occurred in
1864, when the proportion was as 95.3 males, and in 1867, as 116.3
males to 100 females. The above average proportion of 110.1 to 100 is
probably nearly correct in the case of the greyhound, but whether it
would hold with other domesticated breeds is in some degree doubtful.
Mr. Cupples has enquired from several great breeders of dogs, and finds
that all without exception believe that females are produced in excess;
but he suggests that this belief may have arisen from females being
less valued, and from the consequent disappointment producing a
stronger impression on the mind.

SHEEP.

The sexes of sheep are not ascertained by agriculturists until several
months after birth, at the period when the males are castrated; so that
the following returns do not give the proportions at birth. Moreover, I
find that several great breeders in Scotland, who annually raise some
thousand sheep, are firmly convinced that a larger proportion of males
than of females die during the first year or two. Therefore the
proportion of males would be somewhat larger at birth than at the age
of castration. This is a remarkable coincidence with what, as we have
seen, occurs with mankind, and both cases probably depend on the same
cause. I have received returns from four gentlemen in England who have
bred Lowland sheep, chiefly Leicesters, during the last ten to sixteen
years; they amount altogether to 8965 births, consisting of 4407 males
and 4558 females; that is in the proportion of 96.7 males to 100
females. With respect to Cheviot and black-faced sheep bred in
Scotland, I have received returns from six breeders, two of them on a
large scale, chiefly for the years 1867-1869, but some of the returns
extend back to 1862. The total number recorded amounts to 50,685,
consisting of 25,071 males and 25,614 females or in the proportion of
97.9 males to 100 females. If we take the English and Scotch returns
together, the total number amounts to 59,650, consisting of 29,478
males and 30,172 females, or as 97.7 to 100. So that with sheep at the
age of castration the females are certainly in excess of the males, but
probably this would not hold good at birth. (59. I am much indebted to
Mr. Cupples for having procured for me the above returns from Scotland,
as well as some of the following returns on cattle. Mr. R. Elliot, of
Laighwood, first called my attention to the premature deaths of the
males, —a statement subsequently confirmed by Mr. Aitchison and others.
To this latter gentleman, and to Mr. Payan, I owe my thanks for large
returns as to sheep.)

Of CATTLE I have received returns from nine gentlemen of 982 births,
too few to be trusted; these consisted of 477 bull-calves and 505
cow-calves; i.e., in the proportion of 94.4 males to 100 females. The
Rev. W.D. Fox informs me that in 1867 out of 34 calves born on a farm
in Derbyshire only one was a bull. Mr. Harrison Weir has enquired from
several breeders of PIGS, and most of them estimate the male to the
female births as about 7 to 6. This same gentleman has bred RABBITS for
many years, and has noticed that a far greater number of bucks are
produced than does. But estimations are of little value.

Of mammalia in a state of nature I have been able to learn very little.
In regard to the common rat, I have received conflicting statements.
Mr. R. Elliot, of Laighwood, informs me that a rat-catcher assured him
that he had always found the males in great excess, even with the young
in the nest. In consequence of this, Mr. Elliot himself subsequently
examined some hundred old ones, and found the statement true. Mr. F.
Buckland has bred a large number of white rats, and he also believes
that the males greatly exceed the females. In regard to Moles, it is
said that “the males are much more numerous than the females” (60.
Bell, ‘History of British Quadrupeds,’ p. 100.): and as the catching of
these animals is a special occupation, the statement may perhaps be
trusted. Sir A. Smith, in describing an antelope of S. Africa (61.
‘Illustrations of the Zoology of S. Africa,’ 1849, pl. 29.) (Kobus
ellipsiprymnus), remarks, that in the herds of this and other species,
the males are few in number compared with the females: the natives
believe that they are born in this proportion; others believe that the
younger males are expelled from the herds, and Sir A. Smith says, that
though he has himself never seen herds consisting of young males alone,
others affirm that this does occur. It appears probable that the young
when expelled from the herd, would often fall a prey to the many beasts
of prey of the country.

BIRDS.

With respect to the FOWL, I have received only one account, namely,
that out of 1001 chickens of a highly-bred stock of Cochins, reared
during eight years by Mr. Stretch, 487 proved males and 514 females;
i.e., as 94.7 to 100. In regard to domestic pigeons there is good
evidence either that the males are produced in excess, or that they
live longer; for these birds invariably pair, and single males, as Mr.
Tegetmeier informs me, can always be purchased cheaper than females.
Usually the two birds reared from the two eggs laid in the same nest
are a male and a female; but Mr. Harrison Weir, who has been so large a
breeder, says that he has often bred two cocks from the same nest, and
seldom two hens; moreover, the hen is generally the weaker of the two,
and more liable to perish.

With respect to birds in a state of nature, Mr. Gould and others (62.
Brehm (‘Thierleben,’ B. iv. s. 990) comes to the same conclusion.) are
convinced that the males are generally the more numerous; and as the
young males of many species resemble the females, the latter would
naturally appear to be the more numerous. Large numbers of pheasants
are reared by Mr. Baker of Leadenhall from eggs laid by wild birds, and
he informs Mr. Jenner Weir that four or five males to one female are
generally produced. An experienced observer remarks (63. On the
authority of L. Lloyd, ‘Game Birds of Sweden,’ 1867, pp. 12, 132.),
that in Scandinavia the broods of the capercailzie and black-cock
contain more males than females; and that with the Dal-ripa (a kind of
ptarmigan) more males than females attend the leks or places of
courtship; but this latter circumstance is accounted for by some
observers by a greater number of hen birds being killed by vermin. From
various facts given by White of Selborne (64. ‘Nat. Hist. of Selborne,’
letter xxix. edit. of 1825, vol. i. p. 139.), it seems clear that the
males of the partridge must be in considerable excess in the south of
England; and I have been assured that this is the case in Scotland. Mr.
Weir on enquiring from the dealers, who receive at certain seasons
large numbers of ruffs (Machetes pugnax), was told that the males are
much the more numerous. This same naturalist has also enquired for me
from the birdcatchers, who annually catch an astonishing number of
various small species alive for the London market, and he was
unhesitatingly answered by an old and trustworthy man, that with the
chaffinch the males are in large excess: he thought as high as 2 males
to 1 female, or at least as high as 5 to 3. (65. Mr. Jenner Weir
received similar information, on making enquiries during the following
year. To shew the number of living chaffinches caught, I may mention
that in 1869 there was a match between two experts, and one man caught
in a day 62, and another 40, male chaffinches. The greatest number ever
caught by one man in a single day was 70.) The males of the blackbird,
he likewise maintained, were by far the more numerous, whether caught
by traps or by netting at night. These statements may apparently be
trusted, because this same man said that the sexes are about equal with
the lark, the twite (Linaria montana), and goldfinch. On the other
hand, he is certain that with the common linnet, the females
preponderate greatly, but unequally during different years; during some
years he has found the females to the males as four to one. It should,
however, be borne in mind, that the chief season for catching birds
does not begin till September, so that with some species partial
migrations may have begun, and the flocks at this period often consist
of hens alone. Mr. Salvin paid particular attention to the sexes of the
humming-birds in Central America, and is convinced that with most of
the species the males are in excess; thus one year he procured 204
specimens belonging to ten species, and these consisted of 166 males
and of only 38 females. With two other species the females were in
excess: but the proportions apparently vary either during different
seasons or in different localities; for on one occasion the males of
Campylopterus hemileucurus were to the females as 5 to 2, and on
another occasion (66. ‘Ibis,’ vol. ii. p. 260, as quoted in Gould’s
‘Trochilidae,’ 1861, p. 52. For the foregoing proportions, I am
indebted to Mr. Salvin for a table of his results.) in exactly the
reversed ratio. As bearing on this latter point, I may add, that Mr.
Powys found in Corfu and Epirus the sexes of the chaffinch keeping
apart, and “the females by far the most numerous”; whilst in Palestine
Mr. Tristram found “the male flocks appearing greatly to exceed the
female in number.” (67. ‘Ibis,’ 1860, p. 137; and 1867, p. 369.) So
again with the Quiscalus major, Mr. G. Taylor says, that in Florida
there were “very few females in proportion to the males,” (68. ‘Ibis,’
1862, p. 187.) whilst in Honduras the proportion was the other way, the
species there having the character of a polygamist.

FISH.

With fish the proportional numbers of the sexes can be ascertained only
by catching them in the adult or nearly adult state; and there are many
difficulties in arriving at any just conclusion. (69. Leuckart quotes
Bloch (Wagner, ‘Handwörterbuch der Phys.’ B. iv. 1853, s. 775), that
with fish there are twice as many males as females.) Infertile females
might readily be mistaken for males, as Dr. Gunther has remarked to me
in regard to trout. With some species the males are believed to die
soon after fertilising the ova. With many species the males are of much
smaller size than the females, so that a large number of males would
escape from the same net by which the females were caught. M.
Carbonnier (70. Quoted in the ‘Farmer,’ March 18, 1869, p. 369.), who
has especially attended to the natural history of the pike (Esox
lucius), states that many males, owing to their small size, are
devoured by the larger females; and he believes that the males of
almost all fish are exposed from this same cause to greater danger than
the females. Nevertheless, in the few cases in which the proportional
numbers have been actually observed, the males appear to be largely in
excess. Thus Mr. R. Buist, the superintendent of the Stormontfield
experiments, says that in 1865, out of 70 salmon first landed for the
purpose of obtaining the ova, upwards of 60 were males. In 1867 he
again “calls attention to the vast disproportion of the males to the
females. We had at the outset at least ten males to one female.”
Afterwards females sufficient for obtaining ova were procured. He adds,
“from the great proportion of the males, they are constantly fighting
and tearing each other on the spawning-beds.” (71. ‘The Stormontfield
Piscicultural Experiments,’ 1866, p. 23. The ‘Field’ newspaper, June
29, 1867.) This disproportion, no doubt, can be accounted for in part,
but whether wholly is doubtful, by the males ascending the rivers
before the females. Mr. F. Buckland remarks in regard to trout, that
“it is a curious fact that the males preponderate very largely in
number over the females. It INVARIABLY happens that when the first rush
of fish is made to the net, there will be at least seven or eight males
to one female found captive. I cannot quite account for this; either
the males are more numerous than the females, or the latter seek safety
by concealment rather than flight.” He then adds, that by carefully
searching the banks sufficient females for obtaining ova can be found.
(72. ‘Land and Water,’ 1868, p. 41.) Mr. H. Lee informs me that out of
212 trout, taken for this purpose in Lord Portsmouth’s park, 150 were
males and 62 females.

The males of the Cyprinidae likewise seem to be in excess; but several
members of this Family, viz., the carp, tench, bream and minnow, appear
regularly to follow the practice, rare in the animal kingdom, of
polyandry; for the female whilst spawning is always attended by two
males, one on each side, and in the case of the bream by three or four
males. This fact is so well known, that it is always recommended to
stock a pond with two male tenches to one female, or at least with
three males to two females. With the minnow, an excellent observer
states, that on the spawning-beds the males are ten times as numerous
as the females; when a female comes amongst the males, “she is
immediately pressed closely by a male on each side; and when they have
been in that situation for a time, are superseded by other two males.”
(73. Yarrell, ‘Hist. British Fishes,’ vol. i. 1826, p. 307; on the
Cyprinus carpio, p. 331; on the Tinca vulgaris, p. 331; on the Abramis
brama, p. 336. See, for the minnow (Leuciscus phoxinus), ‘Loudon’s
Magazine of Natural History,’ vol. v. 1832, p. 682.)

INSECTS.

In this great Class, the Lepidoptera almost alone afford means for
judging of the proportional numbers of the sexes; for they have been
collected with special care by many good observers, and have been
largely bred from the egg or caterpillar state. I had hoped that some
breeders of silk-moths might have kept an exact record, but after
writing to France and Italy, and consulting various treatises, I cannot
find that this has ever been done. The general opinion appears to be
that the sexes are nearly equal, but in Italy, as I hear from Professor
Canestrini, many breeders are convinced that the females are produced
in excess. This same naturalist, however, informs me, that in the two
yearly broods of the Ailanthus silk-moth (Bombyx cynthia), the males
greatly preponderate in the first, whilst in the second the two sexes
are nearly equal, or the females rather in excess.

In regard to Butterflies in a state of nature, several observers have
been much struck by the apparently enormous preponderance of the males.
(74. Leuckart quotes Meinecke (Wagner, ‘Handwörterbuch der Phys.’ B.
iv. 1853, s. 775) that the males of Butterflies are three or four times
as numerous as the females.) Thus Mr. Bates (75. ‘The Naturalist on the
Amazons,’ vol. ii. 1863, pp. 228, 347.), in speaking of several
species, about a hundred in number, which inhabit the upper Amazons,
says that the males are much more numerous than the females, even in
the proportion of a hundred to one. In North America, Edwards, who had
great experience, estimates in the genus Papilio the males to the
females as four to one; and Mr. Walsh, who informed me of this
statement, says that with P. turnus this is certainly the case. In
South Africa, Mr. R. Trimen found the males in excess in 19 species
(76. Four of these cases are given by Mr. Trimen in his ‘Rhopalocera
Africae Australis.’); and in one of these, which swarms in open places,
he estimated the number of males as fifty to one female. With another
species, in which the males are numerous in certain localities, he
collected only five females during seven years. In the island of
Bourbon, M. Maillard states that the males of one species of Papilio
are twenty times as numerous as the females. (77. Quoted by Trimen,
‘Transactions of the Ent. Society,’ vol. v. part iv. 1866, p. 330.) Mr.
Trimen informs me that as far as he has himself seen, or heard from
others, it is rare for the females of any butterfly to exceed the males
in number; but three South African species perhaps offer an exception.
Mr. Wallace (78. ‘Transactions, Linnean Society,’ vol. xxv. p. 37.)
states that the females of Ornithoptera croesus, in the Malay
archipelago, are more common and more easily caught than the males; but
this is a rare butterfly. I may here add, that in Hyperythra, a genus
of moths, Guenee says, that from four to five females are sent in
collections from India for one male.

When this subject of the proportional numbers of the sexes of insects
was brought before the Entomological Society (79. ‘Proceedings,
Entomological Society,’ Feb. 17, 1868.), it was generally admitted that
the males of most Lepidoptera, in the adult or imago state, are caught
in greater numbers than the females: but this fact was attributed by
various observers to the more retiring habits of the females, and to
the males emerging earlier from the cocoon. This latter circumstance is
well known to occur with most Lepidoptera, as well as with other
insects. So that, as M. Personnat remarks, the males of the
domesticated Bombyx Yamamai, are useless at the beginning of the
season, and the females at the end, from the want of mates. (80. Quoted
by Dr. Wallace in ‘Proceedings, Entomological Society,’ 3rd series,
vol. v. 1867, p. 487.) I cannot, however, persuade myself that these
causes suffice to explain the great excess of males, in the above cases
of certain butterflies which are extremely common in their native
countries. Mr. Stainton, who has paid very close attention during many
years to the smaller moths, informs me that when he collected them in
the imago state, he thought that the males were ten times as numerous
as the females, but that since he has reared them on a large scale from
the caterpillar state, he is convinced that the females are the more
numerous. Several entomologists concur in this view. Mr. Doubleday,
however, and some others, take an opposite view, and are convinced that
they have reared from the eggs and caterpillars a larger proportion of
males than of females.

Besides the more active habits of the males, their earlier emergence
from the cocoon, and in some cases their frequenting more open
stations, other causes may be assigned for an apparent or real
difference in the proportional numbers of the sexes of Lepidoptera,
when captured in the imago state, and when reared from the egg or
caterpillar state. I hear from Professor Canestrini, that it is
believed by many breeders in Italy, that the female caterpillar of the
silk-moth suffers more from the recent disease than the male; and Dr.
Staudinger informs me that in rearing Lepidoptera more females die in
the cocoon than males. With many species the female caterpillar is
larger than the male, and a collector would naturally choose the finest
specimens, and thus unintentionally collect a larger number of females.
Three collectors have told me that this was their practice; but Dr.
Wallace is sure that most collectors take all the specimens which they
can find of the rarer kinds, which alone are worth the trouble of
rearing. Birds when surrounded by caterpillars would probably devour
the largest; and Professor Canestrini informs me that in Italy some
breeders believe, though on insufficient evidence, that in the first
broods of the Ailanthus silk-moth, the wasps destroy a larger number of
the female than of the male caterpillars. Dr. Wallace further remarks
that female caterpillars, from being larger than the males, require
more time for their development, and consume more food and moisture:
and thus they would be exposed during a longer time to danger from
ichneumons, birds, etc., and in times of scarcity would perish in
greater numbers. Hence it appears quite possible that in a state of
nature, fewer female Lepidoptera may reach maturity than males; and for
our special object we are concerned with their relative numbers at
maturity, when the sexes are ready to propagate their kind.

The manner in which the males of certain moths congregate in
extraordinary numbers round a single female, apparently indicates a
great excess of males, though this fact may perhaps be accounted for by
the earlier emergence of the males from their cocoons. Mr. Stainton
informs me that from twelve to twenty males, may often be seen
congregated round a female Elachista rufocinerea. It is well known that
if a virgin Lasiocampa quercus or Saturnia carpini be exposed in a
cage, vast numbers of males collect round her, and if confined in a
room will even come down the chimney to her. Mr. Doubleday believes
that he has seen from fifty to a hundred males of both these species
attracted in the course of a single day by a female in confinement. In
the Isle of Wight Mr. Trimen exposed a box in which a female of the
Lasiocampa had been confined on the previous day, and five males soon
endeavoured to gain admittance. In Australia, Mr. Verreaux, having
placed the female of a small Bombyx in a box in his pocket, was
followed by a crowd of males, so that about 200 entered the house with
him. (81. Blanchard, ‘Metamorphoses, Moeurs des Insectes,’ 1868, pp.
225-226.)

Mr. Doubleday has called my attention to M. Staudinger’s (82.
‘Lepidopteren-Doubletten Liste,’ Berlin, No. x. 1866.) list of
Lepidoptera, which gives the prices of the males and females of 300
species or well-marked varieties of butterflies (Rhopalocera). The
prices for both sexes of the very common species are of course the
same; but in 114 of the rarer species they differ; the males being in
all cases, excepting one, the cheaper. On an average of the prices of
the 113 species, the price of the male to that of the female is as 100
to 149; and this apparently indicates that inversely the males exceed
the females in the same proportion. About 2000 species or varieties of
moths (Heterocera) are catalogued, those with wingless females being
here excluded on account of the difference in habits between the two
sexes: of these 2000 species, 141 differ in price according to sex, the
males of 130 being cheaper, and those of only 11 being dearer than the
females. The average price of the males of the 130 species, to that of
the females, is as 100 to 143. With respect to the butterflies in this
priced list, Mr. Doubleday thinks (and no man in England has had more
experience), that there is nothing in the habits of the species which
can account for the difference in the prices of the two sexes, and that
it can be accounted for only by an excess in the number of the males.
But I am bound to add that Dr. Staudinger informs me, that he is
himself of a different opinion. He thinks that the less active habits
of the females and the earlier emergence of the males will account for
his collectors securing a larger number of males than of females, and
consequently for the lower prices of the former. With respect to
specimens reared from the caterpillar-state, Dr. Staudinger believes,
as previously stated, that a greater number of females than of males
die whilst confined to the cocoons. He adds that with certain species
one sex seems to preponderate over the other during certain years.

Of direct observations on the sexes of Lepidoptera, reared either from
eggs or caterpillars, I have received only the few following cases:
(See following table.)

So that in these eight lots of cocoons and eggs, males were produced in
excess. Taken together the proportion of males is as 122.7 to 100
females. But the numbers are hardly large enough to be trustworthy.

On the whole, from these various sources of evidence, all pointing in
the same direction, I infer that with most species of Lepidoptera, the
mature males generally exceed the females in number, whatever the
proportions may be at their first emergence from the egg.

                                                   Males   Females
  The Rev. J. Hellins* of Exeter reared, during
    1868, imagos of 73 species, which
    consisted of                                     153       137

  Mr. Albert Jones of Eltham reared, during
    1868, imagos of 9 species, which
    consisted of                                     159       126

  During 1869 he reared imagos from 4 species
    consisting of                                    114       112

  Mr. Buckler of Emsworth, Hants, during 1869,
    reared imagos from 74 species,
    consisting of                                    180       169

  Dr. Wallace of Colchester reared from one
    brood of Bombyx cynthia                           52        48

  Dr. Wallace raised, from cocoons of Bombyx
    Pernyi sent from China, during 1869              224       123

  Dr. Wallace raised, during 1868 and 1869, from
    two lots of cocoons of Bombyx yamamai             52        46

                                           Total     934       761

(*83. This naturalist has been so kind as to send me some results from
former years, in which the females seemed to preponderate; but so many
of the figures were estimates, that I found it impossible to tabulate
them.)

With reference to the other Orders of insects, I have been able to
collect very little reliable information. With the stag-beetle (Lucanus
cervus) “the males appear to be much more numerous than the females”;
but when, as Cornelius remarked during 1867, an unusual number of these
beetles appeared in one part of Germany, the females appeared to exceed
the males as six to one. With one of the Elateridae, the males are said
to be much more numerous than the females, and “two or three are often
found united with one female (84. Gunther’s ‘Record of Zoological
Literature,’ 1867, p. 260. On the excess of female Lucanus, ibid, p.
250. On the males of Lucanus in England, Westwood,’ ‘Modern
Classification of Insects,’ vol. i. p. 187. On the Siagonium, ibid. p.
172.); so that here polyandry seems to prevail.” With Siagonium
(Staphylinidae), in which the males are furnished with horns, “the
females are far more numerous than the opposite sex.” Mr. Janson stated
at the Entomological Society that the females of the bark feeding
Tomicus villosus are so common as to be a plague, whilst the males are
so rare as to be hardly known.

It is hardly worth while saying anything about the proportion of the
sexes in certain species and even groups of insects, for the males are
unknown or very rare, and the females are parthenogenetic, that is,
fertile without sexual union; examples of this are afforded by several
of the Cynipidae. (85. Walsh in ‘The American Entomologist,’ vol. i.
1869, p. 103. F. Smith, ‘Record of Zoological Lit.’ 1867, p. 328.) In
all the gall-making Cynipidae known to Mr. Walsh, the females are four
or five times as numerous as the males; and so it is, as he informs me,
with the gall-making Cecidomyiidae (Diptera). With some common species
of Saw-flies (Tenthredinae) Mr. F. Smith has reared hundreds of
specimens from larvae of all sizes, but has never reared a single male;
on the other hand, Curtis says (86. ‘Farm Insects,’ pp. 45-46.), that
with certain species (Athalia), bred by him, the males were to the
females as six to one; whilst exactly the reverse occurred with the
mature insects of the same species caught in the fields. In the family
of bees, Hermann Müller (87. ‘Anwendung der Darwin’schen Lehre,’ Verh.
d. n. Jahrg., xxiv.), collected a large number of specimens of many
species, and reared others from the cocoons, and counted the sexes. He
found that the males of some species greatly exceeded the females in
number; in others the reverse occurred; and in others the two sexes
were nearly equal. But as in most cases the males emerge from the
cocoons before the females, they are at the commencement of the
breeding-season practically in excess. Müller also observed that the
relative number of the two sexes in some species differed much in
different localities. But as H. Müller has himself remarked to me,
these remarks must be received with some caution, as one sex might more
easily escape observation than the other. Thus his brother Fritz Müller
has noticed in Brazil that the two sexes of the same species of bee
sometimes frequent different kinds of flowers. With respect to the
Orthoptera, I know hardly anything about the relative number of the
sexes: Korte (88. ‘Die Strich, Zug oder Wanderheuschrecke,’ 1828, p.
20.), however, says that out of 500 locusts which he examined, the
males were to the females as five to six. With the Neuroptera, Mr.
Walsh states that in many, but by no means in all the species of the
Odonatous group, there is a great overplus of males: in the genus
Hetaerina, also, the males are generally at least four times as
numerous as the females. In certain species in the genus Gomphus the
males are equally in excess, whilst in two other species, the females
are twice or thrice as numerous as the males. In some European species
of Psocus thousands of females may be collected without a single male,
whilst with other species of the same genus both sexes are common. (89.
‘Observations on N. American Neuroptera,’ by H. Hagen and B.D. Walsh,
‘Proceedings, Ent. Soc. Philadelphia,’ Oct. 1863, pp. 168, 223, 239.)
In England, Mr. MacLachlan has captured hundreds of the female Apatania
muliebris, but has never seen the male; and of Boreus hyemalis only
four or five males have been seen here. (90. ‘Proceedings, Ent. Soc.
London,’ Feb. 17, 1868.) With most of these species (excepting the
Tenthredinae) there is at present no evidence that the females are
subject to parthenogenesis; and thus we see how ignorant we are of the
causes of the apparent discrepancy in the proportion of the two sexes.

In the other classes of the Articulata I have been able to collect
still less information. With spiders, Mr. Blackwall, who has carefully
attended to this class during many years, writes to me that the males
from their more erratic habits are more commonly seen, and therefore
appear more numerous. This is actually the case with a few species; but
he mentions several species in six genera, in which the females appear
to be much more numerous than the males. (91. Another great authority
with respect to this class, Prof. Thorell of Upsala (‘On European
Spiders,’ 1869-70, part i. p. 205), speaks as if female spiders were
generally commoner than the males.) The small size of the males in
comparison with the females (a peculiarity which is sometimes carried
to an extreme degree), and their widely different appearance, may
account in some instances for their rarity in collections. (92. See, on
this subject, Mr. O.P. Cambridge, as quoted in ‘Quarterly Journal of
Science,’ 1868, page 429.)

Some of the lower Crustaceans are able to propagate their kind
sexually, and this will account for the extreme rarity of the males;
thus von Siebold (93. ‘Beiträge zur Parthenogenesis,’ p. 174.)
carefully examined no less than 13,000 specimens of Apus from
twenty-one localities, and amongst these he found only 319 males. With
some other forms (as Tanais and Cypris), as Fritz Müller informs me,
there is reason to believe that the males are much shorter-lived than
the females; and this would explain their scarcity, supposing the two
sexes to be at first equal in number. On the other hand, Müller has
invariably taken far more males than females of the Diastylidae and of
Cypridina on the shores of Brazil: thus with a species in the latter
genus, 63 specimens caught the same day included 57 males; but he
suggests that this preponderance may be due to some unknown difference
in the habits of the two sexes. With one of the higher Brazilian crabs,
namely a Gelasimus, Fritz Müller found the males to be more numerous
than the females. According to the large experience of Mr. C. Spence
Bate, the reverse seems to be the case with six common British crabs,
the names of which he has given me.

THE PROPORTION OF THE SEXES IN RELATION TO NATURAL SELECTION.

There is reason to suspect that in some cases man has by selection
indirectly influenced his own sex-producing powers. Certain women tend
to produce during their whole lives more children of one sex than of
the other: and the same holds good of many animals, for instance, cows
and horses; thus Mr. Wright of Yeldersley House informs me that one of
his Arab mares, though put seven times to different horses, produced
seven fillies. Though I have very little evidence on this head, analogy
would lead to the belief, that the tendency to produce either sex would
be inherited like almost every other peculiarity, for instance, that of
producing twins; and concerning the above tendency a good authority,
Mr. J. Downing, has communicated to me facts which seem to prove that
this does occur in certain families of short-horn cattle. Col. Marshall
(94. ‘The Todas,’ 1873, pp. 100, 111, 194, 196.) has recently found on
careful examination that the Todas, a hill-tribe of India, consist of
112 males and 84 females of all ages—that is in a ratio of 133.3 males
to 100 females. The Todas, who are polyandrous in their marriages,
during former times invariably practised female infanticide; but this
practice has now been discontinued for a considerable period. Of the
children born within late years, the males are more numerous than the
females, in the proportion of 124 to 100. Colonel Marshall accounts for
this fact in the following ingenious manner. “Let us for the purpose of
illustration take three families as representing an average of the
entire tribe; say that one mother gives birth to six daughters and no
sons; a second mother has six sons only, whilst the third mother has
three sons and three daughters. The first mother, following the tribal
custom, destroys four daughters and preserves two. The second retains
her six sons. The third kills two daughters and keeps one, as also her
three sons. We have then from the three families, nine sons and three
daughters, with which to continue the breed. But whilst the males
belong to families in which the tendency to produce sons is great, the
females are of those of a converse inclination. Thus the bias
strengthens with each generation, until, as we find, families grow to
have habitually more sons than daughters.”

That this result would follow from the above form of infanticide seems
almost certain; that is if we assume that a sex-producing tendency is
inherited. But as the above numbers are so extremely scanty, I have
searched for additional evidence, but cannot decide whether what I have
found is trustworthy; nevertheless the facts are, perhaps, worth
giving. The Maories of New Zealand have long practised infanticide; and
Mr. Fenton (95. ‘Aboriginal Inhabitants of New Zealand: Government
Report,’ 1859, p. 36.) states that he “has met with instances of women
who have destroyed four, six, and even seven children, mostly females.
However, the universal testimony of those best qualified to judge, is
conclusive that this custom has for many years been almost extinct.
Probably the year 1835 may be named as the period of its ceasing to
exist.” Now amongst the New Zealanders, as with the Todas, male births
are considerably in excess. Mr. Fenton remarks (p. 30), “One fact is
certain, although the exact period of the commencement of this singular
condition of the disproportion of the sexes cannot be demonstratively
fixed, it is quite clear that this course of decrease was in full
operation during the years 1830 to 1844, when the non-adult population
of 1844 was being produced, and has continued with great energy up to
the present time.” The following statements are taken from Mr. Fenton
(p. 26), but as the numbers are not large, and as the census was not
accurate, uniform results cannot be expected. It should be borne in
mind in this and the following cases, that the normal state of every
population is an excess of women, at least in all civilised countries,
chiefly owing to the greater mortality of the male sex during youth,
and partly to accidents of all kinds later in life. In 1858, the native
population of New Zealand was estimated as consisting of 31,667 males
and 24,303 females of all ages, that is in the ratio of 130.3 males to
100 females. But during this same year, and in certain limited
districts, the numbers were ascertained with much care, and the males
of all ages were here 753 and the females 616; that is in the ratio of
122.2 males to 100 females. It is more important for us that during
this same year of 1858, the NON-ADULT males within the same district
were found to be 178, and the NON-ADULT females 142, that is in the
ratio of 125.3 to 100. It may be added that in 1844, at which period
female infanticide had only lately ceased, the NON-ADULT males in one
district were 281, and the NON-ADULT females only 194, that is in the
ratio of 144.8 males to 100 females.

In the Sandwich Islands, the males exceed the females in number.
Infanticide was formerly practised there to a frightful extent, but was
by no means confined to female infants, as is shewn by Mr. Ellis (96.
‘Narrative of a Tour through Hawaii,’ 1826, p. 298.), and as I have
been informed by Bishop Staley and the Rev. Mr. Coan. Nevertheless,
another apparently trustworthy writer, Mr. Jarves (97. ‘History of the
Sandwich Islands,’ 1843, p. 93.), whose observations apply to the whole
archipelago, remarks:—“Numbers of women are to be found, who confess to
the murder of from three to six or eight children,” and he adds,
“females from being considered less useful than males were more often
destroyed.” From what is known to occur in other parts of the world,
this statement is probable; but must be received with much caution. The
practice of infanticide ceased about the year 1819, when idolatry was
abolished and missionaries settled in the Islands. A careful census in
1839 of the adult and taxable men and women in the island of Kauai and
in one district of Oahu (Jarves, p. 404), gives 4723 males and 3776
females; that is in the ratio of 125.08 to 100. At the same time the
number of males under fourteen years in Kauai and under eighteen in
Oahu was 1797, and of females of the same ages 1429; and here we have
the ratio of 125.75 males to 100 females.

In a census of all the islands in 1850 (98. This is given in the Rev.
H.T. Cheever’s ‘Life in the Sandwich Islands,’ 1851, p. 277.), the
males of all ages amount to 36,272, and the females to 33,128, or as
109.49 to 100. The males under seventeen years amounted to 10,773, and
the females under the same age to 9593, or as 112.3 to 100. From the
census of 1872, the proportion of males of all ages (including
half-castes) to females, is as 125.36 to 100. It must be borne in mind
that all these returns for the Sandwich Islands give the proportion of
living males to living females, and not of the births; and judging from
all civilised countries the proportion of males would have been
considerably higher if the numbers had referred to births. (99. Dr.
Coulter, in describing (‘Journal R. Geograph. Soc.’ vol. v. 1835, p.
67) the state of California about the year 1830, says that the natives,
reclaimed by the Spanish missionaries, have nearly all perished, or are
perishing, although well treated, not driven from their native land,
and kept from the use of spirits. He attributes this, in great part, to
the undoubted fact that the men greatly exceed the women in number; but
he does not know whether this is due to a failure of female offspring,
or to more females dying during early youth. The latter alternative,
according to all analogy, is very improbable. He adds that
“infanticide, properly so called, is not common, though very frequent
recourse is had to abortion.” If Dr. Coulter is correct about
infanticide, this case cannot be advanced in support of Colonel
Marshall’s view. From the rapid decrease of the reclaimed natives, we
may suspect that, as in the cases lately given, their fertility has
been diminished from changed habits of life.

I had hoped to gain some light on this subject from the breeding of
dogs; inasmuch as in most breeds, with the exception, perhaps, of
greyhounds, many more female puppies are destroyed than males, just as
with the Toda infants. Mr. Cupples assures me that this is usual with
Scotch deer-hounds. Unfortunately, I know nothing of the proportion of
the sexes in any breed, excepting greyhounds, and there the male births
are to the females as 110.1 to 100. Now from enquiries made from many
breeders, it seems that the females are in some respects more esteemed,
though otherwise troublesome; and it does not appear that the female
puppies of the best-bred dogs are systematically destroyed more than
the males, though this does sometimes take place to a limited extent.
Therefore I am unable to decide whether we can, on the above
principles, account for the preponderance of male births in greyhounds.
On the other hand, we have seen that with horses, cattle, and sheep,
which are too valuable for the young of either sex to be destroyed, if
there is any difference, the females are slightly in excess.)

From the several foregoing cases we have some reason to believe that
infanticide practised in the manner above explained, tends to make a
male-producing race; but I am far from supposing that this practice in
the case of man, or some analogous process with other species, has been
the sole determining cause of an excess of males. There may be some
unknown law leading to this result in decreasing races, which have
already become somewhat infertile. Besides the several causes
previously alluded to, the greater facility of parturition amongst
savages, and the less consequent injury to their male infants, would
tend to increase the proportion of live-born males to females. There
does not, however, seem to be any necessary connection between savage
life and a marked excess of males; that is if we may judge by the
character of the scanty offspring of the lately existing Tasmanians and
of the crossed offspring of the Tahitians now inhabiting Norfolk
Island.

As the males and females of many animals differ somewhat in habits and
are exposed in different degrees to danger, it is probable that in many
cases, more of one sex than of the other are habitually destroyed. But
as far as I can trace out the complication of causes, an indiscriminate
though large destruction of either sex would not tend to modify the
sex-producing power of the species. With strictly social animals, such
as bees or ants, which produce a vast number of sterile and fertile
females in comparison with the males, and to whom this preponderance is
of paramount importance, we can see that those communities would
flourish best which contained females having a strong inherited
tendency to produce more and more females; and in such cases an unequal
sex-producing tendency would be ultimately gained through natural
selection. With animals living in herds or troops, in which the males
come to the front and defend the herd, as with the bisons of North
America and certain baboons, it is conceivable that a male-producing
tendency might be gained by natural selection; for the individuals of
the better defended herds would leave more numerous descendants. In the
case of mankind the advantage arising from having a preponderance of
men in the tribe is supposed to be one chief cause of the practice of
female infanticide.

In no case, as far as we can see, would an inherited tendency to
produce both sexes in equal numbers or to produce one sex in excess, be
a direct advantage or disadvantage to certain individuals more than to
others; for instance, an individual with a tendency to produce more
males than females would not succeed better in the battle for life than
an individual with an opposite tendency; and therefore a tendency of
this kind could not be gained through natural selection. Nevertheless,
there are certain animals (for instance, fishes and cirripedes) in
which two or more males appear to be necessary for the fertilisation of
the female; and the males accordingly largely preponderate, but it is
by no means obvious how this male-producing tendency could have been
acquired. I formerly thought that when a tendency to produce the two
sexes in equal numbers was advantageous to the species, it would follow
from natural selection, but I now see that the whole problem is so
intricate that it is safer to leave its solution for the future.




CHAPTER IX.
SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.


These characters absent in the lowest classes—Brilliant
colours—Mollusca —Annelids—Crustacea, secondary sexual characters
strongly developed; dimorphism; colour; characters not acquired before
maturity—Spiders, sexual colours of; stridulation by the
males—Myriapoda.

With animals belonging to the lower classes, the two sexes are not
rarely united in the same individual, and therefore secondary sexual
characters cannot be developed. In many cases where the sexes are
separate, both are permanently attached to some support, and the one
cannot search or struggle for the other. Moreover it is almost certain
that these animals have too imperfect senses and much too low mental
powers to appreciate each other’s beauty or other attractions, or to
feel rivalry.

Hence in these classes or sub-kingdoms, such as the Protozoa,
Coelenterata, Echinodermata, Scolecida, secondary sexual characters, of
the kind which we have to consider, do not occur: and this fact agrees
with the belief that such characters in the higher classes have been
acquired through sexual selection, which depends on the will, desire,
and choice of either sex. Nevertheless some few apparent exceptions
occur; thus, as I hear from Dr. Baird, the males of certain Entozoa, or
internal parasitic worms, differ slightly in colour from the females;
but we have no reason to suppose that such differences have been
augmented through sexual selection. Contrivances by which the male
holds the female, and which are indispensable for the propagation of
the species, are independent of sexual selection, and have been
acquired through ordinary selection.

Many of the lower animals, whether hermaphrodites or with separate
sexes, are ornamented with the most brilliant tints, or are shaded and
striped in an elegant manner; for instance, many corals and
sea-anemones (Actiniae), some jelly-fish (Medusae, Porpita, etc.), some
Planariae, many star-fishes, Echini, Ascidians, etc.; but we may
conclude from the reasons already indicated, namely, the union of the
two sexes in some of these animals, the permanently affixed condition
of others, and the low mental powers of all, that such colours do not
serve as a sexual attraction, and have not been acquired through sexual
selection. It should be borne in mind that in no case have we
sufficient evidence that colours have been thus acquired, except where
one sex is much more brilliantly or conspicuously coloured than the
other, and where there is no difference in habits between the sexes
sufficient to account for their different colours. But the evidence is
rendered as complete as it can ever be, only when the more ornamented
individuals, almost always the males, voluntarily display their
attractions before the other sex; for we cannot believe that such
display is useless, and if it be advantageous, sexual selection will
almost inevitably follow. We may, however, extend this conclusion to
both sexes, when coloured alike, if their colours are plainly analogous
to those of one sex alone in certain other species of the same group.

How, then, are we to account for the beautiful or even gorgeous colours
of many animals in the lowest classes? It appears doubtful whether such
colours often serve as a protection; but that we may easily err on this
head, will be admitted by every one who reads Mr. Wallace’s excellent
essay on this subject. It would not, for instance, at first occur to
any one that the transparency of the Medusae, or jelly-fish, is of the
highest service to them as a protection; but when we are reminded by
Haeckel that not only the Medusae, but many floating Mollusca,
crustaceans, and even small oceanic fishes partake of this same
glass-like appearance, often accompanied by prismatic colours, we can
hardly doubt that they thus escape the notice of pelagic birds and
other enemies. M. Giard is also convinced (1. ‘Archives de Zoolog.
Exper.’ Oct. 1872, p. 563.) that the bright tints of certain sponges
and ascidians serve as a protection. Conspicuous colours are likewise
beneficial to many animals as a warning to their would-be devourers
that they are distasteful, or that they possess some special means of
defence; but this subject will be discussed more conveniently
hereafter.

We can, in our ignorance of most of the lowest animals, only say that
their bright tints result either from the chemical nature or the minute
structure of their tissues, independently of any benefit thus derived.
Hardly any colour is finer than that of arterial blood; but there is no
reason to suppose that the colour of the blood is in itself any
advantage; and though it adds to the beauty of the maiden’s cheek, no
one will pretend that it has been acquired for this purpose. So again
with many animals, especially the lower ones, the bile is richly
coloured; thus, as I am informed by Mr. Hancock, the extreme beauty of
the Eolidae (naked sea-slugs) is chiefly due to the biliary glands
being seen through the translucent integuments—this beauty being
probably of no service to these animals. The tints of the decaying
leaves in an American forest are described by every one as gorgeous;
yet no one supposes that these tints are of the least advantage to the
trees. Bearing in mind how many substances closely analogous to natural
organic compounds have been recently formed by chemists, and which
exhibit the most splendid colours, it would have been a strange fact if
substances similarly coloured had not often originated, independently
of any useful end thus gained, in the complex laboratory of living
organisms.

THE SUB-KINGDOM OF THE MOLLUSCA.

Throughout this great division of the animal kingdom, as far as I can
discover, secondary sexual characters, such as we are here considering,
never occur. Nor could they be expected in the three lowest classes,
namely, in the Ascidians, Polyzoa, and Brachiopods (constituting the
Molluscoida of some authors), for most of these animals are permanently
affixed to a support or have their sexes united in the same individual.
In the Lamellibranchiata, or bivalve shells, hermaphroditism is not
rare. In the next higher class of the Gasteropoda, or univalve shells,
the sexes are either united or separate. But in the latter case the
males never possess special organs for finding, securing, or charming
the females, or for fighting with other males. As I am informed by Mr.
Gwyn Jeffreys, the sole external difference between the sexes consists
in the shell sometimes differing a little in form; for instance, the
shell of the male periwinkle (Littorina littorea) is narrower and has a
more elongated spire than that of the female. But differences of this
nature, it may be presumed, are directly connected with the act of
reproduction, or with the development of the ova.

The Gasteropoda, though capable of locomotion and furnished with
imperfect eyes, do not appear to be endowed with sufficient mental
powers for the members of the same sex to struggle together in rivalry,
and thus to acquire secondary sexual characters. Nevertheless with the
pulmoniferous gasteropods, or land-snails, the pairing is preceded by
courtship; for these animals, though hermaphrodites, are compelled by
their structure to pair together. Agassiz remarks, “Quiconque a eu
l’occasion d’observer les amours des limaçons, ne saurait mettre en
doute la séduction deployée dans les mouvements et les allures qui
préparent et accomplissent le double embrassement de ces
hermaphrodites.” (2. ‘De l’Espèce et de la Class.’ etc., 1869, p. 106.)
These animals appear also susceptible of some degree of permanent
attachment: an accurate observer, Mr. Lonsdale, informs me that he
placed a pair of land-snails, (Helix pomatia), one of which was weakly,
into a small and ill-provided garden. After a short time the strong and
healthy individual disappeared, and was traced by its track of slime
over a wall into an adjoining well-stocked garden. Mr. Lonsdale
concluded that it had deserted its sickly mate; but after an absence of
twenty-four hours it returned, and apparently communicated the result
of its successful exploration, for both then started along the same
track and disappeared over the wall.

Even in the highest class of the Mollusca, the Cephalopoda or
cuttle-fishes, in which the sexes are separate, secondary sexual
characters of the present kind do not, as far as I can discover, occur.
This is a surprising circumstance, as these animals possess
highly-developed sense-organs and have considerable mental powers, as
will be admitted by every one who has watched their artful endeavours
to escape from an enemy. (3. See, for instance, the account which I
have given in my ‘Journal of Researches,’ 1845, p. 7.) Certain
Cephalopoda, however, are characterised by one extraordinary sexual
character, namely that the male element collects within one of the arms
or tentacles, which is then cast off, and clinging by its sucking-discs
to the female, lives for a time an independent life. So completely does
the cast-off arm resemble a separate animal, that it was described by
Cuvier as a parasitic worm under the name of Hectocotyle. But this
marvellous structure may be classed as a primary rather than as a
secondary sexual character.

Although with the Mollusca sexual selection does not seem to have come
into play; yet many univalve and bivalve shells, such as volutes,
cones, scallops, etc., are beautifully coloured and shaped. The colours
do not appear in most cases to be of any use as a protection; they are
probably the direct result, as in the lowest classes, of the nature of
the tissues; the patterns and the sculpture of the shell depending on
its manner of growth. The amount of light seems to be influential to a
certain extent; for although, as repeatedly stated by Mr. Gwyn
Jeffreys, the shells of some species living at a profound depth are
brightly coloured, yet we generally see the lower surfaces, as well as
the parts covered by the mantle, less highly-coloured than the upper
and exposed surfaces. (4. I have given (‘Geological Observations on
Volcanic Islands,’ 1844, p. 53) a curious instance of the influence of
light on the colours of a frondescent incrustation, deposited by the
surf on the coast-rocks of Ascension and formed by the solution of
triturated sea-shells.) In some cases, as with shells living amongst
corals or brightly-tinted seaweeds, the bright colours may serve as a
protection. (5. Dr. Morse has lately discussed this subject in his
paper on the ‘Adaptive Coloration of Mollusca,’ ‘Proc. Boston Soc. of
Nat. Hist.’ vol. xiv. April 1871.) But that many of the nudibranch
Mollusca, or sea-slugs, are as beautifully coloured as any shells, may
be seen in Messrs. Alder and Hancock’s magnificent work; and from
information kindly given me by Mr. Hancock, it seems extremely doubtful
whether these colours usually serve as a protection. With some species
this may be the case, as with one kind which lives on the green leaves
of algae, and is itself bright-green. But many brightly-coloured,
white, or otherwise conspicuous species, do not seek concealment;
whilst again some equally conspicuous species, as well as other
dull-coloured kinds live under stones and in dark recesses. So that
with these nudibranch molluscs, colour apparently does not stand in any
close relation to the nature of the places which they inhabit.

These naked sea-slugs are hermaphrodites, yet they pair together, as do
land-snails, many of which have extremely pretty shells. It is
conceivable that two hermaphrodites, attracted by each other’s greater
beauty, might unite and leave offspring which would inherit their
parents’ greater beauty. But with such lowly-organised creatures this
is extremely improbable. Nor is it at all obvious how the offspring
from the more beautiful pairs of hermaphrodites would have any
advantage over the offspring of the less beautiful, so as to increase
in number, unless indeed vigour and beauty generally coincided. We have
not here the case of a number of males becoming mature before the
females, with the more beautiful males selected by the more vigorous
females. If, indeed, brilliant colours were beneficial to a
hermaphrodite animal in relation to its general habits of life, the
more brightly-tinted individuals would succeed best and would increase
in number; but this would be a case of natural and not of sexual
selection.

SUB-KINGDOM OF THE VERMES: CLASS, ANNELIDA (OR SEA-WORMS).

In this class, although the sexes, when separate, sometimes differ from
each other in characters of such importance that they have been placed
under distinct genera or even families, yet the differences do not seem
of the kind which can be safely attributed to sexual selection. These
animals are often beautifully coloured, but as the sexes do not differ
in this respect, we are but little concerned with them. Even the
Nemertians, though so lowly organised, “vie in beauty and variety of
colouring with any other group in the invertebrate series”; yet Dr.
McIntosh (6. See his beautiful monograph on ‘British Annelids,’ part i.
1873, p. 3.) cannot discover that these colours are of any service. The
sedentary annelids become duller-coloured, according to M. Quatrefages
(7. See M. Perrier: ‘L’Origine de l’Homme d’après Darwin,’ ‘Revue
Scientifique’, Feb. 1873, p. 866.), after the period of reproduction;
and this I presume may be attributed to their less vigorous condition
at that time. All these worm-like animals apparently stand too low in
the scale for the individuals of either sex to exert any choice in
selecting a partner, or for the individuals of the same sex to struggle
together in rivalry.

SUB-KINGDOM OF THE ARTHROPODA: CLASS, CRUSTACEA.

In this great class we first meet with undoubted secondary sexual
characters, often developed in a remarkable manner. Unfortunately the
habits of crustaceans are very imperfectly known, and we cannot explain
the uses of many structures peculiar to one sex. With the lower
parasitic species the males are of small size, and they alone are
furnished with perfect swimming-legs, antennae and sense-organs; the
females being destitute of these organs, with their bodies often
consisting of a mere distorted mass. But these extraordinary
differences between the two sexes are no doubt related to their widely
different habits of life, and consequently do not concern us. In
various crustaceans, belonging to distinct families, the anterior
antennae are furnished with peculiar thread-like bodies, which are
believed to act as smelling-organs, and these are much more numerous in
the males than in the females. As the males, without any unusual
development of their olfactory organs, would almost certainly be able
sooner or later to find the females, the increased number of the
smelling-threads has probably been acquired through sexual selection,
by the better provided males having been the more successful in finding
partners and in producing offspring. Fritz Müller has described a
remarkable dimorphic species of Tanais, in which the male is
represented by two distinct forms, which never graduate into each
other. In the one form the male is furnished with more numerous
smelling-threads, and in the other form with more powerful and more
elongated chelae or pincers, which serve to hold the female. Fritz
Müller suggests that these differences between the two male forms of
the same species may have originated in certain individuals having
varied in the number of the smelling-threads, whilst other individuals
varied in the shape and size of their chelae; so that of the former,
those which were best able to find the female, and of the latter, those
which were best able to hold her, have left the greatest number of
progeny to inherit their respective advantages. (8. ‘Facts and
Arguments for Darwin,’ English translat., 1869, p. 20. See the previous
discussion on the olfactory threads. Sars has described a somewhat
analogous case (as quoted in ‘Nature,’ 1870, p. 455) in a Norwegian
crustacean, the Pontoporeia affinis.)

[Fig.4. Labidocera Darwinii (from Lubbock). Labelled are: a. Part of
right anterior antenna of male, forming a prehensile organ. b.
Posterior pair of thoracic legs of male. c. Ditto of female.]

In some of the lower crustaceans, the right anterior antenna of the
male differs greatly in structure from the left, the latter resembling
in its simple tapering joints the antennae of the female. In the male
the modified antenna is either swollen in the middle or angularly bent,
or converted (Fig. 4) into an elegant, and sometimes wonderfully
complex, prehensile organ. (9. See Sir J. Lubbock in ‘Annals and Mag.
of Nat. Hist.’ vol. xi. 1853, pl. i. and x.; and vol. xii. (1853), pl.
vii. See also Lubbock in ‘Transactions, Entomological Society,’ vol.
iv. new series, 1856-1858, p. 8. With respect to the zigzagged antennae
mentioned below, see Fritz Müller, ‘Facts and Arguments for Darwin,’
1869, p. 40, foot-note.) It serves, as I hear from Sir J. Lubbock, to
hold the female, and for this same purpose one of the two posterior
legs (b) on the same side of the body is converted into a forceps. In
another family the inferior or posterior antennae are “curiously
zigzagged” in the males alone.

[Fig. 5. Anterior part of body of Callianassa (from Milne-Edwards),
showing the unequal and differently-constructed right and left-hand
chelae of the male. N.B.—The artist by mistake has reversed the
drawing, and made the left-hand chela the largest.

Fig. 6. Second leg of male Orchestia Tucuratinga (from Fritz Müller).

Fig. 7. Ditto of female.]

In the higher crustaceans the anterior legs are developed into chelae
or pincers; and these are generally larger in the male than in the
female,—so much so that the market value of the male edible crab
(Cancer pagurus), according to Mr. C. Spence Bate, is five times as
great as that of the female. In many species the chelae are of unequal
size on the opposite side of the body, the right-hand one being, as I
am informed by Mr. Bate, generally, though not invariably, the largest.
This inequality is also often much greater in the male than in the
female. The two chelae of the male often differ in structure (Figs. 5,
6, and 7), the smaller one resembling that of the female. What
advantage is gained by their inequality in size on the opposite sides
of the body, and by the inequality being much greater in the male than
in the female; and why, when they are of equal size, both are often
much larger in the male than in the female, is not known. As I hear
from Mr. Bate, the chelae are sometimes of such length and size that
they cannot possibly be used for carrying food to the mouth. In the
males of certain fresh-water prawns (Palaemon) the right leg is
actually longer than the whole body. (10. See a paper by Mr. C. Spence
Bate, with figures, in ‘Proceedings, Zoological Society,’ 1868, p. 363;
and on the nomenclature of the genus, ibid. p. 585. I am greatly
indebted to Mr. Spence Bate for nearly all the above statements with
respect to the chelae of the higher crustaceans.) The great size of the
one leg with its chelae may aid the male in fighting with his rivals;
but this will not account for their inequality in the female on the
opposite sides of the body. In Gelasimus, according to a statement
quoted by Milne Edwards (11. ‘Hist. Nat. des Crust.’ tom. ii. 1837, p.
50.), the male and the female live in the same burrow, and this shews
that they pair; the male closes the mouth of the burrow with one of its
chelae, which is enormously developed; so that here it indirectly
serves as a means of defence. Their main use, however, is probably to
seize and to secure the female, and this in some instances, as with
Gammarus, is known to be the case. The male of the hermit or soldier
crab (Pagurus) for weeks together, carries about the shell inhabited by
the female. (12. Mr. C. Spence Bate, ‘British Association, Fourth
Report on the Fauna of S. Devon.’) The sexes, however, of the common
shore-crab (Carcinus maenas), as Mr. Bate informs me, unite directly
after the female has moulted her hard shell, when she is so soft that
she would be injured if seized by the strong pincers of the male; but
as she is caught and carried about by the male before moulting, she
could then be seized with impunity.

[Fig.8. Orchestia Darwinii (from Fritz Müller), showing the
differently-constructed chelae of the two male forms.]

Fritz Müller states that certain species of Melita are distinguished
from all other amphipods by the females having “the coxal lamellae of
the penultimate pair of feet produced into hook-like processes, of
which the males lay hold with the hands of the first pair.” The
development of these hook-like processes has probably followed from
those females which were the most securely held during the act of
reproduction, having left the largest number of offspring. Another
Brazilian amphipod (see Orchestia darwinii, Fig. 8) presents a case of
dimorphism, like that of Tanais; for there are two male forms, which
differ in the structure of their chelae. (13. Fritz Müller, ‘Facts and
Arguments for Darwin,’ 1869, pp. 25-28.) As either chela would
certainly suffice to hold the female,—for both are now used for this
purpose,—the two male forms probably originated by some having varied
in one manner and some in another; both forms having derived certain
special, but nearly equal advantages, from their differently shaped
organs.

It is not known that male crustaceans fight together for the possession
of the females, but it is probably the case; for with most animals when
the male is larger than the female, he seems to owe his greater size to
his ancestors having fought with other males during many generations.
In most of the orders, especially in the highest or the Brachyura, the
male is larger than the female; the parasitic genera, however, in which
the sexes follow different habits of life, and most of the Entomostraca
must be excepted. The chelae of many crustaceans are weapons well
adapted for fighting. Thus when a Devil-crab (Portunus puber) was seen
by a son of Mr. Bate fighting with a Carcinus maenas, the latter was
soon thrown on its back, and had every limb torn from its body. When
several males of a Brazilian Gelasimus, a species furnished with
immense pincers, were placed together in a glass vessel by Fritz
Müller, they mutilated and killed one another. Mr. Bate put a large
male Carcinus maenas into a pan of water, inhabited by a female which
was paired with a smaller male; but the latter was soon dispossessed.
Mr. Bate adds, “if they fought, the victory was a bloodless one, for I
saw no wounds.” This same naturalist separated a male sand-skipper (so
common on our sea-shores), Gammarus marinus, from its female, both of
whom were imprisoned in the same vessel with many individuals of the
same species. The female, when thus divorced, soon joined the others.
After a time the male was put again into the same vessel; and he then,
after swimming about for a time, dashed into the crowd, and without any
fighting at once took away his wife. This fact shews that in the
Amphipoda, an order low in the scale, the males and females recognise
each other, and are mutually attached.

The mental powers of the Crustacea are probably higher than at first
sight appears probable. Any one who tries to catch one of the
shore-crabs, so common on tropical coasts, will perceive how wary and
alert they are. There is a large crab (Birgus latro), found on coral
islands, which makes a thick bed of the picked fibres of the cocoa-nut,
at the bottom of a deep burrow. It feeds on the fallen fruit of this
tree by tearing off the husk, fibre by fibre; and it always begins at
that end where the three eye-like depressions are situated. It then
breaks through one of these eyes by hammering with its heavy front
pincers, and turning round, extracts the albuminous core with its
narrow posterior pincers. But these actions are probably instinctive,
so that they would be performed as well by a young animal as by an old
one. The following case, however, can hardly be so considered: a
trustworthy naturalist, Mr. Gardner (14. ‘Travels in the Interior of
Brazil,’ 1846, p. 111. I have given, in my ‘Journal of Researches,’ p.
463, an account of the habits of the Birgus.), whilst watching a
shore-crab (Gelasimus) making its burrow, threw some shells towards the
hole. One rolled in, and three other shells remained within a few
inches of the mouth. In about five minutes the crab brought out the
shell which had fallen in, and carried it away to a distance of a foot;
it then saw the three other shells lying near, and evidently thinking
that they might likewise roll in, carried them to the spot where it had
laid the first. It would, I think, be difficult to distinguish this act
from one performed by man by the aid of reason.

Mr. Bate does not know of any well-marked case of difference of colour
in the two sexes of our British crustaceans, in which respect the sexes
of the higher animals so often differ. In some cases, however, the
males and females differ slightly in tint, but Mr. Bate thinks not more
than may be accounted for by their different habits of life, such as by
the male wandering more about, and being thus more exposed to the
light. Dr. Power tried to distinguish by colour the sexes of the
several species which inhabit the Mauritius, but failed, except with
one species of Squilla, probably S. stylifera, the male of which is
described as being “of a beautiful bluish-green,” with some of the
appendages cherry-red, whilst the female is clouded with brown and
grey, “with the red about her much less vivid than in the male.” (15.
Mr. Ch. Fraser, in ‘Proc. Zoolog. Soc.’ 1869, p. 3. I am indebted to
Mr. Bate for Dr. Power’s statement.) In this case, we may suspect the
agency of sexual selection. From M. Bert’s observations on Daphnia,
when placed in a vessel illuminated by a prism, we have reason to
believe that even the lowest crustaceans can distinguish colours. With
Saphirina (an oceanic genus of Entomostraca), the males are furnished
with minute shields or cell-like bodies, which exhibit beautiful
changing colours; these are absent in the females, and in both sexes of
one species. (16. Claus, ‘Die freilebenden Copepoden,’ 1863, s. 35.) It
would, however, be extremely rash to conclude that these curious organs
serve to attract the females. I am informed by Fritz Müller, that in
the female of a Brazilian species of Gelasimus, the whole body is of a
nearly uniform greyish-brown. In the male the posterior part of the
cephalo-thorax is pure white, with the anterior part of a rich green,
shading into dark brown; and it is remarkable that these colours are
liable to change in the course of a few minutes—the white becoming
dirty grey or even black, the green “losing much of its brilliancy.” It
deserves especial notice that the males do not acquire their bright
colours until they become mature. They appear to be much more numerous
than the females; they differ also in the larger size of their chelae.
In some species of the genus, probably in all, the sexes pair and
inhabit the same burrow. They are also, as we have seen, highly
intelligent animals. From these various considerations it seems
probable that the male in this species has become gaily ornamented in
order to attract or excite the female.

It has just been stated that the male Gelasimus does not acquire his
conspicuous colours until mature and nearly ready to breed. This seems
a general rule in the whole class in respect to the many remarkable
structural differences between the sexes. We shall hereafter find the
same law prevailing throughout the great sub-kingdom of the Vertebrata;
and in all cases it is eminently distinctive of characters which have
been acquired through sexual selection. Fritz Müller (17. ‘Facts and
Arguments,’ etc., p. 79.) gives some striking instances of this law;
thus the male sand-hopper (Orchestia) does not, until nearly full
grown, acquire his large claspers, which are very differently
constructed from those of the female; whilst young, his claspers
resemble those of the female.

CLASS, ARACHNIDA (SPIDERS).

The sexes do not generally differ much in colour, but the males are
often darker than the females, as may be seen in Mr. Blackwall’s
magnificent work. (18. ‘A History of the Spiders of Great Britain,’
1861-64. For the following facts, see pp. 77, 88, 102.) In some
species, however, the difference is conspicuous: thus the female of
Sparassus smaragdulus is dullish green, whilst the adult male has the
abdomen of a fine yellow, with three longitudinal stripes of rich red.
In certain species of Thomisus the sexes closely resemble each other,
in others they differ much; and analogous cases occur in many other
genera. It is often difficult to say which of the two sexes departs
most from the ordinary coloration of the genus to which the species
belong; but Mr. Blackwall thinks that, as a general rule, it is the
male; and Canestrini (19. This author has recently published a valuable
essay on the ‘Caratteri sessuali secondarii degli Arachnidi,’ in the
‘Atti della Soc. Veneto-Trentina di Sc. Nat. Padova,’ vol. i. Fasc. 3,
1873.) remarks that in certain genera the males can be specifically
distinguished with ease, but the females with great difficulty. I am
informed by Mr. Blackwall that the sexes whilst young usually resemble
each other; and both often undergo great changes in colour during their
successive moults, before arriving at maturity. In other cases the male
alone appears to change colour. Thus the male of the above
bright-coloured Sparassus at first resembles the female, and acquires
his peculiar tints only when nearly adult. Spiders are possessed of
acute senses, and exhibit much intelligence; as is well known, the
females often shew the strongest affection for their eggs, which they
carry about enveloped in a silken web. The males search eagerly for the
females, and have been seen by Canestrini and others to fight for
possession of them. This same author says that the union of the two
sexes has been observed in about twenty species; and he asserts
positively that the female rejects some of the males who court her,
threatens them with open mandibles, and at last after long hesitation
accepts the chosen one. From these several considerations, we may admit
with some confidence that the well-marked differences in colour between
the sexes of certain species are the results of sexual selection;
though we have not here the best kind of evidence,—the display by the
male of his ornaments. From the extreme variability of colour in the
male of some species, for instance of Theridion lineatum, it would
appear that these sexual characters of the males have not as yet become
well fixed. Canestrini draws the same conclusion from the fact that the
males of certain species present two forms, differing from each other
in the size and length of their jaws; and this reminds us of the above
cases of dimorphic crustaceans.

The male is generally much smaller than the female, sometimes to an
extraordinary degree (20. Aug. Vinson (‘Araneides des Iles de la
Reunion,’ pl. vi. figs. 1 and 2) gives a good instance of the small
size of the male, in Epeira nigra. In this species, as I may add, the
male is testaceous and the female black with legs banded with red.
Other even more striking cases of inequality in size between the sexes
have been recorded (‘Quarterly Journal of Science,’ July 1868, p. 429);
but I have not seen the original accounts.), and he is forced to be
extremely cautious in making his advances, as the female often carries
her coyness to a dangerous pitch. De Geer saw a male that “in the midst
of his preparatory caresses was seized by the object of his attentions,
enveloped by her in a web and then devoured, a sight which, as he adds,
filled him with horror and indignation.” (21. Kirby and Spence,
‘Introduction to Entomology,’ vol. i. 1818, p. 280.) The Rev. O.P.
Cambridge (22. ‘Proceedings, Zoological Society,’ 1871, p. 621.)
accounts in the following manner for the extreme smallness of the male
in the genus Nephila. “M. Vinson gives a graphic account of the agile
way in which the diminutive male escapes from the ferocity of the
female, by gliding about and playing hide and seek over her body and
along her gigantic limbs: in such a pursuit it is evident that the
chances of escape would be in favour of the smallest males, while the
larger ones would fall early victims; thus gradually a diminutive race
of males would be selected, until at last they would dwindle to the
smallest possible size compatible with the exercise of their generative
functions,—in fact, probably to the size we now see them, i.e., so
small as to be a sort of parasite upon the female, and either beneath
her notice, or too agile and too small for her to catch without great
difficulty.”

Westring has made the interesting discovery that the males of several
species of Theridion (23. Theridion (Asagena, Sund.) serratipes,
4-punctatum et guttatum; see Westring, in Kroyer, ‘Naturhist.
Tidskrift,’ vol. iv. 1842-1843, p. 349; and vol. ii. 1846-1849, p. 342.
See, also, for other species, ‘Araneae Suecicae,’ p. 184.) have the
power of making a stridulating sound, whilst the females are mute. The
apparatus consists of a serrated ridge at the base of the abdomen,
against which the hard hinder part of the thorax is rubbed; and of this
structure not a trace can be detected in the females. It deserves
notice that several writers, including the well-known arachnologist
Walckenaer, have declared that spiders are attracted by music. (24. Dr.
H.H. van Zouteveen, in his Dutch translation of this work (vol. i. p.
444), has collected several cases.) From the analogy of the Orthoptera
and Homoptera, to be described in the next chapter, we may feel almost
sure that the stridulation serves, as Westring also believes, to call
or to excite the female; and this is the first case known to me in the
ascending scale of the animal kingdom of sounds emitted for this
purpose. (25. Hilgendorf, however, has lately called attention to an
analogous structure in some of the higher crustaceans, which seems
adapted to produce sound; see ‘Zoological Record,’ 1869, p. 603.)

CLASS, MYRIAPODA.

In neither of the two orders in this class, the millipedes and
centipedes, can I find any well-marked instances of such sexual
differences as more particularly concern us. In Glomeris limbata,
however, and perhaps in some few other species, the males differ
slightly in colour from the females; but this Glomeris is a highly
variable species. In the males of the Diplopoda, the legs belonging
either to one of the anterior or of the posterior segments of the body
are modified into prehensile hooks which serve to secure the female. In
some species of Iulus the tarsi of the male are furnished with
membranous suckers for the same purpose. As we shall see when we treat
of Insects, it is a much more unusual circumstance, that it is the
female in Lithobius, which is furnished with prehensile appendages at
the extremity of her body for holding the male. (26. Walckenaer et P.
Gervais, ‘Hist. Nat. des Insectes: Apteres,’ tom. iv. 1847, pp. 17, 19,
68.)




CHAPTER X.
SECONDARY SEXUAL CHARACTERS OF INSECTS.


Diversified structures possessed by the males for seizing the
females—Differences between the sexes, of which the meaning is not
understood—Difference in size between the
sexes—Thysanura—Diptera—Hemiptera—Homoptera, musical powers possessed
by the males alone—Orthoptera, musical instruments of the males, much
diversified in structure; pugnacity; colours—Neuroptera, sexual
differences in colour—Hymenoptera, pugnacity and odours—Coleoptera,
colours; furnished with great horns, apparently as an ornament;
battles, stridulating organs generally common to both sexes.

In the immense class of insects the sexes sometimes differ in their
locomotive-organs, and often in their sense-organs, as in the
pectinated and beautifully plumose antennae of the males of many
species. In Chloeon, one of the Ephemerae, the male has great pillared
eyes, of which the female is entirely destitute. (1. Sir J. Lubbock,
‘Transact. Linnean Soc.’ vol. xxv, 1866, p. 484. With respect to the
Mutillidae see Westwood, ‘Modern Class. of Insects,’ vol. ii. p. 213.)
The ocelli are absent in the females of certain insects, as in the
Mutillidae; and here the females are likewise wingless. But we are
chiefly concerned with structures by which one male is enabled to
conquer another, either in battle or courtship, through his strength,
pugnacity, ornaments, or music. The innumerable contrivances,
therefore, by which the male is able to seize the female, may be
briefly passed over. Besides the complex structures at the apex of the
abdomen, which ought perhaps to be ranked as primary organs (2. These
organs in the male often differ in closely-allied species, and afford
excellent specific characters. But their importance, from a functional
point of view, as Mr. R. MacLachlan has remarked to me, has probably
been overrated. It has been suggested, that slight differences in these
organs would suffice to prevent the intercrossing of well-marked
varieties or incipient species, and would thus aid in their
development. That this can hardly be the case, we may infer from the
many recorded cases (see, for instance, Bronn, ‘Geschichte der Natur,’
B. ii. 1843, s. 164; and Westwood, ‘Transact. Ent. Soc.’ vol. iii.
1842, p. 195) of distinct species having been observed in union. Mr.
MacLachlan informs me (vide ‘Stett. Ent. Zeitung,’ 1867, s. 155) that
when several species of Phryganidae, which present strongly-pronounced
differences of this kind, were confined together by Dr. Aug. Meyer,
THEY COUPLED, and one pair produced fertile ova.), “it is astonishing,”
as Mr. B.D. Walsh (3. ‘The Practical Entomologist,’ Philadelphia, vol.
ii. May 1867, p. 88.) has remarked, “how many different organs are
worked in by nature for the seemingly insignificant object of enabling
the male to grasp the female firmly.” The mandibles or jaws are
sometimes used for this purpose; thus the male Corydalis cornutus (a
neuropterous insect in some degree allied to the Dragon flies, etc.)
has immense curved jaws, many times longer than those of the female;
and they are smooth instead of being toothed, so that he is thus
enabled to seize her without injury. (4. Mr. Walsh, ibid. p. 107.) One
of the stag-beetles of North America (Lucanus elaphus) uses his jaws,
which are much larger than those of the female, for the same purpose,
but probably likewise for fighting. In one of the sand-wasps
(Ammophila) the jaws in the two sexes are closely alike, but are used
for widely different purposes: the males, as Professor Westwood
observes, “are exceedingly ardent, seizing their partners round the
neck with their sickle-shaped jaws” (5. ‘Modern Classification of
Insects,’ vol. ii. 1840, pp. 205, 206. Mr. Walsh, who called my
attention to the double use of the jaws, says that he has repeatedly
observed this fact.); whilst the females use these organs for burrowing
in sand-banks and making their nests.

[Fig. 9. Crabro cribrarius. Upper figure, male; lower figure, female.]

The tarsi of the front-legs are dilated in many male beetles, or are
furnished with broad cushions of hairs; and in many genera of
water-beetles they are armed with a round flat sucker, so that the male
may adhere to the slippery body of the female. It is a much more
unusual circumstance that the females of some water-beetles (Dytiscus)
have their elytra deeply grooved, and in Acilius sulcatus thickly set
with hairs, as an aid to the male. The females of some other
water-beetles (Hydroporus) have their elytra punctured for the same
purpose. (6. We have here a curious and inexplicable case of
dimorphism, for some of the females of four European species of
Dytiscus, and of certain species of Hydroporus, have their elytra
smooth; and no intermediate gradations between the sulcated or
punctured, and the quite smooth elytra have been observed. See Dr. H.
Schaum, as quoted in the ‘Zoologist,’ vols. v.-vi. 1847-48, p. 1896.
Also Kirby and Spence, ‘Introduction to Entomology,’ vol. iii. 1826, p.
305.) In the male of Crabro cribrarius (Fig. 9), it is the tibia which
is dilated into a broad horny plate, with minute membraneous dots,
giving to it a singular appearance like that of a riddle. (7. Westwood,
‘Modern Class.’ vol. ii. p. 193. The following statement about Penthe,
and others in inverted commas, are taken from Mr. Walsh, ‘Practical
Entomologist,’ Philadelphia, vol. iii. p. 88.) In the male of Penthe (a
genus of beetles) a few of the middle joints of the antennae are
dilated and furnished on the inferior surface with cushions of hair,
exactly like those on the tarsi of the Carabidae, “and obviously for
the same end.” In male dragon-flies, “the appendages at the tip of the
tail are modified in an almost infinite variety of curious patterns to
enable them to embrace the neck of the female.” Lastly, in the males of
many insects, the legs are furnished with peculiar spines, knobs or
spurs; or the whole leg is bowed or thickened, but this is by no means
invariably a sexual character; or one pair, or all three pairs are
elongated, sometimes to an extravagant length. (8. Kirby and Spence,
‘Introduct.’ etc., vol. iii. pp. 332-336.)

[Fig. 10. Taphroderes distortus (much enlarged). Upper figure, male;
lower figure, female.]

The sexes of many species in all the orders present differences, of
which the meaning is not understood. One curious case is that of a
beetle (Fig. 10), the male of which has left mandible much enlarged; so
that the mouth is greatly distorted. In another Carabidous beetle,
Eurygnathus (9. ‘Insecta Maderensia,’ 1854, page 20.), we have the
case, unique as far as known to Mr. Wollaston, of the head of the
female being much broader and larger, though in a variable degree, than
that of the male. Any number of such cases could be given. They abound
in the Lepidoptera: one of the most extraordinary is that certain male
butterflies have their fore-legs more or less atrophied, with the
tibiae and tarsi reduced to mere rudimentary knobs. The wings, also, in
the two sexes often differ in neuration (10. E. Doubleday, ‘Annals and
Mag. of Nat. Hist.’ vol. i. 1848, p. 379. I may add that the wings in
certain Hymenoptera (see Shuckard, ‘Fossorial Hymenoptera,’ 1837, pp.
39-43) differ in neuration according to sex.), and sometimes
considerably in outline, as in the Aricoris epitus, which was shewn to
me in the British Museum by Mr. A. Butler. The males of certain South
American butterflies have tufts of hair on the margins of the wings,
and horny excrescences on the discs of the posterior pair. (11. H.W.
Bates, in ‘Journal of Proc. Linn. Soc.’ vol. vi. 1862, p. 74. Mr.
Wonfor’s observations are quoted in ‘Popular Science Review,’ 1868, p.
343.) In several British butterflies, as shewn by Mr. Wonfor, the males
alone are in parts clothed with peculiar scales.

The use of the bright light of the female glow-worm has been subject to
much discussion. The male is feebly luminous, as are the larvae and
even the eggs. It has been supposed by some authors that the light
serves to frighten away enemies, and by others to guide the male to the
female. At last, Mr. Belt (12. ‘The Naturalist in Nicaragua,’ 1874, pp.
316-320. On the phosphorescence of the eggs, see ‘Annals and Magazine
of Natural History,’ Nov. 1871, p. 372.) appears to have solved the
difficulty: he finds that all the Lampyridae which he has tried are
highly distasteful to insectivorous mammals and birds. Hence it is in
accordance with Mr. Bates’ view, hereafter to be explained, that many
insects mimic the Lampyridae closely, in order to be mistaken for them,
and thus to escape destruction. He further believes that the luminous
species profit by being at once recognised as unpalatable. It is
probable that the same explanation may be extended to the Elaters, both
sexes of which are highly luminous. It is not known why the wings of
the female glow-worm have not been developed; but in her present state
she closely resembles a larva, and as larvae are so largely preyed on
by many animals, we can understand why she has been rendered so much
more luminous and conspicuous than the male; and why the larvae
themselves are likewise luminous.

DIFFERENCE IN SIZE BETWEEN THE SEXES.

With insects of all kinds the males are commonly smaller than the
females; and this difference can often be detected even in the larval
state. So considerable is the difference between the male and female
cocoons of the silk-moth (Bombyx mori), that in France they are
separated by a particular mode of weighing. (13. Robinet, ‘Vers a
Soie,’ 1848, p. 207.) In the lower classes of the animal kingdom, the
greater size of the females seems generally to depend on their
developing an enormous number of ova; and this may to a certain extent
hold good with insects. But Dr. Wallace has suggested a much more
probable explanation. He finds, after carefully attending to the
development of the caterpillars of Bombyx cynthia and yamamai, and
especially to that of some dwarfed caterpillars reared from a second
brood on unnatural food, “that in proportion as the individual moth is
finer, so is the time required for its metamorphosis longer; and for
this reason the female, which is the larger and heavier insect, from
having to carry her numerous eggs, will be preceded by the male, which
is smaller and has less to mature.” (14. ‘Transact. Ent. Soc.’ 3rd
series, vol. v. p. 486.) Now as most insects are short-lived, and as
they are exposed to many dangers, it would manifestly be advantageous
to the female to be impregnated as soon as possible. This end would be
gained by the males being first matured in large numbers ready for the
advent of the females; and this again would naturally follow, as Mr.
A.R. Wallace has remarked (15. ‘Journal of Proc. Ent. Soc.’ Feb. 4,
1867, p. lxxi.), through natural selection; for the smaller males would
be first matured, and thus would procreate a large number of offspring
which would inherit the reduced size of their male parents, whilst the
larger males from being matured later would leave fewer offspring.

There are, however, exceptions to the rule of male insects being
smaller than the females: and some of these exceptions are
intelligible. Size and strength would be an advantage to the males,
which fight for the possession of the females; and in these cases, as
with the stag-beetle (Lucanus), the males are larger than the females.
There are, however, other beetles which are not known to fight
together, of which the males exceed the females in size; and the
meaning of this fact is not known; but in some of these cases, as with
the huge Dynastes and Megasoma, we can at least see that there would be
no necessity for the males to be smaller than the females, in order to
be matured before them, for these beetles are not short-lived, and
there would be ample time for the pairing of the sexes. So again, male
dragon-flies (Libellulidae) are sometimes sensibly larger, and never
smaller, than the females (16. For this and other statements on the
size of the sexes, see Kirby and Spence, ibid. vol. iii. p. 300; on the
duration of life in insects, see p. 344.); and as Mr. MacLachlan
believes, they do not generally pair with the females until a week or
fortnight has elapsed, and until they have assumed their proper
masculine colours. But the most curious case, shewing on what complex
and easily-overlooked relations, so trifling a character as difference
in size between the sexes may depend, is that of the aculeate
Hymenoptera; for Mr. F. Smith informs me that throughout nearly the
whole of this large group, the males, in accordance with the general
rule, are smaller than the females, and emerge about a week before
them; but amongst the Bees, the males of Apis mellifica, Anthidium
manicatum, and Anthophora acervorum, and amongst the Fossores, the
males of the Methoca ichneumonides, are larger than the females. The
explanation of this anomaly is that a marriage flight is absolutely
necessary with these species, and the male requires great strength and
size in order to carry the female through the air. Increased size has
here been acquired in opposition to the usual relation between size and
the period of development, for the males, though larger, emerge before
the smaller females.

We will now review the several Orders, selecting such facts as more
particularly concern us. The Lepidoptera (Butterflies and Moths) will
be retained for a separate chapter.

ORDER, THYSANURA.

The members of this lowly organised order are wingless, dull-coloured,
minute insects, with ugly, almost misshapen heads and bodies. Their
sexes do not differ, but they are interesting as shewing us that the
males pay sedulous court to the females even low down in the animal
scale. Sir J. Lubbock (17. ‘Transact. Linnean Soc.’ vol. xxvi. 1868, p.
296.) says: “it is very amusing to see these little creatures
(Smynthurus luteus) coquetting together. The male, which is much
smaller than the female, runs round her, and they butt one another,
standing face to face and moving backward and forward like two playful
lambs. Then the female pretends to run away and the male runs after her
with a queer appearance of anger, gets in front and stands facing her
again; then she turns coyly round, but he, quicker and more active,
scuttles round too, and seems to whip her with his antennae; then for a
bit they stand face to face, play with their antennae, and seem to be
all in all to one another.”

ORDER, DIPTERA (FLIES).

The sexes differ little in colour. The greatest difference, known to
Mr. F. Walker, is in the genus Bibio, in which the males are blackish
or quite black, and the females obscure brownish-orange. The genus
Elaphomyia, discovered by Mr. Wallace (18. ‘The Malay Archipelago,’
vol. ii. 1869, p. 313.) in New Guinea, is highly remarkable, as the
males are furnished with horns, of which the females are quite
destitute. The horns spring from beneath the eyes, and curiously
resemble those of a stag, being either branched or palmated. In one of
the species, they equal the whole body in length. They might be thought
to be adapted for fighting, but as in one species they are of a
beautiful pink colour, edged with black, with a pale central stripe,
and as these insects have altogether a very elegant appearance, it is
perhaps more probable that they serve as ornaments. That the males of
some Diptera fight together is certain; Prof. Westwood (19. ‘Modern
Classification of Insects,’ vol. ii. 1840, p. 526.) has several times
seen this with the Tipulae. The males of other Diptera apparently try
to win the females by their music: H. Müller (20. ‘Anwendung,’ etc.,
‘Verh. d. n. V. Jahrg.’ xxix. p. 80. Mayer, in ‘American Naturalist,’
1874, p. 236.) watched for some time two males of an Eristalis courting
a female; they hovered above her, and flew from side to side, making a
high humming noise at the same time. Gnats and mosquitoes (Culicidae)
also seem to attract each other by humming; and Prof. Mayer has
recently ascertained that the hairs on the antennae of the male vibrate
in unison with the notes of a tuning-fork, within the range of the
sounds emitted by the female. The longer hairs vibrate sympathetically
with the graver notes, and the shorter hairs with the higher ones.
Landois also asserts that he has repeatedly drawn down a whole swarm of
gnats by uttering a particular note. It may be added that the mental
faculties of the Diptera are probably higher than in most other
insects, in accordance with their highly-developed nervous system. (21.
See Mr. B.T. Lowne’s interesting work, ‘On the Anatomy of the Blow-fly,
Musca vomitoria,’ 1870, p. 14. He remarks (p. 33) that, “the captured
flies utter a peculiar plaintive note, and that this sound causes other
flies to disappear.”)

ORDER, HEMIPTERA (FIELD-BUGS).

Mr. J.W. Douglas, who has particularly attended to the British species,
has kindly given me an account of their sexual differences. The males
of some species are furnished with wings, whilst the females are
wingless; the sexes differ in the form of their bodies, elytra,
antennae and tarsi; but as the signification of these differences are
unknown, they may be here passed over. The females are generally larger
and more robust than the males. With British, and, as far as Mr.
Douglas knows, with exotic species, the sexes do not commonly differ
much in colour; but in about six British species the male is
considerably darker than the female, and in about four other species
the female is darker than the male. Both sexes of some species are
beautifully coloured; and as these insects emit an extremely nauseous
odour, their conspicuous colours may serve as a signal that they are
unpalatable to insectivorous animals. In some few cases their colours
appear to be directly protective: thus Prof. Hoffmann informs me that
he could hardly distinguish a small pink and green species from the
buds on the trunks of lime-trees, which this insect frequents.

Some species of Reduvidae make a stridulating noise; and, in the case
of Pirates stridulus, this is said (22. Westwood, ‘Modern
Classification of Insects,’ vol. ii. p. 473.) to be effected by the
movement of the neck within the pro-thoracic cavity. According to
Westring, Reduvius personatus also stridulates. But I have no reason to
suppose that this is a sexual character, excepting that with non-social
insects there seems to be no use for sound-producing organs, unless it
be as a sexual call.

ORDER: HOMOPTERA.

Every one who has wandered in a tropical forest must have been
astonished at the din made by the male Cicadae. The females are mute;
as the Grecian poet Xenarchus says, “Happy the Cicadas live, since they
all have voiceless wives.” The noise thus made could be plainly heard
on board the “Beagle,” when anchored at a quarter of a mile from the
shore of Brazil; and Captain Hancock says it can be heard at the
distance of a mile. The Greeks formerly kept, and the Chinese now keep
these insects in cages for the sake of their song, so that it must be
pleasing to the ears of some men. (23. These particulars are taken from
Westwood’s ‘Modern Classification of Insects,’ vol. ii. 1840, p. 422.
See, also, on the Fulgoridae, Kirby and Spence, ‘Introduct.’ vol. ii.
p. 401.) The Cicadidae usually sing during the day, whilst the
Fulgoridae appear to be night-songsters. The sound, according to
Landois (24. ‘Zeitschrift für wissenschaft. Zoolog.’ B. xvii. 1867, ss.
152-158.), is produced by the vibration of the lips of the spiracles,
which are set into motion by a current of air emitted from the
tracheae; but this view has lately been disputed. Dr. Powell appears to
have proved (25. ‘Transactions of the New Zealand Institute,’ vol. v.
1873, p. 286.) that it is produced by the vibration of a membrane, set
into action by a special muscle. In the living insect, whilst
stridulating, this membrane can be seen to vibrate; and in the dead
insect the proper sound is heard, if the muscle, when a little dried
and hardened, is pulled with the point of a pin. In the female the
whole complex musical apparatus is present, but is much less developed
than in the male, and is never used for producing sound.

With respect to the object of the music, Dr. Hartman, in speaking of
the Cicada septemdecim of the United States, says (26. I am indebted to
Mr. Walsh for having sent me this extract from ‘A Journal of the Doings
of Cicada septemdecim,’ by Dr. Hartman.), “the drums are now (June 6th
and 7th, 1851) heard in all directions. This I believe to be the
marital summons from the males. Standing in thick chestnut sprouts
about as high as my head, where hundreds were around me, I observed the
females coming around the drumming males.” He adds, “this season (Aug.
1868) a dwarf pear-tree in my garden produced about fifty larvae of
Cic. pruinosa; and I several times noticed the females to alight near a
male while he was uttering his clanging notes.” Fritz Müller writes to
me from S. Brazil that he has often listened to a musical contest
between two or three males of a species with a particularly loud voice,
seated at a considerable distance from each other: as soon as one had
finished his song, another immediately began, and then another. As
there is so much rivalry between the males, it is probable that the
females not only find them by their sounds, but that, like female
birds, they are excited or allured by the male with the most attractive
voice.

I have not heard of any well-marked cases of ornamental differences
between the sexes of the Homoptera. Mr. Douglas informs me that there
are three British species, in which the male is black or marked with
black bands, whilst the females are pale-coloured or obscure.

ORDER, ORTHOPTERA (CRICKETS AND GRASSHOPPERS).

The males in the three saltatorial families in this Order are
remarkable for their musical powers, namely the Achetidae or crickets,
the Locustidae for which there is no equivalent English name, and the
Acridiidae or grasshoppers. The stridulation produced by some of the
Locustidae is so loud that it can be heard during the night at the
distance of a mile (27. L. Guilding, ‘Transactions of the Linnean
Society,’ vol. xv. p. 154.); and that made by certain species is not
unmusical even to the human ear, so that the Indians on the Amazons
keep them in wicker cages. All observers agree that the sounds serve
either to call or excite the mute females. With respect to the
migratory locusts of Russia, Korte has given (28. I state this on the
authority of Koppen, ‘Über die Heuschrecken in Südrussland,’ 1866, p.
32, for I have in vain endeavoured to procure Korte’s work.) an
interesting case of selection by the female of a male. The males of
this species (Pachytylus migratorius) whilst coupled with the female
stridulate from anger or jealousy, if approached by other males. The
house-cricket when surprised at night uses its voice to warn its
fellows. (29. Gilbert White, ‘Natural History of Selborne,’ vol. ii.
1825, p. 262.) In North America the Katy-did (Platyphyllum concavum,
one of the Locustidae) is described (30. Harris, ‘Insects of New
England,’ 1842, p. 128.) as mounting on the upper branches of a tree,
and in the evening beginning “his noisy babble, while rival notes issue
from the neighbouring trees, and the groves resound with the call of
Katy-did-she-did the live-long night.” Mr. Bates, in speaking of the
European field-cricket (one of the Achetidae), says “the male has been
observed to place himself in the evening at the entrance of his burrow,
and stridulate until a female approaches, when the louder notes are
succeeded by a more subdued tone, whilst the successful musician
caresses with his antennae the mate he has won.” (31. ‘The Naturalist
on the Amazons,’ vol. i. 1863, p. 252. Mr. Bates gives a very
interesting discussion on the gradations in the musical apparatus of
the three families. See also Westwood, ‘Modern Classification of
Insects,’ vol. ii. pp. 445 and 453.) Dr. Scudder was able to excite one
of these insects to answer him, by rubbing on a file with a quill. (32.
‘Proceedings of the Boston Society of Natural History,’ vol. xi. April
1868.) In both sexes a remarkable auditory apparatus has been
discovered by Von Siebold, situated in the front legs. (33. ‘Nouveau
Manuel d’Anat. Comp.’ (French translat.), tom. 1, 1850, p. 567.)

[Fig.11. Gryllus campestris (from Landois). Right-hand figure, under
side of part of a wing-nervure, much magnified, showing the teeth, st.
Left-hand figure, upper surface of wing-cover, with the projecting,
smooth nervure, r, across which the teeth (st) are scraped.

Fig.12. Teeth of Nervure of Gryllus domesticus (from Landois).]

In the three Families the sounds are differently produced. In the males
of the Achetidae both wing-covers have the same apparatus; and this in
the field-cricket (see Gryllus campestris, Fig. 11) consists, as
described by Landois (34. ‘Zeitschrift für wissenschaft. Zoolog.’ B.
xvii. 1867, s. 117.), of from 131 to 138 sharp, transverse ridges or
teeth (st) on the under side of one of the nervures of the wing-cover.
This toothed nervure is rapidly scraped across a projecting, smooth,
hard nervure (r) on the upper surface of the opposite wing. First one
wing is rubbed over the other, and then the movement is reversed. Both
wings are raised a little at the same time, so as to increase the
resonance. In some species the wing-covers of the males are furnished
at the base with a talc-like plate. (35. Westwood, ‘Modern
Classification of Insects,’ vol. i. p. 440.) I here give a drawing
(Fig. 12) of the teeth on the under side of the nervure of another
species of Gryllus, viz., G. domesticus. With respect to the formation
of these teeth, Dr. Gruber has shewn (36. ‘Ueber der Tonapparat der
Locustiden, ein Beitrag zum Darwinismus,’ ‘Zeitschrift für
wissenschaft. Zoolog.’ B. xxii. 1872, p. 100.) that they have been
developed by the aid of selection, from the minute scales and hairs
with which the wings and body are covered, and I came to the same
conclusion with respect to those of the Coleoptera. But Dr. Gruber
further shews that their development is in part directly due to the
stimulus from the friction of one wing over the other.

[Fig.13. Chlorocoelus Tanana (from Bates). a,b. Lobes of opposite
wing-covers.]

In the Locustidae the opposite wing-covers differ from each other in
structure (Fig. 13), and the action cannot, as in the last family, be
reversed. The left wing, which acts as the bow, lies over the right
wing which serves as the fiddle. One of the nervures (a) on the under
surface of the former is finely serrated, and is scraped across the
prominent nervures on the upper surface of the opposite or right wing.
In our British Phasgonura viridissima it appeared to me that the
serrated nervure is rubbed against the rounded hind-corner of the
opposite wing, the edge of which is thickened, coloured brown, and very
sharp. In the right wing, but not in the left, there is a little plate,
as transparent as talc, surrounded by nervures, and called the
speculum. In Ephippiger vitium, a member of this same family, we have a
curious subordinate modification; for the wing-covers are greatly
reduced in size, but “the posterior part of the pro-thorax is elevated
into a kind of dome over the wing-covers, and which has probably the
effect of increasing the sound.” (37. Westwood ‘Modern Classification
of Insects,’ vol. i. p. 453.)

We thus see that the musical apparatus is more differentiated or
specialised in the Locustidae (which include, I believe, the most
powerful performers in the Order), than in the Achetidae, in which both
wing-covers have the same structure and the same function. (38.
Landois, ‘Zeitschrift für wissenschaft. Zoolog.’ B. xvii. 1867, ss.
121, 122.) Landois, however, detected in one of the Locustidae, namely
in Decticus, a short and narrow row of small teeth, mere rudiments, on
the inferior surface of the right wing-cover, which underlies the other
and is never used as the bow. I observed the same rudimentary structure
on the under side of the right wing-cover in Phasgonura viridissima.
Hence we may infer with confidence that the Locustidae are descended
from a form, in which, as in the existing Achetidae, both wing-covers
had serrated nervures on the under surface, and could be indifferently
used as the bow; but that in the Locustidae the two wing-covers
gradually became differentiated and perfected, on the principle of the
division of labour, the one to act exclusively as the bow, and the
other as the fiddle. Dr. Gruber takes the same view, and has shewn that
rudimentary teeth are commonly found on the inferior surface of the
right wing. By what steps the more simple apparatus in the Achetidae
originated, we do not know, but it is probable that the basal portions
of the wing-covers originally overlapped each other as they do at
present; and that the friction of the nervures produced a grating
sound, as is now the case with the wing-covers of the females. (39. Mr.
Walsh also informs me that he has noticed that the female of the
Platyphyllum concavum, “when captured makes a feeble grating noise by
shuffling her wing-covers together.”) A grating sound thus occasionally
and accidentally made by the males, if it served them ever so little as
a love-call to the females, might readily have been intensified through
sexual selection, by variations in the roughness of the nervures having
been continually preserved.

[Fig.14. Hind-leg of Stenobothrus pratorum: r, the stridulating ridge;
lower figure, the teeth forming the ridge, much magnified (from
Landois).

Fig.15. Pneumora (from specimens in the British Museum). Upper figure,
male; lower figure, female.]

In the last and third family, namely the Acridiidae or grasshoppers,
the stridulation is produced in a very different manner, and according
to Dr. Scudder, is not so shrill as in the preceding Families. The
inner surface of the femur (Fig. 14, r) is furnished with a
longitudinal row of minute, elegant, lancet-shaped, elastic teeth, from
85 to 93 in number (40. Landois, ibid. s. 113.); and these are scraped
across the sharp, projecting nervures on the wing-covers, which are
thus made to vibrate and resound. Harris (41. ‘Insects of New England,’
1842, p. 133.) says that when one of the males begins to play, he first
“bends the shank of the hind-leg beneath the thigh, where it is lodged
in a furrow designed to receive it, and then draws the leg briskly up
and down. He does not play both fiddles together, but alternately,
first upon one and then on the other.” In many species, the base of the
abdomen is hollowed out into a great cavity which is believed to act as
a resounding board. In Pneumora (Fig. 15), a S. African genus belonging
to the same family, we meet with a new and remarkable modification; in
the males a small notched ridge projects obliquely from each side of
the abdomen, against which the hind femora are rubbed. (42. Westwood,
‘Modern Classification,’ vol i. p. 462.) As the male is furnished with
wings (the female being wingless), it is remarkable that the thighs are
not rubbed in the usual manner against the wing-covers; but this may
perhaps be accounted for by the unusually small size of the hind-legs.
I have not been able to examine the inner surface of the thighs, which,
judging from analogy, would be finely serrated. The species of Pneumora
have been more profoundly modified for the sake of stridulation than
any other orthopterous insect; for in the male the whole body has been
converted into a musical instrument, being distended with air, like a
great pellucid bladder, so as to increase the resonance. Mr. Trimen
informs me that at the Cape of Good Hope these insects make a wonderful
noise during the night.

In the three foregoing families, the females are almost always
destitute of an efficient musical apparatus. But there are a few
exceptions to this rule, for Dr. Gruber has shewn that both sexes of
Ephippiger vitium are thus provided; though the organs differ in the
male and female to a certain extent. Hence we cannot suppose that they
have been transferred from the male to the female, as appears to have
been the case with the secondary sexual characters of many other
animals. They must have been independently developed in the two sexes,
which no doubt mutually call to each other during the season of love.
In most other Locustidae (but not according to Landois in Decticus) the
females have rudiments of the stridulatory organs proper to the male;
from whom it is probable that these have been transferred. Landois also
found such rudiments on the under surface of the wing-covers of the
female Achetidae, and on the femora of the female Acridiidae. In the
Homoptera, also, the females have the proper musical apparatus in a
functionless state; and we shall hereafter meet in other divisions of
the animal kingdom with many instances of structures proper to the male
being present in a rudimentary condition in the female.

Landois has observed another important fact, namely, that in the
females of the Acridiidae, the stridulating teeth on the femora remain
throughout life in the same condition in which they first appear during
the larval state in both sexes. In the males, on the other hand, they
become further developed, and acquire their perfect structure at the
last moult, when the insect is mature and ready to breed.

From the facts now given, we see that the means by which the males of
the Orthoptera produce their sounds are extremely diversified, and are
altogether different from those employed by the Homoptera. (43. Landois
has recently found in certain Orthoptera rudimentary structures closely
similar to the sound-producing organs in the Homoptera; and this is a
surprising fact. See ‘Zeitschrift für wissenschaft, Zoolog.’ B. xxii.
Heft 3, 1871, p. 348.) But throughout the animal kingdom we often find
the same object gained by the most diversified means; this seems due to
the whole organisation having undergone multifarious changes in the
course of ages, and as part after part varied different variations were
taken advantage of for the same general purpose. The diversity of means
for producing sound in the three families of the Orthoptera and in the
Homoptera, impresses the mind with the high importance of these
structures to the males, for the sake of calling or alluring the
females. We need feel no surprise at the amount of modification which
the Orthoptera have undergone in this respect, as we now know, from Dr.
Scudder’s remarkable discovery (44. ‘Transactions, Entomological
Society,’ 3rd series, vol. ii. (‘Journal of Proceedings,’ p. 117).),
that there has been more than ample time. This naturalist has lately
found a fossil insect in the Devonian formation of New Brunswick, which
is furnished with “the well-known tympanum or stridulating apparatus of
the male Locustidae.” The insect, though in most respects related to
the Neuroptera, appears, as is so often the case with very ancient
forms, to connect the two related Orders of the Neuroptera and
Orthoptera.

I have but little more to say on the Orthoptera. Some of the species
are very pugnacious: when two male field-crickets (Gryllus campestris)
are confined together, they fight till one kills the other; and the
species of Mantis are described as manoeuvring with their sword-like
front-limbs, like hussars with their sabres. The Chinese keep these
insects in little bamboo cages, and match them like game-cocks. (45.
Westwood, ‘Modern Classification of Insects,’ vol. i. p. 427; for
crickets, p. 445.) With respect to colour, some exotic locusts are
beautifully ornamented; the posterior wings being marked with red,
blue, and black; but as throughout the Order the sexes rarely differ
much in colour, it is not probable that they owe their bright tints to
sexual selection. Conspicuous colours may be of use to these insects,
by giving notice that they are unpalatable. Thus it has been observed
(46. Mr. Ch. Horne, in ‘Proceedings of the Entomological Society,’ May
3, 1869, p. xii.) that a bright-coloured Indian locust was invariably
rejected when offered to birds and lizards. Some cases, however, are
known of sexual differences in colour in this Order. The male of an
American cricket (47. The Oecanthus nivalis, Harris, ‘Insects of New
England,’ 1842, p. 124. The two sexes of OE. pellucidus of Europe
differ, as I hear from Victor Carus, in nearly the same manner.) is
described as being as white as ivory, whilst the female varies from
almost white to greenish-yellow or dusky. Mr. Walsh informs me that the
adult male of Spectrum femoratum (one of the Phasmidae) “is of a
shining brownish-yellow colour; the adult female being of a dull,
opaque, cinereous brown; the young of both sexes being green.” Lastly,
I may mention that the male of one curious kind of cricket (48.
Platyblemnus: Westwood, ‘Modern Classification,’ vol. i. p. 447.) is
furnished with “a long membranous appendage, which falls over the face
like a veil;” but what its use may be, is not known.

ORDER, NEUROPTERA.

Little need here be said, except as to colour. In the Ephemeridae the
sexes often differ slightly in their obscure tints (49. B.D. Walsh, the
‘Pseudo-neuroptera of Illinois,’ in ‘Proceedings of the Entomological
Society of Philadelphia,’ 1862, p. 361.); but it is not probable that
the males are thus rendered attractive to the females. The
Libellulidae, or dragon-flies, are ornamented with splendid green,
blue, yellow, and vermilion metallic tints; and the sexes often differ.
Thus, as Prof. Westwood remarks (50. ‘Modern Classification,’ vol. ii.
p. 37.), the males of some of the Agrionidae, “are of a rich blue with
black wings, whilst the females are fine green with colourless wings.”
But in Agrion Ramburii these colours are exactly reversed in the two
sexes. (51. Walsh, ibid. p. 381. I am indebted to this naturalist for
the following facts on Hetaerina, Anax, and Gomphus.) In the extensive
N. American genus of Hetaerina, the males alone have a beautiful
carmine spot at the base of each wing. In Anax junius the basal part of
the abdomen in the male is a vivid ultramarine blue, and in the female
grass-green. In the allied genus Gomphus, on the other hand, and in
some other genera, the sexes differ but little in colour. In
closely-allied forms throughout the animal kingdom, similar cases of
the sexes differing greatly, or very little, or not at all, are of
frequent occurrence. Although there is so wide a difference in colour
between the sexes of many Libellulidae, it is often difficult to say
which is the more brilliant; and the ordinary coloration of the two
sexes is reversed, as we have just seen, in one species of Agrion. It
is not probable that their colours in any case have been gained as a
protection. Mr. MacLachlan, who has closely attended to this family,
writes to me that dragon-flies—the tyrants of the insect-world—are the
least liable of any insect to be attacked by birds or other enemies,
and he believes that their bright colours serve as a sexual attraction.
Certain dragon-flies apparently are attracted by particular colours:
Mr. Patterson observed (52. ‘Transactions, Ent. Soc.’ vol. i. 1836, p.
lxxxi.) that the Agrionidae, of which the males are blue, settled in
numbers on the blue float of a fishing line; whilst two other species
were attracted by shining white colours.

It is an interesting fact, first noticed by Schelver, that, in several
genera belonging to two sub-families, the males on first emergence from
the pupal state, are coloured exactly like the females; but that their
bodies in a short time assume a conspicuous milky-blue tint, owing to
the exudation of a kind of oil, soluble in ether and alcohol. Mr.
MacLachlan believes that in the male of Libellula depressa this change
of colour does not occur until nearly a fortnight after the
metamorphosis, when the sexes are ready to pair.

Certain species of Neurothemis present, according to Brauer (53. See
abstract in the ‘Zoological Record’ for 1867, p. 450.), a curious case
of dimorphism, some of the females having ordinary wings, whilst others
have them “very richly netted, as in the males of the same species.”
Brauer “explains the phenomenon on Darwinian principles by the
supposition that the close netting of the veins is a secondary sexual
character in the males, which has been abruptly transferred to some of
the females, instead of, as generally occurs, to all of them.” Mr.
MacLachlan informs me of another instance of dimorphism in several
species of Agrion, in which some individuals are of an orange colour,
and these are invariably females. This is probably a case of reversion;
for in the true Libellulae, when the sexes differ in colour, the
females are orange or yellow; so that supposing Agrion to be descended
from some primordial form which resembled the typical Libellulae in its
sexual characters, it would not be surprising that a tendency to vary
in this manner should occur in the females alone.

Although many dragon-flies are large, powerful, and fierce insects, the
males have not been observed by Mr. MacLachlan to fight together,
excepting, as he believes, in some of the smaller species of Agrion. In
another group in this Order, namely, the Termites or white ants, both
sexes at the time of swarming may be seen running about, “the male
after the female, sometimes two chasing one female, and contending with
great eagerness who shall win the prize.” (54. Kirby and Spence,
‘Introduction to Entomology,’ vol. ii. 1818, p. 35.) The Atropos
pulsatorius is said to make a noise with its jaws, which is answered by
other individuals. (55. Houzeau, ‘Les Facultés Mentales,’ etc. Tom. i.
p. 104.)

ORDER, HYMENOPTERA.

That inimitable observer, M. Fabre (56. See an interesting article,
‘The Writings of Fabre,’ in ‘Nat. Hist. Review,’ April 1862, p. 122.),
in describing the habits of Cerceris, a wasp-like insect, remarks that
“fights frequently ensue between the males for the possession of some
particular female, who sits an apparently unconcerned beholder of the
struggle for supremacy, and when the victory is decided, quietly flies
away in company with the conqueror.” Westwood (57. ‘Journal of
Proceedings of Entomological Society,’ Sept. 7, 1863, p. 169.) says
that the males of one of the saw-flies (Tenthredinae) “have been found
fighting together, with their mandibles locked.” As M. Fabre speaks of
the males of Cerceris striving to obtain a particular female, it may be
well to bear in mind that insects belonging to this Order have the
power of recognising each other after long intervals of time, and are
deeply attached. For instance, Pierre Huber, whose accuracy no one
doubts, separated some ants, and when, after an interval of four
months, they met others which had formerly belonged to the same
community, they recognised and caressed one another with their
antennae. Had they been strangers they would have fought together.
Again, when two communities engage in a battle, the ants on the same
side sometimes attack each other in the general confusion, but they
soon perceive their mistake, and the one ant soothes the other. (58. P.
Huber, ‘Recherches sur les Moeurs des Fourmis,’ 1810, pp. 150, 165.)

In this Order slight differences in colour, according to sex, are
common, but conspicuous differences are rare except in the family of
Bees; yet both sexes of certain groups are so brilliantly coloured—for
instance in Chrysis, in which vermilion and metallic greens
prevail—that we are tempted to attribute the result to sexual
selection. In the Ichneumonidae, according to Mr. Walsh (59.
‘Proceedings of the Entomological Society of Philadelphia,’ 1866, pp.
238, 239.), the males are almost universally lighter-coloured than the
females. On the other hand, in the Tenthredinidae the males are
generally darker than the females. In the Siricidae the sexes
frequently differ; thus the male of Sirex juvencus is banded with
orange, whilst the female is dark purple; but it is difficult to say
which sex is the more ornamented. In Tremex columbae the female is much
brighter coloured than the male. I am informed by Mr. F. Smith, that
the male ants of several species are black, the females being
testaceous.

In the family of Bees, especially in the solitary species, as I hear
from the same entomologist, the sexes often differ in colour. The males
are generally the brighter, and in Bombus as well as in Apathus, much
more variable in colour than the females. In Anthophora retusa the male
is of a rich fulvous-brown, whilst the female is quite black: so are
the females of several species of Xylocopa, the males being bright
yellow. On the other hand the females of some species, as of Andraena
fulva, are much brighter coloured than the males. Such differences in
colour can hardly be accounted for by the males being defenceless and
thus requiring protection, whilst the females are well defended by
their stings. H. Müller (60. ‘Anwendung der Darwinschen Lehre auf
Bienen,’ Verh. d. n. V. Jahrg. xxix.), who has particularly attended to
the habits of bees, attributes these differences in colour in chief
part to sexual selection. That bees have a keen perception of colour is
certain. He says that the males search eagerly and fight for the
possession of the females; and he accounts through such contests for
the mandibles of the males being in certain species larger than those
of the females. In some cases the males are far more numerous than the
females, either early in the season, or at all times and places, or
locally; whereas the females in other cases are apparently in excess.
In some species the more beautiful males appear to have been selected
by the females; and in others the more beautiful females by the males.
Consequently in certain genera (Müller, p. 42), the males of the
several species differ much in appearance, whilst the females are
almost indistinguishable; in other genera the reverse occurs. H. Müller
believes (p. 82) that the colours gained by one sex through sexual
selection have often been transferred in a variable degree to the other
sex, just as the pollen-collecting apparatus of the female has often
been transferred to the male, to whom it is absolutely useless. (61. M.
Perrier in his article ‘la Selection sexuelle d’après Darwin’ (‘Revue
Scientifique,’ Feb. 1873, p. 868), without apparently having reflected
much on the subject, objects that as the males of social bees are known
to be produced from unfertilised ova, they could not transmit new
characters to their male offspring. This is an extraordinary objection.
A female bee fertilised by a male, which presented some character
facilitating the union of the sexes, or rendering him more attractive
to the female, would lay eggs which would produce only females; but
these young females would next year produce males; and will it be
pretended that such males would not inherit the characters of their
male grandfathers? To take a case with ordinary animals as nearly
parallel as possible: if a female of any white quadruped or bird were
crossed by a male of a black breed, and the male and female offspring
were paired together, will it be pretended that the grandchildren would
not inherit a tendency to blackness from their male grandfather? The
acquirement of new characters by the sterile worker-bees is a much more
difficult case, but I have endeavoured to shew in my ‘Origin of
Species,’ how these sterile beings are subjected to the power of
natural selection.)

Mutilla Europaea makes a stridulating noise; and according to Goureau
(62. Quoted by Westwood, ‘Modern Classification of Insects,’ vol. ii.
p. 214.) both sexes have this power. He attributes the sound to the
friction of the third and preceding abdominal segments, and I find that
these surfaces are marked with very fine concentric ridges; but so is
the projecting thoracic collar into which the head articulates, and
this collar, when scratched with the point of a needle, emits the
proper sound. It is rather surprising that both sexes should have the
power of stridulating, as the male is winged and the female wingless.
It is notorious that Bees express certain emotions, as of anger, by the
tone of their humming; and according to H. Müller (p. 80), the males of
some species make a peculiar singing noise whilst pursuing the females.

ORDER, COLEOPTERA (BEETLES).

Many beetles are coloured so as to resemble the surfaces which they
habitually frequent, and they thus escape detection by their enemies.
Other species, for instance diamond-beetles, are ornamented with
splendid colours, which are often arranged in stripes, spots, crosses,
and other elegant patterns. Such colours can hardly serve directly as a
protection, except in the case of certain flower-feeding species; but
they may serve as a warning or means of recognition, on the same
principle as the phosphorescence of the glow-worm. As with beetles the
colours of the two sexes are generally alike, we have no evidence that
they have been gained through sexual selection; but this is at least
possible, for they have been developed in one sex and then transferred
to the other; and this view is even in some degree probable in those
groups which possess other well-marked secondary sexual characters.
Blind beetles, which cannot of course behold each other’s beauty,
never, as I hear from Mr. Waterhouse, jun., exhibit bright colours,
though they often have polished coats; but the explanation of their
obscurity may be that they generally inhabit caves and other obscure
stations.

Some Longicorns, especially certain Prionidae, offer an exception to
the rule that the sexes of beetles do not differ in colour. Most of
these insects are large and splendidly coloured. The males in the genus
Pyrodes (63. Pyrodes pulcherrimus, in which the sexes differ
conspicuously, has been described by Mr. Bates in ‘Transact. Ent. Soc.’
1869, p. 50. I will specify the few other cases in which I have heard
of a difference in colour between the sexes of beetles. Kirby and
Spence (‘Introduct. to Entomology,’ vol. iii. p. 301) mention a
Cantharis, Meloe, Rhagium, and the Leptura testacea; the male of the
latter being testaceous, with a black thorax, and the female of a dull
red all over. These two latter beetles belong to the family of
Longicorns. Messrs. R. Trimen and Waterhouse, jun., inform me of two
Lamellicorns, viz., a Peritrichia and Trichius, the male of the latter
being more obscurely coloured than the female. In Tillus elongatus the
male is black, and the female always, as it is believed, of a dark blue
colour, with a red thorax. The male, also, of Orsodacna atra, as I hear
from Mr. Walsh, is black, the female (the so-called O. ruficollis)
having a rufous thorax.), which I saw in Mr. Bates’s collection, are
generally redder but rather duller than the females, the latter being
coloured of a more or less splendid golden-green. On the other hand, in
one species the male is golden-green, the female being richly tinted
with red and purple. In the genus Esmeralda the sexes differ so greatly
in colour that they have been ranked as distinct species; in one
species both are of a beautiful shining green, but the male has a red
thorax. On the whole, as far as I could judge, the females of those
Prionidae, in which the sexes differ, are coloured more richly than the
males, and this does not accord with the common rule in regard to
colour, when acquired through sexual selection.

[Fig.16. Chalcosoma atlas. Upper figure, male (reduced); lower figure,
female (nat. size).

Fig. 17. Copris isidis.

Fig. 18. Phanaeus faunus.

Fig. 19. Dipelicus cantori.

Fig. 20. Onthophagus rangifer, enlarged. (In Figs. 17 to 20 the
left-hand figures are males.)]

A most remarkable distinction between the sexes of many beetles is
presented by the great horns which rise from the head, thorax, and
clypeus of the males; and in some few cases from the under surface of
the body. These horns, in the great family of the Lamellicorns,
resemble those of various quadrupeds, such as stags, rhinoceroses,
etc., and are wonderful both from their size and diversified shapes.
Instead of describing them, I have given figures of the males and
females of some of the more remarkable forms. (Figs. 16 to 20.) The
females generally exhibit rudiments of the horns in the form of small
knobs or ridges; but some are destitute of even the slightest rudiment.
On the other hand, the horns are nearly as well developed in the female
as in the male Phanaeus lancifer; and only a little less well developed
in the females of some other species of this genus and of Copris. I am
informed by Mr. Bates that the horns do not differ in any manner
corresponding with the more important characteristic differences
between the several subdivisions of the family: thus within the same
section of the genus Onthophagus, there are species which have a single
horn, and others which have two.

In almost all cases, the horns are remarkable from their excessive
variability; so that a graduated series can be formed, from the most
highly developed males to others so degenerate that they can barely be
distinguished from the females. Mr. Walsh (64. ‘Proceedings of the
Entomological Society of Philadephia,’ 1864, p. 228.) found that in
Phanaeus carnifex the horns were thrice as long in some males as in
others. Mr. Bates, after examining above a hundred males of Onthophagus
rangifer (Fig. 20), thought that he had at last discovered a species in
which the horns did not vary; but further research proved the contrary.

The extraordinary size of the horns, and their widely different
structure in closely-allied forms, indicate that they have been formed
for some purpose; but their excessive variability in the males of the
same species leads to the inference that this purpose cannot be of a
definite nature. The horns do not shew marks of friction, as if used
for any ordinary work. Some authors suppose (65. Kirby and Spence,
‘Introduction to Entomology,’ vol. iii. p. 300.) that as the males
wander about much more than the females, they require horns as a
defence against their enemies; but as the horns are often blunt, they
do not seem well adapted for defence. The most obvious conjecture is
that they are used by the males for fighting together; but the males
have never been observed to fight; nor could Mr. Bates, after a careful
examination of numerous species, find any sufficient evidence, in their
mutilated or broken condition, of their having been thus used. If the
males had been habitual fighters, the size of their bodies would
probably have been increased through sexual selection, so as to have
exceeded that of the females; but Mr. Bates, after comparing the two
sexes in above a hundred species of the Copridae, did not find any
marked difference in this respect amongst well-developed individuals.
In Lethrus, moreover, a beetle belonging to the same great division of
the Lamellicorns, the males are known to fight, but are not provided
with horns, though their mandibles are much larger than those of the
female.

The conclusion that the horns have been acquired as ornaments is that
which best agrees with the fact of their having been so immensely, yet
not fixedly, developed,—as shewn by their extreme variability in the
same species, and by their extreme diversity in closely-allied species.
This view will at first appear extremely improbable; but we shall
hereafter find with many animals standing much higher in the scale,
namely fishes, amphibians, reptiles and birds, that various kinds of
crests, knobs, horns and combs have been developed apparently for this
sole purpose.

[Fig.21. Onitis furcifer, male viewed from beneath.

Fig.22. Onitis furcifer. Left-hand figure, male, viewed laterally.
Right-hand figure, female. a. Rudiment of cephalic horn. b. Trace of
thoracic horn or crest.]

The males of Onitis furcifer (Fig. 21), and of some other species of
the genus, are furnished with singular projections on their anterior
femora, and with a great fork or pair of horns on the lower surface of
the thorax. Judging from other insects, these may aid the male in
clinging to the female. Although the males have not even a trace of a
horn on the upper surface of the body, yet the females plainly exhibit
a rudiment of a single horn on the head (Fig. 22, a), and of a crest
(b) on the thorax. That the slight thoracic crest in the female is a
rudiment of a projection proper to the male, though entirely absent in
the male of this particular species, is clear: for the female of Bubas
bison (a genus which comes next to Onitis) has a similar slight crest
on the thorax, and the male bears a great projection in the same
situation. So, again, there can hardly be a doubt that the little point
(a) on the head of the female Onitis furcifer, as well as on the head
of the females of two or three allied species, is a rudimentary
representative of the cephalic horn, which is common to the males of so
many Lamellicorn beetles, as in Phanaeus (Fig. 18).

The old belief that rudiments have been created to complete the scheme
of nature is here so far from holding good, that we have a complete
inversion of the ordinary state of things in the family. We may
reasonably suspect that the males originally bore horns and transferred
them to the females in a rudimentary condition, as in so many other
Lamellicorns. Why the males subsequently lost their horns, we know not;
but this may have been caused through the principle of compensation,
owing to the development of the large horns and projections on the
lower surface; and as these are confined to the males, the rudiments of
the upper horns on the females would not have been thus obliterated.

[Fig. 23. Bledius taurus, magnified. Left-hand figure, male; right-hand
figure, female.]

The cases hitherto given refer to the Lamellicorns, but the males of
some few other beetles, belonging to two widely distinct groups,
namely, the Curculionidae and Staphylinidae, are furnished with
horns—in the former on the lower surface of the body (66. Kirby and
Spence, ‘Introduction to Entomology,’ vol. iii. p. 329.), in the latter
on the upper surface of the head and thorax. In the Staphylinidae, the
horns of the males are extraordinarily variable in the same species,
just as we have seen with the Lamellicorns. In Siagonium we have a case
of dimorphism, for the males can be divided into two sets, differing
greatly in the size of their bodies and in the development of their
horns, without intermediate gradations. In a species of Bledius (Fig.
23), also belonging to the Staphylinidae, Professor Westwood states
that, “male specimens can be found in the same locality in which the
central horn of the thorax is very large, but the horns of the head
quite rudimental; and others, in which the thoracic horn is much
shorter, whilst the protuberances on the head are long.” (67. ‘Modern
Classification of Insects,’ vol. i. p. 172: Siagonium, p. 172. In the
British Museum I noticed one male specimen of Siagonium in an
intermediate condition, so that the dimorphism is not strict.) Here we
apparently have a case of compensation, which throws light on that just
given, of the supposed loss of the upper horns by the males of Onitis.

LAW OF BATTLE.

Some male beetles, which seem ill-fitted for fighting, nevertheless
engage in conflicts for the possession of the females. Mr. Wallace (68.
‘The Malay Archipelago,’ vol. ii. 1869, p. 276. Riley, Sixth ‘Report on
Insects of Missouri,’ 1874, p. 115.) saw two males of Leptorhynchus
angustatus, a linear beetle with a much elongated rostrum, “fighting
for a female, who stood close by busy at her boring. They pushed at
each other with their rostra, and clawed and thumped, apparently in the
greatest rage.” The smaller male, however, “soon ran away,
acknowledging himself vanquished.” In some few cases male beetles are
well adapted for fighting, by possessing great toothed mandibles, much
larger than those of the females. This is the case with the common
stag-beetle (Lucanus cervus), the males of which emerge from the pupal
state about a week before the other sex, so that several may often be
seen pursuing the same female. At this season they engage in fierce
conflicts. When Mr. A.H. Davis (69. ‘Entomological Magazine,’ vol. i.
1833, p. 82. See also on the conflicts of this species, Kirby and
Spence, ibid. vol. iii. p. 314; and Westwood, ibid. vol. i. p. 187.)
enclosed two males with one female in a box, the larger male severely
pinched the smaller one, until he resigned his pretensions. A friend
informs me that when a boy he often put the males together to see them
fight, and he noticed that they were much bolder and fiercer than the
females, as with the higher animals. The males would seize hold of his
finger, if held in front of them, but not so the females, although they
have stronger jaws. The males of many of the Lucanidae, as well as of
the above-mentioned Leptorhynchus, are larger and more powerful insects
than the females. The two sexes of Lethrus cephalotes (one of the
Lamellicorns) inhabit the same burrow; and the male has larger
mandibles than the female. If, during the breeding-season, a strange
male attempts to enter the burrow, he is attacked; the female does not
remain passive, but closes the mouth of the burrow, and encourages her
mate by continually pushing him on from behind; and the battle lasts
until the aggressor is killed or runs away. (70. Quoted from Fischer,
in ‘Dict. Class. d’Hist. Nat.’ tom. x. p. 324.) The two sexes of
another Lamellicorn beetle, the Ateuchus cicatricosus, live in pairs,
and seem much attached to each other; the male excites the females to
roll the balls of dung in which the ova are deposited; and if she is
removed, he becomes much agitated. If the male is removed the female
ceases all work, and as M. Brulerie believes, would remain on the same
spot until she died. (71. ‘Ann. Soc. Entomolog. France,’ 1866, as
quoted in ‘Journal of Travel,’ by A. Murray, 1868, p. 135.)

[Fig. 24. Chiasognathus Grantii, reduced. Upper figure, male; lower
figure, female.]

The great mandibles of the male Lucanidae are extremely variable both
in size and structure, and in this respect resemble the horns on the
head and thorax of many male Lamellicorns and Staphylinidae. A perfect
series can be formed from the best-provided to the worst-provided or
degenerate males. Although the mandibles of the common stag-beetle, and
probably of many other species, are used as efficient weapons for
fighting, it is doubtful whether their great size can thus be accounted
for. We have seen that they are used by the Lucanus elaphus of N.
America for seizing the female. As they are so conspicuous and so
elegantly branched, and as owing to their great length they are not
well adapted for pinching, the suspicion has crossed my mind that they
may in addition serve as an ornament, like the horns on the head and
thorax of the various species above described. The male Chiasognathus
grantii of S. Chile—a splendid beetle belonging to the same family—has
enormously developed mandibles (Fig. 24); he is bold and pugnacious;
when threatened he faces round, opens his great jaws, and at the same
time stridulates loudly. But the mandibles were not strong enough to
pinch my finger so as to cause actual pain.

Sexual selection, which implies the possession of considerable
perceptive powers and of strong passions, seems to have been more
effective with the Lamellicorns than with any other family of beetles.
With some species the males are provided with weapons for fighting;
some live in pairs and shew mutual affection; many have the power of
stridulating when excited; many are furnished with the most
extraordinary horns, apparently for the sake of ornament; and some,
which are diurnal in their habits, are gorgeously coloured. Lastly,
several of the largest beetles in the world belong to this family,
which was placed by Linnaeus and Fabricius as the head of the Order.
(72. Westwood, ‘Modern Classification,’ vol. i. p. 184.)

STRIDULATING ORGANS.

Beetles belonging to many and widely distinct families possess these
organs. The sound thus produced can sometimes be heard at the distance
of several feet or even yards (73. Wollaston, ‘On Certain Musical
Curculionidae,’ ‘Annals and Mag. of Nat. Hist.’ vol. vi. 1860, p. 14.),
but it is not comparable with that made by the Orthoptera. The rasp
generally consists of a narrow, slightly-raised surface, crossed by
very fine, parallel ribs, sometimes so fine as to cause iridescent
colours, and having a very elegant appearance under the microscope. In
some cases, as with Typhoeus, minute, bristly or scale-like
prominences, with which the whole surrounding surface is covered in
approximately parallel lines, could be traced passing into the ribs of
the rasp. The transition takes place by their becoming confluent and
straight, and at the same time more prominent and smooth. A hard ridge
on an adjoining part of the body serves as the scraper for the rasp,
but this scraper in some cases has been specially modified for the
purpose. It is rapidly moved across the rasp, or conversely the rasp
across the scraper.

[Fig.25. Necrophorus (from Landois). r. The two rasps. Left-hand
figure, part of the rasp highly magnified.]

These organs are situated in widely different positions. In the
carrion-beetles (Necrophorus) two parallel rasps (r, Fig. 25) stand on
the dorsal surface of the fifth abdominal segment, each rasp (74.
Landois, ‘Zeitschrift fur wissenschaft Zoolog.’ B. xvii. 1867, s. 127.)
consisting of 126 to 140 fine ribs. These ribs are scraped against the
posterior margins of the elytra, a small portion of which projects
beyond the general outline. In many Crioceridae, and in Clythra
4-punctata (one of the Chrysomelidae), and in some Tenebrionidae, etc.
(75. I am greatly indebted to Mr. G.R. Crotch for having sent me many
prepared specimens of various beetles belonging to these three families
and to others, as well as for valuable information. He believes that
the power of stridulation in the Clythra has not been previously
observed. I am also much indebted to Mr. E.W. Janson, for information
and specimens. I may add that my son, Mr. F. Darwin, finds that
Dermestes murinus stridulates, but he searched in vain for the
apparatus. Scolytus has lately been described by Dr. Chapman as a
stridulator, in the ‘Entomologist’s Monthly Magazine,’ vol. vi. p.
130.), the rasp is seated on the dorsal apex of the abdomen, on the
pygidium or pro-pygidium, and is scraped in the same manner by the
elytra. In Heterocerus, which belongs to another family, the rasps are
placed on the sides of the first abdominal segment, and are scraped by
ridges on the femora. (76. Schiodte, translated, in ‘Annals and
Magazine of Natural History,’ vol. xx. 1867, p. 37.) In certain
Curculionidae and Carabidae (77. Westring has described (Kroyer,
‘Naturhist. Tidskrift,’ B. ii. 1848-49, p. 334) the stridulating organs
in these two, as well as in other families. In the Carabidae I have
examined Elaphrus uliginosus and Blethisa multipunctata, sent to me by
Mr. Crotch. In Blethisa the transverse ridges on the furrowed border of
the abdominal segment do not, as far as I could judge, come into play
in scraping the rasps on the elytra.), the parts are completely
reversed in position, for the rasps are seated on the inferior surface
of the elytra, near their apices, or along their outer margins, and the
edges of the abdominal segments serve as the scrapers. In Pelobius
Hermanni (one of Dytiscidae or water-beetles) a strong ridge runs
parallel and near to the sutural margin of the elytra, and is crossed
by ribs, coarse in the middle part, but becoming gradually finer at
both ends, especially at the upper end; when this insect is held under
water or in the air, a stridulating noise is produced by the extreme
horny margin of the abdomen being scraped against the rasps. In a great
number of long-horned beetles (Longicornia) the organs are situated
quite otherwise, the rasp being on the meso-thorax, which is rubbed
against the pro-thorax; Landois counted 238 very fine ribs on the rasp
of Cerambyx heros.

[Fig.26. Hind-leg of Geotrupes stercorarius (from Landois). r. Rasp. c.
Coxa. f. Femur. t. Tibia. tr. Tarsi.]

Many Lamellicorns have the power of stridulating, and the organs differ
greatly in position. Some species stridulate very loudly, so that when
Mr. F. Smith caught a Trox sabulosus, a gamekeeper, who stood by,
thought he had caught a mouse; but I failed to discover the proper
organs in this beetle. In Geotrupes and Typhoeus, a narrow ridge runs
obliquely across (r, Fig. 26) the coxa of each hind-leg (having in G.
stercorarius 84 ribs), which is scraped by a specially projecting part
of one of the abdominal segments. In the nearly allied Copris lunaris,
an excessively narrow fine rasp runs along the sutural margin of the
elytra, with another short rasp near the basal outer margin; but in
some other Coprini the rasp is seated, according to Leconte (78. I am
indebted to Mr. Walsh, of Illinois, for having sent me extracts from
Leconte’s ‘Introduction to Entomology,’ pp. 101, 143.), on the dorsal
surface of the abdomen. In Oryctes it is seated on the pro-pygidium;
and, according to the same entomologist, in some other Dynastini, on
the under surface of the elytra. Lastly, Westring states that in
Omaloplia brunnea the rasp is placed on the pro-sternum, and the
scraper on the meta-sternum, the parts thus occupying the under surface
of the body, instead of the upper surface as in the Longicorns.

We thus see that in the different coleopterous families the
stridulating organs are wonderfully diversified in position, but not
much in structure. Within the same family some species are provided
with these organs, and others are destitute of them. This diversity is
intelligible, if we suppose that originally various beetles made a
shuffling or hissing noise by the rubbing together of any hard and
rough parts of their bodies, which happened to be in contact; and that
from the noise thus produced being in some way useful, the rough
surfaces were gradually developed into regular stridulating organs.
Some beetles as they move, now produce, either intentionally or
unintentionally, a shuffling noise, without possessing any proper
organs for the purpose. Mr. Wallace informs me that the Euchirus
longimanus (a Lamellicorn, with the anterior legs wonderfully elongated
in the male) “makes, whilst moving, a low hissing sound by the
protrusion and contraction of the abdomen; and when seized it produces
a grating sound by rubbing its hind-legs against the edges of the
elytra.” The hissing sound is clearly due to a narrow rasp running
along the sutural margin of each elytron; and I could likewise make the
grating sound by rubbing the shagreened surface of the femur against
the granulated margin of the corresponding elytron; but I could not
here detect any proper rasp; nor is it likely that I could have
overlooked it in so large an insect. After examining Cychrus, and
reading what Westring has written about this beetle, it seems very
doubtful whether it possesses any true rasp, though it has the power of
emitting a sound.

From the analogy of the Orthoptera and Homoptera, I expected to find
the stridulating organs in the Coleoptera differing according to sex;
but Landois, who has carefully examined several species, observed no
such difference; nor did Westring; nor did Mr. G.R. Crotch in preparing
the many specimens which he had the kindness to send me. Any difference
in these organs, if slight, would, however, be difficult to detect, on
account of their great variability. Thus, in the first pair of
specimens of Necrophorus humator and of Pelobius which I examined, the
rasp was considerably larger in the male than in the female; but not so
with succeeding specimens. In Geotrupes stercorarius the rasp appeared
to me thicker, opaquer, and more prominent in three males than in the
same number of females; in order, therefore, to discover whether the
sexes differed in their power of stridulating, my son, Mr. F. Darwin,
collected fifty-seven living specimens, which he separated into two
lots, according as they made a greater or lesser noise, when held in
the same manner. He then examined all these specimens, and found that
the males were very nearly in the same proportion to the females in
both the lots. Mr. F. Smith has kept alive numerous specimens of
Monoynchus pseudacori (Curculionidae), and is convinced that both sexes
stridulate, and apparently in an equal degree.

Nevertheless, the power of stridulating is certainly a sexual character
in some few Coleoptera. Mr. Crotch discovered that the males alone of
two species of Heliopathes (Tenebrionidae) possess stridulating organs.
I examined five males of H. gibbus, and in all these there was a
well-developed rasp, partially divided into two, on the dorsal surface
of the terminal abdominal segment; whilst in the same number of females
there was not even a rudiment of the rasp, the membrane of this segment
being transparent, and much thinner than in the male. In H.
cribratostriatus the male has a similar rasp, excepting that it is not
partially divided into two portions, and the female is completely
destitute of this organ; the male in addition has on the apical margins
of the elytra, on each side of the suture, three or four short
longitudinal ridges, which are crossed by extremely fine ribs, parallel
to and resembling those on the abdominal rasp; whether these ridges
serve as an independent rasp, or as a scraper for the abdominal rasp, I
could not decide: the female exhibits no trace

of this latter structure.

Again, in three species of the Lamellicorn genus Oryctes, we have a
nearly parallel case. In the females of O. gryphus and nasicornis the
ribs on the rasp of the pro-pygidium are less continuous and less
distinct than in the males; but the chief difference is that the whole
upper surface of this segment, when held in the proper light, is seen
to be clothed with hairs, which are absent or are represented by
excessively fine down in the males. It should be noticed that in all
Coleoptera the effective part of the rasp is destitute of hairs. In O.
senegalensis the difference between the sexes is more strongly marked,
and this is best seen when the proper abdominal segment is cleaned and
viewed as a transparent object. In the female the whole surface is
covered with little separate crests, bearing spines; whilst in the male
these crests in proceeding towards the apex, become more and more
confluent, regular, and naked; so that three-fourths of the segment is
covered with extremely fine parallel ribs, which are quite absent in
the female. In the females, however, of all three species of Oryctes, a
slight grating or stridulating sound is produced, when the abdomen of a
softened specimen is pushed backwards and forwards.

In the case of the Heliopathes and Oryctes there can hardly be a doubt
that the males stridulate in order to call or to excite the females;
but with most beetles the stridulation apparently serves both sexes as
a mutual call. Beetles stridulate under various emotions, in the same
manner as birds use their voices for many purposes besides singing to
their mates. The great Chiasognathus stridulates in anger or defiance;
many species do the same from distress or fear, if held so that they
cannot escape; by striking the hollow stems of trees in the Canary
Islands, Messrs. Wollaston and Crotch were able to discover the
presence of beetles belonging to the genus Acalles by their
stridulation. Lastly, the male Ateuchus stridulates to encourage the
female in her work, and from distress when she is removed. (79. M. P.
de la Brulerie, as quoted in ‘Journal of Travel,’ A. Murray, vol. i.
1868, p. 135.) Some naturalists believe that beetles make this noise to
frighten away their enemies; but I cannot think that a quadruped or
bird, able to devour a large beetle, would be frightened by so slight a
sound. The belief that the stridulation serves as a sexual call is
supported by the fact that death-ticks (Anobium tessellatum) are well
known to answer each other’s ticking, and, as I have myself observed, a
tapping noise artificially made. Mr. Doubleday also informs me that he
has sometimes observed a female ticking (80. According to Mr.
Doubleday, “the noise is produced by the insect raising itself on its
legs as high as it can, and then striking its thorax five or six times,
in rapid succession, against the substance upon which it is sitting.”
For references on this subject see Landois, ‘Zeitschrift für wissen.
Zoolog.’ B. xvii. s. 131. Olivier says (as quoted by Kirby and Spence,
‘Introduction to Entomology,’ vol. ii. p. 395) that the female of
Pimelia striata produces a rather loud sound by striking her abdomen
against any hard substance, “and that the male, obedient to this call,
soon attends her, and they pair.”), and in an hour or two afterwards
has found her united with a male, and on one occasion surrounded by
several males. Finally, it is probable that the two sexes of many kinds
of beetles were at first enabled to find each other by the slight
shuffling noise produced by the rubbing together of the adjoining hard
parts of their bodies; and that as those males or females which made
the greatest noise succeeded best in finding partners, rugosities on
various parts of their bodies were gradually developed by means of
sexual selection into true stridulating organs.




CHAPTER XI.
INSECTS, continued. ORDER LEPIDOPTERA. (BUTTERFLIES AND MOTHS.)


Courtship of butterflies—Battles—Ticking noise—Colours common to both

sexes, or more brilliant in the males—Examples—Not due to the direct
action of the conditions of life—Colours adapted for protection—Colours
of moths—Display—Perceptive powers of the
Lepidoptera—Variability—Causes of the difference in colour between the
males and females—Mimicry, female butterflies more brilliantly coloured
than the males—Bright colours of caterpillars—Summary and concluding
remarks on the secondary sexual characters of insects—Birds and insects
compared.

In this great Order the most interesting points for us are the
differences in colour between the sexes of the same species, and
between the distinct species of the same genus. Nearly the whole of the
following chapter will be devoted to this subject; but I will first
make a few remarks on one or two other points. Several males may often
be seen pursuing and crowding round the same female. Their courtship
appears to be a prolonged affair, for I have frequently watched one or
more males pirouetting round a female until I was tired, without seeing
the end of the courtship. Mr. A.G. Butler also informs me that he has
several times watched a male courting a female for a full quarter of an
hour; but she pertinaciously refused him, and at last settled on the
ground and closed her wings, so as to escape from his addresses.

Although butterflies are weak and fragile creatures, they are
pugnacious, and an emperor butterfly (1. Apatura Iris: ‘The
Entomologist’s Weekly Intelligence,’ 1859, p. 139. For the Bornean
Butterflies, see C. Collingwood, ‘Rambles of a Naturalist,’ 1868, p.
183.) has been captured with the tips of its wings broken from a
conflict with another male. Mr. Collingwood, in speaking of the
frequent battles between the butterflies of Borneo, says, “They whirl
round each other with the greatest rapidity, and appear to be incited
by the greatest ferocity.”

The Ageronia feronia makes a noise like that produced by a toothed
wheel passing under a spring catch, and which can be heard at the
distance of several yards: I noticed this sound at Rio de Janeiro, only
when two of these butterflies were chasing each other in an irregular
course, so that it is probably made during the courtship of the sexes.
(2. See my ‘Journal of Researches,’ 1845, p. 33. Mr. Doubleday has
detected (‘Proc. Ent. Soc.’ March 3, 1845, p. 123) a peculiar
membranous sac at the base of the front wings, which is probably
connected with the production of the sound. For the case of Thecophora,
see ‘Zoological Record,’ 1869, p. 401. For Mr. Buchanan White’s
observations, the Scottish Naturalist, July 1872, p. 214.)

Some moths also produce sounds; for instance, the males Theocophora
fovea. On two occasions Mr. F. Buchanan White (3. ‘The Scottish
Naturalist,’ July 1872, p. 213.) heard a sharp quick noise made by the
male of Hylophila prasinana, and which he believes to be produced, as
in Cicada, by an elastic membrane, furnished with a muscle. He quotes,
also, Guenee, that Setina produces a sound like the ticking of a watch,
apparently by the aid of “two large tympaniform vesicles, situated in
the pectoral region”; and these “are much more developed in the male
than in the female.” Hence the sound-producing organs in the
Lepidoptera appear to stand in some relation with the sexual functions.
I have not alluded to the well-known noise made by the Death’s Head
Sphinx, for it is generally heard soon after the moth has emerged from
its cocoon.

Giard has always observed that the musky odour, which is emitted by two
species of Sphinx moths, is peculiar to the males (4. ‘Zoological
Record,’ 1869, p. 347.); and in the higher classes we shall meet with
many instances of the males alone being odoriferous.

Every one must have admired the extreme beauty of many butterflies and
of some moths; and it may be asked, are their colours and diversified
patterns the result of the direct action of the physical conditions to
which these insects have been exposed, without any benefit being thus
derived? Or have successive variations been accumulated and determined
as a protection, or for some unknown purpose, or that one sex may be
attractive to the other? And, again, what is the meaning of the colours
being widely different in the males and females of certain species, and
alike in the two sexes of other species of the same genus? Before
attempting to answer these questions a body of facts must be given.

With our beautiful English butterflies, the admiral, peacock, and
painted lady (Vanessae), as well as many others, the sexes are alike.
This is also the case with the magnificent Heliconidae, and most of the
Danaidae in the tropics. But in certain other tropical groups, and in
some of our English butterflies, as the purple emperor, orange-tip,
etc. (Apatura Iris and Anthocharis cardamines), the sexes differ either
greatly or slightly in colour. No language suffices to describe the
splendour of the males of some tropical species. Even within the same
genus we often find species presenting extraordinary differences
between the sexes, whilst others have their sexes closely alike. Thus
in the South American genus Epicalia, Mr. Bates, to whom I am indebted
for most of the following facts, and for looking over this whole
discussion, informs me that he knows twelve species, the two sexes of
which haunt the same stations (and this is not always the case with
butterflies), and which, therefore, cannot have been differently
affected by external conditions. (5. See also Mr. Bates’s paper in
‘Proc. Ent. Soc. of Philadelphia,’ 1865, p. 206. Also Mr. Wallace on
the same subject, in regard to Diadema, in ‘Transactions, Entomological
Society of London,’ 1869, p. 278.) In nine of these twelve species the
males rank amongst the most brilliant of all butterflies, and differ so
greatly from the comparatively plain females that they were formerly
placed in distinct genera. The females of these nine species resemble
each other in their general type of coloration; and they likewise
resemble both sexes of the species in several allied genera found in
various parts of the world. Hence we may infer that these nine species,
and probably all the others of the genus, are descended from an
ancestral form which was coloured in nearly the same manner. In the
tenth species the female still retains the same general colouring, but
the male resembles her, so that he is coloured in a much less gaudy and
contrasted manner than the males of the previous species. In the
eleventh and twelfth species, the females depart from the usual type,
for they are gaily decorated almost like the males, but in a somewhat
less degree. Hence in these two latter species the bright colours of
the males seem to have been transferred to the females; whilst in the
tenth species the male has either retained or recovered the plain
colours of the female, as well as of the parent-form of the genus. The
sexes in these three cases have thus been rendered nearly alike, though
in an opposite manner. In the allied genus Eubagis, both sexes of some
of the species are plain-coloured and nearly alike; whilst with the
greater number the males are decorated with beautiful metallic tints in
a diversified manner, and differ much from their females. The females
throughout the genus retain the same general style of colouring, so
that they resemble one another much more closely than they resemble
their own males.

In the genus Papilio, all the species of the Aeneas group are
remarkable for their conspicuous and strongly contrasted colours, and
they illustrate the frequent tendency to gradation in the amount of
difference between the sexes. In a few species, for instance in P.
ascanius, the males and females are alike; in others the males are
either a little brighter, or very much more superb than the females.
The genus Junonia, allied to our Vanessae, offers a nearly parallel
case, for although the sexes of most of the species resemble each
other, and are destitute of rich colours, yet in certain species, as in
J. oenone, the male is rather more bright-coloured than the female, and
in a few (for instance J. andremiaja) the male is so different from the
female that he might be mistaken for an entirely distinct species.

Another striking case was pointed out to me in the British Museum by
Mr. A. Butler, namely, one of the tropical American Theclae, in which
both sexes are nearly alike and wonderfully splendid; in another
species the male is coloured in a similarly gorgeous manner, whilst the
whole upper surface of the female is of a dull uniform brown. Our
common little English blue butterflies of the genus Lycaena, illustrate
the various differences in colour between the sexes, almost as well,
though not in so striking a manner, as the above exotic genera. In
Lycaena agestis both sexes have wings of a brown colour, bordered with
small ocellated orange spots, and are thus alike. In L. oegon the wings
of the males are of a fine blue, bordered with black, whilst those of
the female are brown, with a similar border, closely resembling the
wings of L. agestis. Lastly, in L. arion both sexes are of a blue
colour and are very like, though in the female the edges of the wings
are rather duskier, with the black spots plainer; and in a bright blue
Indian species both sexes are still more alike.

I have given the foregoing details in order to shew, in the first
place, that when the sexes of butterflies differ, the male as a general
rule is the more beautiful, and departs more from the usual type of
colouring of the group to which the species belongs. Hence in most
groups the females of the several species resemble each other much more
closely than do the males. In some cases, however, to which I shall
hereafter allude, the females are coloured more splendidly than the
males. In the second place, these details have been given to bring
clearly before the mind that within the same genus, the two sexes
frequently present every gradation from no difference in colour, to so
great a difference that it was long before the two were placed by
entomologists in the same genus. In the third place, we have seen that
when the sexes nearly resemble each other, this appears due either to
the male having transferred his colours to the female, or to the male
having retained, or perhaps recovered, the primordial colours of the
group. It also deserves notice that in those groups in which the sexes
differ, the females usually somewhat resemble the males, so that when
the males are beautiful to an extraordinary degree, the females almost
invariably exhibit some degree of beauty. From the many cases of
gradation in the amount of difference between the sexes, and from the
prevalence of the same general type of coloration throughout the whole
of the same group, we may conclude that the causes have generally been
the same which have determined the brilliant colouring of the males
alone of some species, and of both sexes of other species.

As so many gorgeous butterflies inhabit the tropics, it has often been
supposed that they owe their colours to the great heat and moisture of
these zones; but Mr. Bates (6. ‘The Naturalist on the Amazons,’ vol. i.
1863, p. 19.) has shown by the comparison of various closely-allied
groups of insects from the temperate and tropical regions, that this
view cannot be maintained; and the evidence becomes conclusive when
brilliantly-coloured males and plain-coloured females of the same
species inhabit the same district, feed on the same food, and follow
exactly the same habits of life. Even when the sexes resemble each
other, we can hardly believe that their brilliant and
beautifully-arranged colours are the purposeless result of the nature
of the tissues and of the action of the surrounding conditions.

With animals of all kinds, whenever colour has been modified for some
special purpose, this has been, as far as we can judge, either for
direct or indirect protection, or as an attraction between the sexes.
With many species of butterflies the upper surfaces of the wings are
obscure; and this in all probability leads to their escaping
observation and danger. But butterflies would be particularly liable to
be attacked by their enemies when at rest; and most kinds whilst
resting raise their wings vertically over their backs, so that the
lower surface alone is exposed to view. Hence it is this side which is
often coloured so as to imitate the objects on which these insects
commonly rest. Dr. Rossler, I believe, first noticed the similarity of
the closed wings of certain Vanessae and other butterflies to the bark
of trees. Many analogous and striking facts could be given. The most
interesting one is that recorded by Mr. Wallace (7. See the interesting
article in the ‘Westminster Review,’ July 1867, p. 10. A woodcut of the
Kallima is given by Mr. Wallace in ‘Hardwicke’s Science Gossip,’
September 1867, p. 196.) of a common Indian and Sumatran butterfly
(Kallima) which disappears like magic when it settles on a bush; for it
hides its head and antennae between its closed wings, which, in form,
colour and veining, cannot be distinguished from a withered leaf with
its footstalk. In some other cases the lower surfaces of the wings are
brilliantly coloured, and yet are protective; thus in Thecla rubi the
wings when closed are of an emerald green, and resemble the young
leaves of the bramble, on which in spring this butterfly may often be
seen seated. It is also remarkable that in very many species in which
the sexes differ greatly in colour on their upper surface, the lower
surface is closely similar or identical in both sexes, and serves as a
protection. (8. Mr. G. Fraser, in ‘Nature,’ April 1871, p. 489.)

Although the obscure tints both of the upper and under sides of many
butterflies no doubt serve to conceal them, yet we cannot extend this
view to the brilliant and conspicuous colours on the upper surface of
such species as our admiral and peacock Vanessae, our white
cabbage-butterflies (Pieris), or the great swallow-tail Papilio which
haunts the open fens—for these butterflies are thus rendered visible to
every living creature. In these species both sexes are alike; but in
the common brimstone butterfly (Gonepteryx rhamni), the male is of an
intense yellow, whilst the female is much paler; and in the orange-tip
(Anthocharis cardamines) the males alone have their wings tipped with
bright orange. Both the males and females in these cases are
conspicuous, and it is not credible that their difference in colour
should stand in any relation to ordinary protection. Prof. Weismann
remarks (9. ‘Einfluss der Isolirung auf die Artbildung,’ 1872, p. 58.),
that the female of one of the Lycaenae expands her brown wings when she
settles on the ground, and is then almost invisible; the male, on the
other hand, as if aware of the danger incurred from the bright blue of
the upper surface of his wings, rests with them closed; and this shows
that the blue colour cannot be in any way protective. Nevertheless, it
is probable that conspicuous colours are indirectly beneficial to many
species, as a warning that they are unpalatable. For in certain other
cases, beauty has been gained through the imitation of other beautiful
species, which inhabit the same district and enjoy an immunity from
attack by being in some way offensive to their enemies; but then we
have to account for the beauty of the imitated species.

As Mr. Walsh has remarked to me, the females of our orange-tip
butterfly, above referred to, and of an American species (Anth.
genutia) probably shew us the primordial colours of the parent-species
of the genus; for both sexes of four or five widely-distributed species
are coloured in nearly the same manner. As in several previous cases,
we may here infer that it is the males of Anth. cardamines and genutia
which have departed from the usual type of the genus. In the Anth. sara
from California, the orange-tips to the wings have been partially
developed in the female; but they are paler than in the male, and
slightly different in some other respects. In an allied Indian form,
the Iphias glaucippe, the orange-tips are fully developed in both
sexes. In this Iphias, as pointed out to me by Mr. A. Butler, the under
surface of the wings marvellously resembles a pale-coloured leaf; and
in our English orange-tip, the under surface resembles the flower-head
of the wild parsley, on which the butterfly often rests at night. (10.
See the interesting observations by T.W. Wood, ‘The Student,’ Sept.
1868, p. 81.) The same reason which compels us to believe that the
lower surfaces have here been coloured for the sake of protection,
leads us to deny that the wings have been tipped with bright orange for
the same purpose, especially when this character is confined to the
males.

Most Moths rest motionless during the whole or greater part of the day
with their wings depressed; and the whole upper surface is often shaded
and coloured in an admirable manner, as Mr. Wallace has remarked, for
escaping detection. The front-wings of the Bombycidae and Noctuidae
(11. Mr. Wallace in ‘Hardwicke’s Science Gossip,’ September 1867, p.
193.), when at rest, generally overlap and conceal the hind-wings; so
that the latter might be brightly coloured without much risk; and they
are in fact often thus coloured. During flight, moths would often be
able to escape from their enemies; nevertheless, as the hind-wings are
then fully exposed to view, their bright colours must generally have
been acquired at some little risk. But the following fact shews how
cautious we ought to be in drawing conclusions on this head. The common
Yellow Under-wings (Triphaena) often fly about during the day or early
evening, and are then conspicuous from the colour of their hind-wings.
It would naturally be thought that this would be a source of danger;
but Mr. J. Jenner Weir believes that it actually serves them as a means
of escape, for birds strike at these brightly coloured and fragile
surfaces, instead of at the body. For instance, Mr. Weir turned into
his aviary a vigorous specimen of Triphaena pronuba, which was
instantly pursued by a robin; but the bird’s attention being caught by
the coloured wings, the moth was not captured until after about fifty
attempts, and small portions of the wings were repeatedly broken off.
He tried the same experiment, in the open air, with a swallow and T.
fimbria; but the large size of this moth probably interfered with its
capture. (12. See also, on this subject, Mr. Weir’s paper in
‘Transactions, Entomological Society,’ 1869, p. 23.) We are thus
reminded of a statement made by Mr. Wallace (13. ‘Westminster Review,’
July 1867, p. 16.), namely, that in the Brazilian forests and Malayan
islands, many common and highly-decorated butterflies are weak flyers,
though furnished with a broad expanse of wing; and they “are often
captured with pierced and broken wings, as if they had been seized by
birds, from which they had escaped: if the wings had been much smaller
in proportion to the body, it seems probable that the insect would more
frequently have been struck or pierced in a vital part, and thus the
increased expanse of the wings may have been indirectly beneficial.”

DISPLAY.

The bright colours of many butterflies and of some moths are specially
arranged for display, so that they may be readily seen. During the
night colours are not visible, and there can be no doubt that the
nocturnal moths, taken as a body, are much less gaily decorated than
butterflies, all of which are diurnal in their habits. But the moths of
certain families, such as the Zygaenidae, several Sphingidae,
Uraniidae, some Arctiidae and Saturniidae, fly about during the day or
early evening, and many of these are extremely beautiful, being far
brighter coloured than the strictly nocturnal kinds. A few exceptional
cases, however, of bright-coloured nocturnal species have been
recorded. (14. For instance, Lithosia; but Prof. Westwood (‘Modern
Class. of Insects,’ vol. ii. p. 390) seems surprised at this case. On
the relative colours of diurnal and nocturnal Lepidoptera, see ibid.
pp. 333 and 392; also Harris, ‘Treatise on the Insects of New England,’
1842, p. 315.)

There is evidence of another kind in regard to display. Butterflies, as
before remarked, elevate their wings when at rest, but whilst basking
in the sunshine often alternately raise and depress them, thus exposing
both surfaces to full view; and although the lower surface is often
coloured in an obscure manner as a protection, yet in many species it
is as highly decorated as the upper surface, and sometimes in a very
different manner. In some tropical species the lower surface is even
more brilliantly coloured than the upper. (15. Such differences between
the upper and lower surfaces of the wings of several species of Papilio
may be seen in the beautiful plates to Mr. Wallace’s ‘Memoir on the
Papilionidae of the Malayan Region,’ in ‘Transactions of the Linnean
Society,’ vol. xxv. part i. 1865.) In the English fritillaries
(Argynnis) the lower surface alone is ornamented with shining silver.
Nevertheless, as a general rule, the upper surface, which is probably
more fully exposed, is coloured more brightly and diversely than the
lower. Hence the lower surface generally affords to entomologists the
more useful character for detecting the affinities of the various
species. Fritz Müller informs me that three species of Castnia are
found near his house in S. Brazil: of two of them the hind-wings are
obscure, and are always covered by the front-wings when these
butterflies are at rest; but the third species has black hind-wings,
beautifully spotted with red and white, and these are fully expanded
and displayed whenever the butterfly rests. Other such cases could be
added.

If we now turn to the enormous group of moths, which, as I hear from
Mr. Stainton, do not habitually expose the under surface of their wings
to full view, we find this side very rarely coloured with a brightness
greater than, or even equal to, that of the upper side. Some exceptions
to the rule, either real or apparent, must be noticed, as the case of
Hypopyra. (16. See Mr. Wormald on this moth: ‘Proceedings of the
Entomological Society,’ March 2, 1868.) Mr. Trimen informs me that in
Guenee’s great work, three moths are figured, in which the under
surface is much the more brilliant. For instance, in the Australian
Gastrophora the upper surface of the fore-wing is pale
greyish-ochreous, while the lower surface is magnificently ornamented
by an ocellus of cobalt-blue, placed in the midst of a black mark,
surrounded by orange-yellow, and this by bluish-white. But the habits
of these three moths are unknown; so that no explanation can be given
of their unusual style of colouring. Mr. Trimen also informs me that
the lower surface of the wings in certain other Geometrae (17. See also
an account of the S. American genus Erateina (one of the Geometrae) in
‘Transactions, Ent. Soc.’ new series, vol. v. pl. xv. and xvi.) and
quadrifid Noctuae are either more variegated or more brightly-coloured
than the upper surface; but some of these species have the habit of
“holding their wings quite erect over their backs, retaining them in
this position for a considerable time,” and thus exposing the under
surface to view. Other species, when settled on the ground or herbage,
now and then suddenly and slightly lift up their wings. Hence the lower
surface of the wings being brighter than the upper surface in certain
moths is not so anomalous as it at first appears. The Saturniidae
include some of the most beautiful of all moths, their wings being
decorated, as in our British Emperor moth, with fine ocelli; and Mr.
T.W. Wood (18. ‘Proc Ent. Soc. of London,’ July 6, 1868, p. xxvii.)
observes that they resemble butterflies in some of their movements;
“for instance, in the gentle waving up and down of the wings as if for
display, which is more characteristic of diurnal than of nocturnal
Lepidoptera.”

It is a singular fact that no British moths which are brilliantly
coloured, and, as far as I can discover, hardly any foreign species,
differ much in colour according to sex; though this is the case with
many brilliant butterflies. The male, however, of one American moth,
the Saturnia Io, is described as having its fore-wings deep yellow,
curiously marked with purplish-red spots; whilst the wings of the
female are purple-brown, marked with grey lines. (19. Harris,
‘Treatise,’ etc., edited by Flint, 1862, p. 395.) The British moths
which differ sexually in colour are all brown, or of various dull
yellow tints, or nearly white. In several species the males are much
darker than the females (20. For instance, I observe in my son’s
cabinet that the males are darker than the females in the Lasiocampa
quercus, Odonestis potatoria, Hypogymna dispar, Dasychira pudibunda,
and Cycnia mendica. In this latter species the difference in colour
between the two sexes is strongly marked; and Mr. Wallace informs me
that we here have, as he believes, an instance of protective mimicry
confined to one sex, as will hereafter be more fully explained. The
white female of the Cycnia resembles the very common Spilosoma
menthrasti, both sexes of which are white; and Mr. Stainton observed
that this latter moth was rejected with utter disgust by a whole brood
of young turkeys, which were fond of eating other moths; so that if the
Cycnia was commonly mistaken by British birds for the Spilosoma, it
would escape being devoured, and its white deceptive colour would thus
be highly beneficial.), and these belong to groups which generally fly
about during the afternoon. On the other hand, in many genera, as Mr.
Stainton informs me, the males have the hind-wings whiter than those of
the female—of which fact Agrotis exclamationis offers a good instance.
In the Ghost Moth (Hepialus humuli) the difference is more strongly
marked; the males being white, and the females yellow with darker
markings. (21. It is remarkable, that in the Shetland Islands the male
of this moth, instead of differing widely from the female, frequently
resembles her closely in colour (see Mr. MacLachlan, ‘Transactions,
Entomological Society,’ vol. ii. 1866, p. 459). Mr. G. Fraser suggests
(‘Nature,’ April 1871, p. 489) that at the season of the year when the
ghost-moth appears in these northern islands, the whiteness of the
males would not be needed to render them visible to the females in the
twilight night.) It is probable that in these cases the males are thus
rendered more conspicuous, and more easily seen by the females whilst
flying about in the dusk.

From the several foregoing facts it is impossible to admit that the
brilliant colours of butterflies, and of some few moths, have commonly
been acquired for the sake of protection. We have seen that their
colours and elegant patterns are arranged and exhibited as if for
display. Hence I am led to believe that the females prefer or are most
excited by the more brilliant males; for on any other supposition the
males would, as far as we can see, be ornamented to no purpose. We know
that ants and certain Lamellicorn beetles are capable of feeling an
attachment for each other, and that ants recognise their fellows after
an interval of several months. Hence there is no abstract improbability
in the Lepidoptera, which probably stand nearly or quite as high in the
scale as these insects, having sufficient mental capacity to admire
bright colours. They certainly discover flowers by colour. The
Humming-bird Sphinx may often be seen to swoop down from a distance on
a bunch of flowers in the midst of green foliage; and I have been
assured by two persons abroad, that these moths repeatedly visit
flowers painted on the walls of a room, and vainly endeavour to insert
their proboscis into them. Fritz Müller informs me that several kinds
of butterflies in S. Brazil shew an unmistakable preference for certain
colours over others: he observed that they very often visited the
brilliant red flowers of five or six genera of plants, but never the
white or yellow flowering species of the same and other genera, growing
in the same garden; and I have received other accounts to the same
effect. As I hear from Mr. Doubleday, the common white butterfly often
flies down to a bit of paper on the ground, no doubt mistaking it for
one of its own species. Mr. Collingwood (22. ‘Rambles of a Naturalist
in the Chinese Seas,’ 1868, p. 182.) in speaking of the difficulty in
collecting certain butterflies in the Malay Archipelago, states that “a
dead specimen pinned upon a conspicuous twig will often arrest an
insect of the same species in its headlong flight, and bring it down
within easy reach of the net, especially if it be of the opposite sex.”

The courtship of butterflies is, as before remarked, a prolonged
affair. The males sometimes fight together in rivalry; and many may be
seen pursuing or crowding round the same female. Unless, then, the
females prefer one male to another, the pairing must be left to mere
chance, and this does not appear probable. If, on the other band, the
females habitually, or even occasionally, prefer the more beautiful
males, the colours of the latter will have been rendered brighter by
degrees, and will have been transmitted to both sexes or to one sex,
according to the law of inheritance which has prevailed. The process of
sexual selection will have been much facilitated, if the conclusion can
be trusted, arrived at from various kinds of evidence in the supplement
to the ninth chapter; namely, that the males of many Lepidoptera, at
least in the imago state, greatly exceed the females in number.

Some facts, however, are opposed to the belief that female butterflies
prefer the more beautiful males; thus, as I have been assured by
several collectors, fresh females may frequently be seen paired with
battered, faded, or dingy males; but this is a circumstance which could
hardly fail often to follow from the males emerging from their cocoons
earlier than the females. With moths of the family of the Bombycidae,
the sexes pair immediately after assuming the imago state; for they
cannot feed, owing to the rudimentary condition of their mouths. The
females, as several entomologists have remarked to me, lie in an almost
torpid state, and appear not to evince the least choice in regard to
their partners. This is the case with the common silk-moth (B. mori),
as I have been told by some continental and English breeders. Dr.
Wallace, who has had great experience in breeding Bombyx cynthia, is
convinced that the females evince no choice or preference. He has kept
above 300 of these moths together, and has often found the most
vigorous females mated with stunted males. The reverse appears to occur
seldom; for, as he believes, the more vigorous males pass over the
weakly females, and are attracted by those endowed with most vitality.
Nevertheless, the Bombycidae, though obscurely-coloured, are often
beautiful to our eyes from their elegant and mottled shades.

I have as yet only referred to the species in which the males are
brighter coloured than the females, and I have attributed their beauty
to the females for many generations having chosen and paired with the
more attractive males. But converse cases occur, though rarely, in
which the females are more brilliant than the males; and here, as I
believe, the males have selected the more beautiful females, and have
thus slowly added to their beauty. We do not know why in various
classes of animals the males of some few species have selected the more
beautiful females instead of having gladly accepted any female, as
seems to be the general rule in the animal kingdom: but if, contrary to
what generally occurs with the Lepidoptera, the females were much more
numerous than the males, the latter would be likely to pick out the
more beautiful females. Mr. Butler shewed me several species of
Callidryas in the British Museum, in some of which the females
equalled, and in others greatly surpassed the males in beauty; for the
females alone have the borders of their wings suffused with crimson and
orange, and spotted with black. The plainer males of these species
closely resemble each other, shewing that here the females have been
modified; whereas in those cases, where the males are the more ornate,
it is these which have been modified, the females remaining closely
alike.

In England we have some analogous cases, though not so marked. The
females alone of two species of Thecla have a bright-purple or orange
patch on their fore-wings. In Hipparchia the sexes do not differ much;
but it is the female of H. janira which has a conspicuous light-brown
patch on her wings; and the females of some of the other species are
brighter coloured than their males. Again, the females of Colias edusa
and hyale have “orange or yellow spots on the black marginal border,
represented in the males only by thin streaks”; and in Pieris it is the
females which “are ornamented with black spots on the fore-wings, and
these are only partially present in the males.” Now the males of many
butterflies are known to support the females during their marriage
flight; but in the species just named it is the females which support
the males; so that the part which the two sexes play is reversed, as is
their relative beauty. Throughout the animal kingdom the males commonly
take the more active share in wooing, and their beauty seems to have
been increased by the females having accepted the more attractive
individuals; but with these butterflies, the females take the more
active part in the final marriage ceremony, so that we may suppose that
they likewise do so in the wooing; and in this case we can understand
how it is that they have been rendered the more beautiful. Mr. Meldola,
from whom the foregoing statements have been taken, says in conclusion:
“Though I am not convinced of the action of sexual selection in
producing the colours of insects, it cannot be denied that these facts
are strikingly corroborative of Mr. Darwin’s views.” (23. ‘Nature,’
April 27, 1871, p. 508. Mr. Meldola quotes Donzel, in ‘Soc. Ent. de
France,’ 1837, p. 77, on the flight of butterflies whilst pairing. See
also Mr. G. Fraser, in ‘Nature,’ April 20, 1871, p. 489, on the sexual
differences of several British butterflies.)

As sexual selection primarily depends on variability, a few words must
be added on this subject. In respect to colour there is no difficulty,
for any number of highly variable Lepidoptera could be named. One good
instance will suffice. Mr. Bates shewed me a whole series of specimens
of Papilio sesostris and P. childrenae; in the latter the males varied
much in the extent of the beautifully enamelled green patch on the
fore-wings, and in the size of the white mark, and of the splendid
crimson stripe on the hind-wings; so that there was a great contrast
amongst the males between the most and the least gaudy. The male of
Papilio sesostris is much less beautiful than of P. childrenae; and it
likewise varies a little in the size of the green patch on the
fore-wings, and in the occasional appearance of the small crimson
stripe on the hind-wings, borrowed, as it would seem, from its own
female; for the females of this and of many other species in the Aeneas
group possess this crimson stripe. Hence between the brightest
specimens of P. sesostris and the dullest of P. childrenae, there was
but a small interval; and it was evident that as far as mere
variability is concerned, there would be no difficulty in permanently
increasing the beauty of either species by means of selection. The
variability is here almost confined to the male sex; but Mr. Wallace
and Mr. Bates have shewn (24. Wallace on the Papilionidae of the
Malayan Region, in ‘Transact. Linn. Soc.’ vol. xxv. 1865, pp. 8, 36. A
striking case of a rare variety, strictly intermediate between two
other well-marked female varieties, is given by Mr. Wallace. See also
Mr. Bates, in ‘Proc. Entomolog. Soc.’ Nov. 19, 1866, p. xl.) that the
females of some species are extremely variable, the males being nearly
constant. In a future chapter I shall have occasion to shew that the
beautiful eye-like spots, or ocelli, found on the wings of many
Lepidoptera, are eminently variable. I may here add that these ocelli
offer a difficulty on the theory of sexual selection; for though
appearing to us so ornamental, they are never present in one sex and
absent in the other, nor do they ever differ much in the two sexes.
(25. Mr. Bates was so kind as to lay this subject before the
Entomological Society, and I have received answers to this effect from
several entomologists.) This fact is at present inexplicable; but if it
should hereafter be found that the formation of an ocellus is due to
some change in the tissues of the wings, for instance, occurring at a
very early period of development, we might expect, from what we know of
the laws of inheritance, that it would be transmitted to both sexes,
though arising and perfected in one sex alone.

On the whole, although many serious objections may be urged, it seems
probable that most of the brilliantly-coloured species of Lepidoptera
owe their colours to sexual selection, excepting in certain cases,
presently to be mentioned, in which conspicuous colours have been
gained through mimicry as a protection. From the ardour of the male
throughout the animal kingdom, he is generally willing to accept any
female; and it is the female which usually exerts a choice. Hence, if
sexual selection has been efficient with the Lepidoptera, the male,
when the sexes differ, ought to be the more brilliantly coloured, and
this undoubtedly is the case. When both sexes are brilliantly coloured
and resemble each other, the characters acquired by the males appear to
have been transmitted to both. We are led to this conclusion by cases,
even within the same genus, of gradation from an extraordinary amount
of difference to identity in colour between the two sexes.

But it may be asked whether the difference in colour between the sexes
may not be accounted for by other means besides sexual selection. Thus
the males and females of the same species of butterfly are in several
cases known (26. H.W. Bates, ‘The Naturalist on the Amazons,’ vol. ii.
1863, p. 228. A.R. Wallace, in ‘Transactions, Linnean Society,’ vol.
xxv. 1865, p. 10.) to inhabit different stations, the former commonly
basking in the sunshine, the latter haunting gloomy forests. It is
therefore possible that different conditions of life may have acted
directly on the two sexes; but this is not probable (27. On this whole
subject see ‘The Variation of Animals and Plants under Domestication,’
1868, vol. ii. chap. xxiii.) as in the adult state they are exposed to
different conditions during a very short period; and the larvae of both
are exposed to the same conditions. Mr. Wallace believes that the
difference between the sexes is due not so much to the males having
been modified, as to the females having in all or almost all cases
acquired dull colours for the sake of protection. It seems to me, on
the contrary, far more probable that it is the males which have been
chiefly modified through sexual selection, the females having been
comparatively little changed. We can thus understand how it is that the
females of allied species generally resemble one another so much more
closely than do the males. They thus shew us approximately the
primordial colouring of the parent-species of the group to which they
belong. They have, however, almost always been somewhat modified by the
transfer to them of some of the successive variations, through the
accumulation of which the males were rendered beautiful. But I do not
wish to deny that the females alone of some species may have been
specially modified for protection. In most cases the males and females
of distinct species will have been exposed during their prolonged
larval state to different conditions, and may have been thus affected;
though with the males any slight change of colour thus caused will
generally have been masked by the brilliant tints gained through sexual
selection. When we treat of Birds, I shall have to discuss the whole
question, as to how far the differences in colour between the sexes are
due to the males having been modified through sexual selection for
ornamental purposes, or to the females having been modified through
natural selection for the sake of protection, so that I will here say
but little on the subject.

In all the cases in which the more common form of equal inheritance by
both sexes has prevailed, the selection of bright-coloured males would
tend to make the females bright-coloured; and the selection of
dull-coloured females would tend to make the males dull. If both
processes were carried on simultaneously, they would tend to counteract
each other; and the final result would depend on whether a greater
number of females from being well protected by obscure colours, or a
greater number of males by being brightly-coloured and thus finding
partners, succeeded in leaving more numerous offspring.

In order to account for the frequent transmission of characters to one
sex alone, Mr. Wallace expresses his belief that the more common form
of equal inheritance by both sexes can be changed through natural
selection into inheritance by one sex alone, but in favour of this view
I can discover no evidence. We know from what occurs under
domestication that new characters often appear, which from the first
are transmitted to one sex alone; and by the selection of such
variations there would not be the slightest difficulty in giving bright
colours to the males alone, and at the same time or subsequently, dull
colours to the females alone. In this manner the females of some
butterflies and moths have, it is probable, been rendered inconspicuous
for the sake of protection, and widely different from their males.

I am, however, unwilling without distinct evidence to admit that two
complex processes of selection, each requiring the transference of new
characters to one sex alone, have been carried on with a multitude of
species,—that the males have been rendered more brilliant by beating
their rivals, and the females more dull-coloured by having escaped from
their enemies. The male, for instance, of the common brimstone
butterfly (Gonepteryx), is of a far more intense yellow than the
female, though she is equally conspicuous; and it does not seem
probable that she specially acquired her pale tints as a protection,
though it is probable that the male acquired his bright colours as a
sexual attraction. The female of Anthocharis cardamines does not
possess the beautiful orange wing-tips of the male; consequently she
closely resembles the white butterflies (Pieris) so common in our
gardens; but we have no evidence that this resemblance is beneficial to
her. As, on the other hand, she resembles both sexes of several other
species of the genus inhabiting various quarters of the world, it is
probable that she has simply retained to a large extent her primordial
colours.

Finally, as we have seen, various considerations lead to the conclusion
that with the greater number of brilliantly-coloured Lepidoptera it is
the male which has been chiefly modified through sexual selection; the
amount of difference between the sexes mostly depending on the form of
inheritance which has prevailed. Inheritance is governed by so many
unknown laws or conditions, that it seems to us to act in a capricious
manner (28. The ‘Variation of Animals and Plants under Domestication,’
vol. ii. chap. xii. p. 17.); and we can thus, to a certain extent,
understand how it is that with closely allied species the sexes either
differ to an astonishing degree, or are identical in colour. As all the
successive steps in the process of variation are necessarily
transmitted through the female, a greater or less number of such steps
might readily become developed in her; and thus we can understand the
frequent gradations from an extreme difference to none at all between
the sexes of allied species. These cases of gradation, it may be added,
are much too common to favour the supposition that we here see females
actually undergoing the process of transition and losing their
brightness for the sake of protection; for we have every reason to
conclude that at any one time the greater number of species are in a
fixed condition.

MIMICRY.

This principle was first made clear in an admirable paper by Mr. Bates
(29. ‘Transact. Linn. Soc.’ vol. xxiii. 1862, p. 495.), who thus threw
a flood of light on many obscure problems. It had previously been
observed that certain butterflies in S. America belonging to quite
distinct families, resembled the Heliconidae so closely in every stripe
and shade of colour, that they could not be distinguished save by an
experienced entomologist. As the Heliconidae are coloured in their
usual manner, whilst the others depart from the usual colouring of the
groups to which they belong, it is clear that the latter are the
imitators, and the Heliconidae the imitated. Mr. Bates further observed
that the imitating species are comparatively rare, whilst the imitated
abound, and that the two sets live mingled together. From the fact of
the Heliconidae being conspicuous and beautiful insects, yet so
numerous in individuals and species, he concluded that they must be
protected from the attacks of enemies by some secretion or odour; and
this conclusion has now been amply confirmed (30. ‘Proc. Entomological
Soc.’ Dec. 3, 1866, p. xlv.), especially by Mr. Belt. Hence Mr. Bates
inferred that the butterflies which imitate the protected species have
acquired their present marvellously deceptive appearance through
variation and natural selection, in order to be mistaken for the
protected kinds, and thus to escape being devoured. No explanation is
here attempted of the brilliant colours of the imitated, but only of
the imitating butterflies. We must account for the colours of the
former in the same general manner, as in the cases previously discussed
in this chapter. Since the publication of Mr. Bates’ paper, similar and
equally striking facts have been observed by Mr. Wallace in the Malayan
region, by Mr. Trimen in South Africa, and by Mr. Riley in the United
States. (31. Wallace, ‘Transact. Linn. Soc.’ vol. xxv. 1865 p. i.;
also, ‘Transact. Ent. Soc.’ vol. iv. (3rd series), 1867, p. 301.
Trimen, ‘Linn. Transact.’ vol. xxvi. 1869, p. 497. Riley, ‘Third Annual
Report on the Noxious Insects of Missouri,’ 1871, pp. 163-168. This
latter essay is valuable, as Mr. Riley here discusses all the
objections which have been raised against Mr. Bates’s theory.)

As some writers have felt much difficulty in understanding how the
first steps in the process of mimicry could have been effected through
natural selection, it may be well to remark that the process probably
commenced long ago between forms not widely dissimilar in colour. In
this case even a slight variation would be beneficial, if it rendered
the one species more like the other; and afterwards the imitated
species might be modified to an extreme degree through sexual selection
or other means, and if the changes were gradual, the imitators might
easily be led along the same track, until they differed to an equally
extreme degree from their original condition; and they would thus
ultimately assume an appearance or colouring wholly unlike that of the
other members of the group to which they belonged. It should also be
remembered that many species of Lepidoptera are liable to considerable
and abrupt variations in colour. A few instances have been given in
this chapter; and many more may be found in the papers of Mr. Bates and
Mr. Wallace.

With several species the sexes are alike, and imitate the two sexes of
another species. But Mr. Trimen gives, in the paper already referred
to, three cases in which the sexes of the imitated form differ from
each other in colour, and the sexes of the imitating form differ in a
like manner. Several cases have also been recorded where the females
alone imitate brilliantly-coloured and protected species, the males
retaining “the normal aspect of their immediate congeners.” It is here
obvious that the successive variations by which the female has been
modified have been transmitted to her alone. It is, however, probable
that some of the many successive variations would have been transmitted
to, and developed in, the males had not such males been eliminated by
being thus rendered less attractive to the females; so that only those
variations were preserved which were from the first strictly limited in
their transmission to the female sex. We have a partial illustration of
these remarks in a statement by Mr. Belt (32. ‘The Naturalist in
Nicaragua,’ 1874, p. 385.); that the males of some of the Leptalides,
which imitate protected species, still retain in a concealed manner
some of their original characters. Thus in the males “the upper half of
the lower wing is of a pure white, whilst all the rest of the wings is
barred and spotted with black, red and yellow, like the species they
mimic. The females have not this white patch, and the males usually
conceal it by covering it with the upper wing, so that I cannot imagine
its being of any other use to them than as an attraction in courtship,
when they exhibit it to the females, and thus gratify their deep-seated
preference for the normal colour of the Order to which the Leptalides
belong.”

BRIGHT COLOURS OF CATERPILLARS.

Whilst reflecting on the beauty of many butterflies, it occurred to me
that some caterpillars were splendidly coloured; and as sexual
selection could not possibly have here acted, it appeared rash to
attribute the beauty of the mature insect to this agency, unless the
bright colours of their larvae could be somehow explained. In the first
place, it may be observed that the colours of caterpillars do not stand
in any close correlation with those of the mature insect. Secondly,
their bright colours do not serve in any ordinary manner as a
protection. Mr. Bates informs me, as an instance of this, that the most
conspicuous caterpillar which he ever beheld (that of a Sphinx) lived
on the large green leaves of a tree on the open llanos of South
America; it was about four inches in length, transversely banded with
black and yellow, and with its head, legs, and tail of a bright red.
Hence it caught the eye of any one who passed by, even at the distance
of many yards, and no doubt that of every passing bird.

I then applied to Mr. Wallace, who has an innate genius for solving
difficulties. After some consideration he replied: “Most caterpillars
require protection, as may be inferred from some kinds being furnished
with spines or irritating hairs, and from many being coloured green
like the leaves on which they feed, or being curiously like the twigs
of the trees on which they live.” Another instance of protection,
furnished me by Mr. J. Mansel Weale, may be added, namely, that there
is a caterpillar of a moth which lives on the mimosas in South Africa,
and fabricates for itself a case quite indistinguishable from the
surrounding thorns. From such considerations Mr. Wallace thought it
probable that conspicuously coloured caterpillars were protected by
having a nauseous taste; but as their skin is extremely tender, and as
their intestines readily protrude from a wound, a slight peck from the
beak of a bird would be as fatal to them as if they had been devoured.
Hence, as Mr. Wallace remarks, “distastefulness alone would be
insufficient to protect a caterpillar unless some outward sign
indicated to its would-be destroyer that its prey was a disgusting
morsel.” Under these circumstances it would be highly advantageous to a
caterpillar to be instantaneously and certainly recognised as
unpalatable by all birds and other animals. Thus the most gaudy colours
would be serviceable, and might have been gained by variation and the
survival of the most easily-recognised individuals.

This hypothesis appears at first sight very bold, but when it was
brought before the Entomological Society (33. ‘Proceedings,
Entomological Society,’ Dec. 3, 1866, p. xlv. and March 4, 1867, p.
lxxx.) it was supported by various statements; and Mr. J. Jenner Weir,
who keeps a large number of birds in an aviary, informs me that he has
made many trials, and finds no exception to the rule, that all
caterpillars of nocturnal and retiring habits with smooth skins, all of
a green colour, and all which imitate twigs, are greedily devoured by
his birds. The hairy and spinose kinds are invariably rejected, as were
four conspicuously-coloured species. When the birds rejected a
caterpillar, they plainly shewed, by shaking their heads, and cleansing
their beaks, that they were disgusted by the taste. (34. See Mr. J.
Jenner Weir’s paper on Insects and Insectivorous Birds, in ‘Transact.
Ent. Soc.’ 1869, p. 21; also Mr. Butler’s paper, ibid. p. 27. Mr. Riley
has given analogous facts in the ‘Third Annual Report on the Noxious
Insects of Missouri,’ 1871, p. 148. Some opposed cases are, however,
given by Dr. Wallace and M. H. d’Orville; see ‘Zoological Record,’
1869, p. 349.) Three conspicuous kinds of caterpillars and moths were
also given to some lizards and frogs, by Mr. A. Butler, and were
rejected, though other kinds were eagerly eaten. Thus the probability
of Mr. Wallace’s view is confirmed, namely, that certain caterpillars
have been made conspicuous for their own good, so as to be easily
recognised by their enemies, on nearly the same principle that poisons
are sold in coloured bottles by druggists for the good of man. We
cannot, however, at present thus explain the elegant diversity in the
colours of many caterpillars; but any species which had at some former
period acquired a dull, mottled, or striped appearance, either in
imitation of surrounding objects, or from the direct action of climate,
etc., almost certainly would not become uniform in colour, when its
tints were rendered intense and bright; for in order to make a
caterpillar merely conspicuous, there would be no selection in any
definite direction.

A SUMMARY AND CONCLUDING REMARKS ON INSECTS.

Looking back to the several Orders, we see that the sexes often differ
in various characters, the meaning of which is not in the least
understood. The sexes, also, often differ in their organs of sense and
means of locomotion, so that the males may quickly discover and reach
the females. They differ still oftener in the males possessing
diversified contrivances for retaining the females when found. We are,
however, here concerned only in a secondary degree with sexual
differences of these kinds.

In almost all the Orders, the males of some species, even of weak and
delicate kinds, are known to be highly pugnacious; and some few are
furnished with special weapons for fighting with their rivals. But the
law of battle does not prevail nearly so widely with insects as with
the higher animals. Hence it probably arises, that it is in only a few
cases that the males have been rendered larger and stronger than the
females. On the contrary, they are usually smaller, so that they may be
developed within a shorter time, to be ready in large numbers for the
emergence of the females.

In two families of the Homoptera and in three of the Orthoptera, the
males alone possess sound-producing organs in an efficient state. These
are used incessantly during the breeding-season, not only for calling
the females, but apparently for charming or exciting them in rivalry
with other males. No one who admits the agency of selection of any
kind, will, after reading the above discussion, dispute that these
musical instruments have been acquired through sexual selection. In
four other Orders the members of one sex, or more commonly of both
sexes, are provided with organs for producing various sounds, which
apparently serve merely as call-notes. When both sexes are thus
provided, the individuals which were able to make the loudest or most
continuous noise would gain partners before those which were less
noisy, so that their organs have probably been gained through sexual
selection. It is instructive to reflect on the wonderful diversity of
the means for producing sound, possessed by the males alone, or by both
sexes, in no less than six Orders. We thus learn how effectual sexual
selection has been in leading to modifications which sometimes, as with
the Homoptera, relate to important parts of the organisation.

From the reasons assigned in the last chapter, it is probable that the
great horns possessed by the males of many Lamellicorn, and some other
beetles, have been acquired as ornaments. From the small size of
insects, we are apt to undervalue their appearance. If we could imagine
a male Chalcosoma (Fig. 16), with its polished bronzed coat of mail,
and its vast complex horns, magnified to the size of a horse, or even
of a dog, it would be one of the most imposing animals in the world.

The colouring of insects is a complex and obscure subject. When the
male differs slightly from the female, and neither are
brilliantly-coloured, it is probable that the sexes have varied in a
slightly different manner, and that the variations have been
transmitted by each sex to the same without any benefit or evil thus
accruing. When the male is brilliantly-coloured and differs
conspicuously from the female, as with some dragon-flies and many
butterflies, it is probable that he owes his colours to sexual
selection; whilst the female has retained a primordial or very ancient
type of colouring, slightly modified by the agencies before explained.
But in some cases the female has apparently been made obscure by
variations transmitted to her alone, as a means of direct protection;
and it is almost certain that she has sometimes been made brilliant, so
as to imitate other protected species inhabiting the same district.
When the sexes resemble each other and both are obscurely coloured,
there is no doubt that they have been in a multitude of cases so
coloured for the sake of protection. So it is in some instances when
both are brightly-coloured, for they thus imitate protected species, or
resemble surrounding objects such as flowers; or they give notice to
their enemies that they are unpalatable. In other cases in which the
sexes resemble each other and are both brilliant, especially when the
colours are arranged for display, we may conclude that they have been
gained by the male sex as an attraction, and have been transferred to
the female. We are more especially led to this conclusion whenever the
same type of coloration prevails throughout a whole group, and we find
that the males of some species differ widely in colour from the
females, whilst others differ slightly or not at all with intermediate
gradations connecting these extreme states.

In the same manner as bright colours have often been partially
transferred from the males to the females, so it has been with the
extraordinary horns of many Lamellicorn and some other beetles. So
again, the sound-producing organs proper to the males of the Homoptera
and Orthoptera have generally been transferred in a rudimentary, or
even in a nearly perfect condition, to the females; yet not
sufficiently perfect to be of any use. It is also an interesting fact,
as bearing on sexual selection, that the stridulating organs of certain
male Orthoptera are not fully developed until the last moult; and that
the colours of certain male dragon-flies are not fully developed until
some little time after their emergence from the pupal state, and when
they are ready to breed.

Sexual selection implies that the more attractive individuals are
preferred by the opposite sex; and as with insects, when the sexes
differ, it is the male which, with some rare exceptions, is the more
ornamented, and departs more from the type to which the species
belongs;—and as it is the male which searches eagerly for the female,
we must suppose that the females habitually or occasionally prefer the
more beautiful males, and that these have thus acquired their beauty.
That the females in most or all the Orders would have the power of
rejecting any particular male, is probable from the many singular
contrivances possessed by the males, such as great jaws, adhesive
cushions, spines, elongated legs, etc., for seizing the female; for
these contrivances show that there is some difficulty in the act, so
that her concurrence would seem necessary. Judging from what we know of
the perceptive powers and affections of various insects, there is no
antecedent improbability in sexual selection having come largely into
play; but we have as yet no direct evidence on this head, and some
facts are opposed to the belief. Nevertheless, when we see many males
pursuing the same female, we can hardly believe that the pairing is
left to blind chance—that the female exerts no choice, and is not
influenced by the gorgeous colours or other ornaments with which the
male is decorated.

If we admit that the females of the Homoptera and Orthoptera appreciate
the musical tones of their male partners, and that the various
instruments have been perfected through sexual selection, there is
little improbability in the females of other insects appreciating
beauty in form or colour, and consequently in such characters having
been thus gained by the males. But from the circumstance of colour
being so variable, and from its having been so often modified for the
sake of protection, it is difficult to decide in how large a proportion
of cases sexual selection has played a part. This is more especially
difficult in those Orders, such as Orthoptera, Hymenoptera, and
Coleoptera, in which the two sexes rarely differ much in colour; for we
are then left to mere analogy. With the Coleoptera, however, as before
remarked, it is in the great Lamellicorn group, placed by some authors
at the head of the Order, and in which we sometimes see a mutual
attachment between the sexes, that we find the males of some species
possessing weapons for sexual strife, others furnished with wonderful
horns, many with stridulating organs, and others ornamented with
splendid metallic tints. Hence it seems probable that all these
characters have been gained through the same means, namely sexual
selection. With butterflies we have the best evidence, as the males
sometimes take pains to display their beautiful colours; and we cannot
believe that they would act thus, unless the display was of use to them
in their courtship.

When we treat of Birds, we shall see that they present in their
secondary sexual characters the closest analogy with insects. Thus,
many male birds are highly pugnacious, and some are furnished with
special weapons for fighting with their rivals. They possess organs
which are used during the breeding-season for producing vocal and
instrumental music. They are frequently ornamented with combs, horns,
wattles and plumes of the most diversified kinds, and are decorated
with beautiful colours, all evidently for the sake of display. We shall
find that, as with insects, both sexes in certain groups are equally
beautiful, and are equally provided with ornaments which are usually
confined to the male sex. In other groups both sexes are equally
plain-coloured and unornamented. Lastly, in some few anomalous cases,
the females are more beautiful than the males. We shall often find, in
the same group of birds, every gradation from no difference between the
sexes, to an extreme difference. We shall see that female birds, like
female insects, often possess more or less plain traces or rudiments of
characters which properly belong to the males and are of use only to
them. The analogy, indeed, in all these respects between birds and
insects is curiously close. Whatever explanation applies to the one
class probably applies to the other; and this explanation, as we shall
hereafter attempt to shew in further detail, is sexual selection.




CHAPTER XII.
SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, AND REPTILES.


FISHES: Courtship and battles of the males—Larger size of the
females—Males, bright colours and ornamental appendages; other strange
characters—Colours and appendages acquired by the males during the
breeding-season alone—Fishes with both sexes brilliantly
coloured—Protective colours—The less conspicuous colours of the female
cannot be accounted for on the principle of protection—Male fishes
building nests, and taking charge of the ova and young.

AMPHIBIANS: Differences in structure and colour between the sexes—Vocal
organs.

REPTILES: Chelonians—Crocodiles—Snakes, colours in some cases
protective—Lizards, battles of—Ornamental appendages—Strange
differences in structure between the sexes—Colours—Sexual differences
almost as great as with birds.

We have now arrived at the great sub-kingdom of the Vertebrata, and
will commence with the lowest class, that of fishes. The males of
Plagiostomous fishes (sharks, rays) and of Chimaeroid fishes are
provided with claspers which serve to retain the female, like the
various structures possessed by many of the lower animals. Besides the
claspers, the males of many rays have clusters of strong sharp spines
on their heads, and several rows along “the upper outer surface of
their pectoral fins.” These are present in the males of some species,
which have other parts of their bodies smooth. They are only
temporarily developed during the breeding-season; and Dr. Gunther
suspects that they are brought into action as prehensile organs by the
doubling inwards and downwards of the two sides of the body. It is a
remarkable fact that the females and not the males of some species, as
of Raia clavata, have their backs studded with large hook-formed
spines. (1. Yarrell’s ‘Hist. of British Fishes,’ vol. ii. 1836, pp 417,
425, 436. Dr. Gunther informs me that the spines in R. clavata are
peculiar to the female.)

The males alone of the capelin (Mallotus villosus, one of Salmonidae),
are provided with a ridge of closely-set, brush-like scales, by the aid
of which two males, one on each side, hold the female, whilst she runs
with great swiftness on the sandy beach, and there deposits her spawn.
(2. The ‘American Naturalist,’ April 1871, p. 119.) The widely distinct
Monacanthus scopas presents a somewhat analogous structure. The male,
as Dr. Gunther informs me, has a cluster of stiff, straight spines,
like those of a comb, on the sides of the tail; and these in a specimen
six inches long were nearly one and a half inches in length; the female
has in the same place a cluster of bristles, which may be compared with
those of a tooth-brush. In another species, M. peronii, the male has a
brush like that possessed by the female of the last species, whilst the
sides of the tail in the female are smooth. In some other species of
the same genus the tail can be perceived to be a little roughened in
the male and perfectly smooth in the female; and lastly in others, both
sexes have smooth sides.

The males of many fish fight for the possession of the females. Thus
the male stickleback (Gasterosteus leiurus) has been described as “mad
with delight,” when the female comes out of her hiding-place and
surveys the nest which he has made for her. “He darts round her in
every direction, then to his accumulated materials for the nest, then
back again in an instant; and as she does not advance he endeavours to
push her with his snout, and then tries to pull her by the tail and
side-spine to the nest.” (3. See Mr. R. Warington’s interesting
articles in ‘Annals and Magazine of Natural History,’ October 1852, and
November 1855.) The males are said to be polygamists (4. Noel
Humphreys, ‘River Gardens,’ 1857.); they are extraordinarily bold and
pugnacious, whilst “the females are quite pacific.” Their battles are
at times desperate; “for these puny combatants fasten tight on each
other for several seconds, tumbling over and over again until their
strength appears completely exhausted.” With the rough-tailed
stickleback (G. trachurus) the males whilst fighting swim round and
round each other, biting and endeavouring to pierce each other with
their raised lateral spines. The same writer adds (5. Loudon’s
‘Magazine of Natural History,’ vol. iii. 1830, p. 331.), “the bite of
these little furies is very severe. They also use their lateral spines
with such fatal effect, that I have seen one during a battle absolutely
rip his opponent quite open, so that he sank to the bottom and died.”
When a fish is conquered, “his gallant bearing forsakes him; his gay
colours fade away; and he hides his disgrace among his peaceable
companions, but is for some time the constant object of his conqueror’s
persecution.”

The male salmon is as pugnacious as the little stickleback; and so is
the male trout, as I hear from Dr. Gunther. Mr. Shaw saw a violent
contest between two male salmon which lasted the whole day; and Mr. R.
Buist, Superintendent of Fisheries, informs me that he has often
watched from the bridge at Perth the males driving away their rivals,
whilst the females were spawning. The males “are constantly fighting
and tearing each other on the spawning-beds, and many so injure each
other as to cause the death of numbers, many being seen swimming near
the banks of the river in a state of exhaustion, and apparently in a
dying state.” (6. The ‘Field,’ June 29, 1867. For Mr. Shaw’s Statement,
see ‘Edinburgh Review,’ 1843. Another experienced observer (Scrope’s
‘Days of Salmon Fishing,’ p. 60) remarks that like the stag, the male
would, if he could, keep all other males away.) Mr. Buist informs me,
that in June 1868, the keeper of the Stormontfield breeding-ponds
visited the northern Tyne and found about 300 dead salmon, all of which
with one exception were males; and he was convinced that they had lost
their lives by fighting.

[Fig. 27. Head of male common salmon (Salmo salar) during the
breeding-season. [This drawing, as well as all the others in the
present chapter, have been executed by the well-known artist, Mr. G.
Ford, from specimens in the British Museum, under the kind
superintendence of Dr. Gunther.]

Fig. 28. Head of female salmon.]

The most curious point about the male salmon is that during the
breeding-season, besides a slight change in colour, “the lower jaw
elongates, and a cartilaginous projection turns upwards from the point,
which, when the jaws are closed, occupies a deep cavity between the
intermaxillary bones of the upper jaw.” (7. Yarrell, ‘History of
British Fishes,’ vol. ii. 1836, p. 10.) (Figs. 27 and 28.) In our
salmon this change of structure lasts only during the breeding-season;
but in the Salmo lycaodon of N.W. America the change, as Mr. J.K. Lord
(8. ‘The Naturalist in Vancouver’s Island,’ vol. i. 1866, p. 54.)
believes, is permanent, and best marked in the older males which have
previously ascended the rivers. In these old males the jaw becomes
developed into an immense hook-like projection, and the teeth grow into
regular fangs, often more than half an inch in length. With the
European salmon, according to Mr. Lloyd (9. ‘Scandinavian Adventures,’
vol. i. 1854, pp. 100, 104.), the temporary hook-like structure serves
to strengthen and protect the jaws, when one male charges another with
wonderful violence; but the greatly developed teeth of the male
American salmon may be compared with the tusks of many male mammals,
and they indicate an offensive rather than a protective purpose.

The salmon is not the only fish in which the teeth differ in the two
sexes; as this is the case with many rays. In the thornback (Raia
clavata) the adult male has sharp, pointed teeth, directed backwards,
whilst those of the female are broad and flat, and form a pavement; so
that these teeth differ in the two sexes of the same species more than
is usual in distinct genera of the same family. The teeth of the male
become sharp only when he is adult: whilst young they are broad and
flat like those of the female. As so frequently occurs with secondary
sexual characters, both sexes of some species of rays (for instance R.
batis), when adult, possess sharp pointed teeth; and here a character,
proper to and primarily gained by the male, appears to have been
transmitted to the offspring of both sexes. The teeth are likewise
pointed in both sexes of R. maculata, but only when quite adult; the
males acquiring them at an earlier age than the females. We shall
hereafter meet with analogous cases in certain birds, in which the male
acquires the plumage common to both sexes when adult, at a somewhat
earlier age than does the female. With other species of rays the males
even when old never possess sharp teeth, and consequently the adults of
both sexes are provided with broad, flat teeth like those of the young,
and like those of the mature females of the above-mentioned species.
(10. See Yarrell’s account of the rays in his ‘History of British
Fishes,’ vol. ii. 1836, p. 416, with an excellent figure, and pp. 422,
432.) As the rays are bold, strong and voracious fish, we may suspect
that the males require their sharp teeth for fighting with their
rivals; but as they possess many parts modified and adapted for the
prehension of the female, it is possible that their teeth may be used
for this purpose.

In regard to size, M. Carbonnier (11. As quoted in ‘The Farmer,’ 1868,
p. 369.) maintains that the female of almost all fishes is larger than
the male; and Dr. Gunther does not know of a single instance in which
the male is actually larger than the female. With some Cyprinodonts the
male is not even half as large. As in many kinds of fishes the males
habitually fight together, it is surprising that they have not
generally become larger and stronger than the females through the
effects of sexual selection. The males suffer from their small size,
for according to M. Carbonnier, they are liable to be devoured by the
females of their own species when carnivorous, and no doubt by other
species. Increased size must be in some manner of more importance to
the females, than strength and size are to the males for fighting with
other males; and this perhaps is to allow of the production of a vast
number of ova.

[Fig. 29. Callionymus lyra. Upper figure, male; lower figure, female.
N.B. The lower figure is more reduced than the upper.]

In many species the male alone is ornamented with bright colours; or
these are much brighter in the male than the female. The male, also, is
sometimes provided with appendages which appear to be of no more use to
him for the ordinary purposes of life, than are the tail feathers to
the peacock. I am indebted for most of the following facts to the
kindness of Dr. Gunther. There is reason to suspect that many tropical
fishes differ sexually in colour and structure; and there are some
striking cases with our British fishes. The male Callionymus lyra has
been called the gemmeous dragonet “from its brilliant gem-like
colours.” When fresh caught from the sea the body is yellow of various
shades, striped and spotted with vivid blue on the head; the dorsal
fins are pale brown with dark longitudinal bands; the ventral, caudal,
and anal fins being bluish-black. The female, or sordid dragonet, was
considered by Linnaeus, and by many subsequent naturalists, as a
distinct species; it is of a dingy reddish-brown, with the dorsal fin
brown and the other fins white. The sexes differ also in the
proportional size of the head and mouth, and in the position of the
eyes (12. I have drawn up this description from Yarrell’s ‘British
Fishes,’ vol. i. 1836, pp. 261 and 266.); but the most striking
difference is the extraordinary elongation in the male (Fig. 29) of the
dorsal fin. Mr. W. Saville Kent remarks that this “singular appendage
appears from my observations of the species in confinement, to be
subservient to the same end as the wattles, crests, and other abnormal
adjuncts of the male in gallinaceous birds, for the purpose of
fascinating their mates.” (13. ‘Nature,’ July 1873, p. 264.) The young
males resemble the adult females in structure and colour. Throughout
the genus Callionymus (14. ‘Catalogue of Acanth. Fishes in the British
Museum,’ by Dr. Gunther, 1861, pp. 138-151.), the male is generally
much more brightly spotted than the female, and in several species, not
only the dorsal, but the anal fin is much elongated in the males.

The male of the Cottus scorpius, or sea-scorpion, is slenderer and
smaller than the female. There is also a great difference in colour
between them. It is difficult, as Mr. Lloyd (15. ‘Game Birds of
Sweden,’ etc., 1867, p. 466.) remarks, “for any one, who has not seen
this fish during the spawning-season, when its hues are brightest, to
conceive the admixture of brilliant colours with which it, in other
respects so ill-favoured, is at that time adorned.” Both sexes of the
Labrus mixtus, although very different in colour, are beautiful; the
male being orange with bright blue stripes, and the female bright red
with some black spots on the back.

[Fig. 30. Xiphophorus Hellerii. Upper figure, male; lower figure,
female.]

In the very distinct family of the Cyprinodontidae—inhabitants of the
fresh waters of foreign lands—the sexes sometimes differ much in
various characters. In the male of the Mollienesia petenensis (16. With
respect to this and the following species I am indebted to Dr. Gunther
for information: see also his paper on the ‘Fishes of Central America,’
in ‘Transact. Zoological Soc.’ vol. vi. 1868, p. 485.), the dorsal fin
is greatly developed and is marked with a row of large, round,
ocellated, bright-coloured spots; whilst the same fin in the female is
smaller, of a different shape, and marked only with irregularly curved
brown spots. In the male the basal margin of the anal fin is also a
little produced and dark coloured. In the male of an allied form, the
Xiphophorus Hellerii (Fig. 30), the inferior margin of the caudal fin
is developed into a long filament, which, as I hear from Dr. Gunther,
is striped with bright colours. This filament does not contain any
muscles, and apparently cannot be of any direct use to the fish. As in
the case of the Callionymus, the males whilst young resemble the adult
females in colour and structure. Sexual differences such as these may
be strictly compared with those which are so frequent with gallinaceous
birds. (17. Dr. Gunther makes this remark; ‘Catalogue of Fishes in the
British Museum,’ vol. iii. 1861, p. 141.)

[Fig.31. Plecostomus barbatus. Upper figure, head of male; lower
figure, female.]

In a siluroid fish, inhabiting the fresh waters of South America, the
Plecostomus barbatus (18. See Dr. Gunther on this genus, in
‘Proceedings of the Zoological Society,’ 1868, p. 232.) (Fig. 31), the
male has its mouth and inter-operculum fringed with a beard of stiff
hairs, of which the female shows hardly a trace. These hairs are of the
nature of scales. In another species of the same genus, soft flexible
tentacles project from the front part of the head of the male, which
are absent in the female. These tentacles are prolongations of the true
skin, and therefore are not homologous with the stiff hairs of the
former species; but it can hardly be doubted that both serve the same
purpose. What this purpose may be, it is difficult to conjecture;
ornament does not here seem probable, but we can hardly suppose that
stiff hairs and flexible filaments can be useful in any ordinary way to
the males alone. In that strange monster, the Chimaera monstrosa, the
male has a hook-shaped bone on the top of the head, directed forwards,
with its end rounded and covered with sharp spines; in the female “this
crown is altogether absent,” but what its use may be to the male is
utterly unknown. (19. F. Buckland, in ‘Land and Water,’ July 1868, p.
377, with a figure. Many other cases could be added of structures
peculiar to the male, of which the uses are not known.)

The structures as yet referred to are permanent in the male after he
has arrived at maturity; but with some Blennies, and in another allied
genus (20. Dr. Gunther, ‘Catalogue of Fishes,’ vol. iii. pp. 221 and
240.), a crest is developed on the head of the male only during the
breeding-season, and the body at the same time becomes more
brightly-coloured. There can be little doubt that this crest serves as
a temporary sexual ornament, for the female does not exhibit a trace of
it. In other species of the same genus both sexes possess a crest, and
in at least one species neither sex is thus provided. In many of the
Chromidae, for instance in Geophagus and especially in Cichla, the
males, as I hear from Professor Agassiz (21. See also ‘A Journey in
Brazil,’ by Prof. and Mrs. Agassiz, 1868, p. 220.), have a conspicuous
protuberance on the forehead, which is wholly wanting in the females
and in the young males. Professor Agassiz adds, “I have often observed
these fishes at the time of spawning when the protuberance is largest,
and at other seasons when it is totally wanting, and the two sexes shew
no difference whatever in the outline of the profile of the head. I
never could ascertain that it subserves any special function, and the
Indians on the Amazon know nothing about its use.” These protuberances
resemble, in their periodical appearance, the fleshy carbuncles on the
heads of certain birds; but whether they serve as ornaments must remain
at present doubtful.

I hear from Professor Agassiz and Dr. Gunther, that the males of those
fishes, which differ permanently in colour from the females, often
become more brilliant during the breeding-season. This is likewise the
case with a multitude of fishes, the sexes of which are identical in
colour at all other seasons of the year. The tench, roach, and perch
may be given as instances. The male salmon at this season is “marked on
the cheeks with orange-coloured stripes, which give it the appearance
of a Labrus, and the body partakes of a golden orange tinge. The
females are dark in colour, and are commonly called black-fish.” (22.
Yarrell, ‘History of British Fishes,’ vol. ii. 1836, pp. 10, 12, 35.)
An analogous and even greater change takes place with the Salmo eriox
or bull trout; the males of the char (S. umbla) are likewise at this
season rather brighter in colour than the females. (23. W. Thompson, in
‘Annals and Magazine of Natural History,’ vol. vi. 1841, p. 440.) The
colours of the pike (Esox reticulatus) of the United States, especially
of the male, become, during the breeding-season, exceedingly intense,
brilliant, and iridescent. (24. ‘The American Agriculturalist,’ 1868,
p. 100.) Another striking instance out of many is afforded by the male
stickleback (Gasterosteus leiurus), which is described by Mr. Warington
(25. ‘Annals and Mag. of Nat. Hist.’ Oct. 1852.), as being then
“beautiful beyond description.” The back and eyes of the female are
simply brown, and the belly white. The eyes of the male, on the other
hand, are “of the most splendid green, having a metallic lustre like
the green feathers of some humming-birds. The throat and belly are of a
bright crimson, the back of an ashy-green, and the whole fish appears
as though it were somewhat translucent and glowed with an internal
incandescence.” After the breeding season these colours all change, the
throat and belly become of a paler red, the back more green, and the
glowing tints subside.

With respect to the courtship of fishes, other cases have been observed
since the first edition of this book appeared, besides that already
given of the stickleback. Mr. W.S. Kent says that the male of the
Labrus mixtus, which, as we have seen, differs in colour from the
female, makes “a deep hollow in the sand of the tank, and then
endeavours in the most persuasive manner to induce a female of the same
species to share it with him, swimming backwards and forwards between
her and the completed nest, and plainly exhibiting the greatest anxiety
for her to follow.” The males of Cantharus lineatus become, during the
breeding-season, of deep leaden-black; they then retire from the shoal,
and excavate a hollow as a nest. “Each male now mounts vigilant guard
over his respective hollow, and vigorously attacks and drives away any
other fish of the same sex. Towards his companions of the opposite sex
his conduct is far different; many of the latter are now distended with
spawn, and these he endeavours by all the means in his power to lure
singly to his prepared hollow, and there to deposit the myriad ova with
which they are laden, which he then protects and guards with the
greatest care.” (26. ‘Nature,’ May 1873, p. 25.)

A more striking case of courtship, as well as of display, by the males
of a Chinese Macropus has been given by M. Carbonnier, who carefully
observed these fishes under confinement. (27. ‘Bulletin de la Societé
d’Acclimat.’ Paris, July 1869, and Jan. 1870.) The males are most
beautifully coloured, more so than the females. During the
breeding-season they contend for the possession of the females; and, in
the act of courtship, expand their fins, which are spotted and
ornamented with brightly coloured rays, in the same manner, according
to M. Carbonnier, as the peacock. They then also bound about the
females with much vivacity, and appear by “l’étalage de leurs vives
couleurs chercher a attirer l’attention des femelles, lesquelles ne
paraissaient indifférentes a ce manège, elles nageaient avec une molle
lenteur vers les males et semblaient se complaire dans leur voisinage.”
After the male has won his bride, he makes a little disc of froth by
blowing air and mucus out of his mouth. He then collects the fertilised
ova, dropped by the female, in his mouth; and this caused M. Carbonnier
much alarm, as he thought that they were going to be devoured. But the
male soon deposits them in the disc of froth, afterwards guarding them,
repairing the froth, and taking care of the young when hatched. I
mention these particulars because, as we shall presently see, there are
fishes, the males of which hatch their eggs in their mouths; and those
who do not believe in the principle of gradual evolution might ask how
could such a habit have originated; but the difficulty is much
diminished when we know that there are fishes which thus collect and
carry the eggs; for if delayed by any cause in depositing them, the
habit of hatching them in their mouths might have been acquired.

To return to our more immediate subject. The case stands thus: female
fishes, as far as I can learn, never willingly spawn except in the
presence of the males; and the males never fertilise the ova except in
the presence of the females. The males fight for the possession of the
females. In many species, the males whilst young resemble the females
in colour; but when adult become much more brilliant, and retain their
colours throughout life. In other species the males become brighter
than the females and otherwise more highly ornamented, only during the
season of love. The males sedulously court the females, and in one
case, as we have seen, take pains in displaying their beauty before
them. Can it be believed that they would thus act to no purpose during
their courtship? And this would be the case, unless the females exert
some choice and select those males which please or excite them most. If
the female exerts such choice, all the above facts on the ornamentation
of the males become at once intelligible by the aid of sexual
selection.

We have next to inquire whether this view of the bright colours of
certain male fishes having been acquired through sexual selection can,
through the law of the equal transmission of characters to both sexes,
be extended to those groups in which the males and females are
brilliant in the same, or nearly the same degree and manner. In such a
genus as Labrus, which includes some of the most splendid fishes in the
world—for instance, the Peacock Labrus (L. pavo), described (28. Bory
Saint Vincent, in ‘Dict. Class. d’Hist. Nat.’ tom. ix. 1826, p. 151.),
with pardonable exaggeration, as formed of polished scales of gold,
encrusting lapis-lazuli, rubies, sapphires, emeralds, and amethysts—we
may, with much probability, accept this belief; for we have seen that
the sexes in at least one species of the genus differ greatly in
colour. With some fishes, as with many of the lowest animals, splendid
colours may be the direct result of the nature of their tissues and of
the surrounding conditions, without the aid of selection of any kind.
The gold-fish (Cyprinus auratus), judging from the analogy of the
golden variety of the common carp, is perhaps a case in point, as it
may owe its splendid colours to a single abrupt variation, due to the
conditions to which this fish has been subjected under confinement. It
is, however, more probable that these colours have been intensified
through artificial selection, as this species has been carefully bred
in China from a remote period. (29. Owing to some remarks on this
subject, made in my work ‘On the Variation of Animals under
Domestication,’ Mr. W.F. Mayers (‘Chinese Notes and Queries,’ Aug.
1868, p. 123) has searched the ancient Chinese encyclopedias. He finds
that gold-fish were first reared in confinement during the Sung
Dynasty, which commenced A.D. 960. In the year 1129 these fishes
abounded. In another place it is said that since the year 1548 there
has been “produced at Hangchow a variety called the fire-fish, from its
intensely red colour. It is universally admired, and there is not a
household where it is not cultivated, IN RIVALRY AS TO ITS COLOUR, and
as a source of profit.”) Under natural conditions it does not seem
probable that beings so highly organised as fishes, and which live
under such complex relations, should become brilliantly coloured
without suffering some evil or receiving some benefit from so great a
change, and consequently without the intervention of natural selection.

What, then, are we to conclude in regard to the many fishes, both sexes
of which are splendidly coloured? Mr. Wallace (30. ‘Westminster
Review,’ July 1867, p. 7.) believes that the species which frequent
reefs, where corals and other brightly-coloured organisms abound, are
brightly coloured in order to escape detection by their enemies; but
according to my recollection they were thus rendered highly
conspicuous. In the fresh-waters of the tropics there are no
brilliantly-coloured corals or other organisms for the fishes to
resemble; yet many species in the Amazons are beautifully coloured, and
many of the carnivorous Cyprinidae in India are ornamented with “bright
longitudinal lines of various tints.” (31. ‘Indian Cyprinidae,’ by Mr.
M’Clelland, ‘Asiatic Researches,’ vol. xix. part ii. 1839, p. 230.) Mr.
M’Clelland, in describing these fishes, goes so far as to suppose that
“the peculiar brilliancy of their colours” serves as “a better mark for
king-fishers, terns, and other birds which are destined to keep the
number of these fishes in check”; but at the present day few
naturalists will admit that any animal has been made conspicuous as an
aid to its own destruction. It is possible that certain fishes may have
been rendered conspicuous in order to warn birds and beasts of prey
that they were unpalatable, as explained when treating of caterpillars;
but it is not, I believe, known that any fish, at least any fresh-water
fish, is rejected from being distasteful to fish-devouring animals. On
the whole, the most probable view in regard to the fishes, of which
both sexes are brilliantly coloured, is that their colours were
acquired by the males as a sexual ornament, and were transferred
equally, or nearly so, to the other sex.

We have now to consider whether, when the male differs in a marked
manner from the female in colour or in other ornaments, he alone has
been modified, the variations being inherited by his male offspring
alone; or whether the female has been specially modified and rendered
inconspicuous for the sake of protection, such modifications being
inherited only by the females. It is impossible to doubt that colour
has been gained by many fishes as a protection: no one can examine the
speckled upper surface of a flounder, and overlook its resemblance to
the sandy bed of the sea on which it lives. Certain fishes, moreover,
can through the action of the nervous system change their colours in
adaptation to surrounding objects, and that within a short time. (32.
G. Pouchet, ‘L’Institut.’ Nov. 1, 1871, p. 134.) One of the most
striking instances ever recorded of an animal being protected by its
colour (as far as it can be judged of in preserved specimens), as well
as by its form, is that given by Dr. Gunther (33. ‘Proc. Zoolog. Soc.’
1865, p. 327, pl. xiv. and xv.) of a pipe-fish, which, with its reddish
streaming filaments, is hardly distinguishable from the sea-weed to
which it clings with its prehensile tail. But the question now under
consideration is whether the females alone have been modified for this
object. We can see that one sex will not be modified through natural
selection for the sake of protection more than the other, supposing
both to vary, unless one sex is exposed for a longer period to danger,
or has less power of escaping from such danger than the other; and it
does not appear that with fishes the sexes differ in these respects. As
far as there is any difference, the males, from being generally smaller
and from wandering more about, are exposed to greater danger than the
females; and yet, when the sexes differ, the males are almost always
the more conspicuously coloured. The ova are fertilised immediately
after being deposited; and when this process lasts for several days, as
in the case of the salmon (34. Yarrell, ‘British Fishes,’ vol. ii. p.
11.), the female, during the whole time, is attended by the male. After
the ova are fertilised they are, in most cases, left unprotected by
both parents, so that the males and females, as far as oviposition is
concerned, are equally exposed to danger, and both are equally
important for the production of fertile ova; consequently the more or
less brightly-coloured individuals of either sex would be equally
liable to be destroyed or preserved, and both would have an equal
influence on the colours of their offspring.

Certain fishes, belonging to several families, make nests, and some of
them take care of their young when hatched. Both sexes of the bright
coloured Crenilabrus massa and melops work together in building their
nests with sea-weed, shells, etc. (35. According to the observations of
M. Gerbe; see Gunther’s ‘Record of Zoolog. Literature,’ 1865, p. 194.)
But the males of certain fishes do all the work, and afterwards take
exclusive charge of the young. This is the case with the dull-coloured
gobies (36. Cuvier, ‘Regne Animal,’ vol. ii. 1829, p. 242.), in which
the sexes are not known to differ in colour, and likewise with the
sticklebacks (Gasterosteus), in which the males become brilliantly
coloured during the spawning season. The male of the smooth-tailed
stickleback (G. leiurus) performs the duties of a nurse with exemplary
care and vigilance during a long time, and is continually employed in
gently leading back the young to the nest, when they stray too far. He
courageously drives away all enemies including the females of his own
species. It would indeed be no small relief to the male, if the female,
after depositing her eggs, were immediately devoured by some enemy, for
he is forced incessantly to drive her from the nest. (37. See Mr.
Warington’s most interesting description of the habits of the
Gasterosteus leiurus in ‘Annals and Magazine of Nat. History,’ November
1855.)

The males of certain other fishes inhabiting South America and Ceylon,
belonging to two distinct Orders, have the extraordinary habit of
hatching within their mouths, or branchial cavities, the eggs laid by
the females. (38. Prof. Wyman, in ‘Proc. Boston Soc. of Nat. Hist.’
Sept. 15, 1857. Also Prof. Turner, in ‘Journal of Anatomy and
Physiology,’ Nov. 1, 1866, p. 78. Dr. Gunther has likewise described
other cases.) I am informed by Professor Agassiz that the males of the
Amazonian species which follow this habit, “not only are generally
brighter than the females, but the difference is greater at the
spawning-season than at any other time.” The species of Geophagus act
in the same manner; and in this genus, a conspicuous protuberance
becomes developed on the forehead of the males during the
breeding-season. With the various species of Chromids, as Professor
Agassiz likewise informs me, sexual differences in colour may be
observed, “whether they lay their eggs in the water among aquatic
plants, or deposit them in holes, leaving them to come out without
further care, or build shallow nests in the river mud, over which they
sit, as our Pomotis does. It ought also to be observed that these
sitters are among the brightest species in their respective families;
for instance, Hygrogonus is bright green, with large black ocelli,
encircled with the most brilliant red.” Whether with all the species of
Chromids it is the male alone which sits on the eggs is not known. It
is, however, manifest that the fact of the eggs being protected or
unprotected by the parents, has had little or no influence on the
differences in colour between the sexes. It is further manifest, in all
the cases in which the males take exclusive charge of the nests and
young, that the destruction of the brighter-coloured males would be far
more influential on the character of the race, than the destruction of
the brighter-coloured females; for the death of the male during the
period of incubation or nursing would entail the death of the young, so
that they could not inherit his peculiarities; yet, in many of these
very cases the males are more conspicuously coloured than the females.

In most of the Lophobranchii (Pipe-fish, Hippocampi, etc.) the males
have either marsupial sacks or hemispherical depressions on the
abdomen, in which the ova laid by the female are hatched. The males
also shew great attachment to their young. (39. Yarrell, ‘History of
British Fishes,’ vol. ii. 1836, pp. 329, 338.) The sexes do not
commonly differ much in colour; but Dr. Gunther believes that the male
Hippocampi are rather brighter than the females. The genus Solenostoma,
however, offers a curious exceptional case (40. Dr. Gunther, since
publishing an account of this species in ‘The Fishes of Zanzibar,’ by
Col. Playfair, 1866, p. 137, has re-examined the specimens, and has
given me the above information.), for the female is much more
vividly-coloured and spotted than the male, and she alone has a
marsupial sack and hatches the eggs; so that the female of Solenostoma
differs from all the other Lophobranchii in this latter respect, and
from almost all other fishes, in being more brightly-coloured than the
male. It is improbable that this remarkable double inversion of
character in the female should be an accidental coincidence. As the
males of several fishes, which take exclusive charge of the eggs and
young, are more brightly coloured than the females, and as here the
female Solenostoma takes the same charge and is brighter than the male,
it might be argued that the conspicuous colours of that sex which is
the more important of the two for the welfare of the offspring, must be
in some manner protective. But from the large number of fishes, of
which the males are either permanently or periodically brighter than
the females, but whose life is not at all more important for the
welfare of the species than that of the female, this view can hardly be
maintained. When we treat of birds we shall meet with analogous cases,
where there has been a complete inversion of the usual attributes of
the two sexes, and we shall then give what appears to be the probable
explanation, namely, that the males have selected the more attractive
females, instead of the latter having selected, in accordance with the
usual rule throughout the animal kingdom, the more attractive males.

On the whole we may conclude, that with most fishes, in which the sexes
differ in colour or in other ornamental characters, the males
originally varied, with their variations transmitted to the same sex,
and accumulated through sexual selection by attracting or exciting the
females. In many cases, however, such characters have been transferred,
either partially or completely, to the females. In other cases, again,
both sexes have been coloured alike for the sake of protection; but in
no instance does it appear that the female alone has had her colours or
other characters specially modified for this latter purpose.

The last point which need be noticed is that fishes are known to make
various noises, some of which are described as being musical. Dr.
Dufosse, who has especially attended to this subject, says that the
sounds are voluntarily produced in several ways by different fishes: by
the friction of the pharyngeal bones—by the vibration of certain
muscles attached to the swim bladder, which serves as a resounding
board—and by the vibration of the intrinsic muscles of the swim
bladder. By this latter means the Trigla produces pure and long-drawn
sounds which range over nearly an octave. But the most interesting case
for us is that of two species of Ophidium, in which the males alone are
provided with a sound-producing apparatus, consisting of small movable
bones, with proper muscles, in connection with the swim bladder. (41.
‘Comptes-Rendus,’ tom. xlvi. 1858, p. 353; tom. xlvii. 1858, p. 916;
tom. liv. 1862, p. 393. The noise made by the Umbrinas (Sciaena
aquila), is said by some authors to be more like that of a flute or
organ, than drumming: Dr. Zouteveen, in the Dutch translation of this
work (vol. ii. p. 36), gives some further particulars on the sounds
made by fishes.) The drumming of the Umbrinas in the European seas is
said to be audible from a depth of twenty fathoms; and the fishermen of
Rochelle assert “that the males alone make the noise during the
spawning-time; and that it is possible by imitating it, to take them
without bait.” (42. The Rev. C. Kingsley, in ‘Nature,’ May 1870, p.
40.) From this statement, and more especially from the case of
Ophidium, it is almost certain that in this, the lowest class of the
Vertebrata, as with so many insects and spiders, sound-producing
instruments have, at least in some cases, been developed through sexual
selection, as a means for bringing the sexes together.

AMPHIBIANS.
URODELA.

[Fig. 32. Triton cristatus (half natural size, from Bell’s ‘British
Reptiles’). Upper figure, male during the breeding season; lower
figure, female.]

I will begin with the tailed amphibians. The sexes of salamanders or
newts often differ much both in colour and structure. In some species
prehensile claws are developed on the fore-legs of the males during the
breeding-season: and at this season in the male Triton palmipes the
hind-feet are provided with a swimming-web, which is almost completely
absorbed during the winter; so that their feet then resemble those of
the female. (43. Bell, ‘History of British Reptiles,’ 2nd ed., 1849,
pp. 156-159.) This structure no doubt aids the male in his eager search
and pursuit of the female. Whilst courting her he rapidly vibrates the
end of his tail. With our common newts (Triton punctatus and cristatus)
a deep, much indented crest is developed along the back and tail of the
male during the breeding-season, which disappears during the winter.
Mr. St. George Mivart informs me that it is not furnished with muscles,
and therefore cannot be used for locomotion. As during the season of
courtship it becomes edged with bright colours, there can hardly be a
doubt that it is a masculine ornament. In many species the body
presents strongly contrasted, though lurid tints, and these become more
vivid during the breeding-season. The male, for instance, of our common
little newt (Triton punctatus) is “brownish-grey above, passing into
yellow beneath, which in the spring becomes a rich bright orange,
marked everywhere with round dark spots.” The edge of the crest also is
then tipped with bright red or violet. The female is usually of a
yellowish-brown colour with scattered brown dots, and the lower surface
is often quite plain. (44. Bell, ‘History of British Reptiles,’ 2nd
ed., 1849, pp. 146, 151.) The young are obscurely tinted. The ova are
fertilised during the act of deposition, and are not subsequently
tended by either parent. We may therefore conclude that the males have
acquired their strongly-marked colours and ornamental appendages
through sexual selection; these being transmitted either to the male
offspring alone, or to both sexes.

ANURA OR BATRACHIA.

With many frogs and toads the colours evidently serve as a protection,
such as the bright green tints of tree frogs and the obscure mottled
shades of many terrestrial species. The most conspicuously-coloured
toad which I ever saw, the Phryniscus nigricans (45. ‘Zoology of the
Voyage of the “Beagle,”’ 1843. Bell, ibid. p. 49.), had the whole upper
surface of the body as black as ink, with the soles of the feet and
parts of the abdomen spotted with the brightest vermilion. It crawled
about the bare sandy or open grassy plains of La Plata under a
scorching sun, and could not fail to catch the eye of every passing
creature. These colours are probably beneficial by making this animal
known to all birds of prey as a nauseous mouthful.

In Nicaragua there is a little frog “dressed in a bright livery of red
and blue” which does not conceal itself like most other species, but
hops about during the daytime, and Mr. Belt says (46. ‘The Naturalist
in Nicaragua,’ 1874, p. 321.) that as soon as he saw its happy sense of
security, he felt sure that it was uneatable. After several trials he
succeeded in tempting a young duck to snatch up a young one, but it was
instantly rejected; and the duck “went about jerking its head, as if
trying to throw off some unpleasant taste.”

With respect to sexual differences of colour, Dr. Gunther does not know
of any striking instance either with frogs or toads; yet he can often
distinguish the male from the female by the tints of the former being a
little more intense. Nor does he know of any striking difference in
external structure between the sexes, excepting the prominences which
become developed during the breeding-season on the front legs of the
male, by which he is enabled to hold the female. (47. The male alone of
the Bufo sikimmensis (Dr. Anderson, ‘Proc. Zoolog. Soc.’ 1871, p. 204)
has two plate-like callosities on the thorax and certain rugosities on
the fingers, which perhaps subserve the same end as the above-mentioned
prominences.) It is surprising that these animals have not acquired
more strongly-marked sexual characters; for though cold-blooded their
passions are strong. Dr. Gunther informs me that he has several times
found an unfortunate female toad dead and smothered from having been so
closely embraced by three or four males. Frogs have been observed by
Professor Hoffman in Giessen fighting all day long during the
breeding-season, and with so much violence that one had its body ripped
open.

Frogs and toads offer one interesting sexual difference, namely, in the
musical powers possessed by the males; but to speak of music, when
applied to the discordant and overwhelming sounds emitted by male
bull-frogs and some other species, seems, according to our taste, a
singularly inappropriate expression. Nevertheless, certain frogs sing
in a decidedly pleasing manner. Near Rio Janeiro I used often to sit in
the evening to listen to a number of little Hylae, perched on blades of
grass close to the water, which sent forth sweet chirping notes in
harmony. The various sounds are emitted chiefly by the males during the
breeding-season, as in the case of the croaking of our common frog.
(48. Bell, ‘History British Reptiles,’ 1849, p. 93.) In accordance with
this fact the vocal organs of the males are more highly-developed than
those of the females. In some genera the males alone are provided with
sacs which open into the larynx. (49. J. Bishop, in ‘Todd’s Cyclopaedia
of Anatomy and Physiology,’ vol. iv. p. 1503.) For instance, in the
edible frog (Rana esculenta) “the sacs are peculiar to the males, and
become, when filled with air in the act of croaking, large globular
bladders, standing out one on each side of the head, near the corners
of the mouth.” The croak of the male is thus rendered exceedingly
powerful; whilst that of the female is only a slight groaning noise.
(50. Bell, ibid. pp. 112-114.) In the several genera of the family the
vocal organs differ considerably in structure, and their development in
all cases may be attributed to sexual selection.

REPTILES.
CHELONIA.

Tortoises and turtles do not offer well-marked sexual differences. In
some species, the tail of the male is longer than that of the female.
In some, the plastron or lower surface of the shell of the male is
slightly concave in relation to the back of the female. The male of the
mud-turtle of the United States (Chrysemys picta) has claws on its
front feet twice as long as those of the female; and these are used
when the sexes unite. (51. Mr. C.J. Maynard, ‘The American Naturalist,’
Dec. 1869, p. 555.) With the huge tortoise of the Galapagos Islands
(Testudo nigra) the males are said to grow to a larger size than the
females: during the pairing-season, and at no other time, the male
utters a hoarse bellowing noise, which can be heard at the distance of
more than a hundred yards; the female, on the other hand, never uses
her voice. (52. See my ‘Journal of Researches during the Voyage of the
“Beagle,”’ 1845, p. 384.)

With the Testudo elegans of India, it is said “that the combats of the
males may be heard at some distance, from the noise they produce in
butting against each other.” (53. Dr. Gunther, ‘Reptiles of British
India,’ 1864, p. 7.)

CROCODILIA.

The sexes apparently do not differ in colour; nor do I know that the
males fight together, though this is probable, for some kinds make a
prodigious display before the females. Bartram (54. ‘Travels through
Carolina,’ etc., 1791, p. 128.) describes the male alligator as
striving to win the female by splashing and roaring in the midst of a
lagoon, “swollen to an extent ready to burst, with its head and tail
lifted up, he springs or twirls round on the surface of the water, like
an Indian chief rehearsing his feats of war.” During the season of
love, a musky odour is emitted by the submaxillary glands of the
crocodile, and pervades their haunts. (55. Owen, ‘Anatomy of
Vertebrates,’ vol. i. 1866, p. 615.)

OPHIDIA.

Dr. Gunther informs me that the males are always smaller than the
females, and generally have longer and slenderer tails; but he knows of
no other difference in external structure. In regard to colour, be can
almost always distinguish the male from the female, by his more
strongly-pronounced tints; thus the black zigzag band on the back of
the male English viper is more distinctly defined than in the female.
The difference is much plainer in the rattle-snakes of N. America, the
male of which, as the keeper in the Zoological Gardens shewed me, can
at once be distinguished from the female by having more lurid yellow
about its whole body. In S. Africa the Bucephalus capensis presents an
analogous difference, for the female “is never so fully variegated with
yellow on the sides as the male.” (56. Sir Andrew Smith, ‘Zoology of S.
Africa: Reptilia,’ 1849, pl. x.) The male of the Indian Dipsas cynodon,
on the other hand, is blackish-brown, with the belly partly black,
whilst the female is reddish or yellowish-olive, with the belly either
uniform yellowish or marbled with black. In the Tragops dispar of the
same country the male is bright green, and the female bronze-coloured.
(57. Dr. A. Gunther, ‘Reptiles of British India,’ Ray Soc., 1864, pp.
304, 308.) No doubt the colours of some snakes are protective, as shewn
by the green tints of tree-snakes, and the various mottled shades of
the species which live in sandy places; but it is doubtful whether the
colours of many kinds, for instance of the common English snake and
viper, serve to conceal them; and this is still more doubtful with the
many foreign species which are coloured with extreme elegance. The
colours of certain species are very different in the adult and young
states. (58. Dr. Stoliczka, ‘Journal of Asiatic Society of Bengal,’
vol. xxxix, 1870, pp. 205, 211.)

During the breeding-season the anal scent-glands of snakes are in
active function (59. Owen, ‘Anatomy of Vertebrates,’ vol. i. 1866, p.
615.); and so it is with the same glands in lizards, and as we have
seen with the submaxillary glands of crocodiles. As the males of most
animals search for the females, these odoriferous glands probably serve
to excite or charm the female, rather than to guide her to the spot
where the male may be found. Male snakes, though appearing so sluggish,
are amorous; for many have been observed crowding round the same
female, and even round her dead body. They are not known to fight
together from rivalry. Their intellectual powers are higher than might
have been anticipated. In the Zoological Gardens they soon learn not to
strike at the iron bar with which their cages are cleaned; and Dr. Keen
of Philadelphia informs me that some snakes which he kept learned after
four or five times to avoid a noose, with which they were at first
easily caught. An excellent observer in Ceylon, Mr. E. Layard, saw (60.
‘Rambles in Ceylon,’ in ‘Annals and Magazine of Natural History,’ 2nd
series, vol. ix. 1852, p. 333.) a cobra thrust its head through a
narrow hole and swallow a toad. “With this encumbrance he could not
withdraw himself; finding this, he reluctantly disgorged the precious
morsel, which began to move off; this was too much for snake philosophy
to bear, and the toad was again seized, and again was the snake, after
violent efforts to escape, compelled to part with its prey. This time,
however, a lesson had been learnt, and the toad was seized by one leg,
withdrawn, and then swallowed in triumph.”

The keeper in the Zoological Gardens is positive that certain snakes,
for instance Crotalus and Python, distinguish him from all other
persons. Cobras kept together in the same cage apparently feel some
attachment towards each other. (61. Dr. Gunther, ‘Reptiles of British
India,’ 1864, p. 340.)

It does not, however, follow because snakes have some reasoning power,
strong passions and mutual affection, that they should likewise be
endowed with sufficient taste to admire brilliant colours in their
partners, so as to lead to the adornment of the species through sexual
selection. Nevertheless, it is difficult to account in any other manner
for the extreme beauty of certain species; for instance, of the
coral-snakes of S. America, which are of a rich red with black and
yellow transverse bands. I well remember how much surprise I felt at
the beauty of the first coral-snake which I saw gliding across a path
in Brazil. Snakes coloured in this peculiar manner, as Mr. Wallace
states on the authority of Dr. Gunther (62. ‘Westminster Review,’ July
1st, 1867, p. 32.), are found nowhere else in the world except in S.
America, and here no less than four genera occur. One of these, Elaps,
is venomous; a second and widely-distinct genus is doubtfully venomous,
and the two others are quite harmless. The species belonging to these
distinct genera inhabit the same districts, and are so like each other
that no one “but a naturalist would distinguish the harmless from the
poisonous kinds.” Hence, as Mr. Wallace believes, the innocuous kinds
have probably acquired their colours as a protection, on the principle
of imitation; for they would naturally be thought dangerous by their
enemies. The cause, however, of the bright colours of the venomous
Elaps remains to be explained, and this may perhaps be sexual
selection.

Snakes produce other sounds besides hissing. The deadly Echis carinata
has on its sides some oblique rows of scales of a peculiar structure
with serrated edges; and when this snake is excited these scales are
rubbed against each other, which produces “a curious prolonged, almost
hissing sound.” (63. Dr. Anderson, ‘Proc. Zoolog. Soc.’ 1871, p. 196.)
With respect to the rattling of the rattle-snake, we have at last some
definite information: for Professor Aughey states (64. The ‘American
Naturalist,’ 1873, p. 85.), that on two occasions, being himself
unseen, he watched from a little distance a rattle-snake coiled up with
head erect, which continued to rattle at short intervals for half an
hour: and at last he saw another snake approach, and when they met they
paired. Hence he is satisfied that one of the uses of the rattle is to
bring the sexes together. Unfortunately he did not ascertain whether it
was the male or the female which remained stationary and called for the
other. But it by no means follows from the above fact that the rattle
may not be of use to these snakes in other ways, as a warning to
animals which would otherwise attack them. Nor can I quite disbelieve
the several accounts which have appeared of their thus paralysing their
prey with fear. Some other snakes also make a distinct noise by rapidly
vibrating their tails against the surrounding stalks of plants; and I
have myself heard this in the case of a Trigonocephalus in S. America.

LACERTILIA.

The males of some, probably of many kinds of lizards, fight together
from rivalry. Thus the arboreal Anolis cristatellus of S. America is
extremely pugnacious: “During the spring and early part of the summer,
two adult males rarely meet without a contest. On first seeing one
another, they nod their heads up and down three or four times, and at
the same time expanding the frill or pouch beneath the throat; their
eyes glisten with rage, and after waving their tails from side to side
for a few seconds, as if to gather energy, they dart at each other
furiously, rolling over and over, and holding firmly with their teeth.
The conflict generally ends in one of the combatants losing his tail,
which is often devoured by the victor.” The male of this species is
considerably larger than the female (65. Mr. N.L. Austen kept these
animals alive for a considerable time; see ‘Land and Water,’ July 1867,
p. 9.); and this, as far as Dr. Gunther has been able to ascertain, is
the general rule with lizards of all kinds. The male alone of the
Cyrtodactylus rubidus of the Andaman Islands possesses pre-anal pores;
and these pores, judging from analogy, probably serve to emit an odour.
(66. Stoliczka, ‘Journal of the Asiatic Society of Bengal,’ vol. xxxiv.
1870, p. 166.)

[Fig.33. Sitana minor. Male with the gular pouch expanded (from
Gunther’s ‘Reptiles of India’)’]

The sexes often differ greatly in various external characters. The male
of the above-mentioned Anolis is furnished with a crest which runs
along the back and tail, and can be erected at pleasure; but of this
crest the female does not exhibit a trace. In the Indian Cophotis
ceylanica, the female has a dorsal crest, though much less developed
than in the male; and so it is, as Dr. Gunther informs me, with the
females of many Iguanas, Chameleons, and other lizards. In some
species, however, the crest is equally developed in both sexes, as in
the Iguana tuberculata. In the genus Sitana, the males alone are
furnished with a large throat pouch (Fig. 33), which can be folded up
like a fan, and is coloured blue, black, and red; but these splendid
colours are exhibited only during the pairing-season. The female does
not possess even a rudiment of this appendage. In the Anolis
cristatellus, according to Mr. Austen, the throat pouch, which is
bright red marbled with yellow, is present in the female, though in a
rudimental condition. Again, in certain other lizards, both sexes are
equally well provided with throat pouches. Here we see with species
belonging to the same group, as in so many previous cases, the same
character either confined to the males, or more largely developed in
them than in the females, or again equally developed in both sexes. The
little lizards of the genus Draco, which glide through the air on their
rib-supported parachutes, and which in the beauty of their colours
baffle description, are furnished with skinny appendages to the throat
“like the wattles of gallinaceous birds.” These become erected when the
animal is excited. They occur in both sexes, but are best developed
when the male arrives at maturity, at which age the middle appendage is
sometimes twice as long as the head. Most of the species likewise have
a low crest running along the neck; and this is much more developed in
the full-grown males than in the females or young males. (67. All the
foregoing statements and quotations, in regard to Cophotis, Sitana and
Draco, as well as the following facts in regard to Ceratophora and
Chamaeleon, are from Dr. Gunther himself, or from his magnificent work
on the ‘Reptiles of British India,’ Ray Soc., 1864, pp. 122, 130, 135.)

A Chinese species is said to live in pairs during the spring; “and if
one is caught, the other falls from the tree to the ground, and allows
itself to be captured with impunity”—I presume from despair. (68. Mr.
Swinhoe, ‘Proc. Zoolog. Soc.’ 1870, p. 240.)

[Fig. 34. Ceratophora Stoddartii. Upper figure; lower figure, female.]

There are other and much more remarkable differences between the sexes
of certain lizards. The male of Ceratophora aspera bears on the
extremity of his snout an appendage half as long as the head. It is
cylindrical, covered with scales, flexible, and apparently capable of
erection: in the female it is quite rudimental. In a second species of
the same genus a terminal scale forms a minute horn on the summit of
the flexible appendage; and in a third species (C. Stoddartii, fig. 34)
the whole appendage is converted into a horn, which is usually of a
white colour, but assumes a purplish tint when the animal is excited.
In the adult male of this latter species the horn is half an inch in
length, but it is of quite minute size in the female and in the young.
These appendages, as Dr. Gunther has remarked to me, may be compared
with the combs of gallinaceous birds, and apparently serve as
ornaments.

[Fig. 35. Chamaeleo bifurcus. Upper figure, male; lower figure, female.

Fig. 36. Chamaeleo Owenii. Upper figure, male; lower figure, female.]

In the genus Chamaeleon we come to the acme of difference between the
sexes. The upper part of the skull of the male C. bifurcus (Fig. 35),
an inhabitant of Madagascar, is produced into two great, solid, bony
projections, covered with scales like the rest of the head; and of this
wonderful modification of structure the female exhibits only a
rudiment. Again, in Chamaeleo Owenii (Fig. 36), from the West Coast of
Africa, the male bears on his snout and forehead three curious horns,
of which the female has not a trace. These horns consist of an
excrescence of bone covered with a smooth sheath, forming part of the
general integuments of the body, so that they are identical in
structure with those of a bull, goat, or other sheath-horned ruminant.
Although the three horns differ so much in appearance from the two
great prolongations of the skull in C. bifurcus, we can hardly doubt
that they serve the same general purpose in the economy of these two
animals. The first conjecture, which will occur to every one, is that
they are used by the males for fighting together; and as these animals
are very quarrelsome (69. Dr. Buchholz, ‘Monatsbericht K. Preuss.
Akad.’ Jan. 1874, p. 78.), this is probably a correct view. Mr. T.W.
Wood also informs me that he once watched two individuals of C. pumilus
fighting violently on the branch of a tree; they flung their heads
about and tried to bite each other; they then rested for a time and
afterwards continued their battle.

With many lizards the sexes differ slightly in colour, the tints and
stripes of the males being brighter and more distinctly defined than in
the females. This, for instance, is the case with the above Cophotis
and with the Acanthodactylus capensis of S. Africa. In a Cordylus of
the latter country, the male is either much redder or greener than the
female. In the Indian Calotes nigrilabris there is a still greater
difference; the lips also of the male are black, whilst those of the
female are green. In our common little viviparous lizard (Zootoca
vivipara) “the under side of the body and base of the tail in the male
are bright orange, spotted with black; in the female these parts are
pale-greyish-green without spots.” (70. Bell, ‘History of British
Reptiles,’ 2nd ed., 1849, p. 40.) We have seen that the males alone of
Sitana possess a throat-pouch; and this is splendidly tinted with blue,
black, and red. In the Proctotretus tenuis of Chile the male alone is
marked with spots of blue, green, and coppery-red. (71. For
Proctotretus, see ‘Zoology of the Voyage of the “Beagle”; Reptiles,’ by
Mr. Bell, p. 8. For the Lizards of S. Africa, see ‘Zoology of S.
Africa: Reptiles,’ by Sir Andrew Smith, pl. 25 and 39. For the Indian
Calotes, see ‘Reptiles of British India,’ by Dr. Gunther, p. 143.) In
many cases the males retain the same colours throughout the year, but
in others they become much brighter during the breeding-season; I may
give as an additional instance the Calotes maria, which at this season
has a bright red head, the rest of the body being green. (72. Gunther
in ‘Proceedings, Zoological Society,’ 1870, p. 778, with a coloured
figure.)

Both sexes of many species are beautifully coloured exactly alike; and
there is no reason to suppose that such colours are protective. No
doubt with the bright green kinds which live in the midst of
vegetation, this colour serves to conceal them; and in N. Patagonia I
saw a lizard (Proctotretus multimaculatus) which, when frightened,
flattened its body, closed its eyes, and then from its mottled tints
was hardly distinguishable from the surrounding sand. But the bright
colours with which so many lizards are ornamented, as well as their
various curious appendages, were probably acquired by the males as an
attraction, and then transmitted either to their male offspring alone,
or to both sexes. Sexual selection, indeed, seems to have played almost
as important a part with reptiles as with birds; and the less
conspicuous colours of the females in comparison with the males cannot
be accounted for, as Mr. Wallace believes to be the case with birds, by
the greater exposure of the females to danger during incubation.




CHAPTER XIII.
SECONDARY SEXUAL CHARACTERS OF BIRDS.


Sexual differences—Law of battle—Special weapons—Vocal
organs—Instrumental music—Love-antics and dances—Decorations, permanent
and seasonal—Double and single annual moults—Display of ornaments by
the males.

Secondary sexual characters are more diversified and conspicuous in
birds, though not perhaps entailing more important changes of
structure, than in any other class of animals. I shall, therefore,
treat the subject at considerable length. Male birds sometimes, though
rarely, possess special weapons for fighting with each other. They
charm the female by vocal or instrumental music of the most varied
kinds. They are ornamented by all sorts of combs, wattles,
protuberances, horns, air-distended sacks, top-knots, naked shafts,
plumes and lengthened feathers gracefully springing from all parts of
the body. The beak and naked skin about the head, and the feathers, are
often gorgeously coloured. The males sometimes pay their court by
dancing, or by fantastic antics performed either on the ground or in
the air. In one instance, at least, the male emits a musky odour, which
we may suppose serves to charm or excite the female; for that excellent
observer, Mr. Ramsay (1. ‘Ibis,’ vol. iii. (new series), 1867, p.
414.), says of the Australian musk-duck (Biziura lobata) that “the
smell which the male emits during the summer months is confined to that
sex, and in some individuals is retained throughout the year; I have
never, even in the breeding-season, shot a female which had any smell
of musk.” So powerful is this odour during the pairing-season, that it
can be detected long before the bird can be seen. (2. Gould, ‘Handbook
of the Birds of Australia,’ 1865, vol. ii. p. 383.) On the whole, birds
appear to be the most aesthetic of all animals, excepting of course
man, and they have nearly the same taste for the beautiful as we have.
This is shewn by our enjoyment of the singing of birds, and by our
women, both civilised and savage, decking their heads with borrowed
plumes, and using gems which are hardly more brilliantly coloured than
the naked skin and wattles of certain birds. In man, however, when
cultivated, the sense of beauty is manifestly a far more complex
feeling, and is associated with various intellectual ideas.

Before treating of the sexual characters with which we are here more
particularly concerned, I may just allude to certain differences
between the sexes which apparently depend on differences in their
habits of life; for such cases, though common in the lower, are rare in
the higher classes. Two humming-birds belonging to the genus
Eustephanus, which inhabit the island of Juan Fernandez, were long
thought to be specifically distinct, but are now known, as Mr. Gould
informs me, to be the male and female of the same species, and they
differ slightly in the form of the beak. In another genus of
humming-birds (Grypus), the beak of the male is serrated along the
margin and hooked at the extremity, thus differing much from that of
the female. In the Neomorpha of New Zealand, there is, as we have seen,
a still wider difference in the form of the beak in relation to the
manner of feeding of the two sexes. Something of the same kind has been
observed with the goldfinch (Carduelis elegans), for I am assured by
Mr. J. Jenner Weir that the bird-catchers can distinguish the males by
their slightly longer beaks. The flocks of males are often found
feeding on the seeds of the teazle (Dipsacus), which they can reach
with their elongated beaks, whilst the females more commonly feed on
the seeds of the betony or Scrophularia. With a slight difference of
this kind as a foundation, we can see how the beaks of the two sexes
might be made to differ greatly through natural selection. In some of
the above cases, however, it is possible that the beaks of the males
may have been first modified in relation to their contests with other
males; and that this afterwards led to slightly changed habits of life.

LAW OF BATTLE.

Almost all male birds are extremely pugnacious, using their beaks,
wings, and legs for fighting together. We see this every spring with
our robins and sparrows. The smallest of all birds, namely the
humming-bird, is one of the most quarrelsome. Mr. Gosse (3. Quoted by
Mr. Gould, ‘Introduction to the Trochilidae,’ 1861, page 29.) describes
a battle in which a pair seized hold of each other’s beaks, and whirled
round and round, till they almost fell to the ground; and M. Montes de
Oca, in speaking or another genus of humming-bird, says that two males
rarely meet without a fierce aerial encounter: when kept in cages
“their fighting has mostly ended in the splitting of the tongue of one
of the two, which then surely dies from being unable to feed.” (4.
Gould, ibid. p. 52.) With waders, the males of the common water-hen
(Gallinula chloropus) “when pairing, fight violently for the females:
they stand nearly upright in the water and strike with their feet.” Two
were seen to be thus engaged for half an hour, until one got hold of
the head of the other, which would have been killed had not the
observer interfered; the female all the time looking on as a quiet
spectator. (5. W. Thompson, ‘Natural History of Ireland: Birds,’ vol.
ii. 1850, p. 327.) Mr. Blyth informs me that the males of an allied
bird (Gallicrex cristatus) are a third larger than the females, and are
so pugnacious during the breeding-season that they are kept by the
natives of Eastern Bengal for the sake of fighting. Various other birds
are kept in India for the same purpose, for instance, the bulbuls
(Pycnonotus hoemorrhous) which “fight with great spirit.” (6. Jerdon,
‘Birds of India,’ 1863, vol. ii. p. 96.)

[Fig. 37. The Ruff or Machetes pugnax (from Brehm’s ‘Thierleben’).]

The polygamous ruff (Machetes pugnax, Fig. 37) is notorious for his
extreme pugnacity; and in the spring, the males, which are considerably
larger than the females, congregate day after day at a particular spot,
where the females propose to lay their eggs. The fowlers discover these
spots by the turf being trampled somewhat bare. Here they fight very
much like game-cocks, seizing each other with their beaks and striking
with their wings. The great ruff of feathers round the neck is then
erected, and according to Col. Montagu “sweeps the ground as a shield
to defend the more tender parts”; and this is the only instance known
to me in the case of birds of any structure serving as a shield. The
ruff of feathers, however, from its varied and rich colours probably
serves in chief part as an ornament. Like most pugnacious birds, they
seem always ready to fight, and when closely confined, often kill each
other; but Montagu observed that their pugnacity becomes greater during
the spring, when the long feathers on their necks are fully developed;
and at this period the least movement by any one bird provokes a
general battle. (7. Macgillivray, ‘History of British Birds,’ vol. iv.
1852, pp. 177-181.) Of the pugnacity of web-footed birds, two instances
will suffice: in Guiana “bloody fights occur during the breeding-season
between the males of the wild musk-duck (Cairina moschata); and where
these fights have occurred the river is covered for some distance with
feathers.” (8. Sir R. Schomburgk, in ‘Journal of Royal Geographic
Society,’ vol. xiii. 1843, p. 31.) Birds which seem ill-adapted for
fighting engage in fierce conflicts; thus the stronger males of the
pelican drive away the weaker ones, snapping with their huge beaks and
giving heavy blows with their wings. Male snipe fight together,
“tugging and pushing each other with their bills in the most curious
manner imaginable.” Some few birds are believed never to fight; this is
the case, according to Audubon, with one of the woodpeckers of the
United States (Picu sauratus), although “the hens are followed by even
half a dozen of their gay suitors.” (9. ‘Ornithological Biography,’
vol. i. p. 191. For pelicans and snipes, see vol. iii. pp. 138, 477.)

The males of many birds are larger than the females, and this no doubt
is the result of the advantage gained by the larger and stronger males
over their rivals during many generations. The difference in size
between the two sexes is carried to an extreme point in several
Australian species; thus the male musk-duck (Biziura), and the male
Cincloramphus cruralis (allied to our pipits) are by measurement
actually twice as large as their respective females. (10. Gould,
‘Handbook of Birds of Australia,’ vol. i. p. 395; vol. ii. p. 383.)
With many other birds the females are larger than the males; and, as
formerly remarked, the explanation often given, namely, that the
females have most of the work in feeding their young, will not suffice.
In some few cases, as we shall hereafter see, the females apparently
have acquired their greater size and strength for the sake of
conquering other females and obtaining possession of the males.

The males of many gallinaceous birds, especially of the polygamous
kinds, are furnished with special weapons for fighting with their
rivals, namely spurs, which can be used with fearful effect. It has
been recorded by a trustworthy writer (11. Mr. Hewitt, in the ‘Poultry
Book’ by Tegetmeier, 1866, p. 137.) that in Derbyshire a kite struck at
a game-hen accompanied by her chickens, when the cock rushed to the
rescue, and drove his spur right through the eye and skull of the
aggressor. The spur was with difficulty drawn from the skull, and as
the kite, though dead, retained his grasp, the two birds were firmly
locked together; but the cock when disentangled was very little
injured. The invincible courage of the game-cock is notorious: a
gentleman who long ago witnessed the brutal scene, told me that a bird
had both its legs broken by some accident in the cockpit, and the owner
laid a wager that if the legs could be spliced so that the bird could
stand upright, he would continue fighting. This was effected on the
spot, and the bird fought with undaunted courage until he received his
death-stroke. In Ceylon a closely allied, wild species, the Gallus
Stanleyi, is known to fight desperately “in defence of his seraglio,”
so that one of the combatants is frequently found dead. (12. Layard,
‘Annals and Magazine of Natural History,’ vol. xiv. 1854, p. 63.) An
Indian partridge (Ortygornis gularis), the male of which is furnished
with strong and sharp spurs, is so quarrelsome “that the scars of
former fights disfigure the breast of almost every bird you kill.” (13.
Jerdon, ‘Birds of India,’ vol. iii. p. 574.)

The males of almost all gallinaceous birds, even those which are not
furnished with spurs, engage during the breeding-season in fierce
conflicts. The Capercailzie and Black-cock (Tetrao urogallus and T.
tetrix), which are both polygamists, have regular appointed places,
where during many weeks they congregate in numbers to fight together
and to display their charms before the females. Dr. W. Kovalevsky
informs me that in Russia he has seen the snow all bloody on the arenas
where the capercailzie have fought; and the black-cocks “make the
feathers fly in every direction,” when several “engage in a battle
royal.” The elder Brehm gives a curious account of the Balz, as the
love-dances and love-songs of the Black-cock are called in Germany. The
bird utters almost continuously the strangest noises: “he holds his
tail up and spreads it out like a fan, he lifts up his head and neck
with all the feathers erect, and stretches his wings from the body.
Then he takes a few jumps in different directions, sometimes in a
circle, and presses the under part of his beak so hard against the
ground that the chin feathers are rubbed off. During these movements he
beats his wings and turns round and round. The more ardent he grows the
more lively he becomes, until at last the bird appears like a frantic
creature.” At such times the black-cocks are so absorbed that they
become almost blind and deaf, but less so than the capercailzie: hence
bird after bird may be shot on the same spot, or even caught by the
hand. After performing these antics the males begin to fight: and the
same black-cock, in order to prove his strength over several
antagonists, will visit in the course of one morning several
Balz-places, which remain the same during successive years. (14. Brehm,
‘Thierleben,’ 1867, B. iv. s. 351. Some of the foregoing statements are
taken from L. Lloyd, ‘The Game Birds of Sweden,’ etc., 1867, p. 79.)

The peacock with his long train appears more like a dandy than a
warrior, but he sometimes engages in fierce contests: the Rev. W.
Darwin Fox informs me that at some little distance from Chester two
peacocks became so excited whilst fighting, that they flew over the
whole city, still engaged, until they alighted on the top of St. John’s
tower.

The spur, in those gallinaceous birds which are thus provided, is
generally single; but Polyplectron (Fig. 51) has two or more on each
leg; and one of the Blood-pheasants (Ithaginis cruentus) has been seen
with five spurs. The spurs are generally confined to the male, being
represented by mere knobs or rudiments in the female; but the females
of the Java peacock (Pavo muticus) and, as I am informed by Mr. Blyth,
of the small fire-backed pheasant (Euplocamus erythrophthalmus) possess
spurs. In Galloperdix it is usual for the males to have two spurs, and
for the females to have only one on each leg. (15. Jerdon, ‘Birds of
India’: on Ithaginis, vol. iii. p. 523; on Galloperdix, p. 541.) Hence
spurs may be considered as a masculine structure, which has been
occasionally more or less transferred to the females. Like most other
secondary sexual characters, the spurs are highly variable, both in
number and development, in the same species.

[Fig.38. Palamedea cornuta (from Brehm), shewing the double wing-spurs,
and the filament on the head.]

Various birds have spurs on their wings. But the Egyptian goose
(Chenalopex aegyptiacus) has only “bare obtuse knobs,” and these
probably shew us the first steps by which true spurs have been
developed in other species. In the spur-winged goose, Plectropterus
gambensis, the males have much larger spurs than the females; and they
use them, as I am informed by Mr. Bartlett, in fighting together, so
that, in this case, the wing-spurs serve as sexual weapons; but
according to Livingstone, they are chiefly used in the defence of the
young. The Palamedea (Fig. 38) is armed with a pair of spurs on each
wing; and these are such formidable weapons that a single blow has been
known to drive a dog howling away. But it does not appear that the
spurs in this case, or in that of some of the spur-winged rails, are
larger in the male than in the female. (16. For the Egyptian goose, see
Macgillivray, ‘British Birds,’ vol. iv. p. 639. For Plectropterus,
Livingstone’s ‘Travels,’ p. 254. For Palamedea, Brehm’s ‘Thierleben,’
B. iv. s. 740. See also on this bird Azara, ‘Voyages dans l’Amerique
merid.’ tom. iv. 1809, pp. 179, 253.) In certain plovers, however, the
wing-spurs must be considered as a sexual character. Thus in the male
of our common peewit (Vanellus cristatus) the tubercle on the shoulder
of the wing becomes more prominent during the breeding-season, and the
males fight together. In some species of Lobivanellus a similar
tubercle becomes developed during the breeding-season “into a short
horny spur.” In the Australian L. lobatus both sexes have spurs, but
these are much larger in the males than in the females. In an allied
bird, the Hoplopterus armatus, the spurs do not increase in size during
the breeding-season; but these birds have been seen in Egypt to fight
together, in the same manner as our peewits, by turning suddenly in the
air and striking sideways at each other, sometimes with fatal results.
Thus also they drive away other enemies. (17. See, on our peewit, Mr.
R. Carr in ‘Land and Water,’ Aug. 8th, 1868, p. 46. In regard to
Lobivanellus, see Jerdon’s ‘Birds of India,’ vol. iii. p. 647, and
Gould’s ‘Handbook of Birds of Australia,’ vol. ii. p. 220. For the
Hoplopterus, see Mr. Allen in the ‘Ibis,’ vol. v. 1863, p. 156.)

The season of love is that of battle; but the males of some birds, as
of the game-fowl and ruff, and even the young males of the wild turkey
and grouse (18. Audubon, ‘Ornithological Biography,’ vol. ii. p. 492;
vol. i. pp. 4-13.), are ready to fight whenever they meet. The presence
of the female is the teterrima belli causa. The Bengali baboos make the
pretty little males of the amadavat (Estrelda amandava) fight together
by placing three small cages in a row, with a female in the middle;
after a little time the two males are turned loose, and immediately a
desperate battle ensues. (19. Mr. Blyth, ‘Land and Water,’ 1867, p.
212.) When many males congregate at the same appointed spot and fight
together, as in the case of grouse and various other birds, they are
generally attended by the females (20. Richardson on Tetrao umbellus,
‘Fauna Bor. Amer.: Birds,’ 1831, p. 343. L. Lloyd, ‘Game Birds of
Sweden,’ 1867, pp. 22, 79, on the capercailzie and black-cock. Brehm,
however, asserts (‘Thierleben,’ B. iv. s. 352) that in Germany the
grey-hens do not generally attend the Balzen of the black-cocks, but
this is an exception to the common rule; possibly the hens may lie
hidden in the surrounding bushes, as is known to be the case with the
gray-hens in Scandinavia, and with other species in N. America.), which
afterwards pair with the victorious combatants. But in some cases the
pairing precedes instead of succeeding the combat: thus according to
Audubon (21. ‘Ornithological Biography,’ vol. ii. p. 275.), several
males of the Virginian goat-sucker (Caprimulgus virgianus) “court, in a
highly entertaining manner the female, and no sooner has she made her
choice, than her approved gives chase to all intruders, and drives them
beyond his dominions.” Generally the males try to drive away or kill
their rivals before they pair. It does not, however, appear that the
females invariably prefer the victorious males. I have indeed been
assured by Dr. W. Kovalevsky that the female capercailzie sometimes
steals away with a young male who has not dared to enter the arena with
the older cocks, in the same manner as occasionally happens with the
does of the red-deer in Scotland. When two males contend in presence of
a single female, the victor, no doubt, commonly gains his desire; but
some of these battles are caused by wandering males trying to distract
the peace of an already mated pair. (22. Brehm, ‘Thierleben,’ etc., B.
iv. 1867, p. 990. Audubon, ‘Ornithological Biography,’ vol. ii. p.
492.)

Even with the most pugnacious species it is probable that the pairing
does not depend exclusively on the mere strength and courage of the
male; for such males are generally decorated with various ornaments,
which often become more brilliant during the breeding-season, and which
are sedulously displayed before the females. The males also endeavour
to charm or excite their mates by love-notes, songs, and antics; and
the courtship is, in many instances, a prolonged affair. Hence it is
not probable that the females are indifferent to the charms of the
opposite sex, or that they are invariably compelled to yield to the
victorious males. It is more probable that the females are excited,
either before or after the conflict, by certain males, and thus
unconsciously prefer them. In the case of Tetrao umbellus, a good
observer (23. ‘Land and Water,’ July 25, 1868, p. 14.) goes so far as
to believe that the battles of the male “are all a sham, performed to
show themselves to the greatest advantage before the admiring females
who assemble around; for I have never been able to find a maimed hero,
and seldom more than a broken feather.” I shall have to recur to this
subject, but I may here add that with the Tetrao cupido of the United
States, about a score of males assemble at a particular spot, and,
strutting about, make the whole air resound with their extraordinary
noises. At the first answer from a female the males begin to fight
furiously, and the weaker give way; but then, according to Audubon,
both the victors and vanquished search for the female, so that the
females must either then exert a choice, or the battle must be renewed.
So, again, with one of the field-starlings of the United States
(Sturnella ludoviciana) the males engage in fierce conflicts, “but at
the sight of a female they all fly after her as if mad.” (24. Audubon’s
‘Ornithological Biography;’ on Tetrao cupido, vol. ii. p. 492; on the
Sturnus, vol. ii. p. 219.)

VOCAL AND INSTRUMENTAL MUSIC.

With birds the voice serves to express various emotions, such as
distress, fear, anger, triumph, or mere happiness. It is apparently
sometimes used to excite terror, as in the case of the hissing noise
made by some nestling-birds. Audubon (25. ‘Ornithological Biography,’
vol. v. p. 601.), relates that a night-heron (Ardea nycticorax, Linn.),
which he kept tame, used to hide itself when a cat approached, and then
“suddenly start up uttering one of the most frightful cries, apparently
enjoying the cat’s alarm and flight.” The common domestic cock clucks
to the hen, and the hen to her chickens, when a dainty morsel is found.
The hen, when she has laid an egg, “repeats the same note very often,
and concludes with the sixth above, which she holds for a longer time”
(26. The Hon. Daines Barrington, ‘Philosophical Transactions,’ 1773, p.
252.); and thus she expresses her joy. Some social birds apparently
call to each other for aid; and as they flit from tree to tree, the
flock is kept together by chirp answering chirp. During the nocturnal
migrations of geese and other water-fowl, sonorous clangs from the van
may be heard in the darkness overhead, answered by clangs in the rear.
Certain cries serve as danger signals, which, as the sportsman knows to
his cost, are understood by the same species and by others. The
domestic cock crows, and the humming-bird chirps, in triumph over a
defeated rival. The true song, however, of most birds and various
strange cries are chiefly uttered during the breeding-season, and serve
as a charm, or merely as a call-note, to the other sex.

Naturalists are much divided with respect to the object of the singing
of birds. Few more careful observers ever lived than Montagu, and he
maintained that the “males of song-birds and of many others do not in
general search for the female, but, on the contrary, their business in
the spring is to perch on some conspicuous spot, breathing out their
full and amorous notes, which, by instinct, the female knows, and
repairs to the spot to choose her mate.” (27. ‘Ornithological
Dictionary,’ 1833, p. 475.) Mr. Jenner Weir informs me that this is
certainly the case with the nightingale. Bechstein, who kept birds
during his whole life, asserts, “that the female canary always chooses
the best singer, and that in a state of nature the female finch selects
that male out of a hundred whose notes please her most. (28.
‘Naturgeschichte der Stubenvögel,’ 1840, s. 4. Mr. Harrison Weir
likewise writes to me:—“I am informed that the best singing males
generally get a mate first, when they are bred in the same room.”)
There can be no doubt that birds closely attend to each other’s song.
Mr. Weir has told me of the case of a bullfinch which had been taught
to pipe a German waltz, and who was so good a performer that he cost
ten guineas; when this bird was first introduced into a room where
other birds were kept and he began to sing, all the others, consisting
of about twenty linnets and canaries, ranged themselves on the nearest
side of their cages, and listened with the greatest interest to the new
performer. Many naturalists believe that the singing of birds is almost
exclusively “the effect of rivalry and emulation,” and not for the sake
of charming their mates. This was the opinion of Daines Barrington and
White of Selborne, who both especially attended to this subject. (29.
‘Philosophical Transactions,’ 1773, p. 263. White’s ‘Natural History of
Selborne,’ 1825, vol. i. p. 246.) Barrington, however, admits that
“superiority in song gives to birds an amazing ascendancy over others,
as is well known to bird-catchers.”

It is certain that there is an intense degree of rivalry between the
males in their singing. Bird-fanciers match their birds to see which
will sing longest; and I was told by Mr. Yarrell that a first-rate bird
will sometimes sing till he drops down almost dead, or according to
Bechstein (30. ‘Naturgesch. der Stubenvögel,’ 1840, s. 252.), quite
dead from rupturing a vessel in the lungs. Whatever the cause may be,
male birds, as I hear from Mr. Weir, often die suddenly during the
season of song. That the habit of singing is sometimes quite
independent of love is clear, for a sterile, hybrid canary-bird has
been described (31. Mr. Bold, ‘Zoologist,’ 1843-44, p. 659.) as singing
whilst viewing itself in a mirror, and then dashing at its own image;
it likewise attacked with fury a female canary, when put into the same
cage. The jealousy excited by the act of singing is constantly taken
advantage of by bird-catchers; a male, in good song, is hidden and
protected, whilst a stuffed bird, surrounded by limed twigs, is exposed
to view. In this manner, as Mr. Weir informs me, a man has in the
course of a single day caught fifty, and in one instance, seventy, male
chaffinches. The power and inclination to sing differ so greatly with
birds that although the price of an ordinary male chaffinch is only
sixpence, Mr. Weir saw one bird for which the bird-catcher asked three
pounds; the test of a really good singer being that it will continue to
sing whilst the cage is swung round the owner’s head.

That male birds should sing from emulation as well as for charming the
female, is not at all incompatible; and it might have been expected
that these two habits would have concurred, like those of display and
pugnacity. Some authors, however, argue that the song of the male
cannot serve to charm the female, because the females of some few
species, such as of the canary, robin, lark, and bullfinch, especially
when in a state of widowhood, as Bechstein remarks, pour forth fairly
melodious strains. In some of these cases the habit of singing may be
in part attributed to the females having been highly fed and confined
(32. D. Barrington, ‘Philosophical Transactions,’ 1773, p. 262.
Bechstein, ‘Stubenvögel,’ 1840, s. 4.), for this disturbs all the
functions connected with the reproduction of the species. Many
instances have already been given of the partial transference of
secondary masculine characters to the female, so that it is not at all
surprising that the females of some species should possess the power of
song. It has also been argued, that the song of the male cannot serve
as a charm, because the males of certain species, for instance of the
robin, sing during the autumn. (33. This is likewise the case with the
water-ouzel; see Mr. Hepburn in the ‘Zoologist,’ 1845-46, p. 1068.) But
nothing is more common than for animals to take pleasure in practising
whatever instinct they follow at other times for some real good. How
often do we see birds which fly easily, gliding and sailing through the
air obviously for pleasure? The cat plays with the captured mouse, and
the cormorant with the captured fish. The weaver-bird (Ploceus), when
confined in a cage, amuses itself by neatly weaving blades of grass
between the wires of its cage. Birds which habitually fight during the
breeding-season are generally ready to fight at all times; and the
males of the capercailzie sometimes hold their Balzen or leks at the
usual place of assemblage during the autumn. (34. L. Lloyd, ‘Game Birds
of Sweden,’ 1867, p. 25.) Hence it is not at all surprising that male
birds should continue singing for their own amusement after the season
for courtship is over.

As shewn in a previous chapter, singing is to a certain extent an art,
and is much improved by practice. Birds can be taught various tunes,
and even the unmelodious sparrow has learnt to sing like a linnet. They
acquire the song of their foster parents (35. Barrington, ibid. p. 264,
Bechstein, ibid. s. 5.), and sometimes that of their neighbours. (36.
Dureau de la Malle gives a curious instance (‘Annales des Sc. Nat.’ 3rd
series, Zoolog., tom. x. p. 118) of some wild blackbirds in his garden
in Paris, which naturally learnt a republican air from a caged bird.)
All the common songsters belong to the Order of Insessores, and their
vocal organs are much more complex than those of most other birds; yet
it is a singular fact that some of the Insessores, such as ravens,
crows, and magpies, possess the proper apparatus (37. Bishop, in
‘Todd’s Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1496.),
though they never sing, and do not naturally modulate their voices to
any great extent. Hunter asserts (38. As stated by Barrington in
‘Philosophical Transactions,’ 1773, p. 262.) that with the true
songsters the muscles of the larynx are stronger in the males than in
the females; but with this slight exception there is no difference in
the vocal organs of the two sexes, although the males of most species
sing so much better and more continuously than the females.

It is remarkable that only small birds properly sing. The Australian
genus Menura, however, must be excepted; for the Menura Alberti, which
is about the size of a half-grown turkey, not only mocks other birds,
but “its own whistle is exceedingly beautiful and varied.” The males
congregate and form “corroborying places,” where they sing, raising and
spreading their tails like peacocks, and drooping their wings. (39.
Gould, ‘Handbook to the Birds of Australia,’ vol. i. 1865, pp. 308-310.
See also Mr. T.W. Wood in the ‘Student,’ April 1870, p. 125.) It is
also remarkable that birds which sing well are rarely decorated with
brilliant colours or other ornaments. Of our British birds, excepting
the bullfinch and goldfinch, the best songsters are plain-coloured. The
kingfisher, bee-eater, roller, hoopoe, woodpeckers, etc., utter harsh
cries; and the brilliant birds of the tropics are hardly ever
songsters. (40. See remarks to this effect in Gould’s ‘Introduction to
the Trochilidae,’ 1861, p. 22.) Hence bright colours and the power of
song seem to replace each other. We can perceive that if the plumage
did not vary in brightness, or if bright colours were dangerous to the
species, other means would be employed to charm the females; and melody
of voice offers one such means.

[Fig. 39. Tetrao cupido: male. (T.W. Wood.)]

In some birds the vocal organs differ greatly in the two sexes. In the
Tetrao cupido (Fig. 39) the male has two bare, orange-coloured sacks,
one on each side of the neck; and these are largely inflated when the
male, during the breeding-season, makes his curious hollow sound,
audible at a great distance. Audubon proved that the sound was
intimately connected with this apparatus (which reminds us of the
air-sacks on each side of the mouth of certain male frogs), for he
found that the sound was much diminished when one of the sacks of a
tame bird was pricked, and when both were pricked it was altogether
stopped. The female has “a somewhat similar, though smaller naked space
of skin on the neck; but this is not capable of inflation.” (41. ‘The
Sportsman and Naturalist in Canada,’ by Major W. Ross King, 1866, pp.
144-146. Mr. T.W. Wood gives in the ‘Student’ (April 1870, p. 116) an
excellent account of the attitude and habits of this bird during its
courtship. He states that the ear-tufts or neck-plumes are erected, so
that they meet over the crown of the head. See his drawing, Fig. 39.)
The male of another kind of grouse (Tetrao urophasianus), whilst
courting the female, has his “bare yellow oesophagus inflated to a
prodigious size, fully half as large as the body”; and he then utters
various grating, deep, hollow tones. With his neck-feathers erect, his
wings lowered, and buzzing on the ground, and his long pointed tail
spread out like a fan, he displays a variety of grotesque attitudes.
The oesophagus of the female is not in any way remarkable. (42.
Richardson, ‘Fauna Bor. Americana: Birds,’ 1831, p. 359. Audubon, ibid.
vol. iv. p. 507.)

[Fig. 40. The Umbrella-bird or Cephalopterus ornatus, male (from
Brehm).]

It seems now well made out that the great throat pouch of the European
male bustard (Otis tarda), and of at least four other species, does
not, as was formerly supposed, serve to hold water, but is connected
with the utterance during the breeding-season of a peculiar sound
resembling “oak.” (43. The following papers have been lately written on
this subject: Prof. A. Newton, in the ‘Ibis,’ 1862, p. 107; Dr. Cullen,
ibid. 1865, p. 145; Mr. Flower, in ‘Proc. Zool. Soc.’ 1865, p. 747; and
Dr. Murie, in ‘Proc. Zool. Soc.’ 1868, p. 471. In this latter paper an
excellent figure is given of the male Australian Bustard in full
display with the sack distended. It is a singular fact that the sack is
not developed in all the males of the same species.) A crow-like bird
inhabiting South America (see Cephalopterus ornatus, Fig. 40) is called
the umbrella-bird, from its immense top knot, formed of bare white
quills surmounted by dark-blue plumes, which it can elevate into a
great dome no less than five inches in diameter, covering the whole
head. This bird has on its neck a long, thin, cylindrical fleshy
appendage, which is thickly clothed with scale-like blue feathers. It
probably serves in part as an ornament, but likewise as a resounding
apparatus; for Mr. Bates found that it is connected “with an unusual
development of the trachea and vocal organs.” It is dilated when the
bird utters its singularly deep, loud and long sustained fluty note.
The head-crest and neck-appendage are rudimentary in the female. (44.
Bates, ‘The Naturalist on the Amazons,’ 1863, vol. ii. p. 284; Wallace,
in ‘Proceedings, Zoological Society,’ 1850, p. 206. A new species, with
a still larger neck-appendage (C. penduliger), has lately been
discovered, see ‘Ibis,’ vol. i. p. 457.)

The vocal organs of various web-footed and wading birds are
extraordinarily complex, and differ to a certain extent in the two
sexes. In some cases the trachea is convoluted, like a French horn, and
is deeply embedded in the sternum. In the wild swan (Cygnus ferus) it
is more deeply embedded in the adult male than in the adult female or
young male. In the male Merganser the enlarged portion of the trachea
is furnished with an additional pair of muscles. (45. Bishop, in Todd’s
‘Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1499.) In one of
the ducks, however, namely Anas punctata, the bony enlargement is only
a little more developed in the male than in the female. (46. Prof.
Newton, ‘Proc. Zoolog. Soc.’ 1871, p. 651.) But the meaning of these
differences in the trachea of the two sexes of the Anatidae is not
understood; for the male is not always the more vociferous; thus with
the common duck, the male hisses, whilst the female utters a loud
quack. (47. The spoonbill (Platalea) has its trachea convoluted into a
figure of eight, and yet this bird (Jerdon, ‘Birds of India,’ vol. iii.
p. 763) is mute; but Mr. Blyth informs me that the convolutions are not
constantly present, so that perhaps they are now tending towards
abortion.) In both sexes of one of the cranes (Grus virgo) the trachea
penetrates the sternum, but presents “certain sexual modifications.” In
the male of the black stork there is also a well-marked sexual
difference in the length and curvature of the bronchi. (48. ‘Elements
of Comparative Anatomy,’ by R. Wagner, Eng. translat. 1845, p. 111.
With respect to the swan, as given above, Yarrell’s ‘History of British
Birds,’ 2nd edition, 1845, vol. iii. p. 193.) Highly important
structures have, therefore, in these cases been modified according to
sex.

It is often difficult to conjecture whether the many strange cries and
notes uttered by male birds during the breeding-season serve as a charm
or merely as a call to the female. The soft cooing of the turtle-dove
and of many pigeons, it may be presumed, pleases the female. When the
female of the wild turkey utters her call in the morning, the male
answers by a note which differs from the gobbling noise made, when with
erected feathers, rustling wings and distended wattles, he puffs and
struts before her. (49. C.L. Bonaparte, quoted in the ‘Naturalist
Library: Birds,’ vol. xiv. p. 126.) The spel of the black-cock
certainly serves as a call to the female, for it has been known to
bring four or five females from a distance to a male under confinement;
but as the black-cock continues his spel for hours during successive
days, and in the case of the capercailzie “with an agony of passion,”
we are led to suppose that the females which are present are thus
charmed. (50. L. Lloyd, ‘The Game Birds of Sweden,’ etc., 1867, pp. 22,
81.) The voice of the common rook is known to alter during the
breeding-season, and is therefore in some way sexual. (51. Jenner,
‘Philosophical Transactions,’ 1824, p. 20.) But what shall we say about
the harsh screams of, for instance, some kinds of macaws; have these
birds as bad taste for musical sounds as they apparently have for
colour, judging by the inharmonious contrast of their bright yellow and
blue plumage? It is indeed possible that without any advantage being
thus gained, the loud voices of many male birds may be the result of
the inherited effects of the continued use of their vocal organs when
excited by the strong passions of love, jealousy and rage; but to this
point we shall recur when we treat of quadrupeds.

We have as yet spoken only of the voice, but the males of various birds
practise, during their courtship, what may be called instrumental
music. Peacocks and Birds of Paradise rattle their quills together.
Turkey-cocks scrape their wings against the ground, and some kinds of
grouse thus produce a buzzing sound. Another North American grouse, the
Tetrao umbellus, when with his tail erect, his ruffs displayed, “he
shows off his finery to the females, who lie hid in the neighbourhood,”
drums by rapidly striking his wings together above his back, according
to Mr. R. Haymond, and not, as Audubon thought, by striking them
against his sides. The sound thus produced is compared by some to
distant thunder, and by others to the quick roll of a drum. The female
never drums, “but flies directly to the place where the male is thus
engaged.” The male of the Kalij-pheasant, in the Himalayas, often makes
a singular drumming noise with his wings, not unlike the sound produced
by shaking a stiff piece of cloth.” On the west coast of Africa the
little black-weavers (Ploceus?) congregate in a small party on the
bushes round a small open space, and sing and glide through the air
with quivering wings, “which make a rapid whirring sound like a child’s
rattle.” One bird after another thus performs for hours together, but
only during the courting-season. At this season, and at no other time,
the males of certain night-jars (Caprimulgus) make a strange booming
noise with their wings. The various species of woodpeckers strike a
sonorous branch with their beaks, with so rapid a vibratory movement
that “the head appears to be in two places at once.” The sound thus
produced is audible at a considerable distance but cannot be described;
and I feel sure that its source would never be conjectured by any one
hearing it for the first time. As this jarring sound is made chiefly
during the breeding-season, it has been considered as a love-song; but
it is perhaps more strictly a love-call. The female, when driven from
her nest, has been observed thus to call her mate, who answered in the
same manner and soon appeared. Lastly, the male hoopoe (Upupa epops)
combines vocal and instrumental music; for during the breeding-season
this bird, as Mr. Swinhoe observed, first draws in air, and then taps
the end of its beak perpendicularly down against a stone or the trunk
of a tree, “when the breath being forced down the tubular bill produces
the correct sound.” If the beak is not thus struck against some object,
the sound is quite different. Air is at the same time swallowed, and
the oesophagus thus becomes much swollen; and this probably acts as a
resonator, not only with the hoopoe, but with pigeons and other birds.
(52. For the foregoing facts see, on Birds of Paradise, Brehm,
‘Thierleben,’ Band iii. s. 325. On Grouse, Richardson, ‘Fauna Bor.
Americ.: Birds,’ pp. 343 and 359; Major W. Ross King, ‘The Sportsman in
Canada,’ 1866, p. 156; Mr. Haymond, in Prof. Cox’s ‘Geol. Survey of
Indiana,’ p. 227; Audubon, ‘American Ornitholog. Biograph.’ vol. i. p.
216. On the Kalij-pheasant, Jerdon, ‘Birds of India,’ vol. iii. p. 533.
On the Weavers, Livingstone’s ‘Expedition to the Zambesi,’ 1865, p.
425. On Woodpeckers, Macgillivray, ‘Hist. of British Birds,’ vol. iii.
1840, pp. 84, 88, 89, and 95. On the Hoopoe, Mr. Swinhoe, in ‘Proc.
Zoolog. Soc.’ June 23, 1863 and 1871, p. 348. On the Night-jar,
Audubon, ibid. vol. ii. p. 255, and ‘American Naturalist,’ 1873, p.
672. The English Night-jar likewise makes in the spring a curious noise
during its rapid flight.)

[Fig. 41. Outer tail-feather of Scolopax gallinago (from ‘Proc. Zool.
Soc.’ 1858).

Fig. 42. Outer tail-feather of Scolopax frenata.

Fig. 43. Outer tail-feather of Scolopax javensis.]

In the foregoing cases sounds are made by the aid of structures already
present and otherwise necessary; but in the following cases certain
feathers have been specially modified for the express purpose of
producing sounds. The drumming, bleating, neighing, or thundering noise
(as expressed by different observers) made by the common snipe
(Scolopax gallinago) must have surprised every one who has ever heard
it. This bird, during the pairing-season, flies to “perhaps a thousand
feet in height,” and after zig-zagging about for a time descends to the
earth in a curved line, with outspread tail and quivering pinions, and
surprising velocity. The sound is emitted only during this rapid
descent. No one was able to explain the cause until M. Meves observed
that on each side of the tail the outer feathers are peculiarly formed
(Fig. 41), having a stiff sabre-shaped shaft with the oblique barbs of
unusual length, the outer webs being strongly bound together. He found
that by blowing on these feathers, or by fastening them to a long thin
stick and waving them rapidly through the air, he could reproduce the
drumming noise made by the living bird. Both sexes are furnished with
these feathers, but they are generally larger in the male than in the
female, and emit a deeper note. In some species, as in S. frenata (Fig.
42), four feathers, and in S. javensis (Fig. 43), no less than eight on
each side of the tail are greatly modified. Different tones are emitted
by the feathers of the different species when waved through the air;
and the Scolopax Wilsonii of the United States makes a switching noise
whilst descending rapidly to the earth. (53. See M. Meves’ interesting
paper in ‘Proc. Zool. Soc.’ 1858, p. 199. For the habits of the snipe,
Macgillivray, ‘History of British Birds,’ vol. iv. p. 371. For the
American snipe, Capt. Blakiston, ‘Ibis,’ vol. v. 1863, p. 131.)

[Fig. 44. Primary wing-feather of a Humming-bird, the Selasphorus
platycercus (from a sketch by Mr. Salvin). Upper figure, that of male;
lower figure, corresponding feather of female.]

In the male of the Chamaepetes unicolor (a large gallinaceous bird of
America), the first primary wing-feather is arched towards the tip and
is much more attenuated than in the female. In an allied bird, the
Penelope nigra, Mr. Salvin observed a male, which, whilst it flew
downwards “with outstretched wings, gave forth a kind of crashing
rushing noise,” like the falling of a tree. (54. Mr. Salvin, in
‘Proceedings, Zoological Society,’ 1867, p. 160. I am much indebted to
this distinguished ornithologist for sketches of the feathers of the
Chamaepetes, and for other information.) The male alone of one of the
Indian bustards (Sypheotides auritus) has its primary wing-feathers
greatly acuminated; and the male of an allied species is known to make
a humming noise whilst courting the female. (55. Jerdon, ‘Birds of
India,’ vol. iii. pp. 618, 621.) In a widely different group of birds,
namely Humming-birds, the males alone of certain kinds have either the
shafts of their primary wing-feathers broadly dilated, or the webs
abruptly excised towards the extremity. The male, for instance, of
Selasphorus platycercus, when adult, has the first primary wing-feather
(Fig. 44), thus excised. Whilst flying from flower to flower he makes
“a shrill, almost whistling noise” (56. Gould, ‘Introduction to the
Trochilidae,’ 1861, p. 49. Salvin, ‘Proceedings, Zoological Society,’
1867, p. 160.); but it did not appear to Mr. Salvin that the noise was
intentionally made.

[Fig. 45. Secondary wing-feathers of Pipra deliciosa (from Mr. Sclater,
in ‘Proc. Zool. Soc.’ 1860). The three upper feathers, a, b, c, from
the male; the three lower corresponding feathers, d, e, f, from the
female. a and d, fifth secondary wing-feather of male and female, upper
surface. b and e, sixth secondary, upper surface. c and f, seventh
secondary, lower surface.]

Lastly, in several species of a sub-genus of Pipra or Manakin, the
males, as described by Mr. Sclater, have their SECONDARY wing-feathers
modified in a still more remarkable manner. In the brilliantly-coloured
P. deliciosa the first three secondaries are thick-stemmed and curved
towards the body; in the fourth and fifth (Fig. 45, a) the change is
greater; and in the sixth and seventh (b, c) the shaft “is thickened to
an extraordinary degree, forming a solid horny lump.” The barbs also
are greatly changed in shape, in comparison with the corresponding
feathers (d, e, f) in the female. Even the bones of the wing, which
support these singular feathers in the male, are said by Mr. Fraser to
be much thickened. These little birds make an extraordinary noise, the
first “sharp note being not unlike the crack of a whip.” (57. Sclater,
in ‘Proceedings, Zoological Society,’ 1860, p. 90, and in ‘Ibis,’ vol.
iv. 1862, p. 175. Also Salvin, in ‘Ibis,’ 1860, p. 37.)

The diversity of the sounds, both vocal and instrumental, made by the
males of many birds during the breeding-season, and the diversity of
the means for producing such sounds, are highly remarkable. We thus
gain a high idea of their importance for sexual purposes, and are
reminded of the conclusion arrived at as to insects. It is not
difficult to imagine the steps by which the notes of a bird, primarily
used as a mere call or for some other purpose, might have been improved
into a melodious love song. In the case of the modified feathers, by
which the drumming, whistling, or roaring noises are produced, we know
that some birds during their courtship flutter, shake, or rattle their
unmodified feathers together; and if the females were led to select the
best performers, the males which possessed the strongest or thickest,
or most attenuated feathers, situated on any part of the body, would be
the most successful; and thus by slow degrees the feathers might be
modified to almost any extent. The females, of course, would not notice
each slight successive alteration in shape, but only the sounds thus
produced. It is a curious fact that in the same class of animals,
sounds so different as the drumming of the snipe’s tail, the tapping of
the woodpecker’s beak, the harsh trumpet-like cry of certain
water-fowl, the cooing of the turtle-dove, and the song of the
nightingale, should all be pleasing to the females of the several
species. But we must not judge of the tastes of distinct species by a
uniform standard; nor must we judge by the standard of man’s taste.
Even with man, we should remember what discordant noises, the beating
of tom-toms and the shrill notes of reeds, please the ears of savages.
Sir S. Baker remarks (58. ‘The Nile Tributaries of Abyssinia,’ 1867, p.
203.), that “as the stomach of the Arab prefers the raw meat and
reeking liver taken hot from the animal, so does his ear prefer his
equally coarse and discordant music to all other.”

LOVE ANTICS AND DANCES.

The curious love gestures of some birds have already been incidentally
noticed; so that little need here be added. In Northern America large
numbers of a grouse, the Tetrao phasianellus, meet every morning during
the breeding-season on a selected level spot, and here they run round
and round in a circle of about fifteen or twenty feet in diameter, so
that the ground is worn quite bare, like a fairy-ring. In these
Partridge-dances, as they are called by the hunters, the birds assume
the strangest attitudes, and run round, some to the left and some to
the right. Audubon describes the males of a heron (Ardea herodias) as
walking about on their long legs with great dignity before the females,
bidding defiance to their rivals. With one of the disgusting
carrion-vultures (Cathartes jota) the same naturalist states that “the
gesticulations and parade of the males at the beginning of the
love-season are extremely ludicrous.” Certain birds perform their
love-antics on the wing, as we have seen with the black African weaver,
instead of on the ground. During the spring our little white-throat
(Sylvia cinerea) often rises a few feet or yards in the air above some
bush, and “flutters with a fitful and fantastic motion, singing all the
while, and then drops to its perch.” The great English bustard throws
himself into indescribably odd attitudes whilst courting the female, as
has been figured by Wolf. An allied Indian bustard (Otis bengalensis)
at such times “rises perpendicularly into the air with a hurried
flapping of his wings, raising his crest and puffing out the feathers
of his neck and breast, and then drops to the ground;” he repeats this
manoeuvre several times, at the same time humming in a peculiar tone.
Such females as happen to be near “obey this saltatory summons,” and
when they approach he trails his wings and spreads his tail like a
turkey-cock. (59. For Tetrao phasianellus, see Richardson, ‘Fauna, Bor.
America,’ p. 361, and for further particulars Capt. Blakiston, ‘Ibis,’
1863, p. 125. For the Cathartes and Ardea, Audubon, ‘Ornithological
Biography,’ vol. ii. p. 51, and vol. iii. p. 89. On the White-throat,
Macgillivray, ‘History of British Birds,’ vol. ii. p. 354. On the
Indian Bustard, Jerdon, ‘Birds of India,’ vol. iii. p. 618.)

[Fig. 46. Bower-bird, Chlamydera maculata, with bower (from Brehm).]

But the most curious case is afforded by three allied genera of
Australian birds, the famous Bower-birds,—no doubt the co-descendants
of some ancient species which first acquired the strange instinct of
constructing bowers for performing their love-antics. The bowers (Fig.
46), which, as we shall hereafter see, are decorated with feathers,
shells, bones, and leaves, are built on the ground for the sole purpose
of courtship, for their nests are formed in trees. Both sexes assist in
the erection of the bowers, but the male is the principal workman. So
strong is this instinct that it is practised under confinement, and Mr.
Strange has described (60. Gould, ‘Handbook to the Birds of Australia,’
vol. i. pp. 444, 449, 455. The bower of the Satin Bower-bird may be
seen in the Zoological Society’s Gardens, Regent’s Park.) the habits of
some Satin Bower-birds which he kept in an aviary in New South Wales.
“At times the male will chase the female all over the aviary, then go
to the bower, pick up a gay feather or a large leaf, utter a curious
kind of note, set all his feathers erect, run round the bower and
become so excited that his eyes appear ready to start from his head; he
continues opening first one wing then the other, uttering a low,
whistling note, and, like the domestic cock, seems to be picking up
something from the ground, until at last the female goes gently towards
him.” Captain Stokes has described the habits and “play-houses” of
another species, the Great Bower-bird, which was seen “amusing itself
by flying backwards and forwards, taking a shell alternately from each
side, and carrying it through the archway in its mouth.” These curious
structures, formed solely as halls of assemblage, where both sexes
amuse themselves and pay their court, must cost the birds much labour.
The bower, for instance, of the Fawn-breasted species, is nearly four
feet in length, eighteen inches in height, and is raised on a thick
platform of sticks.

DECORATION.

I will first discuss the cases in which the males are ornamented either
exclusively or in a much higher degree than the females, and in a
succeeding chapter those in which both sexes are equally ornamented,
and finally the rare cases in which the female is somewhat more
brightly-coloured than the male. As with the artificial ornaments used
by savage and civilised men, so with the natural ornaments of birds,
the head is the chief seat of decoration. (61. See remarks to this
effect, on the ‘Feeling of Beauty among Animals,’ by Mr. J. Shaw, in
the ‘Athenaeum,’ Nov. 24th, 1866, p. 681.) The ornaments, as mentioned
at the commencement of this chapter, are wonderfully diversified. The
plumes on the front or back of the head consist of variously-shaped
feathers, sometimes capable of erection or expansion, by which their
beautiful colours are fully displayed. Elegant ear-tufts (Fig. 39) are
occasionally present. The head is sometimes covered with velvety down,
as with the pheasant; or is naked and vividly coloured. The throat,
also, is sometimes ornamented with a beard, wattles, or caruncles. Such
appendages are generally brightly-coloured, and no doubt serve as
ornaments, though not always ornamental in our eyes; for whilst the
male is in the act of courting the female, they often swell and assume
vivid tints, as in the male turkey. At such times the fleshy appendages
about the head of the male Tragopan pheasant (Ceriornis Temminckii)
swell into a large lappet on the throat and into two horns, one on each
side of the splendid top-knot; and these are then coloured of the most
intense blue which I have ever beheld. (62. See Dr. Murie’s account
with coloured figures in ‘Proceedings, Zoological Society,’ 1872, p.
730.) The African hornbill (Bucorax abyssinicus) inflates the scarlet
bladder-like wattle on its neck, and with its wings drooping and tail
expanded “makes quite a grand appearance.” (63. Mr. Monteiro, ‘Ibis,’
vol. iv. 1862, p. 339.) Even the iris of the eye is sometimes more
brightly-coloured in the male than in the female; and this is
frequently the case with the beak, for instance, in our common
blackbird. In Buceros corrugatus, the whole beak and immense casque are
coloured more conspicuously in the male than in the female; and “the
oblique grooves upon the sides of the lower mandible are peculiar to
the male sex.” (64. ‘Land and Water,’ 1868, p. 217.)

The head, again, often supports fleshy appendages, filaments, and solid
protuberances. These, if not common to both sexes, are always confined
to the males. The solid protuberances have been described in detail by
Dr. W. Marshall (65. ‘Ueber die Schädelhöcker,’ etc., ‘Niederland.
Archiv. fur Zoologie,’ B. I. Heft 2, 1872.), who shews that they are
formed either of cancellated bone coated with skin, or of dermal and
other tissues. With mammals true horns are always supported on the
frontal bones, but with birds various bones have been modified for this
purpose; and in species of the same group the protuberances may have
cores of bone, or be quite destitute of them, with intermediate
gradations connecting these two extremes. Hence, as Dr. Marshall justly
remarks, variations of the most different kinds have served for the
development through sexual selection of these ornamental appendages.
Elongated feathers or plumes spring from almost every part of the body.
The feathers on the throat and breast are sometimes developed into
beautiful ruffs and collars. The tail-feathers are frequently increased
in length; as we see in the tail-coverts of the peacock, and in the
tail itself of the Argus pheasant. With the peacock even the bones of
the tail have been modified to support the heavy tail-coverts. (66. Dr.
W. Marshall, ‘Über den Vogelschwanz,’ ibid. B. I. Heft 2, 1872.) The
body of the Argus is not larger than that of a fowl; yet the length
from the end of the beak to the extremity of the tail is no less than
five feet three inches (67. Jardine’s ‘Naturalist Library: Birds,’ vol.
xiv. p. 166.), and that of the beautifully ocellated secondary
wing-feathers nearly three feet. In a small African night-jar
(Cosmetornis vexillarius) one of the primary wing-feathers, during the
breeding-season, attains a length of twenty-six inches, whilst the bird
itself is only ten inches in length. In another closely-allied genus of
night-jars, the shafts of the elongated wing-feathers are naked, except
at the extremity, where there is a disc. (68. Sclater, in the ‘Ibis,’
vol. vi. 1864, p. 114; Livingstone, ‘Expedition to the Zambesi,’ 1865,
p. 66.) Again, in another genus of night-jars, the tail-feathers are
even still more prodigiously developed. In general the feathers of the
tail are more often elongated than those of the wings, as any great
elongation of the latter impedes flight. We thus see that in
closely-allied birds ornaments of the same kind have been gained by the
males through the development of widely different feathers.

It is a curious fact that the feathers of species belonging to very
distinct groups have been modified in almost exactly the same peculiar
manner. Thus the wing-feathers in one of the above-mentioned night-jars
are bare along the shaft, and terminate in a disc; or are, as they are
sometimes called, spoon or racket-shaped. Feathers of this kind occur
in the tail of a motmot (Eumomota superciliaris), of a king-fisher,
finch, humming-bird, parrot, several Indian drongos (Dicrurus and
Edolius, in one of which the disc stands vertically), and in the tail
of certain birds of paradise. In these latter birds, similar feathers,
beautifully ocellated, ornament the head, as is likewise the case with
some gallinaceous birds. In an Indian bustard (Sypheotides auritus) the
feathers forming the ear-tufts, which are about four inches in length,
also terminate in discs. (69. Jerdon, ‘Birds of India,’ vol. iii. p.
620.) It is a most singular fact that the motmots, as Mr. Salvin has
clearly shewn (70. ‘Proceedings, Zoological Society,’ 1873, p. 429.),
give to their tail feathers the racket-shape by biting off the barbs,
and, further, that this continued mutilation has produced a certain
amount of inherited effect.

[Fig. 47. Paradisea Papuana (T.W. Wood).]

Again, the barbs of the feathers in various widely-distinct birds are
filamentous or plumose, as with some herons, ibises, birds of paradise,
and Gallinaceae. In other cases the barbs disappear, leaving the shafts
bare from end to end; and these in the tail of the Paradisea apoda
attain a length of thirty-four inches (71. Wallace, in ‘Annals and
Magazine of Natural History,’ vol. xx. 1857, p. 416, and in his ‘Malay
Archipelago,’ vol. ii. 1869, p. 390.): in P. Papuana (Fig. 47) they are
much shorter and thin. Smaller feathers when thus denuded appear like
bristles, as on the breast of the turkey-cock. As any fleeting fashion
in dress comes to be admired by man, so with birds a change of almost
any kind in the structure or colouring of the feathers in the male
appears to have been admired by the female. The fact of the feathers in
widely distinct groups having been modified in an analogous manner no
doubt depends primarily on all the feathers having nearly the same
structure and manner of development, and consequently tending to vary
in the same manner. We often see a tendency to analogous variability in
the plumage of our domestic breeds belonging to distinct species. Thus
top-knots have appeared in several species. In an extinct variety of
the turkey, the top-knot consisted of bare quills surmounted with
plumes of down, so that they somewhat resembled the racket-shaped
feathers above described. In certain breeds of the pigeon and fowl the
feathers are plumose, with some tendency in the shafts to be naked. In
the Sebastopol goose the scapular feathers are greatly elongated,
curled, or even spirally twisted, with the margins plumose. (72. See my
work on ‘The Variation of Animals and Plants under Domestication,’ vol.
i. pp. 289, 293.)

In regard to colour, hardly anything need here be said, for every one
knows how splendid are the tints of many birds, and how harmoniously
they are combined. The colours are often metallic and iridescent.
Circular spots are sometimes surrounded by one or more differently
shaded zones, and are thus converted into ocelli. Nor need much be said
on the wonderful difference between the sexes of many birds. The common
peacock offers a striking instance. Female birds of paradise are
obscurely coloured and destitute of all ornaments, whilst the males are
probably the most highly decorated of all birds, and in so many
different ways that they must be seen to be appreciated. The elongated
and golden-orange plumes which spring from beneath the wings of the
Paradisea apoda, when vertically erected and made to vibrate, are
described as forming a sort of halo, in the centre of which the head
“looks like a little emerald sun with its rays formed by the two
plumes.” (73. Quoted from M. de Lafresnaye in ‘Annals and Mag. of
Natural History,’ vol. xiii. 1854, p. 157: see also Mr. Wallace’s much
fuller account in vol. xx. 1857, p. 412, and in his ‘Malay
Archipelago.’) In another most beautiful species the head is bald, “and
of a rich cobalt blue, crossed by several lines of black velvety
feathers.” (74. Wallace, ‘The Malay Archipelago,’ vol. ii. 1869, p.
405.)

[Fig. 48. Lophornis ornatus, male and female (from Brehm).

Fig. 49. Spathura underwoodi, male and female (from Brehm).]

Male humming-birds (Figs. 48 and 49) almost vie with birds of paradise
in their beauty, as every one will admit who has seen Mr. Gould’s
splendid volumes, or his rich collection. It is very remarkable in how
many different ways these birds are ornamented. Almost every part of
their plumage has been taken advantage of, and modified; and the
modifications have been carried, as Mr. Gould shewed me, to a wonderful
extreme in some species belonging to nearly every sub-group. Such cases
are curiously like those which we see in our fancy breeds, reared by
man for the sake of ornament; certain individuals originally varied in
one character, and other individuals of the same species in other
characters; and these have been seized on by man and much augmented—as
shewn by the tail of the fantail-pigeon, the hood of the jacobin, the
beak and wattle of the carrier, and so forth. The sole difference
between these cases is that in the one, the result is due to man’s
selection, whilst in the other, as with humming-birds, birds of
paradise, etc., it is due to the selection by the females of the more
beautiful males.

I will mention only one other bird, remarkable from the extreme
contrast in colour between the sexes, namely the famous bell-bird
(Chasmorhynchus niveus) of S. America, the note of which can be
distinguished at the distance of nearly three miles, and astonishes
every one when first hearing it. The male is pure white, whilst the
female is dusky-green; and white is a very rare colour in terrestrial
species of moderate size and inoffensive habits. The male, also, as
described by Waterton, has a spiral tube, nearly three inches in
length, which rises from the base of the beak. It is jet-black, dotted
over with minute downy feathers. This tube can be inflated with air,
through a communication with the palate; and when not inflated hangs
down on one side. The genus consists of four species, the males of
which are very distinct, whilst the females, as described by Mr.
Sclater in a very interesting paper, closely resemble each other, thus
offering an excellent instance of the common rule that within the same
group the males differ much more from each other than do the females.
In a second species (C. nudicollis) the male is likewise snow-white,
with the exception of a large space of naked skin on the throat and
round the eyes, which during the breeding-season is of a fine green
colour. In a third species (C. tricarunculatus) the head and neck alone
of the male are white, the rest of the body being chestnut-brown, and
the male of this species is provided with three filamentous projections
half as long as the body—one rising from the base of the beak, and the
two others from the corners of the mouth. (75. Mr. Sclater,
‘Intellectual Observer,’ Jan. 1867. Waterton’s ‘Wanderings,’ p. 118.
See also Mr. Salvin’s interesting paper, with a plate, in the ‘Ibis,’
1865, p. 90.)

The coloured plumage and certain other ornaments of the adult males are
either retained for life, or are periodically renewed during the summer
and breeding-season. At this same season the beak and naked skin about
the head frequently change colour, as with some herons, ibises, gulls,
one of the bell-birds just noticed, etc. In the white ibis, the cheeks,
the inflatable skin of the throat, and the basal portion of the beak
then become crimson. (76. ‘Land and Water,’ 1867, p. 394.) In one of
the rails, Gallicrex cristatus, a large red caruncle is developed
during this period on the head of the male. So it is with a thin horny
crest on the beak of one of the pelicans, P. erythrorhynchus; for,
after the breeding-season, these horny crests are shed, like horns from
the heads of stags, and the shore of an island in a lake in Nevada was
found covered with these curious exuviae. (77. Mr. D.G. Elliot, in
‘Proc. Zool. Soc.’ 1869, p. 589.)

Changes of colour in the plumage according to the season depend,
firstly on a double annual moult, secondly on an actual change of
colour in the feathers themselves, and thirdly on their dull-coloured
margins being periodically shed, or on these three processes more or
less combined. The shedding of the deciduary margins may be compared
with the shedding of their down by very young birds; for the down in
most cases arises from the summits of the first true feathers. (78.
Nitzsch’s ‘Pterylography,’ edited by P.L. Sclater, Ray Society, 1867,
p. 14.)

With respect to the birds which annually undergo a double moult, there
are, firstly, some kinds, for instance snipes, swallow-plovers
(Glareolae), and curlews, in which the two sexes resemble each other,
and do not change colour at any season. I do not know whether the
winter plumage is thicker and warmer than the summer plumage, but
warmth seems the most probable end attained of a double moult, where
there is no change of colour. Secondly, there are birds, for instance,
certain species of Totanus and other Grallatores, the sexes of which
resemble each other, but in which the summer and winter plumage differ
slightly in colour. The difference, however, in these cases is so small
that it can hardly be an advantage to them; and it may, perhaps, be
attributed to the direct action of the different conditions to which
the birds are exposed during the two seasons. Thirdly, there are many
other birds the sexes of which are alike, but which are widely
different in their summer and winter plumage. Fourthly, there are birds
the sexes of which differ from each other in colour; but the females,
though moulting twice, retain the same colours throughout the year,
whilst the males undergo a change of colour, sometimes a great one, as
with certain bustards. Fifthly and lastly, there are birds the sexes of
which differ from each other in both their summer and winter plumage;
but the male undergoes a greater amount of change at each recurrent
season than the female—of which the ruff (Machetes pugnax) offers a
good instance.

With respect to the cause or purpose of the differences in colour
between the summer and winter plumage, this may in some instances, as
with the ptarmigan (79. The brown mottled summer plumage of the
ptarmigan is of as much importance to it, as a protection, as the white
winter plumage; for in Scandinavia during the spring, when the snow has
disappeared, this bird is known to suffer greatly from birds of prey,
before it has acquired its summer dress: see Wilhelm von Wright, in
Lloyd, ‘Game Birds of Sweden,’ 1867, p. 125.), serve during both
seasons as a protection. When the difference between the two plumages
is slight it may perhaps be attributed, as already remarked, to the
direct action of the conditions of life. But with many birds there can
hardly be a doubt that the summer plumage is ornamental, even when both
sexes are alike. We may conclude that this is the case with many
herons, egrets, etc., for they acquire their beautiful plumes only
during the breeding-season. Moreover, such plumes, top-knots, etc.,
though possessed by both sexes, are occasionally a little more
developed in the male than in the female; and they resemble the plumes
and ornaments possessed by the males alone of other birds. It is also
known that confinement, by affecting the reproductive system of male
birds, frequently checks the development of their secondary sexual
characters, but has no immediate influence on any other characters; and
I am informed by Mr. Bartlett that eight or nine specimens of the Knot
(Tringa canutus) retained their unadorned winter plumage in the
Zoological Gardens throughout the year, from which fact we may infer
that the summer plumage, though common to both sexes, partakes of the
nature of the exclusively masculine plumage of many other birds. (80.
In regard to the previous statements on moulting, see, on snipes, etc.,
Macgillivray, ‘Hist. Brit. Birds,’ vol. iv. p. 371; on Glareolae,
curlews, and bustards, Jerdon, ‘Birds of India,’ vol. iii. pp. 615,
630, 683; on Totanus, ibid. p. 700; on the plumes of herons, ibid. p.
738, and Macgillivray, vol. iv. pp. 435 and 444, and Mr. Stafford
Allen, in the ‘Ibis,’ vol. v. 1863, p. 33.)

From the foregoing facts, more especially from neither sex of certain
birds changing colour during either annual moult, or changing so
slightly that the change can hardly be of any service to them, and from
the females of other species moulting twice yet retaining the same
colours throughout the year, we may conclude that the habit of annually
moulting twice has not been acquired in order that the male should
assume an ornamental character during the breeding-season; but that the
double moult, having been originally acquired for some distinct
purpose, has subsequently been taken advantage of in certain cases for
gaining a nuptial plumage.

It appears at first sight a surprising circumstance that some
closely-allied species should regularly undergo a double annual moult,
and others only a single one. The ptarmigan, for instance, moults twice
or even thrice in the year, and the blackcock only once: some of the
splendidly coloured honey-suckers (Nectariniae) of India and some
sub-genera of obscurely coloured pipits (Anthus) have a double, whilst
others have only a single annual moult. (81. On the moulting of the
ptarmigan, see Gould’s ‘Birds of Great Britain.’ On the honey-suckers,
Jerdon, ‘Birds of India,’ vol. i. pp. 359, 365, 369. On the moulting of
Anthus, see Blyth, in ‘Ibis,’ 1867, p. 32.) But the gradations in the
manner of moulting, which are known to occur with various birds, shew
us how species, or whole groups, might have originally acquired their
double annual moult, or having once gained the habit, have again lost
it. With certain bustards and plovers the vernal moult is far from
complete, some feathers being renewed, and some changed in colour.
There is also reason to believe that with certain bustards and
rail-like birds, which properly undergo a double moult, some of the
older males retain their nuptial plumage throughout the year. A few
highly modified feathers may merely be added during the spring to the
plumage, as occurs with the disc-formed tail-feathers of certain
drongos (Bhringa) in India, and with the elongated feathers on the
back, neck, and crest of certain herons. By such steps as these, the
vernal moult might be rendered more and more complete, until a perfect
double moult was acquired. Some of the birds of paradise retain their
nuptial feathers throughout the year, and thus have only a single
moult; others cast them directly after the breeding-season, and thus
have a double moult; and others again cast them at this season during
the first year, but not afterwards; so that these latter species are
intermediate in their manner of moulting. There is also a great
difference with many birds in the length of time during which the two
annual plumages are retained; so that the one might come to be retained
for the whole year, and the other completely lost. Thus in the spring
Machetes pugnax retains his ruff for barely two months. In Natal the
male widow-bird (Chera progne) acquires his fine plumage and long
tail-feathers in December or January, and loses them in March; so that
they are retained only for about three months. Most species, which
undergo a double moult, keep their ornamental feathers for about six
months. The male, however, of the wild Gallus bankiva retains his
neck-hackles for nine or ten months; and when these are cast off, the
underlying black feathers on the neck are fully exposed to view. But
with the domesticated descendant of this species, the neck-hackles of
the male are immediately replaced by new ones; so that we here see, as
to part of the plumage, a double moult changed under domestication into
a single moult. (82. For the foregoing statements in regard to partial
moults, and on old males retaining their nuptial plumage, see Jerdon,
on bustards and plovers, in ‘Birds of India,’ vol. iii. pp. 617, 637,
709, 711. Also Blyth in ‘Land and Water,’ 1867, p. 84. On the moulting
of Paradisea, see an interesting article by Dr. W. Marshall, ‘Archives
Neerlandaises,’ tom. vi. 1871. On the Vidua, ‘Ibis,’ vol. iii. 1861, p.
133. On the Drongo-shrikes, Jerdon, ibid. vol. i. p. 435. On the vernal
moult of the Herodias bubulcus, Mr. S.S. Allen, in ‘Ibis,’ 1863, p. 33.
On Gallus bankiva, Blyth, in ‘Annals and Mag. of Natural History,’ vol.
i. 1848, p. 455; see, also, on this subject, my ‘Variation of Animals
under Domestication,’ vol. i. p. 236.)

The common drake (Anas boschas), after the breeding-season, is well
known to lose his male plumage for a period of three months, during
which time he assumes that of the female. The male pin-tail duck (Anas
acuta) loses his plumage for the shorter period of six weeks or two
months; and Montagu remarks that “this double moult within so short a
time is a most extraordinary circumstance, that seems to bid defiance
to all human reasoning.” But the believer in the gradual modification
of species will be far from feeling surprise at finding gradations of
all kinds. If the male pin-tail were to acquire his new plumage within
a still shorter period, the new male feathers would almost necessarily
be mingled with the old, and both with some proper to the female; and
this apparently is the case with the male of a not distantly-allied
bird, namely the Merganser serrator, for the males are said to “undergo
a change of plumage, which assimilates them in some measure to the
female.” By a little further acceleration in the process, the double
moult would be completely lost. (83. See Macgillivray, ‘Hist. British
Birds’ (vol. v. pp. 34, 70, and 223), on the moulting of the Anatidae,
with quotations from Waterton and Montagu. Also Yarrell, ‘History of
British Birds,’ vol. iii. p. 243.)

Some male birds, as before stated, become more brightly coloured in the
spring, not by a vernal moult, but either by an actual change of colour
in the feathers, or by their obscurely-coloured deciduary margins being
shed. Changes of colour thus caused may last for a longer or shorter
time. In the Pelecanus onocrotalus a beautiful rosy tint, with
lemon-coloured marks on the breast, overspreads the whole plumage in
the spring; but these tints, as Mr. Sclater states, “do not last long,
disappearing generally in about six weeks or two months after they have
been attained.” Certain finches shed the margins of their feathers in
the spring, and then become brighter coloured, while other finches
undergo no such change. Thus the Fringilla tristis of the United States
(as well as many other American species) exhibits its bright colours
only when the winter is past, whilst our goldfinch, which exactly
represents this bird in habits, and our siskin, which represents it
still more closely in structure, undergo no such annual change. But a
difference of this kind in the plumage of allied species is not
surprising, for with the common linnet, which belongs to the same
family, the crimson forehead and breast are displayed only during the
summer in England, whilst in Madeira these colours are retained
throughout the year. (84. On the pelican, see Sclater, in ‘Proc. Zool.
Soc.’ 1868, p. 265. On the American finches, see Audubon,
‘Ornithological Biography,’ vol. i. pp. 174, 221, and Jerdon, ‘Birds of
India,’ vol. ii. p. 383. On the Fringilla cannabina of Madeira, Mr. E.
Vernon Harcourt, ‘Ibis,’ vol. v. 1863, p. 230.)

DISPLAY BY MALE BIRDS OF THEIR PLUMAGE.

Ornaments of all kinds, whether permanently or temporarily gained, are
sedulously displayed by the males, and apparently serve to excite,
attract, or fascinate the females. But the males will sometimes display
their ornaments, when not in the presence of the females, as
occasionally occurs with grouse at their balz-places, and as may be
noticed with the peacock; this latter bird, however, evidently wishes
for a spectator of some kind, and, as I have often seen, will shew off
his finery before poultry, or even pigs. (85. See also ‘Ornamental
Poultry,’ by Rev. E.S. Dixon, 1848, p. 8.) All naturalists who have
closely attended to the habits of birds, whether in a state of nature
or under confinement, are unanimously of opinion that the males take
delight in displaying their beauty. Audubon frequently speaks of the
male as endeavouring in various ways to charm the female. Mr. Gould,
after describing some peculiarities in a male humming-bird, says he has
no doubt that it has the power of displaying them to the greatest
advantage before the female. Dr. Jerdon (86. ‘Birds of India,’
introduct., vol. i. p. xxiv.; on the peacock, vol. iii. p. 507. See
Gould’s ‘Introduction to Trochilidae,’ 1861, pp. 15 and 111.) insists
that the beautiful plumage of the male serves “to fascinate and attract
the female.” Mr. Bartlett, at the Zoological Gardens, expressed himself
to me in the strongest terms to the same effect.

[Fig. 50. Rupicola crocea, male (T.W. Wood).]

It must be a grand sight in the forests of India “to come suddenly on
twenty or thirty pea-fowl, the males displaying their gorgeous trains,
and strutting about in all the pomp of pride before the gratified
females.” The wild turkey-cock erects his glittering plumage, expands
his finely-zoned tail and barred wing-feathers, and altogether, with
his crimson and blue wattles, makes a superb, though, to our eyes,
grotesque appearance. Similar facts have already been given with
respect to grouse of various kinds. Turning to another Order: The male
Rupicola crocea (Fig. 50) is one of the most beautiful birds in the
world, being of a splendid orange, with some of the feathers curiously
truncated and plumose. The female is brownish-green, shaded with red,
and has a much smaller crest. Sir R. Schomburgk has described their
courtship; he found one of their meeting-places where ten males and two
females were present. The space was from four to five feet in diameter,
and appeared to have been cleared of every blade of grass and smoothed
as if by human hands. A male “was capering, to the apparent delight of
several others. Now spreading its wings, throwing up its head, or
opening its tail like a fan; now strutting about with a hopping gait
until tired, when it gabbled some kind of note, and was relieved by
another. Thus three of them successively took the field, and then, with
self-approbation, withdrew to rest.” The Indians, in order to obtain
their skins, wait at one of the meeting-places till the birds are
eagerly engaged in dancing, and then are able to kill with their
poisoned arrows four or five males, one after the other. (87. ‘Journal
of R. Geograph. Soc.’ vol. x. 1840, p. 236.) With birds of paradise a
dozen or more full-plumaged males congregate in a tree to hold a
dancing-party, as it is called by the natives: and here they fly about,
raise their wings, elevate their exquisite plumes, and make them
vibrate, and the whole tree seems, as Mr. Wallace remarks, to be filled
with waving plumes. When thus engaged, they become so absorbed that a
skilful archer may shoot nearly the whole party. These birds, when kept
in confinement in the Malay Archipelago, are said to take much care in
keeping their feathers clean; often spreading them out, examining them,
and removing every speck of dirt. One observer, who kept several pairs
alive, did not doubt that the display of the male was intended to
please the female. (88. ‘Annals and Mag. of Nat. Hist.’ vol. xiii.
1854, p. 157; also Wallace, ibid. vol. xx. 1857, p. 412, and ‘The Malay
Archipelago,’ vol. ii. 1869, p. 252. Also Dr. Bennett, as quoted by
Brehm, ‘Thierleben,’ B. iii. s. 326.)

[Fig. 51. Polyplectron chinquis, male (T.W. Wood).]

The Gold and Amherst pheasants during their courtship not only expand
and raise their splendid frills, but twist them, as I have myself seen,
obliquely towards the female on whichever side she may be standing,
obviously in order that a large surface may be displayed before her.
(89. Mr. T.W. Wood has given (‘The Student,’ April 1870, p. 115) a full
account of this manner of display, by the Gold pheasant and by the
Japanese pheasant, Ph. versicolor; and he calls it the lateral or
one-sided display.) They likewise turn their beautiful tails and
tail-coverts a little towards the same side. Mr. Bartlett has observed
a male Polyplectron (Fig. 51) in the act of courtship, and has shewn me
a specimen stuffed in the attitude then assumed. The tail and
wing-feathers of this bird are ornamented with beautiful ocelli, like
those on the peacock’s train. Now when the peacock displays himself, he
expands and erects his tail transversely to his body, for he stands in
front of the female, and has to shew off, at the same time, his rich
blue throat and breast. But the breast of the Polyplectron is obscurely
coloured, and the ocelli are not confined to the tail-feathers.
Consequently the Polyplectron does not stand in front of the female;
but he erects and expands his tail-feathers a little obliquely,
lowering the expanded wing on the same side, and raising that on the
opposite side. In this attitude the ocelli over the whole body are
exposed at the same time before the eyes of the admiring female in one
grand bespangled expanse. To whichever side she may turn, the expanded
wings and the obliquely-held tail are turned towards her. The male
Tragopan pheasant acts in nearly the same manner, for he raises the
feathers of the body, though not the wing itself, on the side which is
opposite to the female, and which would otherwise be concealed, so that
nearly all the beautifully spotted feathers are exhibited at the same
time.

[Fig. 52. Side view of male Argus pheasant, whilst displaying before
the female. Observed and sketched from nature by T.W. Wood.]

The Argus pheasant affords a much more remarkable case. The immensely
developed secondary wing-feathers are confined to the male; and each is
ornamented with a row of from twenty to twenty-three ocelli, above an
inch in diameter. These feathers are also elegantly marked with oblique
stripes and rows of spots of a dark colour, like those on the skin of a
tiger and leopard combined. These beautiful ornaments are hidden until
the male shows himself off before the female. He then erects his tail,
and expands his wing-feathers into a great, almost upright, circular
fan or shield, which is carried in front of the body. The neck and head
are held on one side, so that they are concealed by the fan; but the
bird in order to see the female, before whom he is displaying himself,
sometimes pushes his head between two of the long wing-feathers (as Mr.
Bartlett has seen), and then presents a grotesque appearance. This must
be a frequent habit with the bird in a state of nature, for Mr.
Bartlett and his son on examining some perfect skins sent from the
East, found a place between two of the feathers which was much frayed,
as if the head had here frequently been pushed through. Mr. Wood thinks
that the male can also peep at the female on one side, beyond the
margin of the fan.

The ocelli on the wing-feathers are wonderful objects; for they are so
shaded that, as the Duke of Argyll remarks (90. ‘The Reign of Law,’
1867, p. 203.), they stand out like balls lying loosely within sockets.
When I looked at the specimen in the British Museum, which is mounted
with the wings expanded and trailing downwards, I was however greatly
disappointed, for the ocelli appeared flat, or even concave. But Mr.
Gould soon made the case clear to me, for he held the feathers erect,
in the position in which they would naturally be displayed, and now,
from the light shining on them from above, each ocellus at once
resembled the ornament called a ball and socket. These feathers have
been shown to several artists, and all have expressed their admiration
at the perfect shading. It may well be asked, could such artistically
shaded ornaments have been formed by means of sexual selection? But it
will be convenient to defer giving an answer to this question until we
treat in the next chapter of the principle of gradation.

The foregoing remarks relate to the secondary wing-feathers, but the
primary wing-feathers, which in most gallinaceous birds are uniformly
coloured, are in the Argus pheasant equally wonderful. They are of a
soft brown tint with numerous dark spots, each of which consists of two
or three black dots with a surrounding dark zone. But the chief
ornament is a space parallel to the dark-blue shaft, which in outline
forms a perfect second feather lying within the true feather. This
inner part is coloured of a lighter chestnut, and is thickly dotted
with minute white points. I have shewn this feather to several persons,
and many have admired it even more than the ball and socket feathers,
and have declared that it was more like a work of art than of nature.
Now these feathers are quite hidden on all ordinary occasions, but are
fully displayed, together with the long secondary feathers, when they
are all expanded together so as to form the great fan or shield.

The case of the male Argus pheasant is eminently interesting, because
it affords good evidence that the most refined beauty may serve as a
sexual charm, and for no other purpose. We must conclude that this is
the case, as the secondary and primary wing-feathers are not at all
displayed, and the ball and socket ornaments are not exhibited in full
perfection until the male assumes the attitude of courtship. The Argus
pheasant does not possess brilliant colours, so that his success in
love appears to depend on the great size of his plumes, and on the
elaboration of the most elegant patterns. Many will declare that it is
utterly incredible that a female bird should be able to appreciate fine
shading and exquisite patterns. It is undoubtedly a marvellous fact
that she should possess this almost human degree of taste. He who
thinks that he can safely gauge the discrimination and taste of the
lower animals may deny that the female Argus pheasant can appreciate
such refined beauty; but he will then be compelled to admit that the
extraordinary attitudes assumed by the male during the act of
courtship, by which the wonderful beauty of his plumage is fully
displayed, are purposeless; and this is a conclusion which I for one
will never admit.

Although so many pheasants and allied gallinaceous birds carefully
display their plumage before the females, it is remarkable, as Mr.
Bartlett informs me, that this is not the case with the dull-coloured
Eared and Cheer pheasants (Crossoptilon auritum and Phasianus
wallichii); so that these birds seem conscious that they have little
beauty to display. Mr. Bartlett has never seen the males of either of
these species fighting together, though he has not had such good
opportunities for observing the Cheer as the Eared pheasant. Mr. Jenner
Weir, also, finds that all male birds with rich or
strongly-characterised plumage are more quarrelsome than the
dull-coloured species belonging to the same groups. The goldfinch, for
instance, is far more pugnacious than the linnet, and the blackbird
than the thrush. Those birds which undergo a seasonal change of plumage
likewise become much more pugnacious at the period when they are most
gaily ornamented. No doubt the males of some obscurely-coloured birds
fight desperately together, but it appears that when sexual selection
has been highly influential, and has given bright colours to the males
of any species, it has also very often given a strong tendency to
pugnacity. We shall meet with nearly analogous cases when we treat of
mammals. On the other hand, with birds the power of song and brilliant
colours have rarely been both acquired by the males of the same
species; but in this case the advantage gained would have been the
same, namely success in charming the female. Nevertheless it must be
owned that the males of several brilliantly coloured birds have had
their feathers specially modified for the sake of producing
instrumental music, though the beauty of this cannot be compared, at
least according to our taste, with that of the vocal music of many
songsters.

We will now turn to male birds which are not ornamented in any high
degree, but which nevertheless display during their courtship whatever
attractions they may possess. These cases are in some respects more
curious than the foregoing, and have been but little noticed. I owe the
following facts to Mr. Weir, who has long kept confined birds of many
kinds, including all the British Fringillidae and Emberizidae. The
facts have been selected from a large body of valuable notes kindly
sent me by him. The bullfinch makes his advances in front of the
female, and then puffs out his breast, so that many more of the crimson
feathers are seen at once than otherwise would be the case. At the same
time he twists and bows his black tail from side to side in a ludicrous
manner. The male chaffinch also stands in front of the female, thus
shewing his red breast and “blue bell,” as the fanciers call his head;
the wings at the same time being slightly expanded, with the pure white
bands on the shoulders thus rendered conspicuous. The common linnet
distends his rosy breast, slightly expands his brown wings and tail, so
as to make the best of them by exhibiting their white edgings. We must,
however, be cautious in concluding that the wings are spread out solely
for display, as some birds do so whose wings are not beautiful. This is
the case with the domestic cock, but it is always the wing on the side
opposite to the female which is expanded, and at the same time scraped
on the ground. The male goldfinch behaves differently from all other
finches: his wings are beautiful, the shoulders being black, with the
dark-tipped wing-feathers spotted with white and edged with golden
yellow. When he courts the female, he sways his body from side to side,
and quickly turns his slightly expanded wings first to one side, then
to the other, with a golden flashing effect. Mr. Weir informs me that
no other British finch turns thus from side to side during his
courtship, not even the closely-allied male siskin, for he would not
thus add to his beauty.

Most of the British Buntings are plain coloured birds; but in the
spring the feathers on the head of the male reed-bunting (Emberiza
schoeniculus) acquire a fine black colour by the abrasion of the dusky
tips; and these are erected during the act of courtship. Mr. Weir has
kept two species of Amadina from Australia: the A. castanotis is a very
small and chastely coloured finch, with a dark tail, white rump, and
jet-black upper tail-coverts, each of the latter being marked with
three large conspicuous oval spots of white. (91. For the description
of these birds, see Gould’s ‘Handbook to the Birds of Australia,’ vol.
i. 1865, p. 417.) This species, when courting the female, slightly
spreads out and vibrates these parti-coloured tail-coverts in a very
peculiar manner. The male Amadina Lathami behaves very differently,
exhibiting before the female his brilliantly spotted breast, scarlet
rump, and scarlet upper tail-coverts. I may here add from Dr. Jerdon
that the Indian bulbul (Pycnonotus hoemorrhous) has its under
tail-coverts of a crimson colour, and these, it might be thought, could
never be well exhibited; but the bird “when excited often spreads them
out laterally, so that they can be seen even from above.” (92. ‘Birds
of India,’ vol. ii. p. 96.) The crimson under tail-coverts of some
other birds, as with one of the woodpeckers, Picus major, can be seen
without any such display. The common pigeon has iridescent feathers on
the breast, and every one must have seen how the male inflates his
breast whilst courting the female, thus shewing them off to the best
advantage. One of the beautiful bronze-winged pigeons of Australia
(Ocyphaps lophotes) behaves, as described to me by Mr. Weir, very
differently: the male, whilst standing before the female, lowers his
head almost to the ground, spreads out and raises his tail, and half
expands his wings. He then alternately and slowly raises and depresses
his body, so that the iridescent metallic feathers are all seen at
once, and glitter in the sun.

Sufficient facts have now been given to shew with what care male birds
display their various charms, and this they do with the utmost skill.
Whilst preening their feathers, they have frequent opportunities for
admiring themselves, and of studying how best to exhibit their beauty.
But as all the males of the same species display themselves in exactly
the same manner, it appears that actions, at first perhaps intentional,
have become instinctive. If so, we ought not to accuse birds of
conscious vanity; yet when we see a peacock strutting about, with
expanded and quivering tail-feathers, he seems the very emblem of pride
and vanity.

The various ornaments possessed by the males are certainly of the
highest importance to them, for in some cases they have been acquired
at the expense of greatly impeded powers of flight or of running. The
African night-jar (Cosmetornis), which during the pairing-season has
one of its primary wing-feathers developed into a streamer of very
great length, is thereby much retarded in its flight, although at other
times remarkable for its swiftness. The “unwieldy size” of the
secondary wing-feathers of the male Argus pheasant is said “almost
entirely to deprive the bird of flight.” The fine plumes of male birds
of paradise trouble them during a high wind. The extremely long
tail-feathers of the male widow-birds (Vidua) of Southern Africa render
“their flight heavy;” but as soon as these are cast off they fly as
well as the females. As birds always breed when food is abundant, the
males probably do not suffer much inconvenience in searching for food
from their impeded powers of movement; but there can hardly be a doubt
that they must be much more liable to be struck down by birds of prey.
Nor can we doubt that the long train of the peacock and the long tail
and wing-feathers of the Argus pheasant must render them an easier prey
to any prowling tiger-cat than would otherwise be the case. Even the
bright colours of many male birds cannot fail to make them conspicuous
to their enemies of all kinds. Hence, as Mr. Gould has remarked, it
probably is that such birds are generally of a shy disposition, as if
conscious that their beauty was a source of danger, and are much more
difficult to discover or approach, than the sombre coloured and
comparatively tame females or than the young and as yet unadorned
males. (93. On the Cosmetornis, see Livingstone’s ‘Expedition to the
Zambesi,’ 1865, p. 66. On the Argus pheasant, Jardine’s ‘Nat. Hist.
Lib.: Birds,’ vol. xiv. p. 167. On Birds of Paradise, Lesson, quoted by
Brehm, ‘Thierleben,’ B. iii. s. 325. On the widow-bird, Barrow’s
‘Travels in Africa,’ vol. i. p. 243, and ‘Ibis,’ vol. iii. 1861 p. 133.
Mr. Gould, on the shyness of male birds, ‘Handbook to Birds of
Australia,’ vol. i. 1865, pp. 210, 457.)

It is a more curious fact that the males of some birds which are
provided with special weapons for battle, and which in a state of
nature are so pugnacious that they often kill each other, suffer from
possessing certain ornaments. Cock-fighters trim the hackles and cut
off the combs and gills of their cocks; and the birds are then said to
be dubbed. An undubbed bird, as Mr. Tegetmeier insists, “is at a
fearful disadvantage; the comb and gills offer an easy hold to his
adversary’s beak, and as a cock always strikes where he holds, when
once he has seized his foe, he has him entirely in his power. Even
supposing that the bird is not killed, the loss of blood suffered by an
undubbed cock is much greater than that sustained by one that has been
trimmed.” (94. Tegetmeier, ‘The Poultry Book,’ 1866, p. 139.) Young
turkey-cocks in fighting always seize hold of each other’s wattles; and
I presume that the old birds fight in the same manner. It may perhaps
be objected that the comb and wattles are not ornamental, and cannot be
of service to the birds in this way; but even to our eyes, the beauty
of the glossy black Spanish cock is much enhanced by his white face and
crimson comb; and no one who has ever seen the splendid blue wattles of
the male Tragopan pheasant distended in courtship can for a moment
doubt that beauty is the object gained. From the foregoing facts we
clearly see that the plumes and other ornaments of the males must be of
the highest importance to them; and we further see that beauty is even
sometimes more important than success in battle.




CHAPTER XIV.
BIRDS—continued.


Choice exerted by the female—Length of courtship—Unpaired birds—Mental
qualities and taste for the beautiful—Preference or antipathy shewn by
the female for particular males—Variability of birds—Variations
sometimes abrupt—Laws of variation—Formation of ocelli—Gradations of
character—Case of Peacock, Argus pheasant, and Urosticte.

When the sexes differ in beauty or in the power of singing, or in
producing what I have called instrumental music, it is almost
invariably the male who surpasses the female. These qualities, as we
have just seen, are evidently of high importance to the male. When they
are gained for only a part of the year it is always before the
breeding-season. It is the male alone who elaborately displays his
varied attractions, and often performs strange antics on the ground or
in the air, in the presence of the female. Each male drives away, or if
he can, kills his rivals. Hence we may conclude that it is the object
of the male to induce the female to pair with him, and for this purpose
he tries to excite or charm her in various ways; and this is the
opinion of all those who have carefully studied the habits of living
birds. But there remains a question which has an all important bearing
on sexual selection, namely, does every male of the same species excite
and attract the female equally? Or does she exert a choice, and prefer
certain males? This latter question can be answered in the affirmative
by much direct and indirect evidence. It is far more difficult to
decide what qualities determine the choice of the females; but here
again we have some direct and indirect evidence that it is to a large
extent the external attractions of the male; though no doubt his
vigour, courage, and other mental qualities come into play. We will
begin with the indirect evidence.

LENGTH OF COURTSHIP.

The lengthened period during which both sexes of certain birds meet day
after day at an appointed place probably depends partly on the
courtship being a prolonged affair, and partly on reiteration in the
act of pairing. Thus in Germany and Scandinavia the balzen or leks of
the black-cocks last from the middle of March, all through April into
May. As many as forty or fifty, or even more birds congregate at the
leks; and the same place is often frequented during successive years.
The lek of the capercailzie lasts from the end of March to the middle
or even end of May. In North America “the partridge dances” of the
Tetrao phasianellus “last for a month or more.” Other kinds of grouse,
both in North America and Eastern Siberia (1. Nordman describes (‘Bull.
Soc. Imp. des Nat. Moscou,’ 1861, tom. xxxiv. p. 264) the balzen of
Tetrao urogalloides in Amur Land. He estimated the number of birds
assembled at above a hundred, not counting the females, which lie hid
in the surrounding bushes. The noises uttered differ from those of T.
urogallus.), follow nearly the same habits. The fowlers discover the
hillocks where the ruffs congregate by the grass being trampled bare,
and this shews that the same spot is long frequented. The Indians of
Guiana are well acquainted with the cleared arenas, where they expect
to find the beautiful cocks of the Rock; and the natives of New Guinea
know the trees where from ten to twenty male birds of paradise in full
plumage congregate. In this latter case it is not expressly stated that
the females meet on the same trees, but the hunters, if not specially
asked, would probably not mention their presence, as their skins are
valueless. Small parties of an African weaver (Ploceus) congregate,
during the breeding-season, and perform for hours their graceful
evolutions. Large numbers of the Solitary snipe (Scolopax major)
assemble during dusk in a morass; and the same place is frequented for
the same purpose during successive years; here they may be seen running
about “like so many large rats,” puffing out their feathers, flapping
their wings, and uttering the strangest cries. (2. With respect to the
assemblages of the above named grouse, see Brehm, ‘Thierleben,’ B. iv.
s. 350; also L. Lloyd, ‘Game Birds of Sweden,’ 1867, pp. 19, 78.
Richardson, ‘Fauna Bor. Americana: Birds,’ p. 362. References in regard
to the assemblages of other birds have already been given. On
Paradisea, see Wallace, in ‘Annals and Mag. of Nat. Hist.’ vol. xx.
1857, p. 412. On the snipe, Lloyd, ibid. p. 221.)

Some of the above birds,—the black-cock, capercailzie, pheasant-grouse,
ruff, solitary snipe, and perhaps others,—are, as is believed,
polygamists. With such birds it might have been thought that the
stronger males would simply have driven away the weaker, and then at
once have taken possession of as many females as possible; but if it be
indispensable for the male to excite or please the female, we can
understand the length of the courtship and the congregation of so many
individuals of both sexes at the same spot. Certain strictly monogamous
species likewise hold nuptial assemblages; this seems to be the case in
Scandinavia with one of the ptarmigans, and their leks last from the
middle of March to the middle of May. In Australia the lyre-bird
(Menura superba) forms “small round hillocks,” and the M. Alberti
scratches for itself shallow holes, or, as they are called by the
natives, “corroborying places,” where it is believed both sexes
assemble. The meetings of the M. superba are sometimes very large; and
an account has lately been published (3. Quoted by Mr. T.W. Wood, in
the ‘Student,’ April 1870, p. 125.) by a traveller, who heard in a
valley beneath him, thickly covered with scrub, “a din which completely
astonished” him; on crawling onwards he beheld, to his amazement, about
one hundred and fifty of the magnificent lyre-cocks, “ranged in order
of battle, and fighting with indescribable fury.” The bowers of the
Bower-birds are the resort of both sexes during the breeding-season;
and “here the males meet and contend with each other for the favours of
the female, and here the latter assemble and coquet with the males.”
With two of the genera, the same bower is resorted to during many
years. (4. Gould, ‘Handbook to the Birds of Australia,’ vol. i. pp.
300, 308, 448, 451. On the ptarmigan, above alluded to, see Lloyd,
ibid. p. 129.)

The common magpie (Corvus pica, Linn.), as I have been informed by the
Rev. W. Darwin Fox, used to assemble from all parts of Delamere Forest,
in order to celebrate the “great magpie marriage.” Some years ago these
birds abounded in extraordinary numbers, so that a gamekeeper killed in
one morning nineteen males, and another killed by a single shot seven
birds at roost together. They then had the habit of assembling very
early in the spring at particular spots, where they could be seen in
flocks, chattering, sometimes fighting, bustling and flying about the
trees. The whole affair was evidently considered by the birds as one of
the highest importance. Shortly after the meeting they all separated,
and were then observed by Mr. Fox and others to be paired for the
season. In any district in which a species does not exist in large
numbers, great assemblages cannot, of course, be held, and the same
species may have different habits in different countries. For instance,
I have heard of only one instance, from Mr. Wedderburn, of a regular
assemblage of black game in Scotland, yet these assemblages are so well
known in Germany and Scandinavia that they have received special names.

UNPAIRED BIRDS.

From the facts now given, we may conclude that the courtship of birds
belonging to widely different groups, is often a prolonged, delicate,
and troublesome affair. There is even reason to suspect, improbable as
this will at first appear, that some males and females of the same
species, inhabiting the same district, do not always please each other,
and consequently do not pair. Many accounts have been published of
either the male or female of a pair having been shot, and quickly
replaced by another. This has been observed more frequently with the
magpie than with any other bird, owing perhaps to its conspicuous
appearance and nest. The illustrious Jenner states that in Wiltshire
one of a pair was daily shot no less than seven times successively,
“but all to no purpose, for the remaining magpie soon found another
mate”; and the last pair reared their young. A new partner is generally
found on the succeeding day; but Mr. Thompson gives the case of one
being replaced on the evening of the same day. Even after the eggs are
hatched, if one of the old birds is destroyed a mate will often be
found; this occurred after an interval of two days, in a case recently
observed by one of Sir J. Lubbock’s keepers. (5. On magpies, Jenner, in
‘Philosophical Transactions,’ 1824, p. 21. Macgillivray, ‘Hist. British
Birds,’ vol. i. p. 570. Thompson, in ‘Annals and Magazine of Natural
History,’ vol. viii. 1842, p. 494.) The first and most obvious
conjecture is that male magpies must be much more numerous than
females; and that in the above cases, as well as in many others which
could be given, the males alone had been killed. This apparently holds
good in some instances, for the gamekeepers in Delamere Forest assured
Mr. Fox that the magpies and carrion-crows which they formerly killed
in succession in large numbers near their nests, were all males; and
they accounted for this fact by the males being easily killed whilst
bringing food to the sitting females. Macgillivray, however, gives, on
the authority of an excellent observer, an instance of three magpies
successively killed on the same nest, which were all females; and
another case of six magpies successively killed whilst sitting on the
same eggs, which renders it probable that most of them were females;
though, as I hear from Mr. Fox, the male will sit on the eggs when the
female is killed.

Sir J. Lubbock’s gamekeeper has repeatedly shot, but how often he could
not say, one of a pair of jays (Garrulus glandarius), and has never
failed shortly afterwards to find the survivor re-matched. Mr. Fox, Mr.
F. Bond, and others have shot one of a pair of carrion-crows (Corvus
corone), but the nest was soon again tenanted by a pair. These birds
are rather common; but the peregrine-falcon (Falco peregrinus) is rare,
yet Mr. Thompson states that in Ireland “if either an old male or
female be killed in the breeding-season (not an uncommon circumstance),
another mate is found within a very few days, so that the eyries,
notwithstanding such casualties, are sure to turn out their complement
of young.” Mr. Jenner Weir has known the same thing with the
peregrine-falcons at Beachy Head. The same observer informs me that
three kestrels (Falco tinnunculus), all males, were killed one after
the other whilst attending the same nest; two of these were in mature
plumage, but the third was in the plumage of the previous year. Even
with the rare golden eagle (Aquila chrysaetos), Mr. Birkbeck was
assured by a trustworthy gamekeeper in Scotland, that if one is killed,
another is soon found. So with the white owl (Strix flammea), “the
survivor readily found a mate, and the mischief went on.”

White of Selborne, who gives the case of the owl, adds that he knew a
man, who from believing that partridges when paired were disturbed by
the males fighting, used to shoot them; and though he had widowed the
same female several times, she always soon found a fresh partner. This
same naturalist ordered the sparrows, which deprived the house-martins
of their nests, to be shot; but the one which was left, “be it cock or
hen, presently procured a mate, and so for several times following.” I
could add analogous cases relating to the chaffinch, nightingale, and
redstart. With respect to the latter bird (Phoenicura ruticilla), a
writer expresses much surprise how the sitting female could so soon
have given effectual notice that she was a widow, for the species was
not common in the neighbourhood. Mr. Jenner Weir has mentioned to me a
nearly similar case; at Blackheath he never sees or hears the note of
the wild bullfinch, yet when one of his caged males has died, a wild
one in the course of a few days has generally come and perched near the
widowed female, whose call-note is not loud. I will give only one other
fact, on the authority of this same observer; one of a pair of
starlings (Sturnus vulgaris) was shot in the morning; by noon a new
mate was found; this was again shot, but before night the pair was
complete; so that the disconsolate widow or widower was thrice consoled
during the same day. Mr. Engleheart also informs me that he used during
several years to shoot one of a pair of starlings which built in a hole
in a house at Blackheath; but the loss was always immediately repaired.
During one season he kept an account, and found that he had shot
thirty-five birds from the same nest; these consisted of both males and
females, but in what proportion he could not say: nevertheless, after
all this destruction, a brood was reared. (6. On the peregrine falcon,
see Thompson, ‘Nat. Hist. of Ireland: Birds,’ vol. i. 1849, p. 39. On
owls, sparrows, and partridges, see White, ‘Nat. Hist. of Selborne,’
edit. of 1825, vol. i. p. 139. On the Phoenicura, see Loudon’s ‘Mag. of
Nat. Hist.’ vol. vii. 1834, p. 245. Brehm (‘Thierleben,’ B. iv. s. 991)
also alludes to cases of birds thrice mated during the same day.)

These facts well deserve attention. How is it that there are birds
enough ready to replace immediately a lost mate of either sex? Magpies,
jays, carrion-crows, partridges, and some other birds, are always seen
during the spring in pairs, and never by themselves; and these offer at
first sight the most perplexing cases. But birds of the same sex,
although of course not truly paired, sometimes live in pairs or in
small parties, as is known to be the case with pigeons and partridges.
Birds also sometimes live in triplets, as has been observed with
starlings, carrion-crows, parrots, and partridges. With partridges two
females have been known to live with one male, and two males with one
female. In all such cases it is probable that the union would be easily
broken; and one of the three would readily pair with a widow or
widower. The males of certain birds may occasionally be heard pouring
forth their love-song long after the proper time, shewing that they
have either lost or never gained a mate. Death from accident or disease
of one of a pair would leave the other free and single; and there is
reason to believe that female birds during the breeding-season are
especially liable to premature death. Again, birds which have had their
nests destroyed, or barren pairs, or retarded individuals, would easily
be induced to desert their mates, and would probably be glad to take
what share they could of the pleasures and duties of rearing offspring
although not their own. (7. See White (‘Nat. Hist. of Selborne,’ 1825,
vol. i. p. 140) on the existence, early in the season, of small coveys
of male partridges, of which fact I have heard other instances. See
Jenner, on the retarded state of the generative organs in certain
birds, in ‘Phil. Transact.’ 1824. In regard to birds living in
triplets, I owe to Mr. Jenner Weir the cases of the starlings and
parrots, and to Mr. Fox, of partridges; on carrion-crows, see the
‘Field,’ 1868, p. 415. On various male birds singing after the proper
period, see Rev. L. Jenyns, ‘Observations in Natural History,’ 1846, p.
87.) Such contingencies as these probably explain most of the foregoing
cases. (8. The following case has been given (‘The Times,’ Aug. 6,
1868) by the Rev. F.O. Morris, on the authority of the Hon. and Rev.
O.W. Forester. “The gamekeeper here found a hawk’s nest this year, with
five young ones on it. He took four and killed them, but left one with
its wings clipped as a decoy to destroy the old ones by. They were both
shot next day, in the act of feeding the young one, and the keeper
thought it was done with. The next day he came again and found two
other charitable hawks, who had come with an adopted feeling to succour
the orphan. These two he killed, and then left the nest. On returning
afterwards he found two more charitable individuals on the same errand
of mercy. One of these he killed; the other he also shot, but could not
find. No more came on the like fruitless errand.”) Nevertheless, it is
a strange fact that within the same district, during the height of the
breeding-season, there should be so many males and females always ready
to repair the loss of a mated bird. Why do not such spare birds
immediately pair together? Have we not some reason to suspect, and the
suspicion has occurred to Mr. Jenner Weir, that as the courtship of
birds appears to be in many cases prolonged and tedious, so it
occasionally happens that certain males and females do not succeed,
during the proper season, in exciting each other’s love, and
consequently do not pair? This suspicion will appear somewhat less
improbable after we have seen what strong antipathies and preferences
female birds occasionally evince towards particular males.

MENTAL QUALITIES OF BIRDS, AND THEIR TASTE FOR THE BEAUTIFUL.

Before we further discuss the question whether the females select the
more attractive males or accept the first whom they may encounter, it
will be advisable briefly to consider the mental powers of birds. Their
reason is generally, and perhaps justly, ranked as low; yet some facts
could be given leading to an opposite conclusion. (9. I am indebted to
Prof. Newton for the following passage from Mr. Adam’s ‘Travels of a
Naturalist,’ 1870, p. 278. Speaking of Japanese nut-hatches in
confinement, he says: “Instead of the more yielding fruit of the yew,
which is the usual food of the nut-hatch of Japan, at one time I
substituted hard hazel-nuts. As the bird was unable to crack them, he
placed them one by one in his water-glass, evidently with the notion
that they would in time become softer—an interesting proof of
intelligence on the part of these birds.”) Low powers of reasoning,
however, are compatible, as we see with mankind, with strong
affections, acute perception, and a taste for the beautiful; and it is
with these latter qualities that we are here concerned. It has often
been said that parrots become so deeply attached to each other that
when one dies the other pines for a long time; but Mr. Jenner Weir
thinks that with most birds the strength of their affection has been
much exaggerated. Nevertheless when one of a pair in a state of nature
has been shot, the survivor has been heard for days afterwards uttering
a plaintive call; and Mr. St. John gives various facts proving the
attachment of mated birds. (10. ‘A Tour in Sutherlandshire,’ vol. i.
1849, p. 185. Dr. Buller says (‘Birds of New Zealand,’ 1872, p. 56)
that a male King Lory was killed; and the female “fretted and moped,
refused her food, and died of a broken heart.”) Mr. Bennett relates
(11. ‘Wanderings in New South Wales,’ vol. ii. 1834, p. 62.) that in
China after a drake of the beautiful mandarin Teal had been stolen, the
duck remained disconsolate, though sedulously courted by another
mandarin drake, who displayed before her all his charms. After an
interval of three weeks the stolen drake was recovered, and instantly
the pair recognised each other with extreme joy. On the other hand,
starlings, as we have seen, may be consoled thrice in the same day for
the loss of their mates. Pigeons have such excellent local memories,
that they have been known to return to their former homes after an
interval of nine months, yet, as I hear from Mr. Harrison Weir, if a
pair which naturally would remain mated for life be separated for a few
weeks during the winter, and afterwards matched with other birds, the
two when brought together again, rarely, if ever, recognise each other.

Birds sometimes exhibit benevolent feelings; they will feed the
deserted young ones even of distinct species, but this perhaps ought to
be considered as a mistaken instinct. They will feed, as shewn in an
earlier part of this work, adult birds of their own species which have
become blind. Mr. Buxton gives a curious account of a parrot which took
care of a frost-bitten and crippled bird of a distinct species,
cleansed her feathers, and defended her from the attacks of the other
parrots which roamed freely about his garden. It is a still more
curious fact that these birds apparently evince some sympathy for the
pleasures of their fellows. When a pair of cockatoos made a nest in an
acacia tree, “it was ridiculous to see the extravagant interest taken
in the matter by the others of the same species.” These parrots, also,
evinced unbounded curiosity, and clearly had “the idea of property and
possession.” (12. ‘Acclimatization of Parrots,’ by C. Buxton, M.P.,
‘Annals and Mag. of Nat. Hist.’ Nov. 1868, p. 381.) They have good
memories, for in the Zoological Gardens they have plainly recognised
their former masters after an interval of some months.

Birds possess acute powers of observation. Every mated bird, of course,
recognises its fellow. Audubon states that a certain number of
mocking-thrushes (Mimus polyglottus) remain all the year round in
Louisiana, whilst others migrate to the Eastern States; these latter,
on their return, are instantly recognised, and always attacked, by
their southern brethren. Birds under confinement distinguish different
persons, as is proved by the strong and permanent antipathy or
affection which they shew, without any apparent cause, towards certain
individuals. I have heard of numerous instances with jays, partridges,
canaries, and especially bullfinches. Mr. Hussey has described in how
extraordinary a manner a tamed partridge recognised everybody: and its
likes and dislikes were very strong. This bird seemed “fond of gay
colours, and no new gown or cap could be put on without catching his
attention.” (13. The ‘Zoologist,’ 1847-48, p. 1602.) Mr. Hewitt has
described the habits of some ducks (recently descended from wild
birds), which, at the approach of a strange dog or cat, would rush
headlong into the water, and exhaust themselves in their attempts to
escape; but they knew Mr. Hewitt’s own dogs and cats so well that they
would lie down and bask in the sun close to them. They always moved
away from a strange man, and so they would from the lady who attended
them if she made any great change in her dress. Audubon relates that he
reared and tamed a wild turkey which always ran away from any strange
dog; this bird escaped into the woods, and some days afterwards Audubon
saw, as he thought, a wild turkey, and made his dog chase it; but, to
his astonishment, the bird did not run away, and the dog, when he came
up, did not attack the bird, for they mutually recognised each other as
old friends. (14. Hewitt on wild ducks, ‘Journal of Horticulture,’ Jan.
13, 1863, p. 39. Audubon on the wild turkey, ‘Ornithological
Biography,’ vol. i. p. 14. On the mocking-thrush, ibid. vol. i. p.
110.)

Mr. Jenner Weir is convinced that birds pay particular attention to the
colours of other birds, sometimes out of jealousy, and sometimes as a
sign of kinship. Thus he turned a reed-bunting (Emberiza schoeniculus),
which had acquired its black head-dress, into his aviary, and the
new-comer was not noticed by any bird, except by a bullfinch, which is
likewise black-headed. This bullfinch was a very quiet bird, and had
never before quarrelled with any of its comrades, including another
reed-bunting, which had not as yet become black-headed: but the
reed-bunting with a black head was so unmercifully treated that it had
to be removed. Spiza cyanea, during the breeding-season, is of a bright
blue colour; and though generally peaceable, it attacked S. ciris,
which has only the head blue, and completely scalped the unfortunate
bird. Mr. Weir was also obliged to turn out a robin, as it fiercely
attacked all the birds in his aviary with any red in their plumage, but
no other kinds; it actually killed a red-breasted crossbill, and nearly
killed a goldfinch. On the other hand, he has observed that some birds,
when first introduced, fly towards the species which resemble them most
in colour, and settle by their sides.

As male birds display their fine plumage and other ornaments with so
much care before the females, it is obviously probable that these
appreciate the beauty of their suitors. It is, however, difficult to
obtain direct evidence of their capacity to appreciate beauty. When
birds gaze at themselves in a looking-glass (of which many instances
have been recorded) we cannot feel sure that it is not from jealousy of
a supposed rival, though this is not the conclusion of some observers.
In other cases it is difficult to distinguish between mere curiosity
and admiration. It is perhaps the former feeling which, as stated by
Lord Lilford (15. The ‘Ibis,’ vol. ii. 1860, p. 344.), attracts the
ruff towards any bright object, so that, in the Ionian Islands, “it
will dart down to a bright-coloured handkerchief, regardless of
repeated shots.” The common lark is drawn down from the sky, and is
caught in large numbers, by a small mirror made to move and glitter in
the sun. Is it admiration or curiosity which leads the magpie, raven,
and some other birds to steal and secrete bright objects, such as
silver articles or jewels?

Mr. Gould states that certain humming-birds decorate the outsides of
their nests “with the utmost taste; they instinctively fasten thereon
beautiful pieces of flat lichen, the larger pieces in the middle, and
the smaller on the part attached to the branch. Now and then a pretty
feather is intertwined or fastened to the outer sides, the stem being
always so placed that the feather stands out beyond the surface.” The
best evidence, however, of a taste for the beautiful is afforded by the
three genera of Australian bower-birds already mentioned. Their bowers
(Fig. 46), where the sexes congregate and play strange antics, are
variously constructed, but what most concerns us is, that they are
decorated by the several species in a different manner. The Satin
bower-bird collects gaily-coloured articles, such as the blue
tail-feathers of parrakeets, bleached bones and shells, which it sticks
between the twigs or arranges at the entrance. Mr. Gould found in one
bower a neatly-worked stone tomahawk and a slip of blue cotton,
evidently procured from a native encampment. These objects are
continually re-arranged, and carried about by the birds whilst at play.
The bower of the Spotted bower-bird “is beautifully lined with tall
grasses, so disposed that the heads nearly meet, and the decorations
are very profuse.” Round stones are used to keep the grass-stems in
their proper places, and to make divergent paths leading to the bower.
The stones and shells are often brought from a great distance. The
Regent bird, as described by Mr. Ramsay, ornaments its short bower with
bleached land-shells belonging to five or six species, and with
“berries of various colours, blue, red, and black, which give it when
fresh a very pretty appearance. Besides these there were several
newly-picked leaves and young shoots of a pinkish colour, the whole
showing a decided taste for the beautiful.” Well may Mr. Gould say that
“these highly decorated halls of assembly must be regarded as the most
wonderful instances of bird-architecture yet discovered;” and the
taste, as we see, of the several species certainly differs. (16. On the
ornamented nests of humming-birds, Gould, ‘Introduction to the
Trochilidae,’ 1861, p. 19. On the bower-birds, Gould, ‘Handbook to the
Birds of Australia,’ 1865, vol. i. pp. 444-461. Ramsay, in the ‘Ibis,’
1867, p. 456.)

PREFERENCE FOR A PARTICULAR MALES BY THE FEMALES.

Having made these preliminary remarks on the discrimination and taste
of birds, I will give all the facts known to me which bear on the
preference shewn by the female for particular males. It is certain that
distinct species of birds occasionally pair in a state of nature and
produce hybrids. Many instances could be given: thus Macgillivray
relates how a male blackbird and female thrush “fell in love with each
other,” and produced offspring. (17. ‘History of Brit. Birds,’ vol. ii.
p. 92.) Several years ago eighteen cases had been recorded of the
occurrence in Great Britain of hybrids between the black grouse and
pheasant (18. ‘Zoologist,’ 1853-1854, p. 3946.); but most of these
cases may perhaps be accounted for by solitary birds not finding one of
their own species to pair with. With other birds, as Mr. Jenner Weir
has reason to believe, hybrids are sometimes the result of the casual
intercourse of birds building in close proximity. But these remarks do
not apply to the many recorded instances of tamed or domestic birds,
belonging to distinct species, which have become absolutely fascinated
with each other, although living with their own species. Thus Waterton
(19. Waterton, ‘Essays on Nat. Hist.’ 2nd series, pp. 42 and 117. For
the following statements see on the wigeon, ‘Loudon’s Mag. of Nat.
Hist.’ vol. ix. p. 616; L. Lloyd, ‘Scandinavian Adventures,’ vol. i.
1854, p. 452. Dixon, ‘Ornamental and Domestic Poultry,’ p. 137; Hewitt,
in ‘Journal of Horticulture,’ Jan. 13, 1863, p. 40; Bechstein,
‘Stubenvögel,’ 1840, s. 230. Mr. J. Jenner Weir has lately given me an
analogous case with ducks of two species.) states that out of a flock
of twenty-three Canada geese, a female paired with a solitary Bernicle
gander, although so different in appearance and size; and they produced
hybrid offspring. A male wigeon (Mareca penelope), living with females
of the same species, has been known to pair with a pintail duck,
Querquedula acuta. Lloyd describes the remarkable attachment between a
shield-drake (Tadorna vulpanser) and a common duck. Many additional
instances could be given; and the Rev. E.S. Dixon remarks that “those
who have kept many different species of geese together well know what
unaccountable attachments they are frequently forming, and that they
are quite as likely to pair and rear young with individuals of a race
(species) apparently the most alien to themselves as with their own
stock.”

The Rev. W.D. Fox informs me that he possessed at the same time a pair
of Chinese geese (Anser cygnoides), and a common gander with three
geese. The two lots kept quite separate, until the Chinese gander
seduced one of the common geese to live with him. Moreover, of the
young birds hatched from the eggs of the common geese, only four were
pure, the other eighteen proving hybrids; so that the Chinese gander
seems to have had prepotent charms over the common gander. I will give
only one other case; Mr. Hewitt states that a wild duck, reared in
captivity, “after breeding a couple of seasons with her own mallard, at
once shook him off on my placing a male Pintail on the water. It was
evidently a case of love at first sight, for she swam about the
new-comer caressingly, though he appeared evidently alarmed and averse
to her overtures of affection. From that hour she forgot her old
partner. Winter passed by, and the next spring the pintail seemed to
have become a convert to her blandishments, for they nested and
produced seven or eight young ones.”

What the charm may have been in these several cases, beyond mere
novelty, we cannot even conjecture. Colour, however, sometimes comes
into play; for in order to raise hybrids from the siskin (Fringilla
spinus) and the canary, it is much the best plan, according to
Bechstein, to place birds of the same tint together. Mr. Jenner Weir
turned a female canary into his aviary, where there were male linnets,
goldfinches, siskins, greenfinches, chaffinches, and other birds, in
order to see which she would choose; but there never was any doubt, and
the greenfinch carried the day. They paired and produced hybrid
offspring.

The fact of the female preferring to pair with one male rather than
with another of the same species is not so likely to excite attention,
as when this occurs, as we have just seen, between distinct species.
The former cases can best be observed with domesticated or confined
birds; but these are often pampered by high feeding, and sometimes have
their instincts vitiated to an extreme degree. Of this latter fact I
could give sufficient proofs with pigeons, and especially with fowls,
but they cannot be here related. Vitiated instincts may also account
for some of the hybrid unions above mentioned; but in many of these
cases the birds were allowed to range freely over large ponds, and
there is no reason to suppose that they were unnaturally stimulated by
high feeding.

With respect to birds in a state of nature, the first and most obvious
supposition which will occur to every one is that the female at the
proper season accepts the first male whom she may encounter; but she
has at least the opportunity for exerting a choice, as she is almost
invariably pursued by many males. Audubon—and we must remember that he
spent a long life in prowling about the forests of the United States
and observing the birds—does not doubt that the female deliberately
chooses her mate; thus, speaking of a woodpecker, he says the hen is
followed by half-a-dozen gay suitors, who continue performing strange
antics, “until a marked preference is shewn for one.” The female of the
red-winged starling (Agelaeus phoeniceus) is likewise pursued by
several males, “until, becoming fatigued, she alights, receives their
addresses, and soon makes a choice.” He describes also how several male
night-jars repeatedly plunge through the air with astonishing rapidity,
suddenly turning, and thus making a singular noise; “but no sooner has
the female made her choice than the other males are driven away.” With
one of the vultures (Cathartes aura) of the United States, parties of
eight, ten, or more males and females assemble on fallen logs,
“exhibiting the strongest desire to please mutually,” and after many
caresses, each male leads off his partner on the wing. Audubon likewise
carefully observed the wild flocks of Canada geese (Anser canadensis),
and gives a graphic description of their love-antics; he says that the
birds which had been previously mated “renewed their courtship as early
as the month of January, while the others would be contending or
coquetting for hours every day, until all seemed satisfied with the
choice they had made, after which, although they remained together, any
person could easily perceive that they were careful to keep in pairs. I
have observed also that the older the birds the shorter were the
preliminaries of their courtship. The bachelors and old maids whether
in regret, or not caring to be disturbed by the bustle, quietly moved
aside and lay down at some distance from the rest.” (20. Audubon,
‘Ornithological Biography,’ vol. i. pp. 191, 349; vol. ii. pp. 42, 275;
vol. iii. p. 2.) Many similar statements with respect to other birds
could be cited from this same observer.

Turning now to domesticated and confined birds, I will commence by
giving what little I have learnt respecting the courtship of fowls. I
have received long letters on this subject from Messrs. Hewitt and
Tegetmeier, and almost an essay from the late Mr. Brent. It will be
admitted by every one that these gentlemen, so well known from their
published works, are careful and experienced observers. They do not
believe that the females prefer certain males on account of the beauty
of their plumage; but some allowance must be made for the artificial
state under which these birds have long been kept. Mr. Tegetmeier is
convinced that a gamecock, though disfigured by being dubbed and with
his hackles trimmed, would be accepted as readily as a male retaining
all his natural ornaments. Mr. Brent, however, admits that the beauty
of the male probably aids in exciting the female; and her acquiescence
is necessary. Mr. Hewitt is convinced that the union is by no means
left to mere chance, for the female almost invariably prefers the most
vigorous, defiant, and mettlesome male; hence it is almost useless, as
he remarks, “to attempt true breeding if a game-cock in good health and
condition runs the locality, for almost every hen on leaving the
roosting-place will resort to the game-cock, even though that bird may
not actually drive away the male of her own variety.” Under ordinary
circumstances the males and females of the fowl seem to come to a
mutual understanding by means of certain gestures, described to me by
Mr. Brent. But hens will often avoid the officious attentions of young
males. Old hens, and hens of a pugnacious disposition, as the same
writer informs me, dislike strange males, and will not yield until well
beaten into compliance. Ferguson, however, describes how a quarrelsome
hen was subdued by the gentle courtship of a Shanghai cock. (21. ‘Rare
and Prize Poultry,’ 1854, p. 27.)

There is reason to believe that pigeons of both sexes prefer pairing
with birds of the same breed; and dovecot-pigeons dislike all the
highly improved breeds. (22. ‘Variation of Animals and Plants under
Domestication,’ vol. ii. p. 103.) Mr. Harrison Weir has lately heard
from a trustworthy observer, who keeps blue pigeons, that these drive
away all other coloured varieties, such as white, red, and yellow; and
from another observer, that a female dun carrier could not, after
repeated trials, be matched with a black male, but immediately paired
with a dun. Again, Mr. Tegetmeier had a female blue turbit that
obstinately refused to pair with two males of the same breed, which
were successively shut up with her for weeks; but on being let out she
would have immediately accepted the first blue dragon that offered. As
she was a valuable bird, she was then shut up for many weeks with a
silver (i.e., very pale blue) male, and at last mated with him.
Nevertheless, as a general rule, colour appears to have little
influence on the pairing of pigeons. Mr. Tegetmeier, at my request,
stained some of his birds with magenta, but they were not much noticed
by the others.

Female pigeons occasionally feel a strong antipathy towards certain
males, without any assignable cause. Thus MM. Boitard and Corbie, whose
experience extended over forty-five years, state: “Quand une femelle
éprouve de l’antipathie pour un mâle avec lequel on veut l’accoupler,
malgré tous les feux de l’amour, malgré l’alpiste et le chenevis dont
on la nourrit pour augmenter son ardeur, malgré un emprisonnement de
six mois et même d’un an, elle refuse constamment ses caresses; les
avances empressées, les agaceries, les tournoiemens, les tendres
roucoulemens, rien ne peut lui plaire ni l’émouvoir; gonflée, boudeuse,
blottie dans un coin de sa prison, elle n’en sort que pour boire et
manger, ou pour repousser avec une espèce de rage des caresses devenues
trop pressantes.” (23. Boitard and Corbie, ‘Les Pigeons,’ etc., 1824,
p. 12. Prosper Lucas (‘Traité de l’Héréd. Nat.’ tom. ii. 1850, p. 296)
has himself observed nearly similar facts with pigeons.) On the other
hand, Mr. Harrison Weir has himself observed, and has heard from
several breeders, that a female pigeon will occasionally take a strong
fancy for a particular male, and will desert her own mate for him. Some
females, according to another experienced observer, Riedel (24. Die
Taubenzucht, 1824, s. 86.), are of a profligate disposition, and prefer
almost any stranger to their own mate. Some amorous males, called by
our English fanciers “gay birds,” are so successful in their
gallantries, that, as Mr. H. Weir informs me, they must be shut up on
account of the mischief which they cause.

Wild turkeys in the United States, according to Audubon, “sometimes pay
their addresses to the domesticated females, and are generally received
by them with great pleasure.” So that these females apparently prefer
the wild to their own males. (25. ‘Ornithological Biography,’ vol. i.
p. 13. See to the same effect, Dr. Bryant, in Allen’s ‘Mammals and
Birds of Florida,’ p. 344.)

Here is a more curious case. Sir R. Heron during many years kept an
account of the habits of the peafowl, which he bred in large numbers.
He states that “the hens have frequently great preference to a
particular peafowl. They were all so fond of an old pied cock, that one
year, when he was confined, though still in view, they were constantly
assembled close to the trellice-walls of his prison, and would not
suffer a japanned peacock to touch them. On his being let out in the
autumn, the oldest of the hens instantly courted him and was successful
in her courtship. The next year he was shut up in a stable, and then
the hens all courted his rival.” (26. ‘Proceedings, Zoological
Society,’ 1835, p. 54. The japanned peacock is considered by Mr.
Sclater as a distinct species, and has been named Pavo nigripennis; but
the evidence seems to me to show that it is only a variety.) This rival
was a japanned or black-winged peacock, to our eyes a more beautiful
bird than the common kind.

Lichtenstein, who was a good observer and had excellent opportunities
of observation at the Cape of Good Hope, assured Rudolphi that the
female widow-bird (Chera progne) disowns the male when robbed of the
long tail-feathers with which he is ornamented during the
breeding-season. I presume that this observation must have been made on
birds under confinement. (27. Rudolphi, ‘Beiträge zur Anthropologie,’
1812, s. 184.) Here is an analogous case; Dr. Jaeger (28. ‘Die
Darwin’sche Theorie, und ihre Stellung zu Moral und Religion,’ 1869, s.
59.), director of the Zoological Gardens of Vienna, states that a male
silver-pheasant, who had been triumphant over all other males and was
the accepted lover of the females, had his ornamental plumage spoiled.
He was then immediately superseded by a rival, who got the upper hand
and afterwards led the flock.

It is a remarkable fact, as shewing how important colour is in the
courtship of birds, that Mr. Boardman, a well-known collector and
observer of birds for many years in the Northern United States, has
never in his large experience seen an albino paired with another bird;
yet he has had opportunities of observing many albinos belonging to
several species. (29. This statement is given by Mr. A. Leith Adams, in
his ‘Field and Forest Rambles,’ 1873, p. 76, and accords with his own
experience.) It can hardly be maintained that albinos in a state of
nature are incapable of breeding, as they can be raised with the
greatest facility under confinement. It appears, therefore, that we
must attribute the fact that they do not pair to their rejection by
their normally coloured comrades.

Female birds not only exert a choice, but in some few cases they court
the male, or even fight together for his possession. Sir R. Heron
states that with peafowl, the first advances are always made by the
female; something of the same kind takes place, according to Audubon,
with the older females of the wild turkey. With the capercailzie, the
females flit round the male whilst he is parading at one of the places
of assemblage, and solicit his attention. (30. In regard to peafowl,
see Sir R. Heron, ‘Proc. Zoolog. Soc.’ 1835, p. 54, and the Rev. E.S.
Dixon, ‘Ornamental Poultry,’ 1848, p. 8. For the turkey, Audubon, ibid.
p. 4. For the capercailzie, Lloyd, ‘Game Birds of Sweden,’ 1867, p.
23.) We have seen that a tame wild-duck seduced an unwilling pintail
drake after a long courtship. Mr. Bartlett believes that the
Lophophorus, like many other gallinaceous birds, is naturally
polygamous, but two females cannot be placed in the same cage with a
male, as they fight so much together. The following instance of rivalry
is more surprising as it relates to bullfinches, which usually pair for
life. Mr. Jenner Weir introduced a dull-coloured and ugly female into
his aviary, and she immediately attacked another mated female so
unmercifully that the latter had to be separated. The new female did
all the courtship, and was at last successful, for she paired with the
male; but after a time she met with a just retribution, for, ceasing to
be pugnacious, she was replaced by the old female, and the male then
deserted his new and returned to his old love.

In all ordinary cases the male is so eager that he will accept any
female, and does not, as far as we can judge, prefer one to the other;
but, as we shall hereafter see, exceptions to this rule apparently
occur in some few groups. With domesticated birds, I have heard of only
one case of males shewing any preference for certain females, namely,
that of the domestic cock, who, according to the high authority of Mr.
Hewitt, prefers the younger to the older hens. On the other hand, in
effecting hybrid unions between the male pheasant and common hens, Mr.
Hewitt is convinced that the pheasant invariably prefers the older
birds. He does not appear to be in the least influenced by their
colour; but “is most capricious in his attachments” (31. Mr. Hewitt,
quoted in Tegetmeier’s ‘Poultry Book,’ 1866, p. 165.): from some
inexplicable cause he shews the most determined aversion to certain
hens, which no care on the part of the breeder can overcome. Mr. Hewitt
informs me that some hens are quite unattractive even to the males of
their own species, so that they may be kept with several cocks during a
whole season, and not one egg out of forty or fifty will prove fertile.
On the other hand, with the long-tailed duck (Harelda glacialis), “it
has been remarked,” says M. Ekstrom, “that certain females are much
more courted than the rest. Frequently, indeed, one sees an individual
surrounded by six or eight amorous males.” Whether this statement is
credible, I know not; but the native sportsmen shoot these females in
order to stuff them as decoys. (32. Quoted in Lloyd’s ‘Game Birds of
Sweden,’ p. 345.)

With respect to female birds feeling a preference for particular males,
we must bear in mind that we can judge of choice being exerted only by
analogy. If an inhabitant of another planet were to behold a number of
young rustics at a fair courting a pretty girl, and quarrelling about
her like birds at one of their places of assemblage, he would, by the
eagerness of the wooers to please her and to display their finery,
infer that she had the power of choice. Now with birds the evidence
stands thus: they have acute powers of observation, and they seem to
have some taste for the beautiful both in colour and sound. It is
certain that the females occasionally exhibit, from unknown causes, the
strongest antipathies and preferences for particular males. When the
sexes differ in colour or in other ornaments the males with rare
exceptions are the more decorated, either permanently or temporarily
during the breeding-season. They sedulously display their various
ornaments, exert their voices, and perform strange antics in the
presence of the females. Even well-armed males, who, it might be
thought, would altogether depend for success on the law of battle, are
in most cases highly ornamented; and their ornaments have been acquired
at the expense of some loss of power. In other cases ornaments have
been acquired, at the cost of increased risk from birds and beasts of
prey. With various species many individuals of both sexes congregate at
the same spot, and their courtship is a prolonged affair. There is even
reason to suspect that the males and females within the same district
do not always succeed in pleasing each other and pairing.

What then are we to conclude from these facts and considerations? Does
the male parade his charms with so much pomp and rivalry for no
purpose? Are we not justified in believing that the female exerts a
choice, and that she receives the addresses of the male who pleases her
most? It is not probable that she consciously deliberates; but she is
most excited or attracted by the most beautiful, or melodious, or
gallant males. Nor need it be supposed that the female studies each
stripe or spot of colour; that the peahen, for instance, admires each
detail in the gorgeous train of the peacock—she is probably struck only
by the general effect. Nevertheless, after hearing how carefully the
male Argus pheasant displays his elegant primary wing-feathers, and
erects his ocellated plumes in the right position for their full
effect; or again, how the male goldfinch alternately displays his
gold-bespangled wings, we ought not to feel too sure that the female
does not attend to each detail of beauty. We can judge, as already
remarked, of choice being exerted, only from analogy; and the mental
powers of birds do not differ fundamentally from ours. From these
various considerations we may conclude that the pairing of birds is not
left to chance; but that those males, which are best able by their
various charms to please or excite the female, are under ordinary
circumstances accepted. If this be admitted, there is not much
difficulty in understanding how male birds have gradually acquired
their ornamental characters. All animals present individual
differences, and as man can modify his domesticated birds by selecting
the individuals which appear to him the most beautiful, so the habitual
or even occasional preference by the female of the more attractive
males would almost certainly lead to their modification; and such
modifications might in the course of time be augmented to almost any
extent, compatible with the existence of the species.

VARIABILITY OF BIRDS, AND ESPECIALLY OF THEIR SECONDARY SEXUAL
CHARACTERS.

Variability and inheritance are the foundations for the work of
selection. That domesticated birds have varied greatly, their
variations being inherited, is certain. That birds in a state of nature
have been modified into distinct races is now universally admitted.
(33. According to Dr. Blasius (‘Ibis,’ vol. ii. 1860, p. 297), there
are 425 indubitable species of birds which breed in Europe, besides
sixty forms, which are frequently regarded as distinct species. Of the
latter, Blasius thinks that only ten are really doubtful, and that the
other fifty ought to be united with their nearest allies; but this
shews that there must be a considerable amount of variation with some
of our European birds. It is also an unsettled point with naturalists,
whether several North American birds ought to be ranked as specifically
distinct from the corresponding European species. So again many North
American forms which until lately were named as distinct species, are
now considered to be local races.) Variations may be divided into two
classes; those which appear to our ignorance to arise spontaneously,
and those which are directly related to the surrounding conditions, so
that all or nearly all the individuals of the same species are
similarly modified. Cases of the latter kind have recently been
observed with care by Mr. J.A. Allen (34. ‘Mammals and Birds of East
Florida,’ also an ‘Ornithological Reconnaissance of Kansas,’ etc.
Notwithstanding the influence of climate on the colours of birds, it is
difficult to account for the dull or dark tints of almost all the
species inhabiting certain countries, for instance, the Galapagos
Islands under the equator, the wide temperate plains of Patagonia, and,
as it appears, Egypt (see Mr. Hartshorne in the ‘American Naturalist,’
1873, p. 747). These countries are open, and afford little shelter to
birds; but it seems doubtful whether the absence of brightly coloured
species can be explained on the principle of protection, for on the
Pampas, which are equally open, though covered by green grass, and
where the birds would be equally exposed to danger, many brilliant and
conspicuously coloured species are common. I have sometimes speculated
whether the prevailing dull tints of the scenery in the above named
countries may not have affected the appreciation of bright colours by
the birds inhabiting them.), who shews that in the United States many
species of birds gradually become more strongly coloured in proceeding
southward, and more lightly coloured in proceeding westward to the arid
plains of the interior. Both sexes seem generally to be affected in a
like manner, but sometimes one sex more than the other. This result is
not incompatible with the belief that the colours of birds are mainly
due to the accumulation of successive variations through sexual
selection; for even after the sexes have been greatly differentiated,
climate might produce an equal effect on both sexes, or a greater
effect on one sex than on the other, owing to some constitutional
difference.

Individual differences between the members of the same species are
admitted by every one to occur under a state of nature. Sudden and
strongly marked variations are rare; it is also doubtful whether if
beneficial they would often be preserved through selection and
transmitted to succeeding generations. (35. ‘Origin of Species’ fifth
edit. 1869, p.104. I had always perceived, that rare and
strongly-marked deviations of structure, deserving to be called
monstrosities, could seldom be preserved through natural selection, and
that the preservation of even highly-beneficial variations would depend
to a certain extent on chance. I had also fully appreciated the
importance of mere individual differences, and this led me to insist so
strongly on the importance of that unconscious form of selection by
man, which follows from the preservation of the most valued individuals
of each breed, without any intention on his part to modify the
characters of the breed. But until I read an able article in the ‘North
British Review’ (March 1867, p. 289, et seq.), which has been of more
use to me than any other Review, I did not see how great the chances
were against the preservation of variations, whether slight or strongly
pronounced, occurring only in single individuals.) Nevertheless, it may
be worth while to give the few cases which I have been able to collect,
relating chiefly to colour,—simple albinism and melanism being
excluded. Mr. Gould is well known to admit the existence of few
varieties, for he esteems very slight differences as specific; yet he
states (36. ‘Introduction to the Trochlidae,’ p. 102.) that near Bogota
certain humming-birds belonging to the genus Cynanthus are divided into
two or three races or varieties, which differ from each other in the
colouring of the tail—“some having the whole of the feathers blue,
while others have the eight central ones tipped with beautiful green.”
It does not appear that intermediate gradations have been observed in
this or the following cases. In the males alone of one of the
Australian parrakeets “the thighs in some are scarlet, in others
grass-green.” In another parrakeet of the same country “some
individuals have the band across the wing-coverts bright-yellow, while
in others the same part is tinged with red.” (37. Gould, ‘Handbook to
Birds of Australia,’ vol. ii. pp. 32 and 68.) In the United States some
few of the males of the scarlet tanager (Tanagra rubra) have “a
beautiful transverse band of glowing red on the smaller wing-coverts”
(38. Audubon, ‘Ornithological Biography,’ 1838, vol. iv. p. 389.); but
this variation seems to be somewhat rare, so that its preservation
through sexual selection would follow only under usually favourable
circumstances. In Bengal the Honey buzzard (Pernis cristata) has either
a small rudimental crest on its head, or none at all: so slight a
difference, however, would not have been worth notice, had not this
same species possessed in Southern India a well-marked occipital crest
formed of several graduated feathers.” (39. Jerdon, ‘Birds of India,’
vol. i. p. 108; and Mr. Blyth, in ‘Land and Water,’ 1868, p. 381.)

The following case is in some respects more interesting. A pied variety
of the raven, with the head, breast, abdomen, and parts of the wings
and tail-feathers white, is confined to the Feroe Islands. It is not
very rare there, for Graba saw during his visit from eight to ten
living specimens. Although the characters of this variety are not quite
constant, yet it has been named by several distinguished ornithologists
as a distinct species. The fact of the pied birds being pursued and
persecuted with much clamour by the other ravens of the island was the
chief cause which led Brunnich to conclude that they were specifically
distinct; but this is now known to be an error. (40. Graba, ‘Tagebuch
Reise nach Faro,’ 1830, ss. 51-54. Macgillivray, ‘History of British
Birds,’ vol. iii. p. 745, ‘Ibis,’ vol. v. 1863, p. 469.) This case
seems analogous to that lately given of albino birds not pairing from
being rejected by their comrades.

In various parts of the northern seas a remarkable variety of the
common Guillemot (Uria troile) is found; and in Feroe, one out of every
five birds, according to Graba’s estimation, presents this variation.
It is characterised (41. Graba, ibid. s. 54. Macgillivray, ibid. vol.
v. p. 327.) by a pure white ring round the eye, with a curved narrow
white line, an inch and a half in length, extending back from the ring.
This conspicuous character has caused the bird to be ranked by several
ornithologists as a distinct species under the name of U. lacrymans,
but it is now known to be merely a variety. It often pairs with the
common kind, yet intermediate gradations have never been seen; nor is
this surprising, for variations which appear suddenly, are often, as I
have elsewhere shewn (42. ‘Variation of Animals and Plants under
Domestication,’ vol. ii. p. 92.), transmitted either unaltered or not
at all. We thus see that two distinct forms of the same species may
co-exist in the same district, and we cannot doubt that if the one had
possessed any advantage over the other, it would soon have been
multiplied to the exclusion of the latter. If, for instance, the male
pied ravens, instead of being persecuted by their comrades, had been
highly attractive (like the above pied peacock) to the black female
ravens their numbers would have rapidly increased. And this would have
been a case of sexual selection.

With respect to the slight individual differences which are common, in
a greater or less degree, to all the members of the same species, we
have every reason to believe that they are by far the most important
for the work of selection. Secondary sexual characters are eminently
liable to vary, both with animals in a state of nature and under
domestication. (43. On these points see also ‘Variation of Animals and
Plants under Domestication,’ vol. i. p. 253; vol ii. pp. 73, 75.) There
is also reason to believe, as we have seen in our eighth chapter, that
variations are more apt to occur in the male than in the female sex.
All these contingencies are highly favourable for sexual selection.
Whether characters thus acquired are transmitted to one sex or to both
sexes, depends, as we shall see in the following chapter, on the form
of inheritance which prevails.

It is sometimes difficult to form an opinion whether certain slight
differences between the sexes of birds are simply the result of
variability with sexually-limited inheritance, without the aid of
sexual selection, or whether they have been augmented through this
latter process. I do not here refer to the many instances where the
male displays splendid colours or other ornaments, of which the female
partakes to a slight degree; for these are almost certainly due to
characters primarily acquired by the male having been more or less
transferred to the female. But what are we to conclude with respect to
certain birds in which, for instance, the eyes differ slightly in
colour in the two sexes? (44. See, for instance, on the irides of a
Podica and Gallicrex in ‘Ibis,’ vol. ii. 1860, p. 206; and vol. v.
1863, p. 426.) In some cases the eyes differ conspicuously; thus with
the storks of the genus Xenorhynchus, those of the male are
blackish-hazel, whilst those of the females are gamboge-yellow; with
many hornbills (Buceros), as I hear from Mr. Blyth (45. See also
Jerdon, ‘Birds of India,’ vol. i. pp. 243-245.), the males have intense
crimson eyes, and those of the females are white. In the Buceros
bicornis, the hind margin of the casque and a stripe on the crest of
the beak are black in the male, but not so in the female. Are we to
suppose that these black marks and the crimson colour of the eyes have
been preserved or augmented through sexual selection in the males? This
is very doubtful; for Mr. Bartlett shewed me in the Zoological Gardens
that the inside of the mouth of this Buceros is black in the male and
flesh-coloured in the female; and their external appearance or beauty
would not be thus affected. I observed in Chile (46. ‘Zoology of the
Voyage of H.M.S. “Beagle,”’ 1841, p. 6.) that the iris in the condor,
when about a year old, is dark-brown, but changes at maturity into
yellowish-brown in the male, and into bright red in the female. The
male has also a small, longitudinal, leaden-coloured, fleshy crest or
comb. The comb of many gallinaceous birds is highly ornamental, and
assumes vivid colours during the act of courtship; but what are we to
think of the dull-coloured comb of the condor, which does not appear to
us in the least ornamental? The same question may be asked in regard to
various other characters, such as the knob on the base of the beak of
the Chinese goose (Anser cygnoides), which is much larger in the male
than in the female. No certain answer can be given to these questions;
but we ought to be cautious in assuming that knobs and various fleshy
appendages cannot be attractive to the female, when we remember that
with savage races of man various hideous deformities—deep scars on the
face with the flesh raised into protuberances, the septum of the nose
pierced by sticks or bones, holes in the ears and lips stretched widely
open—are all admired as ornamental.

Whether or not unimportant differences between the sexes, such as those
just specified, have been preserved through sexual selection, these
differences, as well as all others, must primarily depend on the laws
of variation. On the principle of correlated development, the plumage
often varies on different parts of the body, or over the whole body, in
the same manner. We see this well illustrated in certain breeds of the
fowl. In all the breeds the feathers on the neck and loins of the males
are elongated, and are called hackles; now when both sexes acquire a
top-knot, which is a new character in the genus, the feathers on the
head of the male become hackle-shaped, evidently on the principle of
correlation; whilst those on the head of the female are of the ordinary
shape. The colour also of the hackles forming the top-knot of the male,
is often correlated with that of the hackles on the neck and loins, as
may be seen by comparing these feathers in the golden and
silver-spangled Polish, the Houdans, and Creve-coeur breeds. In some
natural species we may observe exactly the same correlation in the
colours of these same feathers, as in the males of the splendid Gold
and Amherst pheasants.

The structure of each individual feather generally causes any change in
its colouring to be symmetrical; we see this in the various laced,
spangled, and pencilled breeds of the fowl; and on the principle of
correlation the feathers over the whole body are often coloured in the
same manner. We are thus enabled without much trouble to rear breeds
with their plumage marked almost as symmetrically as in natural
species. In laced and spangled fowls the coloured margins of the
feathers are abruptly defined; but in a mongrel raised by me from a
black Spanish cock glossed with green, and a white game-hen, all the
feathers were greenish-black, excepting towards their extremities,
which were yellowish-white; but between the white extremities and the
black bases, there was on each feather a symmetrical, curved zone of
dark-brown. In some instances the shaft of the feather determines the
distribution of the tints; thus with the body-feathers of a mongrel
from the same black Spanish cock and a silver-spangled Polish hen, the
shaft, together with a narrow space on each side, was greenish-black,
and this was surrounded by a regular zone of dark-brown, edged with
brownish-white. In these cases we have feathers symmetrically shaded,
like those which give so much elegance to the plumage of many natural
species. I have also noticed a variety of the common pigeon with the
wing-bars symmetrically zoned with three bright shades, instead of
being simply black on a slaty-blue ground, as in the parent-species.

In many groups of birds the plumage is differently coloured in the
several species, yet certain spots, marks, or stripes are retained by
all. Analogous cases occur with the breeds of the pigeon, which usually
retain the two wing-bars, though they may be coloured red, yellow,
white, black, or blue, the rest of the plumage being of some wholly
different tint. Here is a more curious case, in which certain marks are
retained, though coloured in a manner almost exactly the opposite of
what is natural; the aboriginal pigeon has a blue tail, with the
terminal halves of the outer webs of the two outer tail feathers white;
now there is a sub-variety having a white instead of a blue tail, with
precisely that part black which is white in the parent-species. (47.
Bechstein, ‘Naturgeschichte Deutschlands,’ B. iv. 1795, s. 31, on a
sub-variety of the Monck pigeon.)

FORMATION AND VARIABILITY OF THE OCELLI OR EYE-LIKE SPOTS ON THE
PLUMAGE OF BIRDS.

[Fig. 53. Cyllo leda, Linn., from a drawing by Mr. Trimen, shewing the
extreme range of variation in the ocelli. A. Specimen, from Mauritius,
upper surface of fore-wing. A1. Specimen, from Natal, ditto. B.
Specimen, from Java, upper surface of hind-wing. B1. Specimen, from
Mauritius, ditto.]

As no ornaments are more beautiful than the ocelli on the feathers of
various birds, on the hairy coats of some mammals, on the scales of
reptiles and fishes, on the skin of amphibians, on the wings of many
Lepidoptera and other insects, they deserve to be especially noticed.
An ocellus consists of a spot within a ring of another colour, like the
pupil within the iris, but the central spot is often surrounded by
additional concentric zones. The ocelli on the tail-coverts of the
peacock offer a familiar example, as well as those on the wings of the
peacock-butterfly (Vanessa). Mr. Trimen has given me a description of a
S. African moth (Gynanisa isis), allied to our Emperor moth, in which a
magnificent ocellus occupies nearly the whole surface of each hinder
wing; it consists of a black centre, including a semi-transparent
crescent-shaped mark, surrounded by successive, ochre-yellow, black,
ochre-yellow, pink, white, pink, brown, and whitish zones. Although we
do not know the steps by which these wonderfully beautiful and complex
ornaments have been developed, the process has probably been a simple
one, at least with insects; for, as Mr. Trimen writes to me, “no
characters of mere marking or coloration are so unstable in the
Lepidoptera as the ocelli, both in number and size.” Mr. Wallace, who
first called my attention to this subject, shewed me a series of
specimens of our common meadow-brown butterfly (Hipparchia janira)
exhibiting numerous gradations from a simple minute black spot to an
elegantly-shaded ocellus. In a S. African butterfly (Cyllo leda,
Linn.), belonging to the same family, the ocelli are even still more
variable. In some specimens (A, Fig. 53) large spaces on the upper
surface of the wings are coloured black, and include irregular white
marks; and from this state a complete gradation can be traced into a
tolerably perfect ocellus (A1), and this results from the contraction
of the irregular blotches of colour. In another series of specimens a
gradation can be followed from excessively minute white dots,
surrounded by a scarcely visible black line (B), into perfectly
symmetrical and large ocelli (B1). (48. This woodcut has been engraved
from a beautiful drawing, most kindly made for me by Mr. Trimen; see
also his description of the wonderful amount of variation in the
coloration and shape of the wings of this butterfly, in his
‘Rhopalocera Africae Australis,’ p. 186.) In cases like these, the
development of a perfect ocellus does not require a long course of
variation and selection.

With birds and many other animals, it seems to follow from the
comparison of allied species that circular spots are often generated by
the breaking up and contraction of stripes. In the Tragopan pheasant
faint white lines in the female represent the beautiful white spots in
the male (49. Jerdon, ‘Birds of India,’ vol. iii. p. 517.); and
something of the same kind may be observed in the two sexes of the
Argus pheasant. However this may be, appearances strongly favour the
belief that on the one hand, a dark spot is often formed by the
colouring matter being drawn towards a central point from a surrounding
zone, which latter is thus rendered lighter; and, on the other hand,
that a white spot is often formed by the colour being driven away from
a central point, so that it accumulates in a surrounding darker zone.
In either case an ocellus is the result. The colouring matter seems to
be a nearly constant quantity, but is redistributed, either
centripetally or centrifugally. The feathers of the common guinea-fowl
offer a good instance of white spots surrounded by darker zones; and
wherever the white spots are large and stand near each other, the
surrounding dark zones become confluent. In the same wing-feather of
the Argus pheasant dark spots may be seen surrounded by a pale zone,
and white spots by a dark zone. Thus the formation of an ocellus in its
most elementary state appears to be a simple affair. By what further
steps the more complex ocelli, which are surrounded by many successive
zones of colour, have been generated, I will not pretend to say. But
the zoned feathers of the mongrels from differently coloured fowls, and
the extraordinary variability of the ocelli on many Lepidoptera, lead
us to conclude that their formation is not a complex process, but
depends on some slight and graduated change in the nature of the
adjoining tissues.

GRADATION OF SECONDARY SEXUAL CHARACTERS.

[Fig. 54. Feather of Peacock, about two-thirds of natural size, drawn
by Mr. Ford. The transparent zone is represented by the outermost white
zone, confined to the upper end of the disc.]

Cases of gradation are important, as shewing us that highly complex
ornaments may be acquired by small successive steps. In order to
discover the actual steps by which the male of any existing bird has
acquired his magnificent colours or other ornaments, we ought to behold
the long line of his extinct progenitors; but this is obviously
impossible. We may, however, generally gain a clue by comparing all the
species of the same group, if it be a large one; for some of them will
probably retain, at least partially, traces of their former characters.
Instead of entering on tedious details respecting various groups, in
which striking instances of gradation could be given, it seems the best
plan to take one or two strongly marked cases, for instance that of the
peacock, in order to see if light can be thrown on the steps by which
this bird has become so splendidly decorated. The peacock is chiefly
remarkable from the extraordinary length of his tail-coverts; the tail
itself not being much elongated. The barbs along nearly the whole
length of these feathers stand separate or are decomposed; but this is
the case with the feathers of many species, and with some varieties of
the domestic fowl and pigeon. The barbs coalesce towards the extremity
of the shaft forming the oval disc or ocellus, which is certainly one
of the most beautiful objects in the world. It consists of an
iridescent, intensely blue, indented centre, surrounded by a rich green
zone, this by a broad coppery-brown zone, and this by five other narrow
zones of slightly different iridescent shades. A trifling character in
the disc deserves notice; the barbs, for a space along one of the
concentric zones are more or less destitute of their barbules, so that
a part of the disc is surrounded by an almost transparent zone, which
gives it a highly finished aspect. But I have elsewhere described (50.
‘Variation of Animals and Plants under Domestication,’ vol. i. p. 254.)
an exactly analogous variation in the hackles of a sub-variety of the
game-cock, in which the tips, having a metallic lustre, “are separated
from the lower part of the feather by a symmetrically shaped
transparent zone, composed of the naked portions of the barbs.” The
lower margin or base of the dark-blue centre of the ocellus is deeply
indented on the line of the shaft. The surrounding zones likewise shew
traces, as may be seen in the drawing (Fig. 54), of indentations, or
rather breaks. These indentations are common to the Indian and Javan
peacocks (Pavo cristatus and P. muticus); and they seem to deserve
particular attention, as probably connected with the development of the
ocellus; but for a long time I could not conjecture their meaning.

If we admit the principle of gradual evolution, there must formerly
have existed many species which presented every successive step between
the wonderfully elongated tail-coverts of the peacock and the short
tail-coverts of all ordinary birds; and again between the magnificent
ocelli of the former, and the simpler ocelli or mere coloured spots on
other birds; and so with all the other characters of the peacock. Let
us look to the allied Gallinaceae for any still-existing gradations.
The species and sub-species of Polyplectron inhabit countries adjacent
to the native land of the peacock; and they so far resemble this bird
that they are sometimes called peacock-pheasants. I am also informed by
Mr. Bartlett that they resemble the peacock in their voice and in some
of their habits. During the spring the males, as previously described,
strut about before the comparatively plain-coloured females, expanding
and erecting their tail and wing-feathers, which are ornamented with
numerous ocelli. I request the reader to turn back to the drawing (Fig.
51) of a Polyplectron; In P. napoleonis the ocelli are confined to the
tail, and the back is of a rich metallic blue; in which respects this
species approaches the Java peacock. P. hardwickii possesses a peculiar
top-knot, which is also somewhat like that of the Java peacock. In all
the species the ocelli on the wings and tail are either circular or
oval, and consist of a beautiful, iridescent, greenish-blue or
greenish-purple disc, with a black border. This border in P. chinquis
shades into brown, edged with cream colour, so that the ocellus is here
surrounded with variously shaded, though not bright, concentric zones.
The unusual length of the tail-coverts is another remarkable character
in Polyplectron; for in some of the species they are half, and in
others two-thirds as long as the true tail-feathers. The tail-coverts
are ocellated as in the peacock. Thus the several species of
Polyplectron manifestly make a graduated approach to the peacock in the
length of their tail-coverts, in the zoning of the ocelli, and in some
other characters.

[Fig. 55. Part of a tail-covert of Polyplectron chinquis, with the two
ocelli of natural size.

Fig. 56. Part of a tail-covert of Polyplectron malaccense, with the two
ocelli, partially confluent, of natural size.]

Notwithstanding this approach, the first species of Polyplectron which
I examined almost made me give up the search; for I found not only that
the true tail-feathers, which in the peacock are quite plain, were
ornamented with ocelli, but that the ocelli on all the feathers
differed fundamentally from those of the peacock, in there being two on
the same feather (Fig. 55), one on each side of the shaft. Hence I
concluded that the early progenitors of the peacock could not have
resembled a Polyplectron. But on continuing my search, I observed that
in some of the species the two ocelli stood very near each other; that
in the tail-feathers of P. hardwickii they touched each other; and,
finally, that on the tail-coverts of this same species as well as of P.
malaccense (Fig. 56) they were actually confluent. As the central part
alone is confluent, an indentation is left at both the upper and lower
ends; and the surrounding coloured zones are likewise indented. A
single ocellus is thus formed on each tail-covert, though still plainly
betraying its double origin. These confluent ocelli differ from the
single ocelli of the peacock in having an indentation at both ends,
instead of only at the lower or basal end. The explanation, however, of
this difference is not difficult; in some species of Polyplectron the
two oval ocelli on the same feather stand parallel to each other; in
other species (as in P. chinquis) they converge towards one end; now
the partial confluence of two convergent ocelli would manifestly leave
a much deeper indentation at the divergent than at the convergent end.
It is also manifest that if the convergence were strongly pronounced
and the confluence complete, the indentation at the convergent end
would tend to disappear.

The tail-feathers in both species of the peacock are entirely destitute
of ocelli, and this apparently is related to their being covered up and
concealed by the long tail-coverts. In this respect they differ
remarkably from the tail-feathers of Polyplectron, which in most of the
species are ornamented with larger ocelli than those on the
tail-coverts. Hence I was led carefully to examine the tail-feathers of
the several species, in order to discover whether their ocelli shewed
any tendency to disappear; and to my great satisfaction, this appeared
to be so. The central tail-feathers of P. napoleonis have the two
ocelli on each side of the shaft perfectly developed; but the inner
ocellus becomes less and less conspicuous on the more exterior
tail-feathers, until a mere shadow or rudiment is left on the inner
side of the outermost feather. Again, in P. malaccense, the ocelli on
the tail-coverts are, as we have seen, confluent; and these feathers
are of unusual length, being two-thirds of the length of the
tail-feathers, so that in both these respects they approach the
tail-coverts of the peacock. Now in P. malaccense, the two central
tail-feathers alone are ornamented, each with two brightly-coloured
ocelli, the inner ocellus having completely disappeared from all the
other tail-feathers. Consequently the tail-coverts and tail-feathers of
this species of Polyplectron make a near approach in structure and
ornamentation to the corresponding feathers of the peacock.

As far, then, as gradation throws light on the steps by which the
magnificent train of the peacock has been acquired, hardly anything
more is needed. If we picture to ourselves a progenitor of the peacock
in an almost exactly intermediate condition between the existing
peacock, with his enormously elongated tail-coverts, ornamented with
single ocelli, and an ordinary gallinaceous bird with short
tail-coverts, merely spotted with some colour, we shall see a bird
allied to Polyplectron—that is, with tail-coverts, capable of erection
and expansion, ornamented with two partially confluent ocelli, and long
enough almost to conceal the tail-feathers, the latter having already
partially lost their ocelli. The indentation of the central disc and of
the surrounding zones of the ocellus, in both species of peacock,
speaks plainly in favour of this view, and is otherwise inexplicable.
The males of Polyplectron are no doubt beautiful birds, but their
beauty, when viewed from a little distance, cannot be compared with
that of the peacock. Many female progenitors of the peacock must,
during a long line of descent, have appreciated this superiority; for
they have unconsciously, by the continued preference for the most
beautiful males, rendered the peacock the most splendid of living
birds.

ARGUS PHEASANT.

Another excellent case for investigation is offered by the ocelli on
the wing-feathers of the Argus pheasant, which are shaded in so
wonderful a manner as to resemble balls lying loose within sockets, and
consequently differ from ordinary ocelli. No one, I presume, will
attribute the shading, which has excited the admiration of many
experienced artists, to chance—to the fortuitous concourse of atoms of
colouring matter. That these ornaments should have been formed through
the selection of many successive variations, not one of which was
originally intended to produce the ball-and-socket effect, seems as
incredible as that one of Raphael’s Madonnas should have been formed by
the selection of chance daubs of paint made by a long succession of
young artists, not one of whom intended at first to draw the human
figure. In order to discover how the ocelli have been developed, we
cannot look to a long line of progenitors, nor to many closely-allied
forms, for such do not now exist. But fortunately the several feathers
on the wing suffice to give us a clue to the problem, and they prove to
demonstration that a gradation is at least possible from a mere spot to
a finished ball-and-socket ocellus.

[Fig. 57. Part of secondary wing-feather of Argus pheasant, shewing two
perfect ocelli, a and b. A, B, C, D, etc., are dark stripes running
obliquely down, each to an ocellus. [Much of the web on both sides,
especially to the left of the shaft, has been cut off.]

Fig.59. Portion of one of the secondary wing-feathers near to the body,
shewing the so-called elliptic ornaments. The right-hand figure is
given merely as a diagram for the sake of the letters of reference. A,
B, C, D, etc. Rows of spots running down to and forming the elliptic
ornaments. b. Lowest spot or mark in row B. c. The next succeeding spot
or mark in the same row. d. Apparently a broken prolongation of the
spot c. in the same row B.]

The wing-feathers, bearing the ocelli, are covered with dark stripes
(Fig. 57) or with rows of dark spots (Fig. 59), each stripe or row of
spots running obliquely down the outer side of the shaft to one of the
ocelli. The spots are generally elongated in a line transverse to the
row in which they stand. They often become confluent either in the line
of the row—and then they form a longitudinal stripe—or transversely,
that is, with the spots in the adjoining rows, and then they form
transverse stripes. A spot sometimes breaks up into smaller spots,
which still stand in their proper places.

It will be convenient first to describe a perfect ball-and-socket
ocellus. This consists of an intensely black circular ring, surrounding
a space shaded so as exactly to resemble a ball. The figure here given
has been admirably drawn by Mr. Ford and well engraved, but a woodcut
cannot exhibit the exquisite shading of the original. The ring is
almost always slightly broken or interrupted (Fig. 57) at a point in
the upper half, a little to the right of and above the white shade on
the enclosed ball; it is also sometimes broken towards the base on the
right hand. These little breaks have an important meaning. The ring is
always much thickened, with the edges ill-defined towards the left-hand
upper corner, the feather being held erect, in the position in which it
is here drawn. Beneath this thickened part there is on the surface of
the ball an oblique almost pure-white mark, which shades off downwards
into a pale-leaden hue, and this into yellowish and brown tints, which
insensibly become darker and darker towards the lower part of the ball.
It is this shading which gives so admirably the effect of light shining
on a convex surface. If one of the balls be examined, it will be seen
that the lower part is of a brown tint and is indistinctly separated by
a curved oblique line from the upper part, which is yellower and more
leaden; this curved oblique line runs at right angles to the longer
axis of the white patch of light, and indeed of all the shading; but
this difference in colour, which cannot of course be shewn in the
woodcut, does not in the least interfere with the perfect shading of
the ball. It should be particularly observed that each ocellus stands
in obvious connection either with a dark stripe, or with a longitudinal
row of dark spots, for both occur indifferently on the same feather.
Thus in Fig. 57 stripe A runs to ocellus a; B runs to ocellus b; stripe
C is broken in the upper part, and runs down to the next succeeding
ocellus, not represented in the woodcut; D to the next lower one, and
so with the stripes E and F. Lastly, the several ocelli are separated
from each other by a pale surface bearing irregular black marks.

[Fig. 58. Basal part of the secondary wing feather, nearest to the
body.]

I will next describe the other extreme of the series, namely, the first
trace of an ocellus. The short secondary wing-feather (Fig. 58),
nearest to the body, is marked like the other feathers, with oblique,
longitudinal, rather irregular, rows of very dark spots. The basal
spot, or that nearest the shaft, in the five lower rows (excluding the
lowest one) is a little larger than the other spots of the same row,
and a little more elongated in a transverse direction. It differs also
from the other spots by being bordered on its upper side with some dull
fulvous shading. But this spot is not in any way more remarkable than
those on the plumage of many birds, and might easily be overlooked. The
next higher spot does not differ at all from the upper ones in the same
row. The larger basal spots occupy exactly the same relative position
on these feathers as do the perfect ocelli on the longer wing-feathers.

By looking to the next two or three succeeding wing-feathers, an
absolutely insensible gradation can be traced from one of the
last-described basal spots, together with the next higher one in the
same row, to a curious ornament, which cannot be called an ocellus, and
which I will name, from the want of a better term, an “elliptic
ornament.” These are shewn in the accompanying figure (Fig. 59). We
here see several oblique rows, A, B, C, D, etc. (see the lettered
diagram on the right hand), of dark spots of the usual character. Each
row of spots runs down to and is connected with one of the elliptic
ornaments, in exactly the same manner as each stripe in Fig. 57 runs
down to and is connected with one of the ball-and-socket ocelli.
Looking to any one row, for instance, B, in Fig. 59, the lowest mark
(b) is thicker and considerably longer than the upper spots, and has
its left extremity pointed and curved upwards. This black mark is
abruptly bordered on its upper side by a rather broad space of richly
shaded tints, beginning with a narrow brown zone, which passes into
orange, and this into a pale leaden tint, with the end towards the
shaft much paler. These shaded tints together fill up the whole inner
space of the elliptic ornament. The mark (b) corresponds in every
respect with the basal shaded spot of the simple feather described in
the last paragraph (Fig. 58), but is more highly developed and more
brightly coloured. Above and to the right of this spot (b, Fig. 59),
with its bright shading, there is a long narrow, black mark (c),
belonging to the same row, and which is arched a little downwards so as
to face (b). This mark is sometimes broken into two portions. It is
also narrowly edged on the lower side with a fulvous tint. To the left
of and above c, in the same oblique direction, but always more or less
distinct from it, there is another black mark (d). This mark is
generally sub-triangular and irregular in shape, but in the one
lettered in the diagram it is unusually narrow, elongated, and regular.
It apparently consists of a lateral and broken prolongation of the mark
(c), together with its confluence with a broken and prolonged part of
the next spot above; but I do not feel sure of this. These three marks,
b, c, and d, with the intervening bright shades, form together the
so-called elliptic ornament. These ornaments placed parallel to the
shaft, manifestly correspond in position with the ball-and-socket
ocelli. Their extremely elegant appearance cannot be appreciated in the
drawing, as the orange and leaden tints, contrasting so well with the
black marks, cannot be shewn.

[Fig. 60. An ocellus in an intermediate condition between the elliptic
ornament and the perfect ball-and-socket ocellus.]

Between one of the elliptic ornaments and a perfect ball-and-socket
ocellus, the gradation is so perfect that it is scarcely possible to
decide when the latter term ought to be used. The passage from the one
into the other is effected by the elongation and greater curvature in
opposite directions of the lower black mark (b, Fig. 59), and more
especially of the upper one (c), together with the contraction of the
elongated sub-triangular or narrow mark (d), so that at last these
three marks become confluent, forming an irregular elliptic ring. This
ring is gradually rendered more and more circular and regular,
increasing at the same time in diameter. I have here given a drawing
(Fig. 60) of the natural size of an ocellus not as yet quite perfect.
The lower part of the black ring is much more curved than is the lower
mark in the elliptic ornament (b, Fig. 59). The upper part of the ring
consists of two or three separate portions; and there is only a trace
of the thickening of the portion which forms the black mark above the
white shade. This white shade itself is not as yet much concentrated;
and beneath it the surface is brighter coloured than in a perfect
ball-and-socket ocellus. Even in the most perfect ocelli traces of the
junction of three or four elongated black marks, by which the ring has
been formed, may often be detected. The irregular sub-triangular or
narrow mark (d, Fig. 59), manifestly forms, by its contraction and
equalisation, the thickened portion of the ring above the white shade
on a perfect ball-and-socket ocellus. The lower part of the ring is
invariably a little thicker than the other parts (Fig. 57), and this
follows from the lower black mark of the elliptic ornament (b, Fig. 59)
having originally been thicker than the upper mark (c). Every step can
be followed in the process of confluence and modification; and the
black ring which surrounds the ball of the ocellus is unquestionably
formed by the union and modification of the three black marks, b, c, d,
of the elliptic ornament. The irregular zigzag black marks between the
successive ocelli (Fig. 57) are plainly due to the breaking up of the
somewhat more regular but similar marks between the elliptic ornaments.

The successive steps in the shading of the ball-and-socket ocelli can
be followed out with equal clearness. The brown, orange, and
pale-leadened narrow zones, which border the lower black mark of the
elliptic ornament, can be seen gradually to become more and more
softened and shaded into each other, with the upper lighter part
towards the left-hand corner rendered still lighter, so as to become
almost white, and at the same time more contracted. But even in the
most perfect ball-and-socket ocelli a slight difference in the tints,
though not in the shading, between the upper and lower parts of the
ball can be perceived, as before noticed; and the line of separation is
oblique, in the same direction as the bright coloured shades of the
elliptic ornaments. Thus almost every minute detail in the shape and
colouring of the ball-and-socket ocelli can be shewn to follow from
gradual changes in the elliptic ornaments; and the development of the
latter can be traced by equally small steps from the union of two
almost simple spots, the lower one (Fig. 58) having some dull fulvous
shading on its upper side.

[Fig. 61. Portion near summit of one of the secondary wing-feathers,
bearing perfect ball-and-socket ocelli. a. Ornamented upper part. b.
Uppermost, imperfect ball-and-socket ocellus. (The shading above the
white mark on the summit of the ocellus is here a little too dark.) c.
Perfect ocellus.]

The extremities of the longer secondary feathers which bear the perfect
ball-and-socket ocelli, are peculiarly ornamented (Fig. 61). The
oblique longitudinal stripes suddenly cease upwards and become
confused; and above this limit the whole upper end of the feather (a)
is covered with white dots, surrounded by little black rings, standing
on a dark ground. The oblique stripe belonging to the uppermost ocellus
(b) is barely represented by a very short irregular black mark with the
usual, curved, transverse base. As this stripe is thus abruptly cut
off, we can perhaps understand from what has gone before, how it is
that the upper thickened part of the ring is here absent; for, as
before stated, this thickened part apparently stands in some relation
with a broken prolongation from the next higher spot. From the absence
of the upper and thickened part of the ring, the uppermost ocellus,
though perfect in all other respects, appears as if its top had been
obliquely sliced off. It would, I think, perplex any one, who believes
that the plumage of the Argus pheasant was created as we now see it, to
account for the imperfect condition of the uppermost ocellus. I should
add that on the secondary wing-feather farthest from the body all the
ocelli are smaller and less perfect than on the other feathers, and
have the upper part of the ring deficient, as in the case just
mentioned. The imperfection here seems to be connected with the fact
that the spots on this feather shew less tendency than usual to become
confluent into stripes; they are, on the contrary, often broken up into
smaller spots, so that two or three rows run down to the same ocellus.

There still remains another very curious point, first observed by Mr.
T.W. Wood (51. The ‘Field,’ May 28, 1870.), which deserves attention.
In a photograph, given me by Mr. Ward, of a specimen mounted as in the
act of display, it may be seen that on the feathers which are held
perpendicularly, the white marks on the ocelli, representing light
reflected from a convex surface, are at the upper or further end, that
is, are directed upwards; and the bird whilst displaying himself on the
ground would naturally be illuminated from above. But here comes the
curious point; the outer feathers are held almost horizontally, and
their ocelli ought likewise to appear as if illuminated from above, and
consequently the white marks ought to be placed on the upper sides of
the ocelli; and, wonderful as is the fact, they are thus placed! Hence
the ocelli on the several feathers, though occupying very different
positions with respect to the light, all appear as if illuminated from
above, just as an artist would have shaded them. Nevertheless they are
not illuminated from strictly the same point as they ought to be; for
the white marks on the ocelli of the feathers which are held almost
horizontally, are placed rather too much towards the further end; that
is, they are not sufficiently lateral. We have, however, no right to
expect absolute perfection in a part rendered ornamental through sexual
selection, any more than we have in a part modified through natural
selection for real use; for instance, in that wondrous organ the human
eye. And we know what Helmholtz, the highest authority in Europe on the
subject, has said about the human eye; that if an optician had sold him
an instrument so carelessly made, he would have thought himself fully
justified in returning it. (52. ‘Popular Lectures on Scientific
Subjects,’ Eng. trans. 1873, pp. 219, 227, 269, 390.)

We have now seen that a perfect series can be followed, from simple
spots to the wonderful ball-and-socket ornaments. Mr. Gould, who kindly
gave me some of these feathers, fully agrees with me in the
completeness of the gradation. It is obvious that the stages in
development exhibited by the feathers on the same bird do not at all
necessarily shew us the steps passed through by the extinct progenitors
of the species; but they probably give us the clue to the actual steps,
and they at least prove to demonstration that a gradation is possible.
Bearing in mind how carefully the male Argus pheasant displays his
plumes before the female, as well as the many facts rendering it
probable that female birds prefer the more attractive males, no one who
admits the agency of sexual selection in any case will deny that a
simple dark spot with some fulvous shading might be converted, through
the approximation and modification of two adjoining spots, together
with some slight increase of colour, into one of the so-called elliptic
ornaments. These latter ornaments have been shewn to many persons, and
all have admitted that they are beautiful, some thinking them even more
so than the ball-and-socket ocelli. As the secondary plumes became
lengthened through sexual selection, and as the elliptic ornaments
increased in diameter, their colours apparently became less bright; and
then the ornamentation of the plumes had to be gained by an improvement
in the pattern and shading; and this process was carried on until the
wonderful ball-and-socket ocelli were finally developed. Thus we can
understand—and in no other way as it seems to me—the present condition
and origin of the ornaments on the wing-feathers of the Argus pheasant.

From the light afforded by the principle of gradation—from what we know
of the laws of variation—from the changes which have taken place in
many of our domesticated birds—and, lastly, from the character (as we
shall hereafter see more clearly) of the immature plumage of young
birds—we can sometimes indicate, with a certain amount of confidence,
the probable steps by which the males have acquired their brilliant
plumage and various ornaments; yet in many cases we are involved in
complete darkness. Mr. Gould several years ago pointed out to me a
humming-bird, the Urosticte benjamini, remarkable for the curious
differences between the sexes. The male, besides a splendid gorget, has
greenish-black tail-feathers, with the four CENTRAL ones tipped with
white; in the female, as with most of the allied species, the three
OUTER tail-feathers on each side are tipped with white, so that the
male has the four central, whilst the female has the six exterior
feathers ornamented with white tips. What makes the case more curious
is that, although the colouring of the tail differs remarkably in both
sexes of many kinds of humming-birds, Mr. Gould does not know a single
species, besides the Urosticte, in which the male has the four central
feathers tipped with white.

The Duke of Argyll, in commenting on this case (53. ‘The Reign of Law,’
1867, p. 247.), passes over sexual selection, and asks, “What
explanation does the law of natural selection give of such specific
varieties as these?” He answers “none whatever”; and I quite agree with
him. But can this be so confidently said of sexual selection? Seeing in
how many ways the tail-feathers of humming-birds differ, why should not
the four central feathers have varied in this one species alone, so as
to have acquired white tips? The variations may have been gradual, or
somewhat abrupt as in the case recently given of the humming-birds near
Bogota, in which certain individuals alone have the “central
tail-feathers tipped with beautiful green.” In the female of the
Urosticte I noticed extremely minute or rudimental white tips to the
two outer of the four central black tail-feathers; so that here we have
an indication of change of some kind in the plumage of this species. If
we grant the possibility of the central tail-feathers of the male
varying in whiteness, there is nothing strange in such variations
having been sexually selected. The white tips, together with the small
white ear-tufts, certainly add, as the Duke of Argyll admits, to the
beauty of the male; and whiteness is apparently appreciated by other
birds, as may be inferred from such cases as the snow-white male of the
Bell-bird. The statement made by Sir R. Heron should not be forgotten,
namely, that his peahens, when debarred from access to the pied
peacock, would not unite with any other male, and during that season
produced no offspring. Nor is it strange that variations in the
tail-feathers of the Urosticte should have been specially selected for
the sake of ornament, for the next succeeding genus in the family takes
its name of Metallura from the splendour of these feathers. We have,
moreover, good evidence that humming-birds take especial pains in
displaying their tail-feathers; Mr. Belt (54. ‘The Naturalist in
Nicaragua,’ 1874, p. 112.), after describing the beauty of the
Florisuga mellivora, says, “I have seen the female sitting on a branch,
and two males displaying their charms in front of her. One would shoot
up like a rocket, then suddenly expanding the snow-white tail, like an
inverted parachute, slowly descend in front of her, turning round
gradually to shew off back and front...The expanded white tail covered
more space than all the rest of the bird, and was evidently the grand
feature in the performance. Whilst one male was descending, the other
would shoot up and come slowly down expanded. The entertainment would
end in a fight between the two performers; but whether the most
beautiful or the most pugnacious was the accepted suitor, I know not.”
Mr. Gould, after describing the peculiar plumage of the Urosticte,
adds, “that ornament and variety is the sole object, I have myself but
little doubt.” (55. ‘Introduction to the Trochilidae,’ 1861, p. 110.)
If this be admitted, we can perceive that the males which during former
times were decked in the most elegant and novel manner would have
gained an advantage, not in the ordinary struggle for life, but in
rivalry with other males, and would have left a larger number of
offspring to inherit their newly-acquired beauty.




CHAPTER XV.
BIRDS—continued.


Discussion as to why the males alone of some species, and both sexes of
others, are brightly coloured—On sexually-limited inheritance, as
applied to various structures and to brightly-coloured
plumage—Nidification in relation to colour—Loss of nuptial plumage
during the winter.

We have in this chapter to consider why the females of many birds have
not acquired the same ornaments as the male; and why, on the other
hand, both sexes of many other birds are equally, or almost equally,
ornamented? In the following chapter we shall consider the few cases in
which the female is more conspicuously coloured than the male.

In my ‘Origin of Species’ (1. Fourth edition, 1866, p. 241.) I briefly
suggested that the long tail of the peacock would be inconvenient and
the conspicuous black colour of the male capercailzie dangerous, to the
female during the period of incubation: and consequently that the
transmission of these characters from the male to the female offspring
had been checked through natural selection. I still think that this may
have occurred in some few instances: but after mature reflection on all
the facts which I have been able to collect, I am now inclined to
believe that when the sexes differ, the successive variations have
generally been from the first limited in their transmission to the same
sex in which they first arose. Since my remarks appeared, the subject
of sexual coloration has been discussed in some very interesting papers
by Mr. Wallace (2. ‘Westminster Review,’ July 1867. ‘Journal of
Travel,’ vol. i. 1868, p. 73.), who believes that in almost all cases
the successive variations tended at first to be transmitted equally to
both sexes; but that the female was saved, through natural selection,
from acquiring the conspicuous colours of the male, owing to the danger
which she would thus have incurred during incubation.

This view necessitates a tedious discussion on a difficult point,
namely, whether the transmission of a character, which is at first
inherited by both sexes can be subsequently limited in its transmission
to one sex alone by means of natural selection. We must bear in mind,
as shewn in the preliminary chapter on sexual selection, that
characters which are limited in their development to one sex are always
latent in the other. An imaginary illustration will best aid us in
seeing the difficulty of the case; we may suppose that a fancier wished
to make a breed of pigeons, in which the males alone should be coloured
of a pale blue, whilst the females retained their former slaty tint. As
with pigeons characters of all kinds are usually transmitted to both
sexes equally, the fancier would have to try to convert this latter
form of inheritance into sexually-limited transmission. All that he
could do would be to persevere in selecting every male pigeon which was
in the least degree of a paler blue; and the natural result of this
process, if steadily carried on for a long time, and if the pale
variations were strongly inherited or often recurred, would be to make
his whole stock of a lighter blue. But our fancier would be compelled
to match, generation after generation, his pale blue males with slaty
females, for he wishes to keep the latter of this colour. The result
would generally be the production either of a mongrel piebald lot, or
more probably the speedy and complete loss of the pale-blue tint; for
the primordial slaty colour would be transmitted with prepotent force.
Supposing, however, that some pale-blue males and slaty females were
produced during each successive generation, and were always crossed
together, then the slaty females would have, if I may use the
expression, much blue blood in their veins, for their fathers,
grandfathers, etc., will all have been blue birds. Under these
circumstances it is conceivable (though I know of no distinct facts
rendering it probable) that the slaty females might acquire so strong a
latent tendency to pale-blueness, that they would not destroy this
colour in their male offspring, their female offspring still inheriting
the slaty tint. If so, the desired end of making a breed with the two
sexes permanently different in colour might be gained.

The extreme importance, or rather necessity in the above case of the
desired character, namely, pale-blueness, being present though in a
latent state in the female, so that the male offspring should not be
deteriorated, will be best appreciated as follows: the male of
Soemmerring’s pheasant has a tail thirty-seven inches in length, whilst
that of the female is only eight inches; the tail of the male common
pheasant is about twenty inches, and that of the female twelve inches
long. Now if the female Soemmerring pheasant with her SHORT tail were
crossed with the male common pheasant, there can be no doubt that the
male hybrid offspring would have a much LONGER tail than that of the
pure offspring of the common pheasant. On the other hand, if the female
common pheasant, with a tail much longer than that of the female
Soemmerring pheasant, were crossed with the male of the latter, the
male hybrid offspring would have a much SHORTER tail than that of the
pure offspring of Soemmerring’s pheasant. (3. Temminck says that the
tail of the female Phasianus Soemmerringii is only six inches long,
‘Planches coloriees,’ vol. v. 1838, pp. 487 and 488: the measurements
above given were made for me by Mr. Sclater. For the common pheasant,
see Macgillivray, ‘History of British Birds,’ vol. i. pp. 118-121.)

Our fancier, in order to make his new breed with the males of a
pale-blue tint, and the females unchanged, would have to continue
selecting the males during many generations; and each stage of paleness
would have to be fixed in the males, and rendered latent in the
females. The task would be an extremely difficult one, and has never
been tried, but might possibly be successfully carried out. The chief
obstacle would be the early and complete loss of the pale-blue tint,
from the necessity of reiterated crosses with the slaty female, the
latter not having at first any LATENT tendency to produce pale-blue
offspring.

On the other hand, if one or two males were to vary ever so slightly in
paleness, and the variations were from the first limited in their
transmission to the male sex, the task of making a new breed of the
desired kind would be easy, for such males would simply have to be
selected and matched with ordinary females. An analogous case has
actually occurred, for there are breeds of the pigeon in Belgium (4.
Dr. Chapuis, ‘Le Pigeon Voyageur Belge,’ 1865, p. 87.) in which the
males alone are marked with black striae. So again Mr. Tegetmeier has
recently shewn (5. The ‘Field,’ Sept. 1872.) that dragons not rarely
produce silver-coloured birds, which are almost always hens; and he
himself has bred ten such females. It is on the other hand a very
unusual event when a silver male is produced; so that nothing would be
easier, if desired, than to make a breed of dragons with blue males and
silver females. This tendency is indeed so strong that when Mr.
Tegetmeier at last got a silver male and matched him with one of the
silver females, he expected to get a breed with both sexes thus
coloured; he was however disappointed, for the young male reverted to
the blue colour of his grandfather, the young female alone being
silver. No doubt with patience this tendency to reversion in the males,
reared from an occasional silver male matched with a silver hen, might
be eliminated, and then both sexes would be coloured alike; and this
very process has been followed with success by Mr. Esquilant in the
case of silver turbits.

With fowls, variations of colour, limited in their transmission to the
male sex, habitually occur. When this form of inheritance prevails, it
might well happen that some of the successive variations would be
transferred to the female, who would then slightly resemble the male,
as actually occurs in some breeds. Or again, the greater number, but
not all, of the successive steps might be transferred to both sexes,
and the female would then closely resemble the male. There can hardly
be a doubt that this is the cause of the male pouter pigeon having a
somewhat larger crop, and of the male carrier pigeon having somewhat
larger wattles, than their respective females; for fanciers have not
selected one sex more than the other, and have had no wish that these
characters should be more strongly displayed in the male than in the
female, yet this is the case with both breeds.

The same process would have to be followed, and the same difficulties
encountered, if it were desired to make a breed with the females alone
of some new colour.

Lastly, our fancier might wish to make a breed with the two sexes
differing from each other, and both from the parent species. Here the
difficulty would be extreme, unless the successive variations were from
the first sexually limited on both sides, and then there would be no
difficulty. We see this with the fowl; thus the two sexes of the
pencilled Hamburghs differ greatly from each other, and from the two
sexes of the aboriginal Gallus bankiva; and both are now kept constant
to their standard of excellence by continued selection, which would be
impossible unless the distinctive characters of both were limited in
their transmission.

The Spanish fowl offers a more curious case; the male has an immense
comb, but some of the successive variations, by the accumulation of
which it was acquired, appear to have been transferred to the female;
for she has a comb many times larger than that of the females of the
parent species. But the comb of the female differs in one respect from
that of the male, for it is apt to lop over; and within a recent period
it has been ordered by the fancy that this should always be the case,
and success has quickly followed the order. Now the lopping of the comb
must be sexually limited in its transmission, otherwise it would
prevent the comb of the male from being perfectly upright, which would
be abhorrent to every fancier. On the other hand, the uprightness of
the comb in the male must likewise be a sexually-limited character,
otherwise it would prevent the comb of the female from lopping over.

From the foregoing illustrations, we see that even with almost
unlimited time at command, it would be an extremely difficult and
complex, perhaps an impossible process, to change one form of
transmission into the other through selection. Therefore, without
distinct evidence in each case, I am unwilling to admit that this has
been effected in natural species. On the other hand, by means of
successive variations, which were from the first

sexually limited in their transmission, there would not be the least
difficulty in rendering a male bird widely different in colour or in
any other character from the female; the latter being left unaltered,
or slightly altered, or specially modified for the sake of protection.

As bright colours are of service to the males in their rivalry with
other males, such colours would be selected whether or not they were
transmitted exclusively to the same sex. Consequently the females might
be expected often to partake of the brightness of the males to a
greater or less degree; and this occurs with a host of species. If all
the successive variations were transmitted equally to both sexes, the
females would be indistinguishable from the males; and this likewise
occurs with many birds. If, however, dull colours were of high
importance for the safety of the female during incubation, as with many
ground birds, the females which varied in brightness, or which received
through inheritance from the males any marked accession of brightness,
would sooner or later be destroyed. But the tendency in the males to
continue for an indefinite period transmitting to their female
offspring their own brightness, would have to be eliminated by a change
in the form of inheritance; and this, as shewn by our previous
illustration, would be extremely difficult. The more probable result of
the long-continued destruction of the more brightly-coloured females,
supposing the equal form of transmission to prevail, would be the
lessening or annihilation of the bright colours of the males, owing to
their continual crossing with the duller females. It would be tedious
to follow out all the other possible results; but I may remind the
reader that if sexually-limited variations in brightness occurred in
the females, even if they were not in the least injurious to them and
consequently were not eliminated, yet they would not be favoured or
selected, for the male usually accepts any female, and does not select
the more attractive individuals; consequently these variations would be
liable to be lost, and would have little influence on the character of
the race; and this will aid in accounting for the females being
commonly duller-coloured than the males.

In the eighth chapter instances were given, to which many might here be
added, of variations occurring at various ages, and inherited at the
corresponding age. It was also shewn that variations which occur late
in life are commonly transmitted to the same sex in which they first
appear; whilst variations occurring early in life are apt to be
transmitted to both sexes; not that all the cases of sexually-limited
transmission can thus be accounted for. It was further shewn that if a
male bird varied by becoming brighter whilst young, such variations
would be of no service until the age for reproduction had arrived, and
there was competition between rival males. But in the case of birds
living on the ground and commonly in need of the protection of dull
colours, bright tints would be far more dangerous to the young and
inexperienced than to the adult males. Consequently the males which
varied in brightness whilst young would suffer much destruction and be
eliminated through natural selection; on the other hand, the males
which varied in this manner when nearly mature, notwithstanding that
they were exposed to some additional danger, might survive, and from
being favoured through sexual selection, would procreate their kind. As
a relation often exists between the period of variation and the form of
transmission, if the bright-coloured young males were destroyed and the
mature ones were successful in their courtship, the males alone would
acquire brilliant colours and would transmit them exclusively to their
male offspring. But I by no means wish to maintain that the influence
of age on the form of transmission, is the sole cause of the great
difference in brilliancy between the sexes of many birds.

When the sexes of birds differ in colour, it is interesting to
determine whether the males alone have been modified by sexual
selection, the females having been left unchanged, or only partially
and indirectly thus changed; or whether the females have been specially
modified through natural selection for the sake of protection. I will
therefore discuss this question at some length, even more fully than
its intrinsic importance deserves; for various curious collateral
points may thus be conveniently considered.

Before we enter on the subject of colour, more especially in reference
to Mr. Wallace’s conclusions, it may be useful to discuss some other
sexual differences under a similar point of view. A breed of fowls
formerly existed in Germany (6. Bechstein, ‘Naturgeschichte
Deutschlands,’ 1793, B. iii. 339.) in which the hens were furnished
with spurs; they were good layers, but they so greatly disturbed their
nests with their spurs that they could not be allowed to sit on their
own eggs. Hence at one time it appeared to me probable that with the
females of the wild Gallinaceae the development of spurs had been
checked through natural selection, from the injury thus caused to their
nests. This seemed all the more probable, as wing-spurs, which would
not be injurious during incubation, are often as well-developed in the
female as in the male; though in not a few cases they are rather larger
in the male. When the male is furnished with leg-spurs the female
almost always exhibits rudiments of them,—the rudiment sometimes
consisting of a mere scale, as in Gallus. Hence it might be argued that
the females had aboriginally been furnished with well-developed spurs,
but that these had subsequently been lost through disuse or natural
selection. But if this view be admitted, it would have to be extended
to innumerable other cases; and it implies that the female progenitors
of the existing spur-bearing species were once encumbered with an
injurious appendage.

In some few genera and species, as in Galloperdix, Acomus, and the
Javan peacock (Pavo muticus), the females, as well as the males,
possess well-developed leg-spurs. Are we to infer from this fact that
they construct a different sort of nest from that made by their nearest
allies, and not liable to be injured by their spurs; so that the spurs
have not been removed? Or are we to suppose that the females of these
several species especially require spurs for their defence? It is a
more probable conclusion that both the presence and absence of spurs in
the females result from different laws of inheritance having prevailed,
independently of natural selection. With the many females in which
spurs appear as rudiments, we may conclude that some few of the
successive variations, through which they were developed in the males,
occurred very early in life, and were consequently transferred to the
females. In the other and much rarer cases, in which the females
possess fully developed spurs, we may conclude that all the successive
variations were transferred to them; and that they gradually acquired
and inherited the habit of not disturbing their nests.

The vocal organs and the feathers variously modified for producing
sound, as well as the proper instincts for using them, often differ in
the two sexes, but are sometimes the same in both. Can such differences
be accounted for by the males having acquired these organs and
instincts, whilst the females have been saved from inheriting them, on
account of the danger to which they would have been exposed by
attracting the attention of birds or beasts of prey? This does not seem
to me probable, when we think of the multitude of birds which with
impunity gladden the country with their voices during the spring. (7.
Daines Barrington, however, thought it probable (‘Philosophical
Transactions,’ 1773, p. 164) that few female birds sing, because the
talent would have been dangerous to them during incubation. He adds,
that a similar view may possibly account for the inferiority of the
female to the male in plumage.) It is a safer conclusion that, as vocal
and instrumental organs are of special service only to the males during
their courtship, these organs were developed through sexual selection
and their constant use in that sex alone—the successive variations and
the effects of use having been from the first more or less limited in
transmission to the male offspring.

Many analogous cases could be adduced; those for instance of the plumes
on the head being generally longer in the male than in the female,
sometimes of equal length in both sexes, and occasionally absent in the
female,—these several cases occurring in the same group of birds. It
would be difficult to account for such a difference between the sexes
by the female having been benefited by possessing a slightly shorter
crest than the male, and its consequent diminution or complete
suppression through natural selection. But I will take a more
favourable case, namely the length of the tail. The long train of the
peacock would have been not only inconvenient but dangerous to the
peahen during the period of incubation and whilst accompanying her
young. Hence there is not the least a priori improbability in the
development of her tail having been checked through natural selection.
But the females of various pheasants, which apparently are exposed on
their open nests to as much danger as the peahen, have tails of
considerable length. The females as well as the males of the Menura
superba have long tails, and they build a domed nest, which is a great
anomaly in so large a bird. Naturalists have wondered how the female
Menura could manage her tail during incubation; but it is now known (8.
Mr. Ramsay, in ‘Proc. Zoolog. Soc.’ 1868, p. 50.) that she “enters the
nest head first, and then turns round with her tail sometimes over her
back, but more often bent round by her side. Thus in time the tail
becomes quite askew, and is a tolerable guide to the length of time the
bird has been sitting.” Both sexes of an Australian kingfisher
(Tanysiptera sylvia) have the middle tail-feathers greatly lengthened,
and the female makes her nest in a hole; and as I am informed by Mr.
R.B. Sharpe these feathers become much crumpled during incubation.

In these two latter cases the great length of the tail-feathers must be
in some degree inconvenient to the female; and as in both species the
tail-feathers of the female are somewhat shorter than those of the
male, it might be argued that their full development had been prevented
through natural selection. But if the development of the tail of the
peahen had been checked only when it became inconveniently or
dangerously great, she would have retained a much longer tail than she
actually possesses; for her tail is not nearly so long, relatively to
the size of her body, as that of many female pheasants, nor longer than
that of the female turkey. It must also be borne in mind that, in
accordance with this view, as soon as the tail of the peahen became
dangerously long, and its development was consequently checked, she
would have continually reacted on her male progeny, and thus have
prevented the peacock from acquiring his present magnificent train. We
may therefore infer that the length of the tail in the peacock and its
shortness in the peahen are the result of the requisite variations in
the male having been from the first transmitted to the male offspring
alone.

We are led to a nearly similar conclusion with respect to the length of
the tail in the various species of pheasants. In the Eared pheasant
(Crossoptilon auritum) the tail is of equal length in both sexes,
namely sixteen or seventeen inches; in the common pheasant it is about
twenty inches long in the male and twelve in the female; in
Soemmerring’s pheasant, thirty-seven inches in the male and only eight
in the female; and lastly in Reeve’s pheasant it is sometimes actually
seventy-two inches long in the male and sixteen in the female. Thus in
the several species, the tail of the female differs much in length,
irrespectively of that of the male; and this can be accounted for, as
it seems to me, with much more probability, by the laws of
inheritance,—that is by the successive variations having been from the
first more or less closely limited in their transmission to the male
sex than by the agency of natural selection, resulting from the length
of tail being more or less injurious to the females of these several
allied species.

We may now consider Mr. Wallace’s arguments in regard to the sexual
coloration of birds. He believes that the bright tints originally
acquired through sexual selection by the males would in all, or almost
all cases, have been transmitted to the females, unless the
transference had been checked through natural selection. I may here
remind the reader that various facts opposed to this view have already
been given under reptiles, amphibians, fishes and lepidoptera. Mr.
Wallace rests his belief chiefly, but not exclusively, as we shall see
in the next chapter, on the following statement (9. ‘Journal of
Travel,’ edited by A. Murray, vol. i. 1868, p. 78.), that when both
sexes are coloured in a very conspicuous manner, the nest is of such a
nature as to conceal the sitting bird; but when there is a marked
contrast of colour between the sexes, the male being gay and the female
dull-coloured, the nest is open and exposes the sitting bird to view.
This coincidence, as far as it goes, certainly seems to favour the
belief that the females which sit on open nests have been specially
modified for the sake of protection; but we shall presently see that
there is another and more probable explanation, namely, that
conspicuous females have acquired the instinct of building domed nests
oftener than dull-coloured birds. Mr. Wallace admits that there are, as
might have been expected, some exceptions to his two rules, but it is a
question whether the exceptions are not so numerous as seriously to
invalidate them.

There is in the first place much truth in the Duke of Argyll’s remark
(10. ‘Journal of Travel,’ edited by A. Murray, vol. i. 1868, p. 281.)
that a large domed nest is more conspicuous to an enemy, especially to
all tree-haunting carnivorous animals, than a smaller open nest. Nor
must we forget that with many birds which build open nests, the male
sits on the eggs and aids the female in feeding the young: this is the
case, for instance, with Pyranga aestiva (11. Audubon, ‘Ornithological
Biography,’ vol. i. p. 233.), one of the most splendid birds in the
United States, the male being vermilion, and the female light
brownish-green. Now if brilliant colours had been extremely dangerous
to birds whilst sitting on their open nests, the males in these cases
would have suffered greatly. It might, however, be of such paramount
importance to the male to be brilliantly coloured, in order to beat his
rivals, that this may have more than compensated some additional
danger.

Mr. Wallace admits that with the King-crows (Dicrurus), Orioles, and
Pittidae, the females are conspicuously coloured, yet build open nests;
but he urges that the birds of the first group are highly pugnacious
and could defend themselves; that those of the second group take
extreme care in concealing their open nests, but this does not
invariably hold good (12. Jerdon, ‘Birds of India,’ vol. ii. p. 108.
Gould’s ‘Handbook of the Birds of Australia,’ vol. i. p. 463.); and
that with the birds of the third group the females are brightly
coloured chiefly on the under surface. Besides these cases, pigeons
which are sometimes brightly, and almost always conspicuously coloured,
and which are notoriously liable to the attacks of birds of prey, offer
a serious exception to the rule, for they almost always build open and
exposed nests. In another large family, that of the humming-birds, all
the species build open nests, yet with some of the most gorgeous
species the sexes are alike; and in the majority, the females, though
less brilliant than the males, are brightly coloured. Nor can it be
maintained that all female humming-birds, which are brightly coloured,
escape detection by their tints being green, for some display on their
upper surfaces red, blue, and other colours. (13. For instance, the
female Eupetomena macroura has the head and tail dark blue with reddish
loins; the female Lampornis porphyrurus is blackish-green on the upper
surface, with the lores and sides of the throat crimson; the female
Eulampis jugularis has the top of the head and back green, but the
loins and the tail are crimson. Many other instances of highly
conspicuous females could be given. See Mr. Gould’s magnificent work on
this family.)

In regard to birds which build in holes or construct domed nests, other
advantages, as Mr. Wallace remarks, besides concealment are gained,
such as shelter from the rain, greater warmth, and in hot countries
protection from the sun (14. Mr. Salvin noticed in Guatemala (‘Ibis,’
1864, p. 375) that humming-birds were much more unwilling to leave
their nests during very hot weather, when the sun was shining brightly,
as if their eggs would be thus injured, than during cool, cloudy, or
rainy weather.); so that it is no valid objection to his view that many
birds having both sexes obscurely coloured build concealed nests. (15.
I may specify, as instances of dull-coloured birds building concealed
nests, the species belonging to eight Australian genera described in
Gould’s ‘Handbook of the Birds of Australia,’ vol. i. pp. 340, 362,
365, 383, 387, 389, 391, 414.) The female Horn-bill (Buceros), for
instance, of India and Africa is protected during incubation with
extraordinary care, for she plasters up with her own excrement the
orifice of the hole in which she sits on her eggs, leaving only a small
orifice through which the male feeds her; she is thus kept a close
prisoner during the whole period of incubation (16. Mr. C. Horne,
‘Proc. Zoolog. Soc.’ 1869. p. 243.); yet female horn-bills are not more
conspicuously coloured than many other birds of equal size which build
open nests. It is a more serious objection to Mr. Wallace’s view, as is
admitted by him, that in some few groups the males are brilliantly
coloured and the females obscure, and yet the latter hatch their eggs
in domed nests. This is the case with the Grallinae of Australia, the
Superb Warblers (Maluridae) of the same country, the Sun-birds
(Nectariniae), and with several of the Australian Honey-suckers or
Meliphagidae. (17. On the nidification and colours of these latter
species, see Gould’s ‘Handbook to the Birds of Australia,’ vol. i. pp.
504, 527.)

If we look to the birds of England we shall see that there is no close
and general relation between the colours of the female and the nature
of the nest which is constructed. About forty of our British birds
(excluding those of large size which could defend themselves) build in
holes in banks, rocks, or trees, or construct domed nests. If we take
the colours of the female goldfinch, bullfinch, or blackbird, as a
standard of the degree of conspicuousness, which is not highly
dangerous to the sitting female, then out of the above forty birds the
females of only twelve can be considered as conspicuous to a dangerous
degree, the remaining twenty-eight being inconspicuous. (18. I have
consulted, on this subject, Macgillivray’s ‘British Birds,’ and though
doubts may be entertained in some cases in regard to the degree of
concealment of the nest, and to the degree of conspicuousness of the
female, yet the following birds, which all lay their eggs in holes or
in domed nests, can hardly be considered, by the above standard, as
conspicuous: Passer, 2 species; Sturnus, of which the female is
considerably less brilliant than the male; Cinclus; Motallica boarula
(?); Erithacus (?); Fruticola, 2 sp.; Saxicola; Ruticilla, 2 sp.;
Sylvia, 3 sp.; Parus, 3 sp.; Mecistura; Anorthura; Certhia; Sitta;
Yunx; Muscicapa, 2 sp.; Hirundo, 3 sp.; and Cypselus. The females of
the following 12 birds may be considered as conspicuous according to
the same standard, viz., Pastor, Motacilla alba, Parus major and P.
caeruleus, Upupa, Picus, 4 sp., Coracias, Alcedo, and Merops.) Nor is
there any close relation within the same genus between a
well-pronounced difference in colour between the sexes, and the nature
of the nest constructed. Thus the male house sparrow (Passer
domesticus) differs much from the female, the male tree-sparrow (P.
montanus) hardly at all, and yet both build well-concealed nests. The
two sexes of the common fly-catcher (Muscicapa grisola) can hardly be
distinguished, whilst the sexes of the pied fly-catcher (M. luctuosa)
differ considerably, and both species build in holes or conceal their
nests. The female blackbird (Turdus merula) differs much, the female
ring-ouzel (T. torquatus) differs less, and the female common thrush
(T. musicus) hardly at all from their respective males; yet all build
open nests. On the other hand, the not very distantly-allied
water-ouzel (Cinclus aquaticus) builds a domed nest, and the sexes
differ about as much as in the ring-ouzel. The black and red grouse
(Tetrao tetrix and T. scoticus) build open nests in equally
well-concealed spots, but in the one species the sexes differ greatly,
and in the other very little.

Notwithstanding the foregoing objections, I cannot doubt, after reading
Mr. Wallace’s excellent essay, that looking to the birds of the world,
a large majority of the species in which the females are conspicuously
coloured (and in this case the males with rare exceptions are equally
conspicuous), build concealed nests for the sake of protection. Mr.
Wallace enumerates (19. ‘Journal of Travel,’ edited by A. Murray, vol.
i. p. 78.) a long series of groups in which this rule holds good; but
it will suffice here to give, as instances, the more familiar groups of
kingfishers, toucans, trogons, puff-birds (Capitonidae),
plantain-eaters (Musophagae, woodpeckers, and parrots. Mr. Wallace
believes that in these groups, as the males gradually acquired through
sexual selection their brilliant colours, these were transferred to the
females and were not eliminated by natural selection, owing to the
protection which they already enjoyed from their manner of
nidification. According to this view, their present manner of nesting
was acquired before their present colours. But it seems to me much more
probable that in most cases, as the females were gradually rendered
more and more brilliant from partaking of the colours of the male, they
were gradually led to change their instincts (supposing that they
originally built open nests), and to seek protection by building domed
or concealed nests. No one who studies, for instance, Audubon’s account
of the differences in the nests of the same species in the Northern and
Southern United States (20. See many statements in the ‘Ornithological
Biography.’ See also some curious observations on the nests of Italian
birds by Eugenio Bettoni, in the ‘Atti della Società Italiana,’ vol.
xi. 1869, p. 487.), will feel any great difficulty in admitting that
birds, either by a change (in the strict sense of the word) of their
habits, or through the natural selection of so-called spontaneous
variations of instinct, might readily be led to modify their manner of
nesting.

This way of viewing the relation, as far as it holds good, between the
bright colours of female birds and their manner of nesting, receives
some support from certain cases occurring in the Sahara Desert. Here,
as in most other deserts, various birds, and many other animals, have
had their colours adapted in a wonderful manner to the tints of the
surrounding surface. Nevertheless there are, as I am informed by the
Rev. Mr. Tristram, some curious exceptions to the rule; thus the male
of the Monticola cyanea is conspicuous from his bright blue colour, and
the female almost equally conspicuous from her mottled brown and white
plumage; both sexes of two species of Dromolaea are of a lustrous
black; so that these three species are far from receiving protection
from their colours, yet they are able to survive, for they have
acquired the habit of taking refuge from danger in holes or crevices in
the rocks.

With respect to the above groups in which the females are conspicuously
coloured and build concealed nests, it is not necessary to suppose that
each separate species had its nidifying instinct specially modified;
but only that the early progenitors of each group were gradually led to
build domed or concealed nests, and afterwards transmitted this
instinct, together with their bright colours, to their modified
descendants. As far as it can be trusted, the conclusion is
interesting, that sexual selection together with equal or nearly equal
inheritance by both sexes, have indirectly determined the manner of
nidification of whole groups of birds.

According to Mr. Wallace, even in the groups in which the females, from
being protected in domed nests during incubation, have not had their
bright colours eliminated through natural selection, the males often
differ in a slight, and occasionally in a considerable degree from the
females. This is a significant fact, for such differences in colour
must be accounted for by some of the variations in the males having
been from the first limited in transmission to the same sex; as it can
hardly be maintained that these differences, especially when very
slight, serve as a protection to the female. Thus all the species in
the splendid group of the Trogons build in holes; and Mr. Gould gives
figures (21. See his Monograph of the Trogonidae, 1st edition.) of both
sexes of twenty-five species, in all of which, with one partial
exception, the sexes differ sometimes slightly, sometimes
conspicuously, in colour,—the males being always finer than the
females, though the latter are likewise beautiful. All the species of
kingfishers build in holes, and with most of the species the sexes are
equally brilliant, and thus far Mr. Wallace’s rule holds good; but in
some of the Australian species the colours of the females are rather
less vivid than those of the male; and in one splendidly-coloured
species, the sexes differ so much that they were at first thought to be
specifically distinct. (22. Namely, Cyanalcyon, Gould’s ‘Handbook to
the Birds of Australia,’ vol. i. p. 133; see, also, pp. 130, 136.) Mr.
R.B. Sharpe, who has especially studied this group, has shewn me some
American species (Ceryle) in which the breast of the male is belted
with black. Again, in Carcineutes, the difference between the sexes is
conspicuous: in the male the upper surface is dull-blue banded with
black, the lower surface being partly fawn-coloured, and there is much
red about the head; in the female the upper surface is reddish-brown
banded with black, and the lower surface white with black markings. It
is an interesting fact, as shewing how the same peculiar style of
sexual colouring often characterises allied forms, that in three
species of Dacelo the male differs from the female only in the tail
being dull-blue banded with black, whilst that of the female is brown
with blackish bars; so that here the tail differs in colour in the two
sexes in exactly the same manner as the whole upper surface in the two
sexes of Carcineutes.

With parrots, which likewise build in holes, we find analogous cases:
in most of the species, both sexes are brilliantly coloured and
indistinguishable, but in not a few species the males are coloured
rather more vividly than the females, or even very differently from
them. Thus, besides other strongly-marked differences, the whole under
surface of the male King Lory (Aprosmictus scapulatus) is scarlet,
whilst the throat and chest of the female is green tinged with red: in
the Euphema splendida there is a similar difference, the face and wing
coverts moreover of the female being of a paler blue than in the male.
(23. Every gradation of difference between the sexes may be followed in
the parrots of Australia. See Gould’s ‘Handbook,’ etc., vol. ii. pp.
14-102.) In the family of the tits (Parinae), which build concealed
nests, the female of our common blue tomtit (Parus caeruleus), is “much
less brightly coloured” than the male: and in the magnificent Sultan
yellow tit of India the difference is greater. (24. Macgillivray’s
‘British Birds,’ vol. ii. p. 433. Jerdon, ‘Birds of India,’ vol. ii. p.
282.)

Again, in the great group of the woodpeckers (25. All the following
facts are taken from M. Malherbe’s magnificent ‘Monographie des
Picidees,’ 1861.), the sexes are generally nearly alike, but in the
Megapicus validus all those parts of the head, neck, and breast, which
are crimson in the male are pale brown in the female. As in several
woodpeckers the head of the male is bright crimson, whilst that of the
female is plain, it occurred to me that this colour might possibly make
the female dangerously conspicuous, whenever she put her head out of
the hole containing her nest, and consequently that this colour, in
accordance with Mr. Wallace’s belief, had been eliminated. This view is
strengthened by what Malherbe states with respect to Indopicus
carlotta; namely, that the young females, like the young males, have
some crimson about their heads, but that this colour disappears in the
adult female, whilst it is intensified in the adult male. Nevertheless
the following considerations render this view extremely doubtful: the
male takes a fair share in incubation (26. Audubon’s ‘Ornithological
Biography,’ vol. ii. p. 75; see also the ‘Ibis,’ vol. i. p. 268.), and
would be thus almost equally exposed to danger; both sexes of many
species have their heads of an equally bright crimson; in other species
the difference between the sexes in the amount of scarlet is so slight
that it can hardly make any appreciable difference in the danger
incurred; and lastly, the colouring of the head in the two sexes often
differs slightly in other ways.

The cases, as yet given, of slight and graduated differences in colour
between the males and females in the groups, in which as a general rule
the sexes resemble each other, all relate to species which build domed
or concealed nests. But similar gradations may likewise be observed in
groups in which the sexes as a general rule resemble each other, but
which build open nests.

As I have before instanced the Australian parrots, so I may here
instance, without giving any details, the Australian pigeons. (27.
Gould’s ‘Handbook to the Birds of Australia,’ vol. ii. pp. 109-149.) It
deserves especial notice that in all these cases the slight differences
in plumage between the sexes are of the same general nature as the
occasionally greater differences. A good illustration of this fact has
already been afforded by those kingfishers in which either the tail
alone or the whole upper surface of the plumage differs in the same
manner in the two sexes. Similar cases may be observed with parrots and
pigeons. The differences in colour between the sexes of the same
species are, also, of the same general nature as the differences in
colour between the distinct species of the same group. For when in a
group in which the sexes are usually alike, the male differs
considerably from the female, he is not coloured in a quite new style.
Hence we may infer that within the same group the special colours of
both sexes when they are alike, and the colours of the male, when he
differs slightly or even considerably from the female, have been in
most cases determined by the same general cause; this being sexual
selection.

It is not probable, as has already been remarked, that differences in
colour between the sexes, when very slight, can be of service to the
female as a protection. Assuming, however, that they are of service,
they might be thought to be cases of transition; but we have no reason
to believe that many species at any one time are undergoing change.
Therefore we can hardly admit that the numerous females which differ
very slightly in colour from their males are now all commencing to
become obscure for the sake of protection. Even if we consider somewhat
more marked sexual differences, is it probable, for instance, that the
head of the female chaffinch,—the crimson on the breast of the female
bullfinch,—the green of the female greenfinch,—the crest of the female
golden-crested wren, have all been rendered less bright by the slow
process of selection for the sake of protection? I cannot think so; and
still less with the slight differences between the sexes of those birds
which build concealed nests. On the other hand, the differences in
colour between the sexes, whether great or small, may to a large extent
be explained on the principle of the successive variations, acquired by
the males through sexual selection, having been from the first more or
less limited in their transmission to the females. That the degree of
limitation should differ in different species of the same group will
not surprise any one who has studied the laws of inheritance, for they
are so complex that they appear to us in our ignorance to be capricious
in their action. (28. See remarks to this effect in ‘Variation of
Animals and Plants under Domestication,’ vol. ii. chap. xii.)

As far as I can discover there are few large groups of birds in which
all the species have both sexes alike and brilliantly coloured, but I
hear from Mr. Sclater, that this appears to be the case with the
Musophagae or plantain-eaters. Nor do I believe that any large group
exists in which the sexes of all the species are widely dissimilar in
colour: Mr. Wallace informs me that the chatterers of S. America
(Cotingidae) offer one of the best instances; but with some of the
species, in which the male has a splendid red breast, the female
exhibits some red on her breast; and the females of other species shew
traces of the green and other colours of the males. Nevertheless we
have a near approach to close sexual similarity or dissimilarity
throughout several groups: and this, from what has just been said of
the fluctuating nature of inheritance, is a somewhat surprising
circumstance. But that the same laws should largely prevail with allied
animals is not surprising. The domestic fowl has produced a great
number of breeds and sub-breeds, and in these the sexes generally
differ in plumage; so that it has been noticed as an unusual
circumstance when in certain sub-breeds they resemble each other. On
the other hand, the domestic pigeon has likewise produced a vast number
of distinct breeds and sub-breeds, and in these, with rare exceptions,
the two sexes are identically alike.

Therefore if other species of Gallus and Columba were domesticated and
varied, it would not be rash to predict that similar rules of sexual
similarity and dissimilarity, depending on the form of transmission,
would hold good in both cases. In like manner the same form of
transmission has generally prevailed under nature throughout the same
groups, although marked exceptions to this rule occur. Thus within the
same family or even genus, the sexes may be identically alike, or very
different in colour. Instances have already been given in the same
genus, as with sparrows, fly-catchers, thrushes and grouse. In the
family of pheasants the sexes of almost all the species are wonderfully
dissimilar, but are quite alike in the eared pheasant or Crossoptilon
auritum. In two species of Chloephaga, a genus of geese, the male
cannot be distinguished from the females, except by size; whilst in two
others, the sexes are so unlike that they might easily be mistaken for
distinct species. (29. The ‘Ibis,’ vol. vi. 1864, p. 122.)

The laws of inheritance can alone account for the following cases, in
which the female acquires, late in life, certain characters proper to
the male, and ultimately comes to resemble him more or less completely.
Here protection can hardly have come into play. Mr. Blyth informs me
that the females of Oriolus melanocephalus and of some allied species,
when sufficiently mature to breed, differ considerably in plumage from
the adult males; but after the second or third moults they differ only
in their beaks having a slight greenish tinge. In the dwarf bitterns
(Ardetta), according to the same authority, “the male acquires his
final livery at the first moult, the female not before the third or
fourth moult; in the meanwhile she presents an intermediate garb, which
is ultimately exchanged for the same livery as that of the male.” So
again the female Falco peregrinus acquires her blue plumage more slowly
than the male. Mr. Swinhoe states that with one of the Drongo shrikes
(Dicrurus macrocercus) the male, whilst almost a nestling, moults his
soft brown plumage and becomes of a uniform glossy greenish-black; but
the female retains for a long time the white striae and spots on the
axillary feathers; and does not completely assume the uniform black
colour of the male for three years. The same excellent observer remarks
that in the spring of the second year the female spoon-bill (Platalea)
of China resembles the male of the first year, and that apparently it
is not until the third spring that she acquires the same adult plumage
as that possessed by the male at a much earlier age. The female
Bombycilla carolinensis differs very little from the male, but the
appendages, which like beads of red sealing-wax ornament the
wing-feathers (30. When the male courts the female, these ornaments are
vibrated, and “are shewn off to great advantage,” on the outstretched
wings: A. Leith Adams, ‘Field and Forest Rambles,’ 1873, p. 153.), are
not developed in her so early in life as in the male. In the male of an
Indian parrakeet (Palaeornis javanicus) the upper mandible is coral-red
from his earliest youth, but in the female, as Mr. Blyth has observed
with caged and wild birds, it is at first black and does not become red
until the bird is at least a year old, at which age the sexes resemble
each other in all respects. Both sexes of the wild turkey are
ultimately furnished with a tuft of bristles on the breast, but in
two-year-old birds the tuft is about four inches long in the male and
hardly apparent in the female; when, however, the latter has reached
her fourth year, it is from four to five inches in length. (31. On
Ardetta, Translation of Cuvier’s ‘Regne Animal,’ by Mr. Blyth,
footnote, p. 159. On the Peregrine Falcon, Mr. Blyth, in Charlesworth’s
‘Mag. of Nat. Hist.’ vol. i. 1837, p. 304. On Dicrurus, ‘Ibis,’ 1863,
p. 44. On the Platalea, ‘Ibis,’ vol. vi. 1864, p. 366. On the
Bombycilla, Audubon’s ‘Ornitholog. Biography,’ vol. i. p. 229. On the
Palaeornis, see, also, Jerdon, ‘Birds of India,’ vol. i. p. 263. On the
wild turkey, Audubon, ibid. vol. i. p. 15; but I hear from Judge Caton
that in Illinois the female very rarely acquires a tuft. Analogous
cases with the females of Petrocossyphus are given by Mr. R. Sharpe,
‘Proceedings of the Zoological Society,’ 1872, p. 496.)

These cases must not be confounded with those where diseased or old
females abnormally assume masculine characters, nor with those where
fertile females, whilst young, acquire the characters of the male,
through variation or some unknown cause. (32. Of these latter cases Mr.
Blyth has recorded (Translation of Cuvier’s ‘Regne Animal,’ p. 158)
various instances with Lanius, Ruticilla, Linaria, and Anas. Audubon
has also recorded a similar case (‘Ornitholog. Biography,’ vol. v. p.
519) with Pyranga aestiva.) But all these cases have so much in common
that they depend, according to the hypothesis of pangenesis, on
gemmules derived from each part of the male being present, though
latent, in the female; their development following on some slight
change in the elective affinities of her constituent tissues.

A few words must be added on changes of plumage in relation to the
season of the year. From reasons formerly assigned there can be little
doubt that the elegant plumes, long pendant feathers, crests, etc., of
egrets, herons, and many other birds, which are developed and retained
only during the summer, serve for ornamental and nuptial purposes,
though common to both sexes. The female is thus rendered more
conspicuous during the period of incubation than during the winter; but
such birds as herons and egrets would be able to defend themselves. As,
however, plumes would probably be inconvenient and certainly of no use
during the winter, it is possible that the habit of moulting twice in
the year may have been gradually acquired through natural selection for
the sake of casting off inconvenient ornaments during the winter. But
this view cannot be extended to the many waders, whose summer and
winter plumages differ very little in colour. With defenceless species,
in which both sexes, or the males alone, become extremely conspicuous
during the breeding-season,—or when the males acquire at this season
such long wing or tail-feathers as to impede their flight, as with
Cosmetornis and Vidua,—it certainly at first appears highly probable
that the second moult has been gained for the special purpose of
throwing off these ornaments. We must, however, remember that many
birds, such as some of the Birds of Paradise, the Argus pheasant and
peacock, do not cast their plumes during the winter; and it can hardly
be maintained that the constitution of these birds, at least of the
Gallinaceae, renders a double moult impossible, for the ptarmigan
moults thrice in the year. (33. See Gould’s ‘Birds of Great Britain.’)
Hence it must be considered as doubtful whether the many species which
moult their ornamental plumes or lose their bright colours during the
winter, have acquired this habit on account of the inconvenience or
danger which they would otherwise have suffered.

I conclude, therefore, that the habit of moulting twice in the year was
in most or all cases first acquired for some distinct purpose, perhaps
for gaining a warmer winter covering; and that variations in the
plumage occurring during the summer were accumulated through sexual
selection, and transmitted to the offspring at the same season of the
year; that such variations were inherited either by both sexes or by
the males alone, according to the form of inheritance which prevailed.
This appears more probable than that the species in all cases
originally tended to retain their ornamental plumage during the winter,
but were saved from this through natural selection, resulting from the
inconvenience or danger thus caused.

I have endeavoured in this chapter to shew that the arguments are not
trustworthy in favour of the view that weapons, bright colours, and
various ornaments, are now confined to the males owing to the
conversion, by natural selection, of the equal transmission of
characters to both sexes, into transmission to the male sex alone. It
is also doubtful whether the colours of many female birds are due to
the preservation, for the sake of protection, of variations which were
from the first limited in their transmission to the female sex. But it
will be convenient to defer any further discussion on this subject
until I treat, in the following chapter, of the differences in plumage
between the young and old.




CHAPTER XVI.
BIRDS—concluded.


The immature plumage in relation to the character of the plumage in
both sexes when adult—Six classes of cases—Sexual differences between
the males of closely-allied or representative species—The female
assuming the characters of the male—Plumage of the young in relation to
the summer and winter plumage of the adults—On the increase of beauty
in the birds of the world—Protective colouring—Conspicuously coloured
birds—Novelty appreciated—Summary of the four chapters on Birds.

We must now consider the transmission of characters, as limited by age,
in reference to sexual selection. The truth and importance of the
principle of inheritance at corresponding ages need not here be
discussed, as enough has already been said on the subject. Before
giving the several rather complex rules or classes of cases, under
which the differences in plumage between the young and the old, as far
as known to me, may be included, it will be well to make a few
preliminary remarks.

With animals of all kinds when the adults differ in colour from the
young, and the colours of the latter are not, as far as we can see, of
any special service, they may generally be attributed, like various
embryological structures, to the retention of a former character. But
this view can be maintained with confidence, only when the young of
several species resemble each other closely, and likewise resemble
other adult species belonging to the same group; for the latter are the
living proofs that such a state of things was formerly possible. Young
lions and pumas are marked with feeble stripes or rows of spots, and as
many allied species both young and old are similarly marked, no
believer in evolution will doubt that the progenitor of the lion and
puma was a striped animal, and that the young have retained vestiges of
the stripes, like the kittens of black cats, which are not in the least
striped when grown up. Many species of deer, which when mature are not
spotted, are whilst young covered with white spots, as are likewise
some few species in the adult state. So again the young in the whole
family of pigs (Suidae), and in certain rather distantly allied
animals, such as the tapir, are marked with dark longitudinal stripes;
but here we have a character apparently derived from an extinct
progenitor, and now preserved by the young alone. In all such cases the
old have had their colours changed in the course of time, whilst the
young have remained but little altered, and this has been effected
through the principle of inheritance at corresponding ages.

This same principle applies to many birds belonging to various groups,
in which the young closely resemble each other, and differ much from
their respective adult parents. The young of almost all the
Gallinaceae, and of some distantly allied birds such as ostriches, are
covered with longitudinally striped down; but this character points
back to a state of things so remote that it hardly concerns us. Young
cross-bills (Loxia) have at first straight beaks like those of other
finches, and in their immature striated plumage they resemble the
mature red-pole and female siskin, as well as the young of the
goldfinch, greenfinch, and some other allied species. The young of many
kinds of buntings (Emberiza) resemble one another, and likewise the
adult state of the common bunting, E. miliaria. In almost the whole
large group of thrushes the young have their breasts spotted—a
character which is retained throughout life by many species, but is
quite lost by others, as by the Turdus migratorius. So again with many
thrushes, the feathers on the back are mottled before they are moulted
for the first time, and this character is retained for life by certain
eastern species. The young of many species of shrikes (Lanius), of some
woodpeckers, and of an Indian pigeon (Chalcophaps indicus), are
transversely striped on the under surface; and certain allied species
or whole genera are similarly marked when adult. In some closely-allied
and resplendent Indian cuckoos (Chrysococcyx), the mature species
differ considerably from one another in colour, but the young cannot be
distinguished. The young of an Indian goose (Sarkidiornis melanonotus)
closely resemble in plumage an allied genus, Dendrocygna, when mature.
(1. In regard to thrushes, shrikes, and woodpeckers, see Mr. Blyth, in
Charlesworth’s ‘Mag. of Nat. Hist.’ vol. i. 1837, p. 304; also footnote
to his translation of Cuvier’s ‘Regne Animal,’ p. 159. I give the case
of Loxia on Mr. Blyth’s information. On thrushes, see also Audubon,
‘Ornith. Biog.’ vol. ii. p. 195. On Chrysococcyx and Chalcophaps,
Blyth, as quoted in Jerdon’s ‘Birds of India,’ vol. iii. p. 485. On
Sarkidiornis, Blyth, in ‘Ibis,’ 1867, p. 175.) Similar facts will
hereafter be given in regard to certain herons. Young black-grouse
(Tetrao tetrix) resemble the young as well as the old of certain other
species, for instance the red-grouse or T. scoticus. Finally, as Mr.
Blyth, who has attended closely to this subject, has well remarked, the
natural affinities of many species are best exhibited in their immature
plumage; and as the true affinities of all organic beings depend on
their descent from a common progenitor, this remark strongly confirms
the belief that the immature plumage approximately shews us the former
or ancestral condition of the species.

Although many young birds, belonging to various families, thus give us
a glimpse of the plumage of their remote progenitors, yet there are
many other birds, both dull-coloured and bright-coloured, in which the
young closely resemble their parents. In such cases the young of the
different species cannot resemble each other more closely than do the
parents; nor can they strikingly resemble allied forms when adult. They
give us but little insight into the plumage of their progenitors,
excepting in so far that, when the young and the old are coloured in
the same general manner throughout a whole group of species, it is
probable that their progenitors were similarly coloured.

We may now consider the classes of cases, under which the differences
and resemblances between the plumage of the young and the old, in both
sexes or in one sex alone, may be grouped. Rules of this kind were
first enounced by Cuvier; but with the progress of knowledge they
require some modification and amplification. This I have attempted to
do, as far as the extreme complexity of the subject permits, from
information derived from various sources; but a full essay on this
subject by some competent ornithologist is much needed. In order to
ascertain to what extent each rule prevails, I have tabulated the facts
given in four great works, namely, by Macgillivray on the birds of
Britain, Audubon on those of North America, Jerdon on those of India,
and Gould on those of Australia. I may here premise, first, that the
several cases or rules graduate into each other; and secondly, that
when the young are said to resemble their parents, it is not meant that
they are identically alike, for their colours are almost always less
vivid, and the feathers are softer and often of a different shape.

RULES OR CLASSES OF CASES.

I. When the adult male is more beautiful or conspicuous than the adult
female, the young of both sexes in their first plumage closely resemble
the adult female, as with the common fowl and peacock; or, as
occasionally occurs, they resemble her much more closely than they do
the adult male.

II. When the adult female is more conspicuous than the adult male, as
sometimes though rarely occurs, the young of both sexes in their first
plumage resemble the adult male.

III. When the adult male resembles the adult female, the young of both
sexes have a peculiar first plumage of their own, as with the robin.

IV. When the adult male resembles the adult female, the young of both
sexes in their first plumage resemble the adults, as with the
kingfisher, many parrots, crows, hedge-warblers.

V. When the adults of both sexes have a distinct winter and summer
plumage, whether or not the male differs from the female, the young
resemble the adults of both sexes in their winter dress, or much more
rarely in their summer dress, or they resemble the females alone. Or
the young may have an intermediate character; or again they may differ
greatly from the adults in both their seasonal plumages.

VI. In some few cases the young in their first plumage differ from each
other according to sex; the young males resembling more or less closely
the adult males, and the young females more or less closely the adult
females.

CLASS I. — In this class, the young of both sexes more or less closely
resemble the adult female, whilst the adult male differs from the adult
female, often in the most conspicuous manner. Innumerable instances in
all Orders could be given; it will suffice to call to mind the common
pheasant, duck, and house-sparrow. The cases under this class graduate
into others. Thus the two sexes when adult may differ so slightly, and
the young so slightly from the adults, that it is doubtful whether such
cases ought to come under the present, or under the third or fourth
classes. So again the young of the two sexes, instead of being quite
alike, may differ in a slight degree from each other, as in our sixth
class. These transitional cases, however, are few, or at least are not
strongly pronounced, in comparison with those which come strictly under
the present class.

The force of the present law is well shewn in those groups, in which,
as a general rule, the two sexes and the young are all alike; for when
in these groups the male does differ from the female, as with certain
parrots, kingfishers, pigeons, etc., the young of both sexes resemble
the adult female. (2. See, for instance, Mr. Gould’s account (‘Handbook
to the Birds of Australia,’ vol. i. p. 133) of Cyanalcyon (one of the
Kingfishers), in which, however, the young male, though resembling the
adult female, is less brilliantly coloured. In some species of Dacelo
the males have blue tails, and the females brown ones; and Mr. R.B.
Sharpe informs me that the tail of the young male of D. gaudichaudi is
at first brown. Mr. Gould has described (ibid. vol. ii. pp. 14, 20, 37)
the sexes and the young of certain black Cockatoos and of the King
Lory, with which the same rule prevails. Also Jerdon (‘Birds of India,’
vol. i. p. 260) on the Palaeornis rosa, in which the young are more
like the female than the male. See Audubon (‘Ornithological Biography,’
vol. ii. p. 475) on the two sexes and the young of Columba passerina.)
We see the same fact exhibited still more clearly in certain anomalous
cases; thus the male of Heliothrix auriculata (one of the
humming-birds) differs conspicuously from the female in having a
splendid gorget and fine ear-tufts, but the female is remarkable from
having a much longer tail than that of the male; now the young of both
sexes resemble (with the exception of the breast being spotted with
bronze) the adult female in all other respects, including the length of
her tail, so that the tail of the male actually becomes shorter as he
reaches maturity, which is a most unusual circumstance. (3. I owe this
information to Mr. Gould, who shewed me the specimens; see also his
‘Introduction to the Trochilidae,’ 1861, p. 120.) Again, the plumage of
the male goosander (Mergus merganser) is more conspicuously coloured
than that of the female, with the scapular and secondary wing-feathers
much longer; but differently from what occurs, as far as I know, in any
other bird, the crest of the adult male, though broader than that of
the female, is considerably shorter, being only a little above an inch
in length; the crest of the female being two and a half inches long.
Now the young of both sexes entirely resemble the adult female, so that
their crests are actually of greater length, though narrower, than in
the adult male. (4. Macgillivray, ‘Hist. Brit. Birds,’ vol. v. pp.
207-214.)

When the young and the females closely resemble each other and both
differ from the males, the most obvious conclusion is that the males
alone have been modified. Even in the anomalous cases of the Heliothrix
and Mergus, it is probable that originally both adult sexes were
furnished—the one species with a much elongated tail, and the other
with a much elongated crest—these characters having since been
partially lost by the adult males from some unexplained cause, and
transmitted in their diminished state to their male offspring alone,
when arrived at the corresponding age of maturity. The belief that in
the present class the male alone has been modified, as far as the
differences between the male and the female together with her young are
concerned, is strongly supported by some remarkable facts recorded by
Mr. Blyth (5. See his admirable paper in the ‘Journal of the Asiatic
Soc. of Bengal,’ vol. xix. 1850, p. 223; see also Jerdon, ‘Birds of
India,’ vol. i. introduction, p. xxix. In regard to Tanysiptera, Prof.
Schlegel told Mr. Blyth that he could distinguish several distinct
races, solely by comparing the adult males.), with respect to
closely-allied species which represent each other in distinct
countries. For with several of these representative species the adult
males have undergone a certain amount of change and can be
distinguished; the females and the young from the distinct countries
being indistinguishable, and therefore absolutely unchanged. This is
the case with certain Indian chats (Thamnobia), with certain
honey-suckers (Nectarinia), shrikes (Tephrodornis), certain kingfishers
(Tanysiptera), Kalij pheasants (Gallophasis), and tree-partridges
(Arboricola).

In some analogous cases, namely with birds having a different summer
and winter plumage, but with the two sexes nearly alike, certain
closely-allied species can easily be distinguished in their summer or
nuptial plumage, yet are indistinguishable in their winter as well as
in their immature plumage. This is the case with some of the
closely-allied Indian wagtails or Motacillae. Mr. Swinhoe (6. See also
Mr. Swinhoe, in ‘Ibis,’ July 1863, p. 131; and a previous paper, with
an extract from a note by Mr. Blyth, in ‘Ibis,’ January, 1861, p. 25.)
informs me that three species of Ardeola, a genus of herons, which
represent one another on separate continents, are “most strikingly
different” when ornamented with their summer plumes, but are hardly, if
at all, distinguishable during the winter. The young also of these
three species in their immature plumage closely resemble the adults in
their winter dress. This case is all the more interesting, because with
two other species of Ardeola both sexes retain, during the winter and
summer, nearly the same plumage as that possessed by the three first
species during the winter and in their immature state; and this
plumage, which is common to several distinct species at different ages
and seasons, probably shews us how the progenitors of the genus were
coloured. In all these cases, the nuptial plumage which we may assume
was originally acquired by the adult males during the breeding-season,
and transmitted to the adults of both sexes at the corresponding
season, has been modified, whilst the winter and immature plumages have
been left unchanged.

The question naturally arises, how is it that in these latter cases the
winter plumage of both sexes, and in the former cases the plumage of
the adult females, as well as the immature plumage of the young, have
not been at all affected? The species which represent each other in
distinct countries will almost always have been exposed to somewhat
different conditions, but we can hardly attribute to this action the
modification of the plumage in the males alone, seeing that the females
and the young, though similarly exposed, have not been affected. Hardly
any fact shews us more clearly how subordinate in importance is the
direct action of the conditions of life, in comparison with the
accumulation through selection of indefinite variations, than the
surprising difference between the sexes of many birds; for both will
have consumed the same food, and have been exposed to the same climate.
Nevertheless we are not precluded from believing that in the course of
time new conditions may produce some direct effect either on both
sexes, or from their constitutional differences chiefly on one sex. We
see only that this is subordinate in importance to the accumulated
results of selection. Judging, however, from a wide-spread analogy,
when a species migrates into a new country (and this must precede the
formation of representative species), the changed conditions to which
they will almost always have been exposed will cause them to undergo a
certain amount of fluctuating variability. In this case sexual
selection, which depends on an element liable to change—the taste or
admiration of the female—will have had new shades of colour or other
differences to act on and accumulate; and as sexual selection is always
at work, it would (from what we know of the results on domestic animals
of man’s unintentional selection), be surprising if animals inhabiting
separate districts, which can never cross and thus blend their
newly-acquired characters, were not, after a sufficient lapse of time,
differently modified. These remarks likewise apply to the nuptial or
summer plumage, whether confined to the males, or common to both sexes.

Although the females of the above closely-allied or representative
species, together with their young, differ hardly at all from one
another, so that the males alone can be distinguished, yet the females
of most species within the same genus obviously differ from each other.
The differences, however, are rarely as great as between the males. We
see this clearly in the whole family of the Gallinaceae: the females,
for instance, of the common and Japan pheasant, and especially of the
gold and Amherst pheasant —of the silver pheasant and the wild
fowl—resemble one another very closely in colour, whilst the males
differ to an extraordinary degree. So it is with the females of most of
the Cotingidae, Fringillidae, and many other families. There can indeed
be no doubt that, as a general rule, the females have been less
modified than the males. Some few birds, however, offer a singular and
inexplicable exception; thus the females of Paradisea apoda and P.
papuana differ from each other more than do their respective males (7.
Wallace, ‘The Malay Archipelago,’ vol. ii. 1869, p. 394.); the female
of the latter species having the under surface pure white, whilst the
female P. apoda is deep brown beneath. So, again, as I hear from
Professor Newton, the males of two species of Oxynotus (shrikes), which
represent each other in the islands of Mauritius and Bourbon (8. These
species are described with coloured figures, by M. F. Pollen, in
‘Ibis,’ 1866, p. 275.), differ but little in colour, whilst the females
differ much. In the Bourbon species the female appears to have
partially retained an immature condition of plumage, for at first sight
she “might be taken for the young of the Mauritian species.” These
differences may be compared with those inexplicable ones, which occur
independently of man’s selection in certain sub-breeds of the
game-fowl, in which the females are very different, whilst the males
can hardly be distinguished. (9. ‘Variation of Animals,’ etc., vol. i.
p. 251.)

As I account so largely by sexual selection for the differences between
the males of allied species, how can the differences between the
females be accounted for in all ordinary cases? We need not here
consider the species which belong to distinct genera; for with these,
adaptation to different habits of life, and other agencies, will have
come into play. In regard to the differences between the females within
the same genus, it appears to me almost certain, after looking through
various large groups, that the chief agent has been the greater or less
transference to the female of the characters acquired by the males
through sexual selection. In the several British finches, the two sexes
differ either very slightly or considerably; and if we compare the
females of the greenfinch, chaffinch, goldfinch, bullfinch, crossbill,
sparrow, etc., we shall see that they differ from one another chiefly
in the points in which they partially resemble their respective males;
and the colours of the males may safely be attributed to sexual
selection. With many gallinaceous species the sexes differ to an
extreme degree, as with the peacock, pheasant, and fowl, whilst with
other species there has been a partial or even complete transference of
character from the male to the female. The females of the several
species of Polyplectron exhibit in a dim condition, and chiefly on the
tail, the splendid ocelli of their males. The female partridge differs
from the male only in the red mark on her breast being smaller; and the
female wild turkey only in her colours being much duller. In the
guinea-fowl the two sexes are indistinguishable. There is no
improbability in the plain, though peculiarly spotted plumage of this
latter bird having been acquired through sexual selection by the males,
and then transmitted to both sexes; for it is not essentially different
from the much more beautifully spotted plumage, characteristic of the
males alone of the Tragopan pheasants.

It should be observed that, in some instances, the transference of
characters from the male to the female has been effected apparently at
a remote period, the male having subsequently undergone great changes,
without transferring to the female any of his later-gained characters.
For instance, the female and the young of the black-grouse (Tetrao
tetrix) resemble pretty closely both sexes and the young of the
red-grouse (T. scoticus); and we may consequently infer that the
black-grouse is descended from some ancient species, of which both
sexes were coloured in nearly the same manner as the red-grouse. As
both sexes of this latter species are more distinctly barred during the
breeding-season than at any other time, and as the male differs
slightly from the female in his more strongly-pronounced red and brown
tints (10. Macgillivray, ‘History of British Birds,’ vol. i. pp.
172-174.), we may conclude that his plumage has been influenced by
sexual selection, at least to a certain extent. If so, we may further
infer that nearly similar plumage of the female black-grouse was
similarly produced at some former period. But since this period the
male black-grouse has acquired his fine black plumage, with his forked
and outwardly-curled tail-feathers; but of these characters there has
hardly been any transference to the female, excepting that she shews in
her tail a trace of the curved fork.

We may therefore conclude that the females of distinct though allied
species have often had their plumage rendered more or less different by
the transference in various degrees of characters acquired by the males
through sexual selection, both during former and recent times. But it
deserves especial attention that brilliant colours have been
transferred much more rarely than other tints. For instance, the male
of the red-throated blue-breast (Cyanecula suecica) has a rich blue
breast, including a sub-triangular red mark; now marks of nearly the
same shape have been transferred to the female, but the central space
is fulvous instead of red, and is surrounded by mottled instead of blue
feathers. The Gallinaceae offer many analogous cases; for none of the
species, such as partridges, quails, guinea-fowls, etc., in which the
colours of the plumage have been largely transferred from the male to
the female, are brilliantly coloured. This is well exemplified with the
pheasants, in which the male is generally so much more brilliant than
the female; but with the Eared and Cheer pheasants (Crossoptilon
auritum and Phasianus wallichii) the sexes closely resemble each other
and their colours are dull. We may go so far as to believe that if any
part of the plumage in the males of these two pheasants had been
brilliantly coloured, it would not have been transferred to the
females. These facts strongly support Mr. Wallace’s view that with
birds which are exposed to much danger during incubation, the
transference of bright colours from the male to the female has been
checked through natural selection. We must not, however, forget that
another explanation, before given, is possible; namely, that the males
which varied and became bright, whilst they were young and
inexperienced, would have been exposed to much danger, and would
generally have been destroyed; the older and more cautious males, on
the other hand, if they varied in a like manner, would not only have
been able to survive, but would have been favoured in their rivalry
with other males. Now variations occurring late in life tend to be
transmitted exclusively to the same sex, so that in this case extremely
bright tints would not have been transmitted to the females. On the
other hand, ornaments of a less conspicuous kind, such as those
possessed by the Eared and Cheer pheasants, would not have been
dangerous, and if they appeared during early youth, would generally
have been transmitted to both sexes.

In addition to the effects of the partial transference of characters
from the males to the females, some of the differences between the
females of closely allied species may be attributed to the direct or
definite action of the conditions of life. (11. See, on this subject,
chap. xxiii. in the ‘Variation of Animals and Plants under
Domestication.’) With the males, any such action would generally have
been masked by the brilliant colours gained through sexual selection;
but not so with the females. Each of the endless diversities in plumage
which we see in our domesticated birds is, of course, the result of
some definite cause; and under natural and more uniform conditions,
some one tint, assuming that it was in no way injurious, would almost
certainly sooner or later prevail. The free intercrossing of the many
individuals belonging to the same species would ultimately tend to make
any change of colour, thus induced, uniform in character.

No one doubts that both sexes of many birds have had their colours
adapted for the sake of protection; and it is possible that the females
alone of some species may have been modified for this end. Although it
would be a difficult, perhaps an impossible process, as shewn in the
last chapter, to convert one form of transmission into another through
selection, there would not be the least difficulty in adapting the
colours of the female, independently of those of the male, to
surrounding objects, through the accumulation of variations which were
from the first limited in their transmission to the female sex. If the
variations were not thus limited, the bright tints of the male would be
deteriorated or destroyed. Whether the females alone of many species
have been thus specially modified, is at present very doubtful. I wish
I could follow Mr. Wallace to the full extent; for the admission would
remove some difficulties. Any variations which were of no service to
the female as a protection would be at once obliterated, instead of
being lost simply by not being selected, or from free intercrossing, or
from being eliminated when transferred to the male and in any way
injurious to him. Thus the plumage of the female would be kept constant
in character. It would also be a relief if we could admit that the
obscure tints of both sexes of many birds had been acquired and
preserved for the sake of protection,—for example, of the hedge-warbler
or kitty-wren (Accentor modularis and Troglodytes vulgaris), with
respect to which we have no sufficient evidence of the action of sexual
selection. We ought, however, to be cautious in concluding that colours
which appear to us dull, are not attractive to the females of certain
species; we should bear in mind such cases as that of the common
house-sparrow, in which the male differs much from the female, but does
not exhibit any bright tints. No one probably will dispute that many
gallinaceous birds which live on the open ground, have acquired their
present colours, at least in part, for the sake of protection. We know
how well they are thus concealed; we know that ptarmigans, whilst
changing from their winter to their summer plumage, both of which are
protective, suffer greatly from birds of prey. But can we believe that
the very slight differences in tints and markings between, for
instance, the female black-grouse and red-grouse serve as a protection?
Are partridges, as they are now coloured, better protected than if they
had resembled quails? Do the slight differences between the females of
the common pheasant, the Japan and gold pheasants, serve as a
protection, or might not their plumages have been interchanged with
impunity? From what Mr. Wallace has observed of the habits of certain
gallinaceous birds in the East, he thinks that such slight differences
are beneficial. For myself, I will only say that I am not convinced.

Formerly when I was inclined to lay much stress on protection as
accounting for the duller colours of female birds, it occurred to me
that possibly both sexes and the young might aboriginally have been
equally bright coloured; but that subsequently, the females from the
danger incurred during incubation, and the young from being
inexperienced, had been rendered dull as a protection. But this view is
not supported by any evidence, and is not probable; for we thus in
imagination expose during past times the females and the young to
danger, from which it has subsequently been necessary to shield their
modified descendants. We have, also, to reduce, through a gradual
process of selection, the females and the young to almost exactly the
same tints and markings, and to transmit them to the corresponding sex
and period of life. On the supposition that the females and the young
have partaken during each stage of the process of modification of a
tendency to be as brightly coloured as the males, it is also a somewhat
strange fact that the females have never been rendered dull-coloured
without the young participating in the same change; for there are no
instances, as far as I can discover, of species with the females dull
and the young bright coloured. A partial exception, however, is offered
by the young of certain woodpeckers, for they have “the whole upper
part of the head tinged with red,” which afterwards either decreases
into a mere circular red line in the adults of both sexes, or quite
disappears in the adult females. (12. Audubon, ‘Ornith. Biography,’
vol. i. p. 193. Macgillivray, ‘History of British Birds,’ vol. iii. p.
85. See also the case before given of Indopicus carlotta.)

Finally, with respect to our present class of cases, the most probable
view appears to be that successive variations in brightness or in other
ornamental characters, occurring in the males at a rather late period
of life have alone been preserved; and that most or all of these
variations, owing to the late period of life at which they appeared,
have been from the first transmitted only to the adult male offspring.
Any variations in brightness occurring in the females or in the young,
would have been of no service to them, and would not have been
selected; and moreover, if dangerous, would have been eliminated. Thus
the females and the young will either have been left unmodified, or (as
is much more common) will have been partially modified by receiving
through transference from the males some of his successive variations.
Both sexes have perhaps been directly acted on by the conditions of
life to which they have long been exposed: but the females from not
being otherwise much modified, will best exhibit any such effects.
These changes and all others will have been kept uniform by the free
intercrossing of many individuals. In some cases, especially with
ground birds, the females and the young may possibly have been
modified, independently of the males, for the sake of protection, so as
to have acquired the same dull-coloured plumage.

CLASS II. — WHEN THE ADULT FEMALE IS MORE CONSPICUOUS THAN THE ADULT
MALE, THE YOUNG OF BOTH SEXES IN THEIR FIRST PLUMAGE RESEMBLE THE ADULT
MALE.

This class is exactly the reverse of the last, for the females are here
brighter coloured or more conspicuous than the males; and the young, as
far as they are known, resemble the adult males instead of the adult
females. But the difference between the sexes is never nearly so great
as with many birds in the first class, and the cases are comparatively
rare. Mr. Wallace, who first called attention to the singular relation
which exists between the less bright colours of the males and their
performing the duties of incubation, lays great stress on this point
(13. ‘Westminster Review,’ July 1867, and A. Murray, ‘Journal of
Travel,’ 1868, p. 83.), as a crucial test that obscure colours have
been acquired for the sake of protection during the period of nesting.
A different view seems to me more probable. As the cases are curious
and not numerous, I will briefly give all that I have been able to
find.

In one section of the genus Turnix, quail-like birds, the female is
invariably larger than the male (being nearly twice as large in one of
the Australian species), and this is an unusual circumstance with the
Gallinaceae. In most of the species the female is more distinctly
coloured and brighter than the male (14. For the Australian species,
see Gould’s ‘Handbook,’ etc., vol. ii. pp. 178, 180, 186, and 188. In
the British Museum specimens of the Australian Plain-wanderer
(Pedionomus torquatus) may be seen, shewing similar sexual
differences.), but in some few species the sexes are alike. In Turnix
taigoor of India the male “wants the black on the throat and neck, and
the whole tone of the plumage is lighter and less pronounced than that
of the female.” The female appears to be noisier, and is certainly much
more pugnacious than the male; so that the females and not the males
are often kept by the natives for fighting, like game-cocks. As male
birds are exposed by the English bird-catchers for a decoy near a trap,
in order to catch other males by exciting their rivalry, so the females
of this Turnix are employed in India. When thus exposed the females
soon begin their “loud purring call, which can be heard a long way off,
and any females within ear-shot run rapidly to the spot, and commence
fighting with the caged bird.” In this way from twelve to twenty birds,
all breeding females, may be caught in the course of a single day. The
natives assert that the females after laying their eggs associate in
flocks, and leave the males to sit on them. There is no reason to doubt
the truth of this assertion, which is supported by some observations
made in China by Mr. Swinhoe. (15. Jerdon, ‘Birds of India,’ vol. iii.
p. 596. Mr. Swinhoe, in ‘Ibis,’ 1865, p. 542; 1866, pp. 131, 405.) Mr.
Blyth believes, that the young of both sexes resemble the adult male.

[Fig. 62. Rhynchaea capensis (from Brehm).]

The females of the three species of Painted Snipes (Rhynchaea, Fig. 62)
“are not only larger but much more richly coloured than the males.”
(16. Jerdon, ‘Birds of India,’ vol. iii. p. 677.) With all other birds
in which the trachea differs in structure in the two sexes it is more
developed and complex in the male than in the female; but in the
Rhynchaea australis it is simple in the male, whilst in the female it
makes four distinct convolutions before entering the lungs. (17.
Gould’s ‘Handbook to the Birds of Australia,’ vol. ii. p. 275.) The
female therefore of this species has acquired an eminently masculine
character. Mr. Blyth ascertained, by examining many specimens, that the
trachea is not convoluted in either sex of R. bengalensis, which
species resembles R. australis so closely, that it can hardly be
distinguished except by its shorter toes. This fact is another striking
instance of the law that secondary sexual characters are often widely
different in closely-allied forms, though it is a very rare
circumstance when such differences relate to the female sex. The young
of both sexes of R. bengalensis in their first plumage are said to
resemble the mature male. (18. ‘The Indian Field,’ Sept. 1858, p. 3.)
There is also reason to believe that the male undertakes the duty of
incubation, for Mr. Swinhoe (19. ‘Ibis,’ 1866, p. 298.) found the
females before the close of the summer associated in flocks, as occurs
with the females of the Turnix.

The females of Phalaropus fulicarius and P. hyperboreus are larger, and
in their summer plumage “more gaily attired than the males.” But the
difference in colour between the sexes is far from conspicuous.
According to Professor Steenstrup, the male alone of P. fulicarius
undertakes the duty of incubation; this is likewise shewn by the state
of his breast-feathers during the breeding-season. The female of the
dotterel plover (Eudromias morinellus) is larger than the male, and has
the red and black tints on the lower surface, the white crescent on the
breast, and the stripes over the eyes, more strongly pronounced. The
male also takes at least a share in hatching the eggs; but the female
likewise attends to the young. (20. For these several statements, see
Mr. Gould’s ‘Birds of Great Britain.’ Prof. Newton informs me that he
has long been convinced, from his own observations and from those of
others, that the males of the above-named species take either the whole
or a large share of the duties of incubation, and that they “shew much
greater devotion towards their young, when in danger, than do the
females.” So it is, as he informs me, with Limosa lapponica and some
few other Waders, in which the females are larger and have more
strongly contrasted colours than the males.) I have not been able to
discover whether with these species the young resemble the adult males
more closely than the adult females; for the comparison is somewhat
difficult to make on account of the double moult.

Turning now to the ostrich Order: the male of the common cassowary
(Casuarius galeatus) would be thought by any one to be the female, from
his smaller size and from the appendages and naked skin about his head
being much less brightly coloured; and I am informed by Mr. Bartlett
that in the Zoological Gardens, it is certainly the male alone who sits
on the eggs and takes care of the young. (21. The natives of Ceram
(Wallace, ‘Malay Archipelago,’ vol. ii. p. 150) assert that the male
and female sit alternately on the eggs; but this assertion, as Mr.
Bartlett thinks, may be accounted for by the female visiting the nest
to lay her eggs.) The female is said by Mr. T.W. Wood (22. The
‘Student,’ April 1870, p. 124.) to exhibit during the breeding-season a
most pugnacious disposition; and her wattles then become enlarged and
more brilliantly coloured. So again the female of one of the emus
(Dromoeus irroratus) is considerably larger than the male, and she
possesses a slight top-knot, but is otherwise indistinguishable in
plumage. She appears, however, “to have greater power, when angry or
otherwise excited, of erecting, like a turkey-cock, the feathers of her
neck and breast. She is usually the more courageous and pugilistic. She
makes a deep hollow guttural boom especially at night, sounding like a
small gong. The male has a slenderer frame and is more docile, with no
voice beyond a suppressed hiss when angry, or a croak.” He not only
performs the whole duty of incubation, but has to defend the young from
their mother; “for as soon as she catches sight of her progeny she
becomes violently agitated, and notwithstanding the resistance of the
father appears to use her utmost endeavours to destroy them. For months
afterwards it is unsafe to put the parents together, violent quarrels
being the inevitable result, in which the female generally comes off
conqueror.” (23. See the excellent account of the habits of this bird
under confinement, by Mr. A.W. Bennett, in ‘Land and Water,’ May 1868,
p. 233.) So that with this emu we have a complete reversal not only of
the parental and incubating instincts, but of the usual moral qualities
of the two sexes; the females being savage, quarrelsome, and noisy, the
males gentle and good. The case is very different with the African
ostrich, for the male is somewhat larger than the female and has finer
plumes with more strongly contrasted colours; nevertheless he
undertakes the whole duty of incubation. (24. Mr. Sclater, on the
incubation of the Struthiones, ‘Proc. Zool. Soc.’ June 9, 1863. So it
is with the Rhea darwinii: Captain Musters says (‘At Home with the
Patagonians,’ 1871, p. 128), that the male is larger, stronger and
swifter than the female, and of slightly darker colours; yet he takes
sole charge of the eggs and of the young, just as does the male of the
common species of Rhea.)

I will specify the few other cases known to me, in which the female is
more conspicuously coloured than the male, although nothing is known
about the manner of incubation. With the carrion-hawk of the Falkland
Islands (Milvago leucurus) I was much surprised to find by dissection
that the individuals, which had all their tints strongly pronounced,
with the cere and legs orange-coloured, were the adult females; whilst
those with duller plumage and grey legs were the males or the young. In
an Australian tree-creeper (Climacteris erythrops) the female differs
from the male in “being adorned with beautiful, radiated, rufous
markings on the throat, the male having this part quite plain.” Lastly,
in an Australian night-jar “the female always exceeds the male in size
and in the brilliance of her tints; the males, on the other hand, have
two white spots on the primaries more conspicuous than in the female.”
(25. For the Milvago, see ‘Zoology of the Voyage of the “Beagle,”
Birds,’ 1841, p. 16. For the Climacteris and night-jar (Eurostopodus),
see Gould’s ‘Handbook to the Birds of Australia,’ vol. i. pp. 602 and
97. The New Zealand shieldrake (Tadorna variegata) offers a quite
anomalous case; the head of the female is pure white, and her back is
redder than that of the male; the head of the male is of a rich dark
bronzed colour, and his back is clothed with finely pencilled
slate-coloured feathers, so that altogether he may be considered as the
more beautiful of the two. He is larger and more pugnacious than the
female, and does not sit on the eggs. So that in all these respects
this species comes under our first class of cases; but Mr. Sclater
(‘Proceedings of the Zoological Society,’ 1866, p. 150) was much
surprised to observe that the young of both sexes, when about three
months old, resembled in their dark heads and necks the adult males,
instead of the adult females; so that it would appear in this case that
the females have been modified, whilst the males and the young have
retained a former state of plumage.)

We thus see that the cases in which female birds are more conspicuously
coloured than the males, with the young in their immature plumage
resembling the adult males instead of the adult females, as in the
previous class, are not numerous, though they are distributed in
various Orders. The amount of difference, also, between the sexes is
incomparably less than that which frequently occurs in the last class;
so that the cause of the difference, whatever it may have been, has
here acted on the females either less energetically or less
persistently than on the males in the last class. Mr. Wallace believes
that the males have had their colours rendered less conspicuous for the
sake of protection during the period of incubation; but the difference
between the sexes in hardly any of the foregoing cases appears
sufficiently great for this view to be safely accepted. In some of the
cases, the brighter tints of the female are almost confined to the
lower surface, and the males, if thus coloured, would not have been
exposed to danger whilst sitting on the eggs. It should also be borne
in mind that the males are not only in a slight degree less
conspicuously coloured than the females, but are smaller and weaker.
They have, moreover, not only acquired the maternal instinct of
incubation, but are less pugnacious and vociferous than the females,
and in one instance have simpler vocal organs. Thus an almost complete
transposition of the instincts, habits, disposition, colour, size, and
of some points of structure, has been effected between the two sexes.

Now if we might assume that the males in the present class have lost
some of that ardour which is usual to their sex, so that they no longer
search eagerly for the females; or, if we might assume that the females
have become much more numerous than the males—and in the case of one
Indian Turnix the females are said to be “much more commonly met with
than the males” (26. Jerdon, ‘Birds of India,’ vol. iii. p. 598.)—then
it is not improbable that the females would have been led to court the
males, instead of being courted by them. This indeed is the case to a
certain extent with some birds, as we have seen with the peahen, wild
turkey, and certain kinds of grouse. Taking as our guide the habits of
most male birds, the greater size and strength as well as the
extraordinary pugnacity of the females of the Turnix and emu, must mean
that they endeavour to drive away rival females, in order to gain
possession of the male; and on this view all the facts become clear;
for the males would probably be most charmed or excited by the females
which were the most attractive to them by their bright colours, other
ornaments, or vocal powers. Sexual selection would then do its work,
steadily adding to the attractions of the females; the males and the
young being left not at all, or but little modified.

CLASS III. — WHEN THE ADULT MALE RESEMBLES THE ADULT FEMALE, THE YOUNG
OF BOTH SEXES HAVE A PECULIAR FIRST PLUMAGE OF THEIR OWN.

In this class the sexes when adult resemble each other, and differ from
the young. This occurs with many birds of many kinds. The male robin
can hardly be distinguished from the female, but the young are widely
different, with their mottled dusky-olive and brown plumage. The male
and female of the splendid scarlet ibis are alike, whilst the young are
brown; and the scarlet colour, though common to both sexes, is
apparently a sexual character, for it is not well developed in either
sex under confinement; and a loss of colour often occurs with brilliant
males when they are confined. With many species of herons the young
differ greatly from the adults; and the summer plumage of the latter,
though common to both sexes, clearly has a nuptial character. Young
swans are slate-coloured, whilst the mature birds are pure white; but
it would be superfluous to give additional instances. These differences
between the young and the old apparently depend, as in the last two
classes, on the young having retained a former or ancient state of
plumage, whilst the old of both sexes have acquired a new one. When the
adults are bright coloured, we may conclude from the remarks just made
in relation to the scarlet ibis and to many herons, and from the
analogy of the species in the first class, that such colours have been
acquired through sexual selection by the nearly mature males; but that,
differently from what occurs in the first two classes, the
transmission, though limited to the same age, has not been limited to
the same sex. Consequently, the sexes when mature resemble each other
and differ from the young.

CLASS IV. — WHEN THE ADULT MALE RESEMBLES THE ADULT FEMALE, THE YOUNG
OF BOTH SEXES IN THEIR FIRST PLUMAGE RESEMBLE THE ADULTS.

In this class the young and the adults of both sexes, whether
brilliantly or obscurely coloured, resemble each other. Such cases are,
I think, more common than those in the last class. We have in England
instances in the kingfisher, some woodpeckers, the jay, magpie, crow,
and many small dull-coloured birds, such as the hedge-warbler or
kitty-wren. But the similarity in plumage between the young and the old
is never complete, and graduates away into dissimilarity. Thus the
young of some members of the kingfisher family are not only less
vividly coloured than the adults, but many of the feathers on the lower
surface are edged with brown (27. Jerdon, ‘Birds of India,’ vol. i. pp.
222, 228. Gould’s ‘Handbook to the Birds of Australia,’ vol. i. pp.
124, 130.),—a vestige probably of a former state of the plumage.
Frequently in the same group of birds, even within the same genus, for
instance in an Australian genus of parrakeets (Platycercus), the young
of some species closely resemble, whilst the young of other species
differ considerably, from their parents of both sexes, which are alike.
(28. Gould, ibid. vol. ii. pp. 37, 46, 56.) Both sexes and the young of
the common jay are closely similar; but in the Canada jay (Perisoreus
canadensis) the young differ so much from their parents that they were
formerly described as distinct species. (29. Audubon, ‘Ornith.
Biography,’ vol. ii. p. 55.)

I may remark before proceeding that, under the present and next two
classes of cases, the facts are so complex and the conclusions so
doubtful, that any one who feels no especial interest in the subject
had better pass them over.

The brilliant or conspicuous colours which characterise many birds in
the present class, can rarely or never be of service to them as a
protection; so that they have probably been gained by the males through
sexual selection, and then transferred to the females and the young. It
is, however, possible that the males may have selected the more
attractive females; and if these transmitted their characters to their
offspring of both sexes, the same results would follow as from the
selection of the more attractive males by the females. But there is
evidence that this contingency has rarely, if ever, occurred in any of
those groups of birds in which the sexes are generally alike; for, if
even a few of the successive variations had failed to be transmitted to
both sexes, the females would have slightly exceeded the males in
beauty. Exactly the reverse occurs under nature; for, in almost every
large group in which the sexes generally resemble each other, the males
of some few species are in a slight degree more brightly coloured than
the females. It is again possible that the females may have selected
the more beautiful males, these males having reciprocally selected the
more beautiful females; but it is doubtful whether this double process
of selection would be likely to occur, owing to the greater eagerness
of one sex than the other, and whether it would be more efficient than
selection on one side alone. It is, therefore, the most probable view
that sexual selection has acted, in the present class, as far as
ornamental characters are concerned, in accordance with the general
rule throughout the animal kingdom, that is, on the males; and that
these have transmitted their gradually-acquired colours, either equally
or almost equally, to their offspring of both sexes.

Another point is more doubtful, namely, whether the successive
variations first appeared in the males after they had become nearly
mature, or whilst quite young. In either case sexual selection must
have acted on the male when he had to compete with rivals for the
possession of the female; and in both cases the characters thus
acquired have been transmitted to both sexes and all ages. But these
characters if acquired by the males when adult, may have been
transmitted at first to the adults alone, and at some subsequent period
transferred to the young. For it is known that, when the law of
inheritance at corresponding ages fails, the offspring often inherit
characters at an earlier age than that at which they first appeared in
their parents. (30. ‘Variation of Animals and Plants under
Domestication,’ vol. ii. p. 79.) Cases apparently of this kind have
been observed with birds in a state of nature. For instance Mr. Blyth
has seen specimens of Lanius rufus and of Colymbus glacialis which had
assumed whilst young, in a quite anomalous manner, the adult plumage of
their parents. (31. ‘Charlesworth’s Magazine of Natural History,’ vol.
i. 1837, pp. 305, 306.) Again, the young of the common swan (Cygnus
olor) do not cast off their dark feathers and become white until
eighteen months or two years old; but Dr. F. Forel has described the
case of three vigorous young birds, out of a brood of four, which were
born pure white. These young birds were not albinos, as shewn by the
colour of their beaks and legs, which nearly resembled the same parts
in the adults. (32. ‘Bulletin de la Soc. Vaudoise des Sc. Nat.’ vol. x.
1869, p. 132. The young of the Polish swan, Cygnus immutabilis of
Yarrell, are always white; but this species, as Mr. Sclater informs me,
is believed to be nothing more than a variety of the domestic swan
(Cygnus olor).)

It may be worth while to illustrate the above three modes by which, in
the present class, the two sexes and the young may have come to
resemble each other, by the curious case of the genus Passer. (33. I am
indebted to Mr. Blyth for information in regard to this genus. The
sparrow of Palestine belongs to the sub-genus Petronia.) In the
house-sparrow (P. domesticus) the male differs much from the female and
from the young. The young and the females are alike, and resemble to a
large extent both sexes and the young of the sparrow of Palestine (P.
brachydactylus), as well as of some allied species. We may therefore
assume that the female and young of the house-sparrow approximately
shew us the plumage of the progenitor of the genus. Now with the
tree-sparrow (P. montanus) both sexes and the young closely resemble
the male of the house-sparrow; so that they have all been modified in
the same manner, and all depart from the typical colouring of their
early progenitor. This may have been effected by a male ancestor of the
tree-sparrow having varied, firstly, when nearly mature; or, secondly,
whilst quite young, and by having in either case transmitted his
modified plumage to the females and the young; or, thirdly, he may have
varied when adult and transmitted his plumage to both adult sexes, and,
owing to the failure of the law of inheritance at corresponding ages,
at some subsequent period to his young.

It is impossible to decide which of these three modes has generally
prevailed throughout the present class of cases. That the males varied
whilst young, and transmitted their variations to their offspring of
both sexes, is the most probable. I may here add that I have, with
little success, endeavoured, by consulting various works, to decide how
far the period of variation in birds has generally determined the
transmission of characters to one sex or to both. The two rules, often
referred to (namely, that variations occurring late in life are
transmitted to one and the same sex, whilst those which occur early in
life are transmitted to both sexes), apparently hold good in the first
(34. For instance, the males of Tanagra aestiva and Fringilla cyanea
require three years, the male of Fringilla ciris four years, to
complete their beautiful plumage. (See Audubon, ‘Ornith. Biography,’
vol. i. pp. 233, 280, 378). The Harlequin duck takes three years (ibid.
vol. iii. p. 614). The male of the Gold pheasant, as I hear from Mr.
Jenner Weir, can be distinguished from the female when about three
months old, but he does not acquire his full splendour until the end of
the September in the following year.), second, and fourth classes of
cases; but they fail in the third, often in the fifth (35. Thus the
Ibis tantalus and Grus americanus take four years, the Flamingo several
years, and the Ardea ludovicana two years, before they acquire their
perfect plumage. See Audubon, ibid. vol. i. p. 221; vol. iii. pp. 133,
139, 211.), and in the sixth small class. They apply, however, as far
as I can judge, to a considerable majority of the species; and we must
not forget the striking generalisation by Dr. W. Marshall with respect
to the protuberances on the heads of birds. Whether or not the two
rules generally hold good, we may conclude from the facts given in the
eighth chapter, that the period of variation is one important element
in determining the form of transmission.

With birds it is difficult to decide by what standard we ought to judge
of the earliness or lateness of the period of variation, whether by the
age in reference to the duration of life, or to the power of
reproduction, or to the number of moults through which the species
passes. The moulting of birds, even within the same family, sometimes
differs much without any assignable cause. Some birds moult so early,
that nearly all the body feathers are cast off before the first
wing-feathers are fully grown; and we cannot believe that this was the
primordial state of things. When the period of moulting has been
accelerated, the age at which the colours of the adult plumage are
first developed will falsely appear to us to be earlier than it really
is. This may be illustrated by the practice followed by some
bird-fanciers, who pull out a few feathers from the breast of nestling
bullfinches, and from the head or neck of young gold-pheasants, in
order to ascertain their sex; for in the males, these feathers are
immediately replaced by coloured ones. (36. Mr. Blyth, in
Charlesworth’s ‘Magazine of Natural History,’ vol. i. 1837, p. 300. Mr.
Bartlett has informed me in regard to gold pheasants.) The actual
duration of life is known in but few birds, so that we can hardly judge
by this standard. And, with reference to the period at which the power
of reproduction is gained, it is a remarkable fact that various birds
occasionally breed whilst retaining their immature plumage. (37. I have
noticed the following cases in Audubon’s ‘Ornith. Biography.’ The
redstart of America (Muscapica ruticilla, vol. i. p. 203). The Ibis
tantalus takes four years to come to full maturity, but sometimes
breeds in the second year (vol. iii. p. 133). The Grus americanus takes
the same time, but breeds before acquiring its full plumage (vol. iii.
p. 211). The adults of Ardea caerulea are blue, and the young white;
and white, mottled, and mature blue birds may all be seen breeding
together (vol. iv. p. 58): but Mr. Blyth informs me that certain herons
apparently are dimorphic, for white and coloured individuals of the
same age may be observed. The Harlequin duck (Anas histrionica, Linn.)
takes three years to acquire its full plumage, though many birds breed
in the second year (vol. iii. p. 614). The White-headed Eagle (Falco
leucocephalus, vol. iii. p. 210) is likewise known to breed in its
immature state. Some species of Oriolus (according to Mr. Blyth and Mr.
Swinhoe, in ‘Ibis,’ July 1863, p. 68) likewise breed before they attain
their full plumage.)

The fact of birds breeding in their immature plumage seems opposed to
the belief that sexual selection has played as important a part, as I
believe it has, in giving ornamental colours, plumes, etc., to the
males, and, by means of equal transmission, to the females of many
species. The objection would be a valid one, if the younger and less
ornamented males were as successful in winning females and propagating
their kind, as the older and more beautiful males. But we have no
reason to suppose that this is the case. Audubon speaks of the breeding
of the immature males of Ibis tantalus as a rare event, as does Mr.
Swinhoe, in regard to the immature males of Oriolus. (38. See footnote
37 above.) If the young of any species in their immature plumage were
more successful in winning partners than the adults, the adult plumage
would probably soon be lost, as the males would prevail, which retained
their immature dress for the longest period, and thus the character of
the species would ultimately be modified. (39. Other animals, belonging
to quite distinct classes, are either habitually or occasionally
capable of breeding before they have fully acquired their adult
characters. This is the case with the young males of the salmon.
Several amphibians have been known to breed whilst retaining their
larval structure. Fritz Müller has shewn (‘Facts and arguments for
Darwin,’ Eng. trans. 1869, p. 79) that the males of several amphipod
crustaceans become sexually mature whilst young; and I infer that this
is a case of premature breeding, because they have not as yet acquired
their fully-developed claspers. All such facts are highly interesting,
as bearing on one means by which species may undergo great
modifications of character.) If, on the other hand, the young never
succeeded in obtaining a female, the habit of early reproduction would
perhaps be sooner or later eliminated, from being superfluous and
entailing waste of power.

The plumage of certain birds goes on increasing in beauty during many
years after they are fully mature; this is the case with the train of
the peacock, with some of the birds of paradise, and with the crest and
plumes of certain herons, for instance, the Ardea ludovicana. (40.
Jerdon, ‘Birds of India,’ vol. iii. p. 507, on the peacock. Dr.
Marshall thinks that the older and more brilliant males of birds of
paradise, have an advantage over the younger males; see ‘Archives
Neerlandaises,’ tom. vi. 1871.—On Ardea, Audubon, ibid. vol. iii. p.
139.) But it is doubtful whether the continued development of such
feathers is the result of the selection of successive beneficial
variations (though this is the most probable view with birds of
paradise) or merely of continuous growth. Most fishes continue
increasing in size, as long as they are in good health and have plenty
of food; and a somewhat similar law may prevail with the plumes of
birds.

CLASS V. — WHEN THE ADULTS OF BOTH SEXES HAVE A DISTINCT WINTER AND
SUMMER PLUMAGE, WHETHER OR NOT THE MALE DIFFERS FROM THE FEMALE, THE
YOUNG RESEMBLE THE ADULTS OF BOTH SEXES IN THEIR WINTER DRESS, OR MUCH
MORE RARELY IN THEIR SUMMER DRESS, OR THEY RESEMBLE THE FEMALES ALONE.
OR THE YOUNG MAY HAVE AN INTERMEDIATE CHARACTER; OR, AGAIN, THEY MAY
DIFFER GREATLY FROM THE ADULTS IN BOTH THEIR SEASONAL PLUMAGES.

The cases in this class are singularly complex; nor is this surprising,
as they depend on inheritance, limited in a greater or less degree in
three different ways, namely, by sex, age, and the season of the year.
In some cases the individuals of the same species pass through at least
five distinct states of plumage. With the species, in which the male
differs from the female during the summer season alone, or, which is
rarer, during both seasons (41. For illustrative cases, see vol. iv. of
Macgillivray’s ‘History of British Birds;’ on Tringa, etc., pp. 229,
271; on the Machetes, p. 172; on the Charadrius hiaticula, p. 118; on
the Charadrius pluvialis, p. 94.), the young generally resemble the
females,—as with the so-called goldfinch of North America, and
apparently with the splendid Maluri of Australia. (42. For the
goldfinch of N. America, Fringilla tristis, Linn., see Audubon,
‘Ornithological Biography,’ vol. i. p. 172. For the Maluri, Gould’s
‘Handbook of the Birds of Australia,’ vol. i. p. 318.) With those
species, the sexes of which are alike during both the summer and
winter, the young may resemble the adults, firstly, in their winter
dress; secondly, and this is of much rarer occurrence, in their summer
dress; thirdly, they may be intermediate between these two states; and,
fourthly, they may differ greatly from the adults at all seasons. We
have an instance of the first of these four cases in one of the egrets
of India (Buphus coromandus), in which the young and the adults of both
sexes are white during the winter, the adults becoming golden-buff
during the summer.

With the gaper (Anastomus oscitans) of India we have a similar case,
but the colours are reversed: for the young and the adults of both
sexes are grey and black during the winter, the adults becoming white
during the summer. (43. I am indebted to Mr. Blyth for information as
to the Buphus; see also Jerdon, ‘Birds of India,’ vol. iii. p. 749. On
the Anastomus, see Blyth, in ‘Ibis,’ 1867, p. 173.) As an instance of
the second case, the young of the razor-bill (Alca torda, Linn.), in an
early state of plumage, are coloured like the adults during the summer;
and the young of the white-crowned sparrow of North America (Fringilla
leucophrys), as soon as fledged, have elegant white stripes on their
heads, which are lost by the young and the old during the winter. (44.
On the Alca, see Macgillivray, ‘Hist. Brit. Birds,’ vol. v. p. 347. On
the Fringilla leucophrys, Audubon, ibid. vol. ii. p. 89. I shall have
hereafter to refer to the young of certain herons and egrets being
white.) With respect to the third case, namely, that of the young
having an intermediate character between the summer and winter adult
plumages, Yarrell (45. ‘History of British Birds,’ vol. i. 1839, p.
159.) insists that this occurs with many waders. Lastly, in regard to
the young differing greatly from both sexes in their adult summer and
winter plumages, this occurs with some herons and egrets of North
America and India,—the young alone being white.

I will make only a few remarks on these complicated cases. When the
young resemble the females in their summer dress, or the adults of both
sexes in their winter dress, the cases differ from those given under
Classes I. and III. only in the characters originally acquired by the
males during the breeding-season, having been limited in their
transmission to the corresponding season. When the adults have a
distinct summer and winter plumage, and the young differ from both, the
case is more difficult to understand. We may admit as probable that the
young have retained an ancient state of plumage; we can account by
sexual selection for the summer or nuptial plumage of the adults, but
how are we to account for their distinct winter plumage? If we could
admit that this plumage serves in all cases as a protection, its
acquirement would be a simple affair; but there seems no good reason
for this admission. It may be suggested that the widely different
conditions of life during the winter and summer have acted in a direct
manner on the plumage; this may have had some effect, but I have not
much confidence in so great a difference as we sometimes see between
the two plumages, having been thus caused. A more probable explanation
is, that an ancient style of plumage, partially modified through the
transference of some characters from the summer plumage, has been
retained by the adults during the winter. Finally, all the cases in our
present class apparently depend on characters acquired by the adult
males, having been variously limited in their transmission according to
age, season, and sex; but it would not be worth while to attempt to
follow out these complex relations.

CLASS VI. — THE YOUNG IN THEIR FIRST PLUMAGE DIFFER FROM EACH OTHER
ACCORDING TO SEX; THE YOUNG MALES RESEMBLING MORE OR LESS CLOSELY THE
ADULT MALES, AND THE YOUNG FEMALES MORE OR LESS CLOSELY THE ADULT
FEMALES.

The cases in the present class, though occurring in various groups, are
not numerous; yet it seems the most natural thing that the young should
at first somewhat resemble the adults of the same sex, and gradually
become more and more like them. The adult male blackcap (Sylvia
atricapilla) has a black head, that of the female being reddish-brown;
and I am informed by Mr. Blyth, that the young of both sexes can be
distinguished by this character even as nestlings. In the family of
thrushes an unusual number of similar cases have been noticed; thus,
the male blackbird (Turdus merula) can be distinguished in the nest
from the female. The two sexes of the mocking bird (Turdus polyglottus,
Linn.) differ very little from each other, yet the males can easily be
distinguished at a very early age from the females by showing more pure
white. (46. Audubon, ‘Ornith. Biography,’ vol. i. p. 113.) The males of
a forest-thrush and of a rock-thrush (Orocetes erythrogastra and
Petrocincla cyanea) have much of their plumage of a fine blue, whilst
the females are brown; and the nestling males of both species have
their main wing and tail-feathers edged with blue whilst those of the
female are edged with brown. (47. Mr. C.A. Wright, in ‘Ibis,’ vol. vi.
1864, p. 65. Jerdon, ‘Birds of India,’ vol. i. p. 515. See also on the
blackbird, Blyth in Charlesworth’s ‘Magazine of Natural History,’ vol.
i. 1837, p. 113.) In the young blackbird the wing-feathers assume their
mature character and become black after the others; on the other hand,
in the two species just named the wing-feathers become blue before the
others. The most probable view with reference to the cases in the
present class is that the males, differently from what occurs in Class
I., have transmitted their colours to their male offspring at an
earlier age than that at which they were first acquired; for, if the
males had varied whilst quite young, their characters would probably
have been transmitted to both sexes. (48. The following additional
cases may be mentioned; the young males of Tanagra rubra can be
distinguished from the young females (Audubon, ‘Ornith. Biography,’
vol. iv. p. 392), and so it is within the nestlings of a blue nuthatch,
Dendrophila frontalis of India (Jerdon, ‘Birds of India,’ vol. i. p.
389). Mr. Blyth also informs me that the sexes of the stonechat,
Saxicola rubicola, are distinguishable at a very early age. Mr. Salvin
gives (‘Proc. Zoolog. Soc.’ 1870, p. 206) the case of a humming-bird,
like the following one of Eustephanus.)

In Aithurus polytmus, a humming-bird, the male is splendidly coloured
black and green, and two of the tail-feathers are immensely lengthened;
the female has an ordinary tail and inconspicuous colours; now the
young males, instead of resembling the adult female, in accordance with
the common rule, begin from the first to assume the colours proper to
their sex, and their tail-feathers soon become elongated. I owe this
information to Mr. Gould, who has given me the following more striking
and as yet unpublished case. Two humming-birds belonging to the genus
Eustephanus, both beautifully coloured, inhabit the small island of
Juan Fernandez, and have always been ranked as specifically distinct.
But it has lately been ascertained that the one which is of a rich
chestnut-brown colour with a golden-red head, is the male, whilst the
other which is elegantly variegated with green and white with a
metallic green head is the female. Now the young from the first
somewhat resemble the adults of the corresponding sex, the resemblance
gradually becoming more and more complete.

In considering this last case, if as before we take the plumage of the
young as our guide, it would appear that both sexes have been rendered
beautiful independently; and not that one sex has partially transferred
its beauty to the other. The male apparently has acquired his bright
colours through sexual selection in the same manner as, for instance,
the peacock or pheasant in our first class of cases; and the female in
the same manner as the female Rhynchaea or Turnix in our second class
of cases. But there is much difficulty in understanding how this could
have been effected at the same time with the two sexes of the same
species. Mr. Salvin states, as we have seen in the eighth chapter, that
with certain humming-birds the males greatly exceed the females in
number, whilst with other species inhabiting the same country the
females greatly exceed the males. If, then, we might assume that during
some former lengthened period the males of the Juan Fernandez species
had greatly exceeded the females in number, but that during another
lengthened period the females had far exceeded the males, we could
understand how the males at one time, and the females at another, might
have been rendered beautiful by the selection of the brighter coloured
individuals of either sex; both sexes transmitting their characters to
their young at a rather earlier age than usual. Whether this is the
true explanation I will not pretend to say; but the case is too
remarkable to be passed over without notice.

We have now seen in all six classes, that an intimate relation exists
between the plumage of the young and the adults, either of one sex or
both. These relations are fairly well explained on the principle that
one sex—this being in the great majority of cases the male—first
acquired through variation and sexual selection bright colours or other
ornaments, and transmitted them in various ways, in accordance with the
recognised laws of inheritance. Why variations have occurred at
different periods of life, even sometimes with species of the same
group, we do not know, but with respect to the form of transmission,
one important determining cause seems to be the age at which the
variations first appear.

From the principle of inheritance at corresponding ages, and from any
variations in colour which occurred in the males at an early age not
being then selected—on the contrary being often eliminated as
dangerous—whilst similar variations occurring at or near the period of
reproduction have been preserved, it follows that the plumage of the
young will often have been left unmodified, or but little modified. We
thus get some insight into the colouring of the progenitors of our
existing species. In a vast number of species in five out of our six
classes of cases, the adults of one sex or of both are bright coloured,
at least during the breeding-season, whilst the young are invariably
less brightly coloured than the adults, or are quite dull coloured; for
no instance is known, as far as I can discover, of the young of
dull-coloured species displaying bright colours, or of the young of
bright-coloured species being more brilliant than their parents. In the
fourth class, however, in which the young and the old resemble each
other, there are many species (though by no means all), of which the
young are bright-coloured, and as these form old groups, we may infer
that their early progenitors were likewise bright. With this exception,
if we look to the birds of the world, it appears that their beauty has
been much increased since that period, of which their immature plumage
gives us a partial record.

ON THE COLOUR OF THE PLUMAGE IN RELATION TO PROTECTION.

It will have been seen that I cannot follow Mr. Wallace in the belief
that dull colours, when confined to the females, have been in most
cases specially gained for the sake of protection. There can, however,
be no doubt, as formerly remarked, that both sexes of many birds have
had their colours modified, so as to escape the notice of their
enemies; or in some instances, so as to approach their prey unobserved,
just as owls have had their plumage rendered soft, that their flight
may not be overheard. Mr. Wallace remarks (49. ‘Westminster Review,’
July 1867, p. 5.) that “it is only in the tropics, among forests which
never lose their foliage, that we find whole groups of birds, whose
chief colour is green.” It will be admitted by every one, who has ever
tried, how difficult it is to distinguish parrots in a leaf-covered
tree. Nevertheless, we must remember that many parrots are ornamented
with crimson, blue, and orange tints, which can hardly be protective.
Woodpeckers are eminently arboreal, but besides green species, there
are many black, and black-and-white kinds—all the species being
apparently exposed to nearly the same dangers. It is therefore probable
that with tree-haunting birds, strongly-pronounced colours have been
acquired through sexual selection, but that a green tint has been
acquired oftener than any other, from the additional advantage of
protection.

In regard to birds which live on the ground, every one admits that they
are coloured so as to imitate the surrounding surface. How difficult it
is to see a partridge, snipe, woodcock, certain plovers, larks, and
night-jars when crouched on ground. Animals inhabiting deserts offer
the most striking cases, for the bare surface affords no concealment,
and nearly all the smaller quadrupeds, reptiles, and birds depend for
safety on their colours. Mr. Tristram has remarked in regard to the
inhabitants of the Sahara, that all are protected by their “isabelline
or sand-colour.” (50. ‘Ibis,’ 1859, vol. i. p. 429, et seq. Dr. Rohlfs,
however, remarks to me in a letter that according to his experience of
the Sahara, this statement is too strong.) Calling to my recollection
the desert-birds of South America, as well as most of the ground-birds
of Great Britain, it appeared to me that both sexes in such cases are
generally coloured nearly alike. Accordingly, I applied to Mr. Tristram
with respect to the birds of the Sahara, and he has kindly given me the
following information. There are twenty-six species belonging to
fifteen genera, which manifestly have their plumage coloured in a
protective manner; and this colouring is all the more striking, as with
most of these birds it differs from that of their congeners. Both sexes
of thirteen out of the twenty-six species are coloured in the same
manner; but these belong to genera in which this rule commonly
prevails, so that they tell us nothing about the protective colours
being the same in both sexes of desert-birds. Of the other thirteen
species, three belong to genera in which the sexes usually differ from
each other, yet here they have the sexes alike. In the remaining ten
species, the male differs from the female; but the difference is
confined chiefly to the under surface of the plumage, which is
concealed when the bird crouches on the ground; the head and back being
of the same sand-coloured hue in the two sexes. So that in these ten
species the upper surfaces of both sexes have been acted on and
rendered alike, through natural selection, for the sake of protection;
whilst the lower surfaces of the males alone have been diversified,
through sexual selection, for the sake of ornament. Here, as both sexes
are equally well protected, we clearly see that the females have not
been prevented by natural selection from inheriting the colours of
their male parents; so that we must look to the law of sexually-limited
transmission.

In all parts of the world both sexes of many soft-billed birds,
especially those which frequent reeds or sedges, are obscurely
coloured. No doubt if their colours had been brilliant, they would have
been much more conspicuous to their enemies; but whether their dull
tints have been specially gained for the sake of protection seems, as
far as I can judge, rather doubtful. It is still more doubtful whether
such dull tints can have been gained for the sake of ornament. We must,
however, bear in mind that male birds, though dull-coloured, often
differ much from their females (as with the common sparrow), and this
leads to the belief that such colours have been gained through sexual
selection, from being attractive. Many of the soft-billed birds are
songsters; and a discussion in a former chapter should not be
forgotten, in which it was shewn that the best songsters are rarely
ornamented with bright tints. It would appear that female birds, as a
general rule, have selected their mates either for their sweet voices
or gay colours, but not for both charms combined. Some species, which
are manifestly coloured for the sake of protection, such as the
jack-snipe, woodcock, and night-jar, are likewise marked and shaded,
according to our standard of taste, with extreme elegance. In such
cases we may conclude that both natural and sexual selection have acted
conjointly for protection and ornament. Whether any bird exists which
does not possess some special attraction, by which to charm the
opposite sex, may be doubted. When both sexes are so obscurely coloured
that it would be rash to assume the agency of sexual selection, and
when no direct evidence can be advanced shewing that such colours serve
as a protection, it is best to own complete ignorance of the cause, or,
which comes to nearly the same thing, to attribute the result to the
direct action of the conditions of life.

Both sexes of many birds are conspicuously, though not brilliantly
coloured, such as the numerous black, white, or piebald species; and
these colours are probably the result of sexual selection. With the
common blackbird, capercailzie, blackcock, black scoter-duck (Oidemia),
and even with one of the birds of paradise (Lophorina atra), the males
alone are black, whilst the females are brown or mottled; and there can
hardly be a doubt that blackness in these cases has been a sexually
selected character. Therefore it is in some degree probable that the
complete or partial blackness of both sexes in such birds as crows,
certain cockatoos, storks, and swans, and many marine birds, is
likewise the result of sexual selection, accompanied by equal
transmission to both sexes; for blackness can hardly serve in any case
as a protection. With several birds, in which the male alone is black,
and in others in which both sexes are black, the beak or skin about the
head is brightly coloured, and the contrast thus afforded adds much to
their beauty; we see this in the bright yellow beak of the male
blackbird, in the crimson skin over the eyes of the blackcock and
capercailzie, in the brightly and variously coloured beak of the
scoter-drake (Oidemia), in the red beak of the chough (Corvus graculus,
Linn.), of the black swan, and the black stork. This leads me to remark
that it is not incredible that toucans may owe the enormous size of
their beaks to sexual selection, for the sake of displaying the
diversified and vivid stripes of colour, with which these organs are
ornamented. (51. No satisfactory explanation has ever been offered of
the immense size, and still less of the bright colours, of the toucan’s
beak. Mr. Bates (‘The Naturalist on the Amazons,’ vol. ii. 1863, p.
341) states that they use their beaks for reaching fruit at the extreme
tips of the branches; and likewise, as stated by other authors, for
extracting eggs and young birds from the nests of other birds. But, as
Mr. Bates admits, the beak “can scarcely be considered a very
perfectly-formed instrument for the end to which it is applied.” The
great bulk of the beak, as shewn by its breadth, depth, as well as
length, is not intelligible on the view, that it serves merely as an
organ of prehension. Mr. Belt believes (‘The Naturalist in Nicaragua,’
p. 197) that the principal use of the beak is as a defence against
enemies, especially to the female whilst nesting in a hole in a tree.)
The naked skin, also, at the base of the beak and round the eyes is
likewise often brilliantly coloured; and Mr. Gould, in speaking of one
species (52. Rhamphastos carinatus, Gould’s ‘Monograph of
Ramphastidae.’), says that the colours of the beak “are doubtless in
the finest and most brilliant state during the time of pairing.” There
is no greater improbability that toucans should be encumbered with
immense beaks, though rendered as light as possible by their
cancellated structure, for the display of fine colours (an object
falsely appearing to us unimportant), than that the male Argus pheasant
and some other birds should be encumbered with plumes so long as to
impede their flight.

In the same manner, as the males alone of various species are black,
the females being dull-coloured; so in a few cases the males alone are
either wholly or partially white, as with the several bell-birds of
South America (Chasmorhynchus), the Antarctic goose (Bernicla
antarctica), the silver pheasant, etc., whilst the females are brown or
obscurely mottled. Therefore, on the same principle as before, it is
probable that both sexes of many birds, such as white cockatoos,
several egrets with their beautiful plumes, certain ibises, gulls,
terns, etc., have acquired their more or less completely white plumage
through sexual selection. In some of these cases the plumage becomes
white only at maturity. This is the case with certain gannets,
tropic-birds, etc., and with the snow-goose (Anser hyperboreus). As the
latter breeds on the “barren grounds,” when not covered with snow, and
as it migrates southward during the winter, there is no reason to
suppose that its snow-white adult plumage serves as a protection. In
the Anastomus oscitans, we have still better evidence that the white
plumage is a nuptial character, for it is developed only during the
summer; the young in their immature state, and the adults in their
winter dress, being grey and black. With many kinds of gulls (Larus),
the head and neck become pure white during the summer, being grey or
mottled during the winter and in the young state. On the other hand,
with the smaller gulls, or sea-mews (Gavia), and with some terns
(Sterna), exactly the reverse occurs; for the heads of the young birds
during the first year, and of the adults during the winter, are either
pure white, or much paler coloured than during the breeding-season.
These latter cases offer another instance of the capricious manner in
which sexual selection appears often to have acted. (53. On Larus,
Gavia, and Sterna, see Macgillivray, ‘History of British Birds,’ vol.
v. pp. 515, 584, 626. On the Anser hyperboreus, Audubon,
‘Ornithological Biography,’ vol. iv. p. 562. On the Anastomus, Mr.
Blyth, in ‘Ibis,’ 1867, p. 173.)

That aquatic birds have acquired a white plumage so much oftener than
terrestrial birds, probably depends on their large size and strong
powers of flight, so that they can easily defend themselves or escape
from birds of prey, to which moreover they are not much exposed.
Consequently, sexual selection has not here been interfered with or
guided for the sake of protection. No doubt with birds which roam over
the open ocean, the males and females could find each other much more
easily, when made conspicuous either by being perfectly white or
intensely black; so that these colours may possibly serve the same end
as the call-notes of many land-birds. (54. It may be noticed that with
vultures, which roam far and wide high in the air, like marine birds
over the ocean, three or four species are almost wholly or largely
white, and that many others are black. So that here again conspicuous
colours may possibly aid the sexes in finding each other during the
breeding-season.) A white or black bird when it discovers and flies
down to a carcase floating on the sea or cast up on the beach, will be
seen from a great distance, and will guide other birds of the same and
other species, to the prey; but as this would be a disadvantage to the
first finders, the individuals which were the whitest or blackest would
not thus procure more food than the less strongly coloured individuals.
Hence conspicuous colours cannot have been gradually acquired for this
purpose through natural selection.

As sexual selection depends on so fluctuating an element as taste, we
can understand how it is that, within the same group of birds having
nearly the same habits, there should exist white or nearly white, as
well as black, or nearly black species,—for instance, both white and
black cockatoos, storks, ibises, swans, terns, and petrels. Piebald
birds likewise sometimes occur in the same groups together with black
and white species; for instance, the black-necked swan, certain terns,
and the common magpie. That a strong contrast in colour is agreeable to
birds, we may conclude by looking through any large collection, for the
sexes often differ from each other in the male having the pale parts of
a purer white, and the variously coloured dark parts of still darker
tints than the female.

It would even appear that mere novelty, or slight changes for the sake
of change, have sometimes acted on female birds as a charm, like
changes of fashion with us. Thus the males of some parrots can hardly
be said to be more beautiful than the females, at least according to
our taste, but they differ in such points, as in having a rose-coloured
collar instead of “a bright emeraldine narrow green collar”; or in the
male having a black collar instead of “a yellow demi-collar in front,”
with a pale roseate instead of a plum-blue head. (55. See Jerdon on the
genus Palaeornis, ‘Birds of India,’ vol. i. pp. 258-260.) As so many
male birds have elongated tail-feathers or elongated crests for their
chief ornament, the shortened tail, formerly described in the male of a
humming-bird, and the shortened crest of the male goosander, seem like
one of the many changes of fashion which we admire in our own dresses.

Some members of the heron family offer a still more curious case of
novelty in colouring having, as it appears, been appreciated for the
sake of novelty. The young of the Ardea asha are white, the adults
being dark slate-coloured; and not only the young, but the adults in
their winter plumage, of the allied Buphus coromandus are white, this
colour changing into a rich golden-buff during the breeding-season. It
is incredible that the young of these two species, as well as of some
other members of the same family (56. The young of Ardea rufescens and
A. caerulea of the United States are likewise white, the adults being
coloured in accordance with their specific names. Audubon
(‘Ornithological Biography,’ vol. iii. p. 416; vol. iv. p. 58) seems
rather pleased at the thought that this remarkable change of plumage
will greatly “disconcert the systematists.”), should for any special
purpose have been rendered pure white and thus made conspicuous to
their enemies; or that the adults of one of these two species should
have been specially rendered white during the winter in a country which
is never covered with snow. On the other hand we have good reason to
believe that whiteness has been gained by many birds as a sexual
ornament. We may therefore conclude that some early progenitor of the
Ardea asha and the Buphus acquired a white plumage for nuptial
purposes, and transmitted this colour to their young; so that the young
and the old became white like certain existing egrets; and that the
whiteness was afterwards retained by the young, whilst it was exchanged
by the adults for more strongly-pronounced tints. But if we could look
still further back to the still earlier progenitors of these two
species, we should probably see the adults dark-coloured. I infer that
this would be the case, from the analogy of many other birds, which are
dark whilst young, and when adult are white; and more especially from
the case of the Ardea gularis, the colours of which are the reverse of
those of A. asha, for the young are dark-coloured and the adults white,
the young having retained a former state of plumage. It appears
therefore that, during a long line of descent, the adult progenitors of
the Ardea asha, the Buphus, and of some allies, have undergone the
following changes of colour: first, a dark shade; secondly, pure white;
and thirdly, owing to another change of fashion (if I may so express
myself), their present slaty, reddish, or golden-buff tints. These
successive changes are intelligible only on the principle of novelty
having been admired by birds for its own sake.

Several writers have objected to the whole theory of sexual selection,
by assuming that with animals and savages the taste of the female for
certain colours or other ornaments would not remain constant for many
generations; that first one colour and then another would be admired,
and consequently that no permanent effect could be produced. We may
admit that taste is fluctuating, but it is not quite arbitrary. It
depends much on habit, as we see in mankind; and we may infer that this
would hold good with birds and other animals. Even in our own dress,
the general character lasts long, and the changes are to a certain
extent graduated. Abundant evidence will be given in two places in a
future chapter, that savages of many races have admired for many
generations the same cicatrices on the skin, the same hideously
perforated lips, nostrils, or ears, distorted heads, etc.; and these
deformities present some analogy to the natural ornaments of various
animals. Nevertheless, with savages such fashions do not endure for
ever, as we may infer from the differences in this respect between
allied tribes on the same continent. So again the raisers of fancy
animals certainly have admired for many generations and still admire
the same breeds; they earnestly desire slight changes, which are
considered as improvements, but any great or sudden change is looked at
as the greatest blemish. With birds in a state of nature we have no
reason to suppose that they would admire an entirely new style of
coloration, even if great and sudden variations often occurred, which
is far from being the case. We know that dovecot pigeons do not
willingly associate with the variously coloured fancy breeds; that
albino birds do not commonly get partners in marriage; and that the
black ravens of the Feroe Islands chase away their piebald brethren.
But this dislike of a sudden change would not preclude their
appreciating slight changes, any more than it does in the case of man.
Hence with respect to taste, which depends on many elements, but partly
on habit and partly on a love of novelty, there seems no improbability
in animals admiring for a very long period the same general style of
ornamentation or other attractions, and yet appreciating slight changes
in colours, form, or sound.

A SUMMARY OF THE FOUR CHAPTERS ON BIRDS.

Most male birds are highly pugnacious during the breeding-season, and
some possess weapons adapted for fighting with their rivals. But the
most pugnacious and the best armed males rarely or never depend for
success solely on their power to drive away or kill their rivals, but
have special means for charming the female. With some it is the power
of song, or of giving forth strange cries, or instrumental music, and
the males in consequence differ from the females in their vocal organs,
or in the structure of certain feathers. From the curiously diversified
means for producing various sounds, we gain a high idea of the
importance of this means of courtship. Many birds endeavour to charm
the females by love-dances or antics, performed on the ground or in the
air, and sometimes at prepared places. But ornaments of many kinds, the
most brilliant tints, combs and wattles, beautiful plumes, elongated
feathers, top-knots, and so forth, are by far the commonest means. In
some cases mere novelty appears to have acted as a charm. The ornaments
of the males must be highly important to them, for they have been
acquired in not a few cases at the cost of increased danger from
enemies, and even at some loss of power in fighting with their rivals.
The males of very many species do not assume their ornamental dress
until they arrive at maturity, or they assume it only during the
breeding-season, or the tints then become more vivid. Certain
ornamental appendages become enlarged, turgid, and brightly coloured
during the act of courtship. The males display their charms with
elaborate care and to the best effect; and this is done in the presence
of the females. The courtship is sometimes a prolonged affair, and many
males and females congregate at an appointed place. To suppose that the
females do not appreciate the beauty of the males, is to admit that
their splendid decorations, all their pomp and display, are useless;
and this is incredible. Birds have fine powers of discrimination, and
in some few instances it can be shewn that they have a taste for the
beautiful. The females, moreover, are known occasionally to exhibit a
marked preference or antipathy for certain individual males.

If it be admitted that the females prefer, or are unconsciously excited
by the more beautiful males, then the males would slowly but surely be
rendered more and more attractive through sexual selection. That it is
this sex which has been chiefly modified, we may infer from the fact
that, in almost every genus where the sexes differ, the males differ
much more from one another than do the females; this is well shewn in
certain closely-allied representative species, in which the females can
hardly be distinguished, whilst the males are quite distinct. Birds in
a state of nature offer individual differences which would amply
suffice for the work of sexual selection; but we have seen that they
occasionally present more strongly marked variations which recur so
frequently that they would immediately be fixed, if they served to
allure the female. The laws of variation must determine the nature of
the initial changes, and will have largely influenced the final result.
The gradations, which may be observed between the males of allied
species, indicate the nature of the steps through which they have
passed. They explain also in the most interesting manner how certain
characters have originated, such as the indented ocelli on the
tail-feathers of the peacock, and the ball-and-socket ocelli on the
wing-feathers of the Argus pheasant. It is evident that the brilliant
colours, top-knots, fine plumes, etc., of many male birds cannot have
been acquired as a protection; indeed, they sometimes lead to danger.
That they are not due to the direct and definite action of the
conditions of life, we may feel assured, because the females have been
exposed to the same conditions, and yet often differ from the males to
an extreme degree. Although it is probable that changed conditions
acting during a lengthened period have in some cases produced a
definite effect on both sexes, or sometimes on one sex alone, the more
important result will have been an increased tendency to vary or to
present more strongly-marked individual differences; and such
differences will have afforded an excellent ground-work for the action
of sexual selection.

The laws of inheritance, irrespectively of selection, appear to have
determined whether the characters acquired by the males for the sake of
ornament, for producing various sounds, and for fighting together, have
been transmitted to the males alone or to both sexes, either
permanently, or periodically during certain seasons of the year. Why
various characters should have been transmitted sometimes in one way
and sometimes in another, is not in most cases known; but the period of
variability seems often to have been the determining cause. When the
two sexes have inherited all characters in common they necessarily
resemble each other; but as the successive variations may be
differently transmitted, every possible gradation may be found, even
within the same genus, from the closest similarity to the widest
dissimilarity between the sexes. With many closely-allied species,
following nearly the same habits of life, the males have come to differ
from each other chiefly through the action of sexual selection; whilst
the females have come to differ chiefly from partaking more or less of
the characters thus acquired by the males. The effects, moreover, of
the definite action of the conditions of life, will not have been
masked in the females, as in the males, by the accumulation through
sexual selection of strongly-pronounced colours and other ornaments.
The individuals of both sexes, however affected, will have been kept at
each successive period nearly uniform by the free intercrossing of many
individuals.

With species, in which the sexes differ in colour, it is possible or
probable that some of the successive variations often tended to be
transmitted equally to both sexes; but that when this occurred the
females were prevented from acquiring the bright colours of the males,
by the destruction which they suffered during incubation. There is no
evidence that it is possible by natural selection to convert one form
of transmission into another. But there would not be the least
difficulty in rendering a female dull-coloured, the male being still
kept bright-coloured, by the selection of successive variations, which
were from the first limited in their transmission to the same sex.
Whether the females of many species have actually been thus modified,
must at present remain doubtful. When, through the law of the equal
transmission of characters to both sexes, the females were rendered as
conspicuously coloured as the males, their instincts appear often to
have been modified so that they were led to build domed or concealed
nests.

In one small and curious class of cases the characters and habits of
the two sexes have been completely transposed, for the females are
larger, stronger, more vociferous and brighter coloured than the males.
They have, also, become so quarrelsome that they often fight together
for the possession of the males, like the males of other pugnacious
species for the possession of the females. If, as seems probable, such
females habitually drive away their rivals, and by the display of their
bright colours or other charms endeavour to attract the males, we can
understand how it is that they have gradually been rendered, by sexual
selection and sexually-limited transmission, more beautiful than the
males—the latter being left unmodified or only slightly modified.

Whenever the law of inheritance at corresponding ages prevails but not
that of sexually-limited transmission, then if the parents vary late in
life—and we know that this constantly occurs with our poultry, and
occasionally with other birds—the young will be left unaffected, whilst
the adults of both sexes will be modified. If both these laws of
inheritance prevail and either sex varies late in life, that sex alone
will be modified, the other sex and the young being unaffected. When
variations in brightness or in other conspicuous characters occur early
in life, as no doubt often happens, they will not be acted on through
sexual selection until the period of reproduction arrives; consequently
if dangerous to the young, they will be eliminated through natural
selection. Thus we can understand how it is that variations arising
late in life have so often been preserved for the ornamentation of the
males; the females and the young being left almost unaffected, and
therefore like each other. With species having a distinct summer and
winter plumage, the males of which either resemble or differ from the
females during both seasons or during the summer alone, the degrees and
kinds of resemblance between the young and the old are exceedingly
complex; and this complexity apparently depends on characters, first
acquired by the males, being transmitted in various ways and degrees,
as limited by age, sex, and season.

As the young of so many species have been but little modified in colour
and in other ornaments, we are enabled to form some judgment with
respect to the plumage of their early progenitors; and we may infer
that the beauty of our existing species, if we look to the whole class,
has been largely increased since that period, of which the immature
plumage gives us an indirect record. Many birds, especially those which
live much on the ground, have undoubtedly been obscurely coloured for
the sake of protection. In some instances the upper exposed surface of
the plumage has been thus coloured in both sexes, whilst the lower
surface in the males alone has been variously ornamented through sexual
selection. Finally, from the facts given in these four chapters, we may
conclude that weapons for battle, organs for producing sound, ornaments
of many kinds, bright and conspicuous colours, have generally been
acquired by the males through variation and sexual selection, and have
been transmitted in various ways according to the several laws of
inheritance—the females and the young being left comparatively but
little modified. (57. I am greatly indebted to the kindness of Mr.
Sclater for having looked over these four chapters on birds, and the
two following ones on mammals. In this way I have been saved from
making mistakes about the names of the species, and from stating
anything as a fact which is known to this distinguished naturalist to
be erroneous. But, of course, he is not at all answerable for the
accuracy of the statements quoted by me from various authorities.)




CHAPTER XVII.
SECONDARY SEXUAL CHARACTERS OF MAMMALS.


The law of battle—Special weapons, confined to the males—Cause of
absence of weapons in the female—Weapons common to both sexes, yet
primarily acquired by the male—Other uses of such weapons—Their high
importance—Greater size of the male—Means of defence—On the preference
shown by either sex in the pairing of quadrupeds.

With mammals the male appears to win the female much more through the
law of battle than through the display of his charms. The most timid
animals, not provided with any special weapons for fighting, engage in
desperate conflicts during the season of love. Two male hares have been
seen to fight together until one was killed; male moles often fight,
and sometimes with fatal results; male squirrels engage in frequent
contests, “and often wound each other severely”; as do male beavers, so
that “hardly a skin is without scars.” (1. See Waterton’s account of
two hares fighting, ‘Zoologist,’ vol. i. 1843, p. 211. On moles, Bell,
‘Hist. of British Quadrupeds,’ 1st ed., p. 100. On squirrels, Audubon
and Bachman, Viviparous Quadrupeds of N. America, 1846, p. 269. On
beavers, Mr. A.H. Green, in ‘Journal of Linnean Society, Zoology,’ vol.
x. 1869, p. 362.) I observed the same fact with the hides of the
guanacoes in Patagonia; and on one occasion several were so absorbed in
fighting that they fearlessly rushed close by me. Livingstone speaks of
the males of the many animals in Southern Africa as almost invariably
shewing the scars received in former contests.

The law of battle prevails with aquatic as with terrestrial mammals. It
is notorious how desperately male seals fight, both with their teeth
and claws, during the breeding-season; and their hides are likewise
often covered with scars. Male sperm-whales are very jealous at this
season; and in their battles “they often lock their jaws together, and
turn on their sides and twist about”; so that their lower jaws often
become distorted. (2. On the battles of seals, see Capt. C. Abbott in
‘Proc. Zool. Soc.’ 1868, p. 191; Mr. R. Brown, ibid. 1868, p. 436; also
L. Lloyd, ‘Game Birds of Sweden,’ 1867, p. 412; also Pennant. On the
sperm-whale see Mr. J.H. Thompson, in ‘Proc. Zool. Soc.’ 1867, p. 246.)

All male animals which are furnished with special weapons for fighting,
are well known to engage in fierce battles. The courage and the
desperate conflicts of stags have often been described; their skeletons
have been found in various parts of the world, with the horns
inextricably locked together, shewing how miserably the victor and
vanquished had perished. (3. See Scrope (‘Art of Deer-stalking,’ p. 17)
on the locking of the horns with the Cervus elaphus. Richardson, in
‘Fauna Bor. Americana,’ 1829, p. 252, says that the wapiti, moose, and
reindeer have been found thus locked together. Sir A. Smith found at
the Cape of Good Hope the skeletons of two gnus in the same condition.)
No animal in the world is so dangerous as an elephant in must. Lord
Tankerville has given me a graphic description of the battles between
the wild bulls in Chillingham Park, the descendants, degenerated in
size but not in courage, of the gigantic Bos primigenius. In 1861
several contended for mastery; and it was observed that two of the
younger bulls attacked in concert the old leader of the herd, overthrew
and disabled him, so that he was believed by the keepers to be lying
mortally wounded in a neighbouring wood. But a few days afterwards one
of the young bulls approached the wood alone; and then the “monarch of
the chase,” who had been lashing himself up for vengeance, came out
and, in a short time, killed his antagonist. He then quietly joined the
herd, and long held undisputed sway. Admiral Sir B.J. Sulivan informs
me that, when he lived in the Falkland Islands, he imported a young
English stallion, which frequented the hills near Port William with
eight mares. On these hills there were two wild stallions, each with a
small troop of mares; “and it is certain that these stallions would
never have approached each other without fighting. Both had tried
singly to fight the English horse and drive away his mares, but had
failed. One day they came in TOGETHER and attacked him. This was seen
by the capitan who had charge of the horses, and who, on riding to the
spot, found one of the two stallions engaged with the English horse,
whilst the other was driving away the mares, and had already separated
four from the rest. The capitan settled the matter by driving the whole
party into the corral, for the wild stallions would not leave the
mares.”

Male animals which are provided with efficient cutting or tearing teeth
for the ordinary purposes of life, such as the carnivora, insectivora,
and rodents, are seldom furnished with weapons especially adapted for
fighting with their rivals. The case is very different with the males
of many other animals. We see this in the horns of stags and of certain
kinds of antelopes in which the females are hornless. With many animals
the canine teeth in the upper or lower jaw, or in both, are much larger
in the males than in the females, or are absent in the latter, with the
exception sometimes of a hidden rudiment. Certain antelopes, the
musk-deer, camel, horse, boar, various apes, seals, and the walrus,
offer instances. In the females of the walrus the tusks are sometimes
quite absent. (4. Mr. Lamont (‘Seasons with the Sea-Horses,’ 1861, p.
143) says that a good tusk of the male walrus weighs 4 pounds, and is
longer than that of the female, which weighs about 3 pounds. The males
are described as fighting ferociously. On the occasional absence of the
tusks in the female, see Mr. R. Brown, ‘Proceedings, Zoological
Society,’ 1868, p. 429.) In the male elephant of India and in the male
dugong (5. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 283.) the upper
incisors form offensive weapons. In the male narwhal the left canine
alone is developed into the well-known, spirally-twisted, so-called
horn, which is sometimes from nine to ten feet in length. It is
believed that the males use these horns for fighting together; for “an
unbroken one can rarely be got, and occasionally one may be found with
the point of another jammed into the broken place.” (6. Mr. R. Brown,
in ‘Proc. Zool. Soc.’ 1869, p. 553. See Prof. Turner, in ‘Journal of
Anat. and Phys.’ 1872, p. 76, on the homological nature of these tusks.
Also Mr. J.W. Clarke on two tusks being developed in the males, in
‘Proceedings of the Zoological Society,’ 1871, p. 42.) The tooth on the
opposite side of the head in the male consists of a rudiment about ten
inches in length, which is embedded in the jaw; but sometimes, though
rarely, both are equally developed on the two sides. In the female both
are always rudimentary. The male cachalot has a larger head than that
of the female, and it no doubt aids him in his aquatic battles. Lastly,
the adult male ornithorhynchus is provided with a remarkable apparatus,
namely a spur on the foreleg, closely resembling the poison-fang of a
venomous snake; but according to Harting, the secretion from the gland
is not poisonous; and on the leg of the female there is a hollow,
apparently for the reception of the spur. (7. Owen on the cachalot and
Ornithorhynchus, ibid. vol. iii. pp. 638, 641. Harting is quoted by Dr.
Zouteveen in the Dutch translation of this work, vol. ii. p. 292.)

When the males are provided with weapons which in the females are
absent, there can be hardly a doubt that these serve for fighting with
other males; and that they were acquired through sexual selection, and
were transmitted to the male sex alone. It is not probable, at least in
most cases, that the females have been prevented from acquiring such
weapons, on account of their being useless, superfluous, or in some way
injurious. On the contrary, as they are often used by the males for
various purposes, more especially as a defence against their enemies,
it is a surprising fact that they are so poorly developed, or quite
absent, in the females of so many animals. With female deer the
development during each recurrent season of great branching horns, and
with female elephants the development of immense tusks, would be a
great waste of vital power, supposing that they were of no use to the
females. Consequently, they would have tended to be eliminated in the
female through natural selection; that is, if the successive variations
were limited in their transmission to the female sex, for otherwise the
weapons of the males would have been injuriously affected, and this
would have been a greater evil. On the whole, and from the
consideration of the following facts, it seems probable that when the
various weapons differ in the two sexes, this has generally depended on
the kind of transmission which has prevailed.

As the reindeer is the one species in the whole family of Deer, in
which the female is furnished with horns, though they are somewhat
smaller, thinner, and less branched than in the male, it might
naturally be thought that, at least in this case, they must be of some
special service to her. The female retains her horns from the time when
they are fully developed, namely, in September, throughout the winter
until April or May, when she brings forth her young. Mr. Crotch made
particular enquiries for me in Norway, and it appears that the females
at this season conceal themselves for about a fortnight in order to
bring forth their young, and then reappear, generally hornless. In Nova
Scotia, however, as I hear from Mr. H. Reeks, the female sometimes
retains her horns longer. The male on the other hand casts his horns
much earlier, towards the end of November. As both sexes have the same
requirements and follow the same habits of life, and as the male is
destitute of horns during the winter, it is improbable that they can be
of any special service to the female during this season, which includes
the larger part of the time during which she is horned. Nor is it
probable that she can have inherited horns from some ancient progenitor
of the family of deer, for, from the fact of the females of so many
species in all quarters of the globe not having horns, we may conclude
that this was the primordial character of the group. (8. On the
structure and shedding of the horns of the reindeer, Hoffberg,
‘Amoenitates Acad.’ vol. iv. 1788, p. 149. See Richardson, ‘Fauna Bor.
Americana,’ p. 241, in regard to the American variety or species: also
Major W. Ross King, ‘The Sportsman in Canada,’ 1866, p. 80.

The horns of the reindeer are developed at a most unusually early age;
but what the cause of this may be is not known. The effect has
apparently been the transference of the horns to both sexes. We should
bear in mind that horns are always transmitted through the female, and
that she has a latent capacity for their development, as we see in old
or diseased females. (9. Isidore Geoffroy St.-Hilaire, ‘Essais de
Zoolog. Générale,’ 1841, p. 513. Other masculine characters, besides
the horns, are sometimes similarly transferred to the female; thus Mr.
Boner, in speaking of an old female chamois (‘Chamois Hunting in the
Mountains of Bavaria,’ 1860, 2nd ed., p. 363), says, “not only was the
head very male-looking, but along the back there was a ridge of long
hair, usually to be found only in bucks.”) Moreover the females of some
other species of deer exhibit, either normally or occasionally,
rudiments of horns; thus the female of Cervulus moschatus has “bristly
tufts, ending in a knob, instead of a horn”; and “in most specimens of
the female wapiti (Cervus canadensis) there is a sharp bony
protuberance in the place of the horn.” (10. On the Cervulus, Dr. Gray,
‘Catalogue of Mammalia in the British Museum,’ part iii. p. 220. On the
Cervus canadensis or wapiti, see Hon. J.D. Caton, ‘Ottawa Academy of
Nat. Sciences,’ May 1868, p. 9.) From these several considerations we
may conclude that the possession of fairly well-developed horns by the
female reindeer, is due to the males having first acquired them as
weapons for fighting with other males; and secondarily to their
development from some unknown cause at an unusually early age in the
males, and their consequent transference to both sexes.

Turning to the sheath-horned ruminants: with antelopes a graduated
series can be formed, beginning with species, the females of which are
completely destitute of horns—passing on to those which have horns so
small as to be almost rudimentary (as with the Antilocapra americana,
in which species they are present in only one out of four or five
females (11. I am indebted to Dr. Canfield for this information; see
also his paper in the ‘Proceedings of the Zoological Society,’ 1866, p.
105.))—to those which have fairly developed horns, but manifestly
smaller and thinner than in the male and sometimes of a different shape
(12. For instance the horns of the female Ant. euchore resemble those
of a distinct species, viz. the Ant. dorcas var. Corine, see Desmarest,
‘Mammalogie,’ p. 455.),—and ending with those in which both sexes have
horns of equal size. As with the reindeer, so with antelopes, there
exists, as previously shewn, a relation between the period of the
development of the horns and their transmission to one or both sexes;
it is therefore probable that their presence or absence in the females
of some species, and their more or less perfect condition in the
females of other species, depends, not on their being of any special
use, but simply on inheritance. It accords with this view that even in
the same restricted genus both sexes of some species, and the males
alone of others, are thus provided. It is also a remarkable fact that,
although the females of Antilope bezoartica are normally destitute of
horns, Mr. Blyth has seen no less than three females thus furnished;
and there was no reason to suppose that they were old or diseased.

In all the wild species of goats and sheep the horns are larger in the
male than in the female, and are sometimes quite absent in the latter.
(13. Gray, ‘Catalogue of Mammalia, the British Museum,’ part iii. 1852,
p. 160.) In several domestic breeds of these two animals, the males
alone are furnished with horns; and in some breeds, for instance, in
the sheep of North Wales, though both sexes are properly horned, the
ewes are very liable to be hornless. I have been informed by a
trustworthy witness, who purposely inspected a flock of these same
sheep during the lambing season, that the horns at birth are generally
more fully developed in the male than in the female. Mr. J. Peel
crossed his Lonk sheep, both sexes of which always bear horns, with
hornless Leicesters and hornless Shropshire Downs; and the result was
that the male offspring had their horns considerably reduced, whilst
the females were wholly destitute of them. These several facts indicate
that, with sheep, the horns are a much less firmly fixed character in
the females than in the males; and this leads us to look at the horns
as properly of masculine origin.

With the adult musk-ox (Ovibos moschatus) the horns of the male are
larger than those of the female, and in the latter the bases do not
touch. (14. Richardson, ‘Fauna Bor. Americana,’ p. 278.) In regard to
ordinary cattle Mr. Blyth remarks: “In most of the wild bovine animals
the horns are both longer and thicker in the bull than in the cow, and
in the cow-banteng (Bos sondaicus) the horns are remarkably small, and
inclined much backwards. In the domestic races of cattle, both of the
humped and humpless types, the horns are short and thick in the bull,
longer and more slender in the cow and ox; and in the Indian buffalo,
they are shorter and thicker in the bull, longer and more slender in
the cow. In the wild gaour (B. gaurus) the horns are mostly both longer
and thicker in the bull than in the cow.” (15. ‘Land and Water,’ 1867,
p. 346.) Dr. Forsyth Major also informs me that a fossil skull,
believed to be that of the female Bos etruscus, has been found in Val
d’Arno, which is wholly without horns. In the Rhinoceros simus, as I
may add, the horns of the female are generally longer but less powerful
than in the male; and in some other species of rhinoceros they are said
to be shorter in the female. (16. Sir Andrew Smith, ‘Zoology of S.
Africa,’ pl. xix. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 624.)
From these various facts we may infer as probable that horns of all
kinds, even when they are equally developed in the two sexes, were
primarily acquired by the male in order to conquer other males, and
have been transferred more or less completely to the female.

The effects of castration deserve notice, as throwing light on this
same point. Stags after the operation never renew their horns. The male
reindeer, however, must be excepted, as after castration he does renew
them. This fact, as well as the possession of horns by both sexes,
seems at first to prove that the horns in this species do not
constitute a sexual character (17. This is the conclusion of Seidlitz,
‘Die Darwinsche Theorie,’ 1871, p. 47.); but as they are developed at a
very early age, before the sexes differ in constitution, it is not
surprising that they should be unaffected by castration, even if they
were aboriginally acquired by the male. With sheep both sexes properly
bear horns; and I am informed that with Welch sheep the horns of the
males are considerably reduced by castration; but the degree depends
much on the age at which the operation is performed, as is likewise the
case with other animals. Merino rams have large horns, whilst the ewes
“generally speaking are without horns”; and in this breed castration
seems to produce a somewhat greater effect, so that if performed at an
early age the horns “remain almost undeveloped.” (18. I am much obliged
to Prof. Victor Carus, for having made enquiries for me in Saxony on
this subject. H. von Nathusius (‘Viehzucht,’ 1872, p. 64) says that the
horns of sheep castrated at an early period, either altogether
disappear or remain as mere rudiments; but I do not know whether he
refers to merinos or to ordinary breeds.) On the Guinea coast there is
a breed in which the females never bear horns, and, as Mr. Winwood
Reade informs me, the rams after castration are quite destitute of
them. With cattle, the horns of the males are much altered by
castration; for instead of being short and thick, they become longer
than those of the cow, but otherwise resemble them. The Antilope
bezoartica offers a somewhat analogous case: the males have long
straight spiral horns, nearly parallel to each other, and directed
backwards; the females occasionally bear horns, but these when present
are of a very different shape, for they are not spiral, and spreading
widely, bend round with the points forwards. Now it

is a remarkable fact that, in the castrated male, as Mr. Blyth informs
me, the horns are of the same peculiar shape as in the female, but
longer and thicker. If we may judge from analogy, the female probably
shews us, in these two cases of cattle and the antelope, the former
condition of the horns in some early progenitor of each species. But
why castration should lead to the reappearance of an early condition of
the horns cannot be explained with any certainty. Nevertheless, it
seems probable, that in nearly the same manner as the constitutional
disturbance in the offspring, caused by a cross between two distinct
species or races, often leads to the reappearance of long-lost
characters (19. I have given various experiments and other evidence
proving that this is the case, in my ‘Variation of Animals and Plants
under Domestication,’ vol. ii. 1868, pp. 39-47.); so here, the
disturbance in the constitution of the individual, resulting from
castration, produces the same effect.

The tusks of the elephant, in the different species or races, differ
according to sex, nearly as do the horns of ruminants. In India and
Malacca the males alone are provided with well-developed tusks. The
elephant of Ceylon is considered by most naturalists as a distinct
race, but by some as a distinct species, and here “not one in a hundred
is found with tusks, the few that possess them being exclusively
males.” (20. Sir J. Emerson Tennent, ‘Ceylon,’ 1859, vol. ii. p. 274.
For Malacca, ‘Journal of Indian Archipelago,’ vol. iv. p. 357.) The
African elephant is undoubtedly distinct, and the female has large
well-developed tusks, though not so large as those of the male.

These differences in the tusks of the several races and species of
elephants—the great variability of the horns of deer, as notably in the
wild reindeer—the occasional presence of horns in the female Antilope
Bezoartica, and their frequent absence in the female of Antilocapra
americana—the presence of two tusks in some few male narwhals—the
complete absence of tusks in some female walruses—are all instances of
the extreme variability of secondary sexual characters, and of their
liability to differ in closely-allied forms.

Although tusks and horns appear in all cases to have been primarily
developed as sexual weapons, they often serve other purposes. The
elephant uses his tusks in attacking the tiger; according to Bruce, he
scores the trunks of trees until they can be thrown down easily, and he
likewise thus extracts the farinaceous cores of palms; in Africa he
often uses one tusk, always the same, to probe the ground and thus
ascertain whether it will bear his weight. The common bull defends the
herd with his horns; and the elk in Sweden has been known, according to
Lloyd, to strike a wolf dead with a single blow of his great horns.
Many similar facts could be given. One of the most curious secondary
uses to which the horns of an animal may be occasionally put is that
observed by Captain Hutton (21. ‘Calcutta Journal of Natural History,’
vol. ii, 1843, p. 526.) with the wild goat (Capra aegagrus) of the
Himalayas and, as it is also said with the ibex, namely that when the
male accidentally falls from a height he bends inwards his head, and by
alighting on his massive horns, breaks the shock. The female cannot
thus use her horns, which are smaller, but from her more quiet
disposition she does not need this strange kind of shield so much.

Each male animal uses his weapons in his own peculiar fashion. The
common ram makes a charge and butts with such force with the bases of
his horns, that I have seen a powerful man knocked over like a child.
Goats and certain species of sheep, for instance the Ovis cycloceros of
Afghanistan (22. Mr. Blyth, in ‘Land and Water,’ March, 1867, p. 134,
on the authority of Capt. Hutton and others. For the wild Pembrokeshire
goats, see the ‘Field,’ 1869, p. 150.), rear on their hind legs, and
then not only butt, but “make a cut down and a jerk up, with the ribbed
front of their scimitar-shaped horn, as with a sabre. When the O.
cycloceros attacked a large domestic ram, who was a noted bruiser, he
conquered him by the sheer novelty of his mode of fighting, always
closing at once with his adversary, and catching him across the face
and nose with a sharp drawing jerk of the head, and then bounding out
of the way before the blow could be returned.” In Pembrokeshire a male
goat, the master of a flock which during several generations had run
wild, was known to have killed several males in single combat; this
goat possessed enormous horns, measuring thirty-nine inches in a
straight line from tip to tip. The common bull, as every one knows,
gores and tosses his opponent; but the Italian buffalo is said never to
use his horns: he gives a tremendous blow with his convex forehead, and
then tramples on his fallen enemy with his knees—an instinct which the
common bull does not possess. (23. M. E.M. Bailly, “Sur l’usage des
cornes,” etc., .Annal des Sciences Nat.’ tom. ii. 1824, p. 369.) Hence
a dog who pins a buffalo by the nose is immediately crushed. We must,
however, remember that the Italian buffalo has been long domesticated,
and it is by no means certain that the wild parent-form had similar
horns. Mr. Bartlett informs me that when a female Cape buffalo (Bubalus
caffer) was turned into an enclosure with a bull of the same species,
she attacked him, and he in return pushed her about with great
violence. But it was manifest to Mr. Bartlett that, had not the bull
shewn dignified forbearance, he could easily have killed her by a
single lateral thrust with his immense horns. The giraffe uses his
short, hair-covered horns, which are rather longer in the male than in
the female, in a curious manner; for, with his long neck, he swings his
head to either side, almost upside down, with such force that I have
seen a hard plank deeply indented by a single blow.

[Fig. 63. Oryx leucoryx, male (from the Knowsley Menagerie).]

With antelopes it is sometimes difficult to imagine how they can
possibly use their curiously-shaped horns; thus the springboc (Ant.
euchore) has rather short upright horns, with the sharp points bent
inwards almost at right angles, so as to face each other; Mr. Bartlett
does not know how they are used, but suggests that they would inflict a
fearful wound down each side of the face of an antagonist. The
slightly-curved horns of the Oryx leucoryx (Fig. 63) are directed
backwards, and are of such length that their points reach beyond the
middle of the back, over which they extend in almost parallel lines.
Thus they seem singularly ill-fitted for fighting; but Mr. Bartlett
informs me that when two of these animals prepare for battle, they
kneel down, with their heads between their fore legs, and in this
attitude the horns stand nearly parallel and close to the ground, with
the points directed forwards and a little upwards. The combatants then
gradually approach each other, and each endeavours to get the upturned
points under the body of the other; if one succeeds in doing this, he
suddenly springs up, throwing up his head at the same time, and can
thus wound or perhaps even transfix his antagonist. Both animals always
kneel down, so as to guard as far as possible against this manoeuvre.
It has been recorded that one of these antelopes has used his horn with
effect even against a lion; yet from being forced to place his head
between the forelegs in order to bring the points of the horns forward,
he would generally be under a great disadvantage when attacked by any
other animal. It is, therefore, not probable that the horns have been
modified into their present great length and peculiar position, as a
protection against beasts of prey. We can however see that, as soon as
some ancient male progenitor of the Oryx acquired moderately long
horns, directed a little backwards, he would be compelled, in his
battles with rival males, to bend his head somewhat inwards or
downwards, as is now done by certain stags; and it is not improbable
that he might have acquired the habit of at first occasionally and
afterwards of regularly kneeling down. In this case it is almost
certain that the males which possessed the longest horns would have had
a great advantage over others with shorter horns; and then the horns
would gradually have been rendered longer and longer, through sexual
selection, until they acquired their present extraordinary length and
position.

With stags of many kinds the branches of the horns offer a curious case
of difficulty; for certainly a single straight point would inflict a
much more serious wound than several diverging ones. In Sir Philip
Egerton’s museum there is a horn of the red-deer (Cervus elaphus),
thirty inches in length, with “not fewer than fifteen snags or
branches”; and at Moritzburg there is still preserved a pair of antlers
of a red-deer, shot in 1699 by Frederick I., one of which bears the
astonishing number of thirty-three branches and the other twenty-seven,
making altogether sixty branches. Richardson figures a pair of antlers
of the wild reindeer with twenty-nine points. (24. On the horns of
red-deer, Owen, ‘British Fossil Mammals,’ 1846, p. 478; Richardson on
the horns of the reindeer, ‘Fauna Bor. Americana,’ 1829, p. 240. I am
indebted to Prof. Victor Carus, for the Moritzburg case.) From the
manner in which the horns are branched, and more especially from deer
being known occasionally to fight together by kicking with their
fore-feet (25. Hon. J.D. Caton (‘Ottawa Acad. of Nat. Science,’ May
1868, p. 9) says that the American deer fight with their fore-feet,
after “the question of superiority has been once settled and
acknowledged in the herd.” Bailly, ‘Sur l’Usage des cornes,’ ‘Annales
des Sciences Nat.’ tom. ii. 1824, p. 371.), M. Bailly actually comes to
the conclusion that their horns are more injurious than useful to them.
But this author overlooks the pitched battles between rival males. As I
felt much perplexed about the use or advantage of the branches, I
applied to Mr. McNeill of Colonsay, who has long and carefully observed
the habits of red-deer, and he informs me that he has never seen some
of the branches brought into use, but that the brow antlers, from
inclining downwards, are a great protection to the forehead, and their
points are likewise used in attack. Sir Philip Egerton also informs me
both as to red-deer and fallow-deer that, in fighting, they suddenly
dash together, and getting their horns fixed against each other’s
bodies, a desperate struggle ensues. When one is at last forced to
yield and turn round, the victor endeavours to plunge his brow antlers
into his defeated foe. It thus appears that the upper branches are used
chiefly or exclusively for pushing and fencing. Nevertheless in some
species the upper branches are used as weapons of offence; when a man
was attacked by a wapiti deer (Cervus canadensis) in Judge Caton’s park
in Ottawa, and several men tried to rescue him, the stag “never raised
his head from the ground; in fact he kept his face almost flat on the
ground, with his nose nearly between his fore feet, except when he
rolled his head to one side to take a new observation preparatory to a
plunge.” In this position the ends of the horns were directed against
his adversaries. “In rolling his head he necessarily raised it
somewhat, because his antlers were so long that he could not roll his
head without raising them on one side, while, on the other side they
touched the ground.” The stag by this procedure gradually drove the
party of rescuers backwards to a distance of 150 or 200 feet; and the
attacked man was killed. (26. See a most interesting account in the
Appendix to Hon. J.D. Caton’s paper, as above quoted.)

[Fig. 64. Strepsiceros Kudu (from Sir Andrew Smith’s ‘Zoology of South
Africa.’]

Although the horns of stags are efficient weapons, there can, I think,
be no doubt that a single point would have been much more dangerous
than a branched antler; and Judge Caton, who has had large experience
with deer, fully concurs in this conclusion. Nor do the branching
horns, though highly important as a means of defence against rival
stags, appear perfectly well adapted for this purpose, as they are
liable to become interlocked. The suspicion has therefore crossed my
mind that they may serve in part as ornaments. That the branched
antlers of stags as well as the elegant lyrated horns of certain
antelopes, with their graceful double curvature (Fig. 64), are
ornamental in our eyes, no one will dispute. If, then, the horns, like
the splendid accoutrements of the knights of old, add to the noble
appearance of stags and antelopes, they may have been modified partly
for this purpose, though mainly for actual service in battle; but I
have no evidence in favour of this belief.

An interesting case has lately been published, from which it appears
that the horns of a deer in one district in the United States are now
being modified through sexual and natural selection. A writer in an
excellent American Journal (27. The ‘American Naturalist,’ Dec. 1869,
p. 552.) says, that he has hunted for the last twenty-one years in the
Adirondacks, where the Cervus virginianus abounds. About fourteen years
ago he first heard of SPIKE-HORN BUCKS. These became from year to year
more common; about five years ago he shot one, and afterwards another,
and now they are frequently killed. “The spike-horn differs greatly
from the common antler of the C. virginianus. It consists of a single
spike, more slender than the antler, and scarcely half so long,
projecting forward from the brow, and terminating in a very sharp
point. It gives a considerable advantage to its possessor over the
common buck. Besides enabling him to run more swiftly through the thick
woods and underbrush (every hunter knows that does and yearling bucks
run much more rapidly than the large bucks when armed with their
cumbrous antlers), the spike-horn is a more effective weapon than the
common antler. With this advantage the spike-horn bucks are gaining
upon the common bucks, and may, in time, entirely supersede them in the
Adirondacks. Undoubtedly, the first spike-horn buck was merely an
accidental freak of nature. But his spike-horns gave him an advantage,
and enabled him to propagate his peculiarity. His descendants having a
like advantage, have propagated the peculiarity in a constantly
increasing ratio, till they are slowly crowding the antlered deer from
the region they inhabit.” A critic has well objected to this account by
asking, why, if the simple horns are now so advantageous, were the
branched antlers of the parent-form ever developed? To this I can only
answer by remarking, that a new mode of attack with new weapons might
be a great advantage, as shewn by the case of the Ovis cycloceros, who
thus conquered a domestic ram famous for his fighting power. Though the
branched antlers of a stag are well adapted for fighting with his
rivals, and though it might be an advantage to the prong-horned variety
slowly to acquire long and branched horns, if he had to fight only with
others of the same kind, yet it by no means follows that branched horns
would be the best fitted for conquering a foe differently armed. In the
foregoing case of the Oryx leucoryx, it is almost certain that the
victory would rest with an antelope having short horns, and who
therefore did not need to kneel down, though an oryx might profit by
having still longer horns, if he fought only with his proper rivals.

Male quadrupeds, which are furnished with tusks, use them in various
ways, as in the case of horns. The boar strikes laterally and upwards;
the musk-deer downwards with serious effect. (28. Pallas, ‘Spicilegia
Zoologica,’ fasc. xiii. 1779, p. 18.) The walrus, though having so
short a neck and so unwieldy a body, “can strike either upwards, or
downwards, or sideways, with equal dexterity.” (29. Lamont, ‘Seasons
with the Sea-Horses,’ 1861, p. 141.) I was informed by the late Dr.
Falconer, that the Indian elephant fights in a different manner
according to the position and curvature of his tusks. When they are
directed forwards and upwards he is able to fling a tiger to a great
distance—it is said to even thirty feet; when they are short and turned
downwards he endeavours suddenly to pin the tiger to the ground and, in
consequence, is dangerous to the rider, who is liable to be jerked off
the howdah. (30. See also Corse (‘Philosophical Transactions,’ 1799, p.
212) on the manner in which the short-tusked Mooknah variety attacks
other elephants.)

Very few male quadrupeds possess weapons of two distinct kinds
specially adapted for fighting with rival males. The male muntjac-deer
(Cervulus), however, offers an exception, as he is provided with horns
and exserted canine teeth. But we may infer from what follows that one
form of weapon has often been replaced in the course of ages by
another. With ruminants the development of horns generally stands in an
inverse relation with that of even moderately developed canine teeth.
Thus camels, guanacoes, chevrotains, and musk-deer, are hornless, and
they have efficient canines; these teeth being “always of smaller size
in the females than in the males.” The Camelidae have, in addition to
their true canines, a pair of canine-shaped incisors in their upper
jaws. (31. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 349.) Male deer
and antelopes, on the other hand, possess horns, and they rarely have
canine teeth; and these, when present, are always of small size, so
that it is doubtful whether they are of any service in their battles.
In Antilope montana they exist only as rudiments in the young male,
disappearing as he grows old; and they are absent in the female at all
ages; but the females of certain other antelopes and of certain deer
have been known occasionally to exhibit rudiments of these teeth. (32.
See Ruppell (in ‘Proc. Zoolog. Soc.’ Jan. 12, 1836, p. 3) on the
canines in deer and antelopes, with a note by Mr. Martin on a female
American deer. See also Falconer (‘Palaeont. Memoirs and Notes,’ vol.
i. 1868, p. 576) on canines in an adult female deer. In old males of
the musk-deer the canines (Pallas, ‘Spic. Zoolog.’ fasc. xiii. 1779, p.
18) sometimes grow to the length of three inches, whilst in old females
a rudiment projects scarcely half an inch above the gums.) Stallions
have small canine teeth, which are either quite absent or rudimentary
in the mare; but they do not appear to be used in fighting, for
stallions bite with their incisors, and do not open their mouths wide
like camels and guanacoes. Whenever the adult male possesses canines,
now inefficient, whilst the female has either none or mere rudiments,
we may conclude that the early male progenitor of the species was
provided with efficient canines, which have been partially transferred
to the females. The reduction of these teeth in the males seems to have
followed from some change in their manner of fighting, often (but not
in the horse) caused by the development of new weapons.

Tusks and horns are manifestly of high importance to their possessors,
for their development consumes much organised matter. A single tusk of
the Asiatic elephant—one of the extinct woolly species—and of the
African elephant, have been known to weigh respectively 150, 160, and
180 pounds; and even greater weights have been given by some authors.
(33. Emerson Tennent, ‘Ceylon,’ 1859, vol. ii. p. 275; Owen, ‘British
Fossil Mammals,’ 1846, p. 245.) With deer, in which the horns are
periodically renewed, the drain on the constitution must be greater;
the horns, for instance, of the moose weigh from fifty to sixty pounds,
and those of the extinct Irish elk from sixty to seventy pounds—the
skull of the latter weighing on an average only five pounds and a
quarter. Although the horns are not periodically renewed in sheep, yet
their development, in the opinion of many agriculturists, entails a
sensible loss to the breeder. Stags, moreover, in escaping from beasts
of prey are loaded with an additional weight for the race, and are
greatly retarded in passing through a woody country. The moose, for
instance, with horns extending five and a half feet from tip to tip,
although so skilful in their use that he will not touch or break a twig
when walking quietly, cannot act so dexterously whilst rushing away
from a pack of wolves. “During his progress he holds his nose up, so as
to lay the horns horizontally back; and in this attitude cannot see the
ground distinctly.” (34. Richardson, ‘Fauna Bor. Americana,’ on the
moose, Alces palmata, pp. 236, 237; on the expanse of the horns, ‘Land
and Water,’ 1869, p. 143. See also Owen, ‘British Fossil Mammals,’ on
the Irish elk, pp. 447, 455.) The tips of the horns of the great Irish
elk were actually eight feet apart! Whilst the horns are covered with
velvet, which lasts with red-deer for about twelve weeks, they are
extremely sensitive to a blow; so that in Germany the stags at this
time somewhat change their habits, and avoiding dense forests, frequent
young woods and low thickets. (35. ‘Forest Creatures,’ by C. Boner,
1861, p. 60.) These facts remind us that male birds have acquired
ornamental plumes at the cost of retarded flight, and other ornaments
at the cost of some loss of power in their battles with rival males.

With mammals, when, as is often the case, the sexes differ in size, the
males are almost always larger and stronger. I am informed by Mr. Gould
that this holds good in a marked manner with the marsupials of
Australia, the males of which appear to continue growing until an
unusually late age. But the most extraordinary case is that of one of
the seals (Callorhinus ursinus), a full-grown female weighing less than
one-sixth of a full-grown male. (36. See the very interesting paper by
Mr. J.A. Allen in ‘Bull. Mus. Comp. Zoology of Cambridge, United
States,’ vol. ii. No. 1, p. 82. The weights were ascertained by a
careful observer, Capt. Bryant. Dr. Gill in ‘The American Naturalist,’
January, 1871, Prof. Shaler on the relative size of the sexes of
whales, ‘American Naturalist,’ January, 1873.) Dr. Gill remarks that it
is with the polygamous seals, the males of which are well known to
fight savagely together, that the sexes differ much in size; the
monogamous species differing but little. Whales also afford evidence of
the relation existing between the pugnacity of the males and their
large size compared with that of the female; the males of the
right-whales do not fight together, and they are not larger, but rather
smaller, than their females; on the other hand, male sperm-whales fight
much together, and their bodies are “often found scarred with the
imprint of their rival’s teeth,” and they are double the size of the
females. The greater strength of the male, as Hunter long ago remarked
(37. ‘Animal Economy,’ p. 45.), is invariably displayed in those parts
of the body which are brought into action in fighting with rival
males—for instance, in the massive neck of the bull. Male quadrupeds
are also more courageous and pugnacious than the females. There can be
little doubt that these characters have been gained, partly through
sexual selection, owing to a long series of victories, by the stronger
and more courageous males over the weaker, and partly through the
inherited effects of use. It is probable that the successive variations
in strength, size, and courage, whether due to mere variability or to
the effects of use, by the accumulation of which male quadrupeds have
acquired these characteristic qualities, occurred rather late in life,
and were consequently to a large extent limited in their transmission
to the same sex.

From these considerations I was anxious to obtain information as to the
Scotch deer-hound, the sexes of which differ more in size than those of
any other breed (though blood-hounds differ considerably), or than in
any wild canine species known to me. Accordingly, I applied to Mr.
Cupples, well known for his success with this breed, who has weighed
and measured many of his own dogs, and who has with great kindness
collected for me the following facts from various sources. Fine male
dogs, measured at the shoulder, range from 28 inches, which is low, to
33 or even 34 inches in height; and in weight from 80 pounds, which is
light, to 120 pounds, or even more. The females range in height from 23
to 27, or even to 28 inches; and in weight from 50 to 70, or even 80
pounds. (38. See also Richardson’s ‘Manual on the Dog,’ p. 59. Much
valuable information on the Scottish deer-hound is given by Mr.
McNeill, who first called attention to the inequality in size between
the sexes, in Scrope’s ‘Art of Deer-Stalking.’ I hope that Mr. Cupples
will keep to his intention of publishing a full account and history of
this famous breed.) Mr. Cupples concludes that from 95 to 100 pounds
for the male, and 70 for the female, would be a safe average; but there
is reason to believe that formerly both sexes attained a greater
weight. Mr. Cupples has weighed puppies when a fortnight old; in one
litter the average weight of four males exceeded that of two females by
six and a half ounces; in another litter the average weight of four
males exceeded that of one female by less than one ounce; the same
males when three weeks old, exceeded the female by seven and a half
ounces, and at the age of six weeks by nearly fourteen ounces. Mr.
Wright of Yeldersley House, in a letter to Mr. Cupples, says: “I have
taken notes on the sizes and weights of puppies of many litters, and as
far as my experience goes, dog-puppies as a rule differ very little
from bitches till they arrive at about five or six months old; and then
the dogs begin to increase, gaining upon the bitches both in weight and
size. At birth, and for several weeks afterwards, a bitch-puppy will
occasionally be larger than any of the dogs, but they are invariably
beaten by them later.” Mr. McNeill, of Colonsay, concludes that “the
males do not attain their full growth till over two years old, though
the females attain it sooner.” According to Mr. Cupples’ experience,
male dogs go on growing in stature till they are from twelve to
eighteen months old, and in weight till from eighteen to twenty-four
months old; whilst the females cease increasing in stature at the age
of from nine to fourteen or fifteen months, and in weight at the age of
from twelve to fifteen months. From these various statements it is
clear that the full difference in size between the male and female
Scotch deer-hound is not acquired until rather late in life. The males
almost exclusively are used for coursing, for, as Mr. McNeill informs
me, the females have not sufficient strength and weight to pull down a
full-grown deer. From the names used in old legends, it appears, as I
hear from Mr. Cupples, that, at a very ancient period, the males were
the most celebrated, the females being mentioned only as the mothers of
famous dogs. Hence, during many generations, it is the male which has
been chiefly tested for strength, size, speed, and courage, and the
best will have been bred from. As, however, the males do not attain
their full dimensions until rather late in life, they will have tended,
in accordance with the law often indicated, to transmit their
characters to their male offspring alone; and thus the great inequality
in size between the sexes of the Scotch deer-hound may probably be
accounted for.

[Fig. 65. Head of Common wild boar, in prime of life (from Brehm).]

The males of some few quadrupeds possess organs or parts developed
solely as a means of defence against the attacks of other males. Some
kinds of deer use, as we have seen, the upper branches of their horns
chiefly or exclusively for defending themselves; and the Oryx antelope,
as I am informed by Mr. Bartlett, fences most skilfully with his long,
gently curved horns; but these are likewise used as organs of offence.
The same observer remarks that rhinoceroses in fighting, parry each
other’s sidelong blows with their horns, which clatter loudly together,
as do the tusks of boars. Although wild boars fight desperately, they
seldom, according to Brehm, receive fatal wounds, as the blows fall on
each other’s tusks, or on the layer of gristly skin covering the
shoulder, called by the German hunters, the shield; and here we have a
part specially modified for defence. With boars in the prime of life
(Fig. 65) the tusks in the lower jaw are used for fighting, but they
become in old age, as Brehm states, so much curved inwards and upwards
over the snout that they can no longer be used in this way. They may,
however, still serve, and even more effectively, as a means of defence.
In compensation for the loss of the lower tusks as weapons of offence,
those in the upper jaw, which always project a little laterally,
increase in old age so much in length and curve so much upwards that
they can be used for attack. Nevertheless, an old boar is not so
dangerous to man as one at the age of six or seven years. (39. Brehm,
‘Thierleben,’ B. ii. ss. 729-732.)

[Fig. 66. Skull of the Babirusa Pig (from Wallace’s ‘Malay
Archipelago’).]

In the full-grown male Babirusa pig of Celebes (Fig. 66), the lower
tusks are formidable weapons, like those of the European boar in the
prime of life, whilst the upper tusks are so long and have their points
so much curled inwards, sometimes even touching the forehead, that they
are utterly useless as weapons of attack. They more nearly resemble
horns than teeth, and are so manifestly useless as teeth that the
animal was formerly supposed to rest his head by hooking them on to a
branch! Their convex surfaces, however, if the head were held a little
laterally, would serve as an excellent guard; and hence, perhaps, it is
that in old animals they “are generally broken off, as if by fighting.”
(40. See Mr. Wallace’s interesting account of this animal, ‘The Malay
Archipelago,’ 1869, vol. i. p. 435.) Here, then, we have the curious
case of the upper tusks of the Babirusa regularly assuming during the
prime of life a structure which apparently renders them fitted only for
defence; whilst in the European boar the lower tusks assume in a less
degree and only during old age nearly the same form, and then serve in
like manner solely for defence.

[Fig. 67. Head of female Aethiopian wart-hog, from ‘Proc. Zool. Soc.’
1869, shewing the same characters as the male, though on a reduced
scale. N.B. When the engraving was first made, I was under the
impression that it represented the male.]

In the wart-hog (see Phacochoerus aethiopicus, Fig. 67) the tusks in
the upper jaw of the male curve upwards during the prime of life, and
from being pointed serve as formidable weapons. The tusks in the lower
jaw are sharper than those in the upper, but from their shortness it
seems hardly possible that they can be used as weapons of attack. They
must, however, greatly strengthen those in the upper jaw, from being
ground so as to fit closely against their bases. Neither the upper nor
the lower tusks appear to have been specially modified to act as
guards, though no doubt they are to a certain extent used for this
purpose. But the wart-hog is not destitute of other special means of
protection, for it has, on each side of the face, beneath the eyes, a
rather stiff, yet flexible, cartilaginous, oblong pad (Fig. 67), which
projects two or three inches outwards; and it appeared to Mr. Bartlett
and myself, when viewing the living animal, that these pads, when
struck from beneath by the tusks of an opponent, would be turned
upwards, and would thus admirably protect the somewhat prominent eyes.
I may add, on the authority of Mr. Bartlett, that these boars when
fighting stand directly face to face.

Lastly, the African river-hog (Potomochoerus penicillatus) has a hard
cartilaginous knob on each side of the face beneath the eyes, which
answers to the flexible pad of the wart-hog; it has also two bony
prominences on the upper jaw above the nostrils. A boar of this species
in the Zoological Gardens recently broke into the cage of the wart-hog.
They fought all night long, and were found in the morning much
exhausted, but not seriously wounded. It is a significant fact, as
shewing the purposes of the above-described projections and
excrescences, that these were covered with blood, and were scored and
abraded in an extraordinary manner.

Although the males of so many members of the pig family are provided
with weapons, and as we have just seen with means of defence, these
weapons seem to have been acquired within a rather late geological
period. Dr. Forsyth Major specifies (41. ‘Atti della Soc. Italiana di
Sc. Nat.’ 1873, vol. xv. fasc. iv.) several miocene species, in none of
which do the tusks appear to have been largely developed in the males;
and Professor Rutimeyer was formerly struck with this same fact.

The mane of the lion forms a good defence against the attacks of rival
lions, the one danger to which he is liable; for the males, as Sir A.
Smith informs me, engage in terrible battles, and a young lion dares
not approach an old one. In 1857 a tiger at Bromwich broke into the
cage of a lion and a fearful scene ensued: “the lion’s mane saved his
neck and head from being much injured, but the tiger at last succeeded
in ripping up his belly, and in a few minutes he was dead.” (42. ‘The
Times,’ Nov. 10, 1857. In regard to the Canada lynx, see Audubon and
Bachman, ‘Quadrupeds of North America,’ 1846, p. 139.) The broad ruff
round the throat and chin of the Canadian lynx (Felis canadensis) is
much longer in the male than in the female; but whether it serves as a
defence I do not know. Male seals are well known to fight desperately
together, and the males of certain kinds (Otaria jubata) (43. Dr.
Murie, on Otaria, ‘Proc. Zoolog. Soc.’ 1869, p. 109. Mr. J.A. Allen, in
the paper above quoted (p. 75), doubts whether the hair, which is
longer on the neck in the male than in the female, deserves to be
called a mane.) have great manes, whilst the females have small ones or
none. The male baboon of the Cape of Good Hope (Cynocephalus porcarius)
has a much longer mane and larger canine teeth than the female; and the
mane probably serves as a protection, for, on asking the keepers in the
Zoological Gardens, without giving them any clue to my object, whether
any of the monkeys especially attacked each other by the nape of the
neck, I was answered that this was not the case, except with the above
baboon. In the Hamadryas baboon, Ehrenberg compares the mane of the
adult male to that of a young lion, whilst in the young of both sexes
and in the female the mane is almost absent.

It appeared to me probable that the immense woolly mane of the male
American bison, which reaches almost to the ground, and is much more
developed in the males than in the females, served as a protection to
them in their terrible battles; but an experienced hunter told Judge
Caton that he had never observed anything which favoured this belief.
The stallion has a thicker and fuller mane than the mare; and I have
made particular inquiries of two great trainers and breeders, who have
had charge of many entire horses, and am assured that they “invariably
endeavour to seize one another by the neck.” It does not, however,
follow from the foregoing statements, that when the hair on the neck
serves as a defence, that it was originally developed for this purpose,
though this is probable in some cases, as in that of the lion. I am
informed by Mr. McNeill that the long hairs on the throat of the stag
(Cervus elaphus) serve as a great protection to him when hunted, for
the dogs generally endeavour to seize him by the throat; but it is not
probable that these hairs were specially developed for this purpose;
otherwise the young and the females would have been equally protected.

CHOICE IN PAIRING BY EITHER SEX OF QUADRUPEDS.

Before describing in the next chapter, the differences between the
sexes in voice, odours emitted, and ornaments, it will be convenient
here to consider whether the sexes exert any choice in their unions.
Does the female prefer any particular male, either before or after the
males may have fought together for supremacy; or does the male, when
not a polygamist, select any particular female? The general impression
amongst breeders seems to be that the male accepts any female; and this
owing to his eagerness, is, in most cases, probably the truth. Whether
the female as a general rule indifferently accepts any male is much
more doubtful. In the fourteenth chapter, on Birds, a considerable body
of direct and indirect evidence was advanced, shewing that the female
selects her partner; and it would be a strange anomaly if female
quadrupeds, which stand higher in the scale and have higher mental
powers, did not generally, or at least often, exert some choice. The
female could in most cases escape, if wooed by a male that did not
please or excite her; and when pursued by several males, as commonly
occurs, she would often have the opportunity, whilst they were fighting
together, of escaping with some one male, or at least of temporarily
pairing with him. This latter contingency has often been observed in
Scotland with female red-deer, as I am informed by Sir Philip Egerton
and others. (44. Mr. Boner, in his excellent description of the habits
of the red-deer in Germany (‘Forest Creatures,’ 1861, p. 81) says,
“while the stag is defending his rights against one intruder, another
invades the sanctuary of his harem, and carries off trophy after
trophy.” Exactly the same thing occurs with seals; see Mr. J.A. Allen,
ibid. p. 100.)

It is scarcely possible that much should be known about female
quadrupeds in a state of nature making any choice in their marriage
unions. The following curious details on the courtship of one of the
eared seals (Callorhinus ursinus) are given (45. Mr. J.A. Allen in
‘Bull. Mus. Comp. Zoolog. of Cambridge, United States,’ vol. ii. No. 1,
p. 99.) on the authority of Capt. Bryant, who had ample opportunities
for observation. He says, “Many of the females on their arrival at the
island where they breed appear desirous of returning to some particular
male, and frequently climb the outlying rocks to overlook the
rookeries, calling out and listening as if for a familiar voice. Then
changing to another place they do the same again...As soon as a female
reaches the shore, the nearest male goes down to meet her, making
meanwhile a noise like the clucking of a hen to her chickens. He bows
to her and coaxes her until he gets between her and the water so that
she cannot escape him. Then his manner changes, and with a harsh growl
he drives her to a place in his harem. This continues until the lower
row of harems is nearly full. Then the males higher up select the time
when their more fortunate neighbours are off their guard to steal their
wives. This they do by taking them in their mouths and lifting them
over the heads of the other females, and carefully placing them in
their own harem, carrying them as cats do their kittens. Those still
higher up pursue the same method until the whole space is occupied.
Frequently a struggle ensues between two males for the possession of
the same female, and both seizing her at once pull her in two or
terribly lacerate her with their teeth. When the space is all filled,
the old male walks around complacently reviewing his family, scolding
those who crowd or disturb the others, and fiercely driving off all
intruders. This surveillance always keeps him actively occupied.”

As so little is known about the courtship of animals in a state of
nature, I have endeavoured to discover how far our domesticated
quadrupeds evince any choice in their unions. Dogs offer the best
opportunity for observation, as they are carefully attended to and well
understood. Many breeders have expressed a strong opinion on this head.
Thus, Mr. Mayhew remarks, “The females are able to bestow their
affections; and tender recollections are as potent over them as they
are known to be in other cases, where higher animals are concerned.
Bitches are not always prudent in their loves, but are apt to fling
themselves away on curs of low degree. If reared with a companion of
vulgar appearance, there often springs up between the pair a devotion
which no time can afterwards subdue. The passion, for such it really
is, becomes of a more than romantic endurance.” Mr. Mayhew, who
attended chiefly to the smaller breeds, is convinced that the females
are strongly attracted by males of a large size. (46. ‘Dogs: their
Management,’ by E. Mayhew, M.R.C.V.S., 2nd ed., 1864, pp. 187-192.) The
well-known veterinary Blaine states (47. Quoted by Alex. Walker, ‘On
Intermarriage,’ 1838, p. 276; see also p. 244.) that his own female pug
dog became so attached to a spaniel, and a female setter to a cur, that
in neither case would they pair with a dog of their own breed until
several weeks had elapsed. Two similar and trustworthy accounts have
been given me in regard to a female retriever and a spaniel, both of
which became enamoured with terrier-dogs.

Mr. Cupples informs me that he can personally vouch for the accuracy of
the following more remarkable case, in which a valuable and
wonderfully-intelligent female terrier loved a retriever belonging to a
neighbour to such a degree, that she had often to be dragged away from
him. After their permanent separation, although repeatedly shewing milk
in her teats, she would never acknowledge the courtship of any other
dog, and to the regret of her owner never bore puppies. Mr. Cupples
also states, that in 1868, a female deerhound in his kennel thrice
produced puppies, and on each occasion shewed a marked preference for
one of the largest and handsomest, but not the most eager, of four
deerhounds living with her, all in the prime of life. Mr. Cupples has
observed that the female generally favours a dog whom she has
associated with and knows; her shyness and timidity at first incline
her against a strange dog. The male, on the contrary, seems rather
inclined towards strange females. It appears to be rare when the male
refuses any particular female, but Mr. Wright, of Yeldersley House, a
great breeder of dogs, informs me that he has known some instances; he
cites the case of one of his own deerhounds, who would not take any
notice of a particular female mastiff, so that another deerhound had to
be employed. It would be superfluous to give, as I could, other
instances, and I will only add that Mr. Barr, who has carefully bred
many bloodhounds, states that in almost every instance particular
individuals of opposite sexes shew a decided preference for each other.
Finally, Mr. Cupples, after attending to this subject for another year,
has written to me, “I have had full confirmation of my former
statement, that dogs in breeding form decided preferences for each
other, being often influenced by size, bright colour, and individual
characters, as well as by the degree of their previous familiarity.”

In regard to horses, Mr. Blenkiron, the greatest breeder of race-horses
in the world, informs me that stallions are so frequently capricious in
their choice, rejecting one mare and without any apparent cause taking
to another, that various artifices have to be habitually used. The
famous Monarque, for instance, would never consciously look at the dam
of Gladiateur, and a trick had to be practised. We can partly see the
reason why valuable race-horse stallions, which are in such demand as
to be exhausted, should be so particular in their choice. Mr. Blenkiron
has never known a mare reject a horse; but this has occurred in Mr.
Wright’s stable, so that the mare had to be cheated. Prosper Lucas (48.
‘Traité de l’Héréd. Nat.’ tom. ii. 1850, p. 296.) quotes various
statements from French authorities, and remarks, “On voit des étalons
qui s’eprennent d’une jument, et negligent toutes les autres.” He
gives, on the authority of Baelen, similar facts in regard to bulls;
and Mr. H. Reeks assures me that a famous short-horn bull belonging to
his father “invariably refused to be matched with a black cow.”
Hoffberg, in describing the domesticated reindeer of Lapland says,
“Foeminae majores et fortiores mares prae caeteris admittunt, ad eos
confugiunt, a junioribus agitatae, qui hos in fugam conjiciunt.” (49.
‘Amoenitates Acad.’ vol. iv. 1788, p. 160.) A clergyman, who has bred
many pigs, asserts that sows often reject one boar and immediately
accept another.

From these facts there can be no doubt that, with most of our
domesticated quadrupeds, strong individual antipathies and preferences
are frequently exhibited, and much more commonly by the female than by
the male. This being the case, it is improbable that the unions of
quadrupeds in a state of nature should be left to mere chance. It is
much more probable that the females are allured or excited by
particular males, who possess certain characters in a higher degree
than other males; but what these characters are, we can seldom or never
discover with certainty.




CHAPTER XVIII.
SECONDARY SEXUAL CHARACTERS OF MAMMALS—continued.


Voice—Remarkable sexual peculiarities in seals—Odour—Development of the
hair—Colour of the hair and skin—Anomalous case of the female being
more ornamented than the male—Colour and ornaments due to sexual
selection—Colour acquired for the sake of protection—Colour, though
common to both sexes, often due to sexual selection—On the
disappearance of spots and stripes in adult quadrupeds—On the colours
and ornaments of the Quadrumana—Summary.

Quadrupeds use their voices for various purposes, as a signal of
danger, as a call from one member of a troop to another, or from the
mother to her lost offspring, or from the latter for protection to
their mother; but such uses need not here be considered. We are
concerned only with the difference between the voices of the sexes, for
instance between that of the lion and lioness, or of the bull and cow.
Almost all male animals use their voices much more during the
rutting-season than at any other time; and some, as the giraffe and
porcupine (1. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 585.), are
said to be completely mute excepting at this season. As the throats
(i.e. the larynx and thyroid bodies (2. Ibid. p. 595.)) of stags
periodically become enlarged at the beginning of the breeding-season,
it might be thought that their powerful voices must be somehow of high
importance to them; but this is very doubtful. From information given
to me by two experienced observers, Mr. McNeill and Sir P. Egerton, it
seems that young stags under three years old do not roar or bellow; and
that the old ones begin bellowing at the commencement of the
breeding-season, at first only occasionally and moderately, whilst they
restlessly wander about in search of the females. Their battles are
prefaced by loud and prolonged bellowing, but during the actual
conflict they are silent. Animals of all kinds which habitually use
their voices utter various noises under any strong emotion, as when
enraged and preparing to fight; but this may merely be the result of
nervous excitement, which leads to the spasmodic contraction of almost
all the muscles of the body, as when a man grinds his teeth and
clenches his fists in rage or agony. No doubt stags challenge each
other to mortal combat by bellowing; but those with the more powerful
voices, unless at the same time the stronger, better-armed, and more
courageous, would not gain any advantage over their rivals.

It is possible that the roaring of the lion may be of some service to
him by striking terror into his adversary; for when enraged he likewise
erects his mane and thus instinctively tries to make himself appear as
terrible as possible. But it can hardly be supposed that the bellowing
of the stag, even if it be of service to him in this way, can have been
important enough to have led to the periodical enlargement of the
throat. Some writers suggest that the bellowing serves as a call to the
female; but the experienced observers above quoted inform me that
female deer do not search for the male, though the males search eagerly
for the females, as indeed might be expected from what we know of the
habits of other male quadrupeds. The voice of the female, on the other
hand, quickly brings to her one or more stags (3. See, for instance,
Major W. Ross King (‘The Sportsman in Canada,’ 1866, pp. 53, 131) on
the habits of the moose and wild reindeer.), as is well known to the
hunters who in wild countries imitate her cry. If we could believe that
the male had the power to excite or allure the female by his voice, the
periodical enlargement of his vocal organs would be intelligible on the
principle of sexual selection, together with inheritance limited to the
same sex and season; but we have no evidence in favour of this view. As
the case stands, the loud voice of the stag during the breeding-season
does not seem to be of any special service to him, either during his
courtship or battles, or in any other way. But may we not believe that
the frequent use of the voice, under the strong excitement of love,
jealousy, and rage, continued during many generations, may at last have
produced an inherited effect on the vocal organs of the stag, as well
as of other male animals? This appears to me, in our present state of
knowledge, the most probable view.

The voice of the adult male gorilla is tremendous, and he is furnished
with a laryngeal sack, as is the adult male orang. (4. Owen ‘Anatomy of
Vertebrates,’ vol. iii. p. 600.) The gibbons rank among the noisiest of
monkeys, and the Sumatra species (Hylobates syndactylus) is also
furnished with an air sack; but Mr. Blyth, who has had opportunities
for observation, does not believe that the male is noisier than the
female. Hence, these latter monkeys probably use their voices as a
mutual call; and this is certainly the case with some quadrupeds, for
instance the beaver. (5. Mr. Green, in ‘Journal of Linnean Society,’
vol. x. ‘Zoology,’ 1869, note 362.) Another gibbon, the H. agilis, is
remarkable, from having the power of giving a complete and correct
octave of musical notes (6. C.L. Martin, ‘General Introduction to the
Natural History of Mamm. Animals,’ 1841, p. 431.), which we may
reasonably suspect serves as a sexual charm; but I shall have to recur
to this subject in the next chapter. The vocal organs of the American
Mycetes caraya are one-third larger in the male than in the female, and
are wonderfully powerful. These monkeys in warm weather make the
forests resound at morning and evening with their overwhelming voices.
The males begin the dreadful concert, and often continue it during many
hours, the females sometimes joining in with their less powerful
voices. An excellent observer, Rengger (7. ‘Naturgeschichte der
Säugethiere von Paraguay,’ 1830, ss. 15, 21.), could not perceive that
they were excited to begin by any special cause; he thinks that, like
many birds, they delight in their own music, and try to excel each
other. Whether most of the foregoing monkeys have acquired their
powerful voices in order to beat their rivals and charm the females—or
whether the vocal organs have been strengthened and enlarged through
the inherited effects of long-continued use without any particular good
being thus gained—I will not pretend to say; but the former view, at
least in the case of the Hylobates agilis, seems the most probable.

I may here mention two very curious sexual peculiarities occurring in
seals, because they have been supposed by some writers to affect the
voice. The nose of the male sea-elephant (Macrorhinus proboscideus)
becomes greatly elongated during the breeding-season, and can then be
erected. In this state it is sometimes a foot in length. The female is
not thus provided at any period of life. The male makes a wild, hoarse,
gurgling noise, which is audible at a great distance and is believed to
be strengthened by the proboscis; the voice of the female being
different. Lesson compares the erection of the proboscis, with the
swelling of the wattles of male gallinaceous birds whilst courting the
females. In another allied kind of seal, the bladder-nose (Cystophora
cristata), the head is covered by a great hood or bladder. This is
supported by the septum of the nose, which is produced far backwards
and rises into an internal crest seven inches in height. The hood is
clothed with short hair, and is muscular; can be inflated until it more
than equals the whole head in size! The males when rutting, fight
furiously on the ice, and their roaring “is said to be sometimes so
loud as to be heard four miles off.” When attacked they likewise roar
or bellow; and whenever irritated the bladder is inflated and quivers.
Some naturalists believe that the voice is thus strengthened, but
various other uses have been assigned to this extraordinary structure.
Mr. R. Brown thinks that it serves as a protection against accidents of
all kinds; but this is not probable, for, as I am assured by Mr. Lamont
who killed 600 of these animals, the hood is rudimentary in the
females, and it is not developed in the males during youth. (8. On the
sea-elephant, see an article by Lesson, in ‘Dict. Class. Hist. Nat.’
tom. xiii. p. 418. For the Cystophora, or Stemmatopus, see Dr. Dekay,
‘Annals of Lyceum of Nat. Hist.’ New York, vol. i. 1824, p. 94. Pennant
has also collected information from the sealers on this animal. The
fullest account is given by Mr. Brown, in ‘Proc. Zoolog. Soc.’ 1868, p.
435.)

ODOUR.

With some animals, as with the notorious skunk of America, the
overwhelming odour which they emit appears to serve exclusively as a
defence. With shrew-mice (Sorex) both sexes possess abdominal
scent-glands, and there can be little doubt, from the rejection of
their bodies by birds and beasts of prey, that the odour is protective;
nevertheless, the glands become enlarged in the males during the
breeding-season. In many other quadrupeds the glands are of the same
size in both sexes (9. As with the castoreum of the beaver, see Mr.
L.H. Morgan’s most interesting work, ‘The American Beaver,’ 1868, p.
300. Pallas (‘Spic. Zoolog.’ fasc. viii. 1779, p. 23) has well
discussed the odoriferous glands of mammals. Owen (‘Anat. of
Vertebrates,’ vol. iii. p. 634) also gives an account of these glands,
including those of the elephant, and (p. 763) those of shrew-mice. On
bats, Mr. Dobson in ‘Proceedings of the Zoological Society’ 1873, p.
241.), but their uses are not known. In other species the glands are
confined to the males, or are more developed than in the females; and
they almost always become more active during the rutting-season. At
this period the glands on the sides of the face of the male elephant
enlarge, and emit a secretion having a strong musky odour. The males,
and rarely the females, of many kinds of bats have glands and
protrudable sacks situated in various parts; and it is believed that
these are odoriferous.

The rank effluvium of the male goat is well known, and that of certain
male deer is wonderfully strong and persistent. On the banks of the
Plata I perceived the air tainted with the odour of the male Cervus
campestris, at half a mile to leeward of a herd; and a silk
handkerchief, in which I carried home a skin, though often used and
washed, retained, when first unfolded, traces of the odour for one year
and seven months. This animal does not emit its strong odour until more
than a year old, and if castrated whilst young never emits it. (10.
Rengger, ‘Naturgeschichte der Säugethiere von Paraguay,’ 1830, s. 355.
This observer also gives some curious particulars in regard to the
odour.) Besides the general odour, permeating the whole body of certain
ruminants (for instance, Bos moschatus) in the breeding-season, many
deer, antelopes, sheep, and goats possess odoriferous glands in various
situations, more especially on their faces. The so-called tear-sacks,
or suborbital pits, come under this head. These glands secrete a
semi-fluid fetid matter which is sometimes so copious as to stain the
whole face, as I have myself seen in an antelope. They are “usually
larger in the male than in the female, and their development is checked
by castration.” (11. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 632.
See also Dr. Murie’s observations on those glands in the ‘Proc. Zoolog.
Soc.’ 1870, p. 340. Desmarest, ‘On the Antilope subgutturosa,
‘Mammalogie,’ 1820, p. 455.) According to Desmarest they are altogether
absent in the female of Antilope subgutturosa. Hence, there can be no
doubt that they stand in close relation with the reproductive
functions. They are also sometimes present, and sometimes absent, in
nearly allied forms. In the adult male musk-deer (Moschus moschiferus),
a naked space round the tail is bedewed with an odoriferous fluid,
whilst in the adult female, and in the male until two years old, this
space is covered with hair and is not odoriferous. The proper musk-sack
of this deer is from its position necessarily confined to the male, and
forms an additional scent-organ. It is a singular fact that the matter
secreted by this latter gland, does not, according to Pallas, change in
consistence, or increase in quantity, during the rutting-season;
nevertheless this naturalist admits that its presence is in some way
connected with the act of reproduction. He gives, however, only a
conjectural and unsatisfactory explanation of its use. (12. Pallas,
‘Spicilegia Zoolog.’ fasc. xiii. 1799, p. 24; Desmoulins, ‘Dict. Class.
d’Hist. Nat.’ tom. iii. p. 586.)

In most cases, when only the male emits a strong odour during the
breeding-season, it probably serves to excite or allure the female. We
must not judge on this head by our own taste, for it is well known that
rats are enticed by certain essential oils, and cats by valerian,
substances far from agreeable to us; and that dogs, though they will
not eat carrion, sniff and roll on it. From the reasons given when
discussing the voice of the stag, we may reject the idea that the odour
serves to bring the females from a distance to the males. Active and
long-continued use cannot here have come into play, as in the case of
the vocal organs. The odour emitted must be of considerable importance
to the male, inasmuch as large and complex glands, furnished with
muscles for everting the sack, and for closing or opening the orifice,
have in some cases been developed. The development of these organs is
intelligible through sexual selection, if the most odoriferous males
are the most successful in winning the females, and in leaving
offspring to inherit their gradually perfected glands and odours.

DEVELOPMENT OF THE HAIR.

We have seen that male quadrupeds often have the hair on their necks
and shoulders much more developed than the females; and many additional
instances could be given. This sometimes serves as a defence to the
male during his battles; but whether the hair in most cases has been
specially developed for this purpose, is very doubtful. We may feel
almost certain that this is not the case, when only a thin and narrow
crest runs along the back; for a crest of this kind would afford
scarcely any protection, and the ridge of the back is not a place
likely to be injured; nevertheless such crests are sometimes confined
to the males, or are much more developed in them than in the females.
Two antelopes, the Tragelaphus scriptus (13. Dr. Gray, ‘Gleanings from
the Menagerie at Knowsley,’ pl. 28.) (Fig. 70) and Portax picta may be
given as instances. When stags, and the males of the wild goat, are
enraged or terrified, these crests stand erect (14. Judge Caton on the
Wapiti, ‘Transact. Ottawa Acad. Nat. Sciences,’ 1868, pp. 36, 40;
Blyth, ‘Land and Water,’ on Capra aegagrus 1867, p. 37.); but it cannot
be supposed that they have been developed merely for the sake of
exciting fear in their enemies. One of the above-named antelopes, the
Portax picta, has a large well-defined brush of black hair on the
throat, and this is much larger in the male than in the female. In the
Ammotragus tragelaphus of North Africa, a member of the sheep-family,
the fore-legs are almost concealed by an extraordinary growth of hair,
which depends from the neck and upper halves of the legs; but Mr.
Bartlett does not believe that this mantle is of the least use to the
male, in whom it is much more developed than in the female.

[Fig. 68. Pithecia satanas, male (from Brehm).]

Male quadrupeds of many kinds differ from the females in having more
hair, or hair of a different character, on certain parts of their
faces. Thus the bull alone has curled hair on the forehead. (15.
Hunter’s ‘Essays and Observations,’ edited by Owen, 1861. vol. i. p.
236.) In three closely-allied sub-genera of the goat family, only the
males possess beards, sometimes of large size; in two other sub-genera
both sexes have a beard, but it disappears in some of the domestic
breeds of the common goat; and neither sex of the Hemitragus has a
beard. In the ibex the beard is not developed during the summer, and is
so small at other times that it may be called rudimentary. (16. See Dr.
Gray’s ‘Catalogue of Mammalia in the British Museum,’ part iii. 1852,
p. 144.) With some monkeys the beard is confined to the male, as in the
orang; or is much larger in the male than in the female, as in the
Mycetes caraya and Pithecia satanas (Fig. 68). So it is with the
whiskers of some species of Macacus (17. Rengger, ‘Säugethiere,’ etc.,
s. 14; Desmarest, ‘Mammalogie,’ p. 86.), and, as we have seen, with the
manes of some species of baboons. But with most kinds of monkeys the
various tufts of hair about the face and head are alike in both sexes.

The males of various members of the ox family (Bovidae), and of certain
antelopes, are furnished with a dewlap, or great fold of skin on the
neck, which is much less developed in the female.

Now, what must we conclude with respect to such sexual differences as
these? No one will pretend that the beards of certain male goats, or
the dewlaps of the bull, or the crests of hair along the backs of
certain male antelopes, are of any use to them in their ordinary
habits. It is possible that the immense beard of the male Pithecia, and
the large beard of the male orang, may protect their throats when
fighting; for the keepers in the Zoological Gardens inform me that many
monkeys attack each other by the throat; but it is not probable that
the beard has been developed for a distinct purpose from that served by
the whiskers, moustache, and other tufts of hair on the face; and no
one will suppose that these are useful as a protection. Must we
attribute all these appendages of hair or skin to mere purposeless
variability in the male? It cannot be denied that this is possible; for
in many domesticated quadrupeds, certain characters, apparently not
derived through reversion from any wild parent form, are confined to
the males, or are more developed in them than in the females—for
instance, the hump on the male zebu-cattle of India, the tail of
fat-tailed rams, the arched outline of the forehead in the males of
several breeds of sheep, and lastly, the mane, the long hairs on the
hind legs, and the dewlap of the male of the Berbura goat. (18. See the
chapters on these several animals in vol. i. of my ‘Variation of
Animals under Domestication;’ also vol. ii. p. 73; also chap. xx. on
the practice of selection by semi-civilised people. For the Berbura
goat, see Dr. Gray, ‘Catalogue,’ ibid. p. 157.) The mane, which occurs
only in the rams of an African breed of sheep, is a true secondary
sexual character, for, as I hear from Mr. Winwood Reade, it is not
developed if the animal be castrated. Although we ought to be extremely
cautious, as shewn in my work on ‘Variation under Domestication,’ in
concluding that any character, even with animals kept by semi-civilised
people, has not been subjected to selection by man, and thus augmented,
yet in the cases just specified this is improbable; more especially as
the characters are confined to the males, or are more strongly
developed in them than in the females. If it were positively known that
the above African ram is a descendant of the same primitive stock as
the other breeds of sheep, and if the Berbura male-goat with his mane,
dewlap, etc., is descended from the same stock as other goats, then,
assuming that selection has not been applied to these characters, they
must be due to simple variability, together with sexually-limited
inheritance.

Hence it appears reasonable to extend this same view to all analogous
cases with animals in a state of nature. Nevertheless I cannot persuade
myself that it generally holds good, as in the case of the
extraordinary development of hair on the throat and fore-legs of the
male Ammotragus, or in that of the immense beard of the male Pithecia.
Such study as I have been able to give to nature makes me believe that
parts or organs which are highly developed, were acquired at some
period for a special purpose. With those antelopes in which the adult
male is more strongly-coloured than the female, and with those monkeys
in which the hair on the face is elegantly arranged and coloured in a
diversified manner, it seems probable that the crests and tufts of hair
were gained as ornaments; and this I know is the opinion of some
naturalists. If this be correct, there can be little doubt that they
were gained or at least modified through sexual selection; but how far
the same view may be extended to other mammals is doubtful.

COLOUR OF THE HAIR AND OF THE NAKED SKIN.

I will first give briefly all the cases known to me of male quadrupeds
differing in colour from the females. With Marsupials, as I am informed
by Mr. Gould, the sexes rarely differ in this respect; but the great
red kangaroo offers a striking exception, “delicate blue being the
prevailing tint in those parts of the female which in the male are
red.” (19. Osphranter rufus, Gould, ‘Mammals of Australia,’ 1863, vol.
ii. On the Didelphis, Desmarest, ‘Mammalogie,’ p. 256.) In the
Didelphis opossum of Cayenne the female is said to be a little more red
than the male. Of the Rodents, Dr. Gray remarks: “African squirrels,
especially those found in the tropical regions, have the fur much
brighter and more vivid at some seasons of the year than at others, and
the fur of the male is generally brighter than that of the female.”
(20. ‘Annals and Magazine of Natural History,’ Nov. 1867, p. 325. On
the Mus minutus, Desmarest, ‘Mammalogie,’ p. 304.) Dr. Gray informs me
that he specified the African squirrels, because, from their unusually
bright colours, they best exhibit this difference. The female of the
Mus minutus of Russia is of a paler and dirtier tint than the male. In
a large number of bats the fur of the male is lighter than in the
female. (21. J.A. Allen, in ‘Bulletin of Mus. Comp. Zoolog. of
Cambridge, United States,’ 1869, p. 207. Mr. Dobson on sexual
characters in the Chiroptera, ‘Proceedings of the Zoological Society,’
1873, p. 241. Dr. Gray on Sloths, ibid. 1871, p. 436.) Mr. Dobson also
remarks, with respect to these animals: “Differences, depending partly
or entirely on the possession by the male of fur of a much more
brilliant hue, or distinguished by different markings or by the greater
length of certain portions, are met only, to any appreciable extent, in
the frugivorous bats in which the sense of sight is well developed.”
This last remark deserves attention, as bearing on the question whether
bright colours are serviceable to male animals from being ornamental.
In one genus of sloths, it is now established, as Dr. Gray states,
“that the males are ornamented differently from the females—that is to
say, that they have a patch of soft short hair between the shoulders,
which is generally of a more or less orange colour, and in one species
pure white. The females, on the contrary, are destitute of this mark.”

The terrestrial Carnivora and Insectivora rarely exhibit sexual
differences of any kind, including colour. The ocelot (Felis pardalis),
however, is exceptional, for the colours of the female, compared with
those of the male, are “moins apparentes, le fauve, étant plus terne,
le blanc moins pur, les raies ayant moins de largeur et les taches
moins de diamètre.” (22. Desmarest, ‘Mammalogie,’ 1820, p. 220. On
Felis mitis, Rengger, ibid. s. 194.) The sexes of the allied Felis
mitis also differ, but in a less degree; the general hues of the female
being rather paler than in the male, with the spots less black. The
marine Carnivora or seals, on the other hand, sometimes differ
considerably in colour, and they present, as we have already seen,
other remarkable sexual differences. Thus the male of the Otaria
nigrescens of the southern hemisphere is of a rich brown shade above;
whilst the female, who acquires her adult tints earlier in life than
the male, is dark-grey above, the young of both sexes being of a deep
chocolate colour. The male of the northern Phoca groenlandica is tawny
grey, with a curious saddle-shaped dark mark on the back; the female is
much smaller, and has a very different appearance, being “dull white or
yellowish straw-colour, with a tawny hue on the back”; the young at
first are pure white, and can “hardly be distinguished among the icy
hummocks and snow, their colour thus acting as a protection.” (23. Dr.
Murie on the Otaria, ‘Proceedings Zoological Society,’ 1869, p. 108.
Mr. R. Brown on the P. groenlandica, ibid. 1868, p. 417. See also on
the colours of seals, Desmarest, ibid. pp. 243, 249.)

With Ruminants sexual differences of colour occur more commonly than in
any other order. A difference of this kind is general in the
Strepsicerene antelopes; thus the male nilghau (Portax picta) is
bluish-grey and much darker than the female, with the square white
patch on the throat, the white marks on the fetlocks, and the black
spots on the ears all much more distinct. We have seen that in this
species the crests and tufts of hair are likewise more developed in the
male than in the hornless female. I am informed by Mr. Blyth that the
male, without shedding his hair, periodically becomes darker during the
breeding-season. Young males cannot be distinguished from young females
until about twelve months old; and if the male is emasculated before
this period, he never, according to the same authority, changes colour.
The importance of this latter fact, as evidence that the colouring of
the Portax is of sexual origin, becomes obvious, when we hear (24.
Judge Caton, in ‘Transactions of the Ottawa Academy of Natural
Sciences,’ 1868, p. 4.) that neither the red summer-coat nor the blue
winter-coat of the Virginian deer is at all affected by emasculation.
With most or all of the highly-ornamented species of Tragelaphus the
males are darker than the hornless females, and their crests of hair
are more fully developed. In the male of that magnificent antelope, the
Derbyan eland, the body is redder, the whole neck much blacker, and the
white band which separates these colours broader than in the female. In
the Cape eland, also, the male is slightly darker than the female. (25.
Dr. Gray, ‘Cat. of Mamm. in Brit. Mus.’ part iii. 1852, pp. 134-142;
also Dr. Gray, ‘Gleanings from the Menagerie of Knowsley,’ in which
there is a splendid drawing of the Oreas derbianus: see the text on
Tragelaphus. For the Cape eland (Oreas canna), see Andrew Smith,
‘Zoology of S. Africa,’ pl. 41 and 42. There are also many of these
Antelopes in the Zoological Gardens.)

In the Indian black-buck (A. bezoartica), which belongs to another
tribe of antelopes, the male is very dark, almost black; whilst the
hornless female is fawn-coloured. We meet in this species, as Mr. Blyth
informs me, with an exactly similar series of facts, as in the Portax
picta, namely, in the male periodically changing colour during the
breeding-season, in the effects of emasculation on this change, and in
the young of both sexes being indistinguishable from each other. In the
Antilope niger the male is black, the female, as well as the young of
both sexes, being brown; in A. sing-sing the male is much brighter
coloured than the hornless female, and his chest and belly are blacker;
in the male A. caama, the marks and lines which occur on various parts
of the body are black, instead of brown as in the female; in the
brindled gnu (A. gorgon) “the colours of the male are nearly the same
as those of the female, only deeper and of a brighter hue.” (26. On the
Ant. niger, see ‘Proc. Zool. Soc.’ 1850, p. 133. With respect to an
allied species, in which there is an equal sexual difference in colour,
see Sir S. Baker, ‘The Albert Nyanza,’ 1866, vol. ii. p. 627. For the
A. sing-sing, Gray, ‘Cat. B. Mus.’ p. 100. Desmarest, ‘Mammalogie,’ p.
468, on the A. caama. Andrew Smith, ‘Zoology of S. Africa,’ on the
Gnu.) Other analogous cases could be added.

The Banteng bull (Bos sondaicus) of the Malayan Archipelago is almost
black, with white legs and buttocks; the cow is of a bright dun, as are
the young males until about the age of three years, when they rapidly
change colour. The emasculated bull reverts to the colour of the
female. The female Kemas goat is paler, and both it and the female
Capra aegagrus are said to be more uniformly tinted than their males.
Deer rarely present any sexual differences in colour. Judge Caton,
however, informs me that in the males of the wapiti deer (Cervus
canadensis) the neck, belly, and legs are much darker than in the
female; but during the winter the darker tints gradually fade away and
disappear. I may here mention that Judge Caton has in his park three
races of the Virginian deer, which differ slightly in colour, but the
differences are almost exclusively confined to the blue winter or
breeding-coat; so that this case may be compared with those given in a
previous chapter of closely-allied or representative species of birds,
which differ from each other only in their breeding plumage. (27.
‘Ottawa Academy of Sciences,’ May 21, 1868, pp. 3, 5.) The females of
Cervus paludosus of S. America, as well as the young of both sexes, do
not possess the black stripes on the nose and the blackish-brown line
on the breast, which are characteristic of the adult males. (28. S.
Muller, on the Banteng, ‘Zoog. Indischen Archipel.’ 1839-1844, tab. 35;
see also Raffles, as quoted by Mr. Blyth, in ‘Land and Water,’ 1867, p.
476. On goats, Dr. Gray, ‘Catalogue of the British Museum,’ p. 146;
Desmarest, ‘Mammalogie,’ p. 482. On the Cervus paludosus, Rengger,
ibid. s. 345.) Lastly, as I am informed by Mr. Blyth, the mature male
of the beautifully coloured and spotted axis deer is considerably
darker than the female: and this hue the castrated male never acquires.

The last Order which we need consider is that of the Primates. The male
of the Lemur macaco is generally coal-black, whilst the female is
brown. (29. Sclater, ‘Proc. Zool. Soc.’ 1866, p. i. The same fact has
also been fully ascertained by MM. Pollen and van Dam. See, also, Dr.
Gray in ‘Annals and Magazine of Natural History,’ May 1871, p. 340.) Of
the Quadrumana of the New World, the females and young of Mycetes
caraya are greyish-yellow and like each other; in the second year the
young male becomes reddish-brown; in the third, black, excepting the
stomach, which, however, becomes quite black in the fourth or fifth
year. There is also a strongly-marked difference in colour between the
sexes of Mycetes seniculus and Cebus capucinus; the young of the
former, and I believe of the latter species, resembling the females.
With Pithecia leucocephala the young likewise resemble the females,
which are brownish-black above and light rusty-red beneath, the adult
males being black. The ruff of hair round the face of Ateles marginatus
is tinted yellow in the male and white in the female. Turning to the
Old World, the males of Hylobates hoolock are always black, with the
exception of a white band over the brows; the females vary from
whity-brown to a dark tint mixed with black, but are never wholly
black. (30. On Mycetes, Rengger, ibid. s. 14; and Brehm, ‘Thierleben,’
B. i. s. 96, 107. On Ateles Desmarest, ‘Mammalogie,’ p. 75. On
Hylobates, Blyth, ‘Land and Water,’ 1867, p. 135. On the Semnopithecus,
S. Muller, ‘Zoog. Indischen Archipel.’ tab. x.) In the beautiful
Cercopithecus diana, the head of the adult male is of an intense black,
whilst that of the female is dark grey; in the former the fur between
the thighs is of an elegant fawn-colour, in the latter it is paler. In
the beautiful and curious moustache monkey (Cercopithecus cephus) the
only difference between the sexes is that the tail of the male is
chestnut and that of the female grey; but Mr. Bartlett informs me that
all the hues become more pronounced in the male when adult, whilst in
the female they remain as they were during youth. According to the
coloured figures given by Solomon Muller, the male of Semnopithecus
chrysomelas is nearly black, the female being pale brown. In the
Cercopithecus cynosurus and griseo-viridis one part of the body, which
is confined to the male sex, is of the most brilliant blue or green,
and contrasts strikingly with the naked skin on the hinder part of the
body, which is vivid red.

[Fig. 69. Head of male Mandrill (from Gervais, ‘Hist. Nat. des
Mammifères’).]

Lastly, in the baboon family, the adult male of Cynocephalus hamadryas
differs from the female not only by his immense mane, but slightly in
the colour of the hair and of the naked callosities. In the drill (C.
leucophaeus) the females and young are much paler-coloured, with less
green, than the adult males. No other member in the whole class of
mammals is coloured in so extraordinary a manner as the adult male
mandrill (C. mormon). The face at this age becomes of a fine blue, with
the ridge and tip of the nose of the most brilliant red. According to
some authors, the face is also marked with whitish stripes, and is
shaded in parts with black, but the colours appear to be variable. On
the forehead there is a crest of hair, and on the chin a yellow beard.
“Toutes les parties supérieures de leurs cuisses et le grand espace nu
de leurs fesses sont également colorés du rouge le plus vif, avec un
mélange de bleu qui ne manque reellement pas d’élégance.” (31. Gervais,
‘Hist. Nat. des Mammifères,’ 1854, p. 103. Figures are given of the
skull of the male. Also Desmarest, ‘Mammalogie,’ p. 70. Geoffroy
St.-Hilaire and F. Cuvier, ‘Hist. Nat. des Mammifères,’ 1824, tom. i.)
When the animal is excited all the naked parts become much more vividly
tinted. Several authors have used the strongest expressions in
describing these resplendent colours, which they compare with those of
the most brilliant birds. Another remarkable peculiarity is that when
the great canine teeth are fully developed, immense protuberances of
bone are formed on each cheek, which are deeply furrowed
longitudinally, and the naked skin over them is brilliantly-coloured,
as just-described. (Fig. 69.) In the adult females and in the young of
both sexes these protuberances are scarcely perceptible; and the naked
parts are much less bright coloured, the face being almost black,
tinged with blue. In the adult female, however, the nose at certain
regular intervals of time becomes tinted with red.

In all the cases hitherto given the male is more strongly or brighter
coloured than the female, and differs from the young of both sexes. But
as with some few birds it is the female which is brighter coloured than
the male, so with the Rhesus monkey (Macacus rhesus), the female has a
large surface of naked skin round the tail, of a brilliant carmine red,
which, as I was assured by the keepers in the Zoological Gardens,
periodically becomes even yet more vivid, and her face also is pale
red. On the other hand, in the adult male and in the young of both
sexes (as I saw in the Gardens), neither the naked skin at the
posterior end of the body, nor the face, shew a trace of red. It
appears, however, from some published accounts, that the male does
occasionally, or during certain seasons, exhibit some traces of the
red. Although he is thus less ornamented than the female, yet in the
larger size of his body, larger canine teeth, more developed whiskers,
more prominent superciliary ridges, he follows the common rule of the
male excelling the female.

I have now given all the cases known to me of a difference in colour
between the sexes of mammals. Some of these may be the result of
variations confined to one sex and transmitted to the same sex, without
any good being gained, and therefore without the aid of selection. We
have instances of this with our domesticated animals, as in the males
of certain cats being rusty-red, whilst the females are tortoise-shell
coloured. Analogous cases occur in nature: Mr. Bartlett has seen many
black varieties of the jaguar, leopard, vulpine phalanger, and wombat;
and he is certain that all, or nearly all these animals, were males. On
the other hand, with wolves, foxes, and apparently American squirrels,
both sexes are occasionally born black. Hence it is quite possible that
with some mammals a difference in colour between the sexes, especially
when this is congenital, may simply be the result, without the aid of
selection, of the occurrence of one or more variations, which from the
first were sexually limited in their transmission. Nevertheless it is
improbable that the diversified, vivid, and contrasted colours of
certain quadrupeds, for instance, of the above monkeys and antelopes,
can thus be accounted for. We should bear in mind that these colours do
not appear in the male at birth, but only at or near maturity; and that
unlike ordinary variations, they are lost if the male be emasculated.
It is on the whole probable that the strongly-marked colours and other
ornamental characters of male quadrupeds are beneficial to them in
their rivalry with other males, and have consequently been acquired
through sexual selection. This view is strengthened by the differences
in colour between the sexes occurring almost exclusively, as may be
collected from the previous details, in those groups and sub-groups of
mammals which present other and strongly-marked secondary sexual
characters; these being likewise due to sexual selection.

Quadrupeds manifestly take notice of colour. Sir S. Baker repeatedly
observed that the African elephant and rhinoceros attacked white or
grey horses with special fury. I have elsewhere shewn (32. The
‘Variation of Animals and Plants under Domestication,’ 1868, vol. ii.
pp. 102, 103.) that half-wild horses apparently prefer to pair with
those of the same colour, and that herds of fallow-deer of different
colours, though living together, have long kept distinct. It is a more
significant fact that a female zebra would not admit the addresses of a
male ass until he was painted so as to resemble a zebra, and then, as
John Hunter remarks, “she received him very readily. In this curious
fact, we have instinct excited by mere colour, which had so strong an
effect as to get the better of everything else. But the male did not
require this, the female being an animal somewhat similar to himself,
was sufficient to rouse him.” (33. ‘Essays and Observations,’ by J.
Hunter, edited by Owen, 1861, vol. i. p. 194.)

In an earlier chapter we have seen that the mental powers of the higher
animals do not differ in kind, though greatly in degree, from the
corresponding powers of man, especially of the lower and barbarous
races; and it would appear that even their taste for the beautiful is
not widely different from that of the Quadrumana. As the negro of
Africa raises the flesh on his face into parallel ridges “or
cicatrices, high above the natural surface, which unsightly deformities
are considered great personal attractions” (34. Sir S. Baker, ‘The Nile
Tributaries of Abyssinia,’ 1867.);—as negroes and savages in many parts
of the world paint their faces with red, blue, white, or black bars,—so
the male mandrill of Africa appears to have acquired his
deeply-furrowed and gaudily-coloured face from having been thus
rendered attractive to the female. No doubt it is to us a most
grotesque notion that the posterior end of the body should be coloured
for the sake of ornament even more brilliantly than the face; but this
is not more strange than that the tails of many birds should be
especially decorated.

With mammals we do not at present possess any evidence that the males
take pains to display their charms before the female; and the elaborate
manner in which this is performed by male birds and other animals is
the strongest argument in favour of the belief that the females admire,
or are excited by, the ornaments and colours displayed before them.
There is, however, a striking parallelism between mammals and birds in
all their secondary sexual characters, namely in their weapons for
fighting with rival males, in their ornamental appendages, and in their
colours. In both classes, when the male differs from the female, the
young of both sexes almost always resemble each other, and in a large
majority of cases resemble the adult female. In both classes the male
assumes the characters proper to his sex shortly before the age of
reproduction; and if emasculated at an early period, loses them. In
both classes the change of colour is sometimes seasonal, and the tints
of the naked parts sometimes become more vivid during the act of
courtship. In both classes the male is almost always more vividly or
strongly coloured than the female, and is ornamented with larger crests
of hair or feathers, or other such appendages. In a few exceptional
cases the female in both classes is more highly ornamented than the
male. With many mammals, and at least in the case of one bird, the male
is more odoriferous than the female. In both classes the voice of the
male is more powerful than that of the female. Considering this
parallelism, there can be little doubt that the same cause, whatever it
may be, has acted on mammals and birds; and the result, as far as
ornamental characters are concerned, may be attributed, as it appears
to me, to the long-continued preference of the individuals of one sex
for certain individuals of the opposite sex, combined with their
success in leaving a larger number of offspring to inherit their
superior attractions.

EQUAL TRANSMISSION OF ORNAMENTAL CHARACTERS TO BOTH SEXES.

With many birds, ornaments, which analogy leads us to believe were
primarily acquired by the males, have been transmitted equally, or
almost equally, to both sexes; and we may now enquire how far this view
applies to mammals. With a considerable number of species, especially
of the smaller kinds, both sexes have been coloured, independently of
sexual selection, for the sake of protection; but not, as far as I can
judge, in so many cases, nor in so striking a manner, as in most of the
lower classes. Audubon remarks that he often mistook the musk-rat (35.
Fiber zibethicus, Audubon and Bachman, ‘The Quadrupeds of North
America,’ 1846, p. 109.), whilst sitting on the banks of a muddy
stream, for a clod of earth, so complete was the resemblance. The hare
on her form is a familiar instance of concealment through colour; yet
this principle partly fails in a closely-allied species, the rabbit,
for when running to its burrow, it is made conspicuous to the
sportsman, and no doubt to all beasts of prey, by its upturned white
tail. No one doubts that the quadrupeds inhabiting snow-clad regions
have been rendered white to protect them from their enemies, or to
favour their stealing on their prey. In regions where snow never lies
for long, a white coat would be injurious; consequently, species of
this colour are extremely rare in the hotter parts of the world. It
deserves notice that many quadrupeds inhabiting moderately cold
regions, although they do not assume a white winter dress, become paler
during this season; and this apparently is the direct result of the
conditions to which they have long been exposed. Pallas (36. ‘Novae
species Quadrupedum e Glirium ordine,’ 1778, p. 7. What I have called
the roe is the Capreolus sibiricus subecaudatus of Pallas.) states that
in Siberia a change of this nature occurs with the wolf, two species of
Mustela, the domestic horse, the Equus hemionus, the domestic cow, two
species of antelopes, the musk-deer, the roe, elk, and reindeer. The
roe, for instance, has a red summer and a greyish-white winter coat;
and the latter may perhaps serve as a protection to the animal whilst
wandering through the leafless thickets, sprinkled with snow and
hoar-frost. If the above-named animals were gradually to extend their
range into regions perpetually covered with snow, their pale
winter-coats would probably be rendered through natural selection,
whiter and whiter, until they became as white as snow.

Mr. Reeks has given me a curious instance of an animal profiting by
being peculiarly coloured. He raised from fifty to sixty white and
brown piebald rabbits in a large walled orchard; and he had at the same
time some similarly coloured cats in his house. Such cats, as I have
often noticed, are very conspicuous during day; but as they used to lie
in watch during the dusk at the mouths of the burrows, the rabbits
apparently did not distinguish them from their parti-coloured brethren.
The result was that, within eighteen months, every one of these
parti-coloured rabbits was destroyed; and there was evidence that this
was effected by the cats. Colour seems to be advantageous to another
animal, the skunk, in a manner of which we have had many instances in
other classes. No animal will voluntarily attack one of these creatures
on account of the dreadful odour which it emits when irritated; but
during the dusk it would not easily be recognised and might be attacked
by a beast of prey. Hence it is, as Mr. Belt believes (37. ‘The
Naturalist in Nicaragua,’ p. 249.), that the skunk is provided with a
great white bushy tail, which serves as a conspicuous warning.

[Fig. 70. Tragelaphus scriptus, male (from the Knowsley Menagerie).

Fig. 71. Damalis pygarga, male (from the Knowsley Menagerie).]

Although we must admit that many quadrupeds have received their present
tints either as a protection, or as an aid in procuring prey, yet with
a host of species, the colours are far too conspicuous and too
singularly arranged to allow us to suppose that they serve for these
purposes. We may take as an illustration certain antelopes; when we see
the square white patch on the throat, the white marks on the fetlocks,
and the round black spots on the ears, all more distinct in the male of
the Portax picta, than in the female;—when we see that the colours are
more vivid, that the narrow white lines on the flank and the broad
white bar on the shoulder are more distinct in the male Oreas derbyanus
than in the female;—when we see a similar difference between the sexes
of the curiously-ornamented Tragelaphus scriptus (Fig. 70),—we cannot
believe that differences of this kind are of any service to either sex
in their daily habits of life. It seems a much more probable conclusion
that the various marks were first acquired by the males and their
colours intensified through sexual selection, and then partially
transferred to the females. If this view be admitted, there can be
little doubt that the equally singular colours and marks of many other
antelopes, though common to both sexes, have been gained and
transmitted in a like manner. Both sexes, for instance, of the koodoo
(Strepsiceros kudu) (Fig. 64) have narrow white vertical lines on their
hind flanks, and an elegant angular white mark on their foreheads. Both
sexes in the genus Damalis are very oddly coloured; in D. pygarga the
back and neck are purplish-red, shading on the flanks into black; and
these colours are abruptly separated from the white belly and from a
large white space on the buttocks; the head is still more oddly
coloured, a large oblong white mask, narrowly-edged with black, covers
the face up to the eyes (Fig. 71); there are three white stripes on the
forehead, and the ears are marked with white. The fawns of this species
are of a uniform pale yellowish-brown. In Damalis albifrons the
colouring of the head differs from that in the last species in a single
white stripe replacing the three stripes, and in the ears being almost
wholly white. (38. See the fine plates in A. Smith’s ‘Zoology of South
Africa,’ and Dr. Gray’s ‘Gleanings from the Menagerie of Knowsley.’)
After having studied to the best of my ability the sexual differences
of animals belonging to all classes, I cannot avoid the conclusion that
the curiously-arranged colours of many antelopes, though common to both
sexes, are the result of sexual selection primarily applied to the
male.

The same conclusion may perhaps be extended to the tiger, one of the
most beautiful animals in the world, the sexes of which cannot be
distinguished by colour, even by the dealers in wild beasts. Mr.
Wallace believes (39. ‘Westminster Review,’ July 1, 1867, p. 5.) that
the striped coat of the tiger “so assimilates with the vertical stems
of the bamboo, as to assist greatly in concealing him from his
approaching prey.” But this view does not appear to me satisfactory. We
have some slight evidence that his beauty may be due to sexual
selection, for in two species of Felis the analogous marks and colours
are rather brighter in the male than in the female. The zebra is
conspicuously striped, and stripes cannot afford any protection in the
open plains of South Africa. Burchell (40. ‘Travels in South Africa,’
1824, vol. ii. p. 315.) in describing a herd says, “their sleek ribs
glistened in the sun, and the brightness and regularity of their
striped coats presented a picture of extraordinary beauty, in which
probably they are not surpassed by any other quadruped.” But as
throughout the whole group of the Equidae the sexes are identical in
colour, we have here no evidence of sexual selection. Nevertheless he
who attributes the white and dark vertical stripes on the flanks of
various antelopes to this process, will probably extend the same view
to the Royal Tiger and beautiful Zebra.

We have seen in a former chapter that when young animals belonging to
any class follow nearly the same habits of life as their parents, and
yet are coloured in a different manner, it may be inferred that they
have retained the colouring of some ancient and extinct progenitor. In
the family of pigs, and in the tapirs, the young are marked with
longitudinal stripes, and thus differ from all the existing adult
species in these two groups. With many kinds of deer the young are
marked with elegant white spots, of which their parents exhibit not a
trace. A graduated series can be followed from the axis deer, both
sexes of which at all ages and during all seasons are beautifully
spotted (the male being rather more strongly coloured than the female),
to species in which neither the old nor the young are spotted. I will
specify some of the steps in this series. The Mantchurian deer (Cervus
mantchuricus) is spotted during the whole year, but, as I have seen in
the Zoological Gardens, the spots are much plainer during the summer,
when the general colour of the coat is lighter, than during the winter,
when the general colour is darker and the horns are fully developed. In
the hog-deer (Hyelaphus porcinus) the spots are extremely conspicuous
during the summer when the coat is reddish-brown, but quite disappear
during the winter when the coat is brown. (41. Dr. Gray, ‘Gleanings
from the Menagerie of Knowsley,’ p. 64. Mr. Blyth, in speaking (‘Land
and Water,’ 1869, p. 42) of the hog-deer of Ceylon, says it is more
brightly spotted with white than the common hog-deer, at the season
when it renews its horns.) In both these species the young are spotted.
In the Virginian deer the young are likewise spotted, and about five
per cent. of the adult animals living in Judge Caton’s park, as I am
informed by him, temporarily exhibit at the period when the red summer
coat is being replaced by the bluish winter coat, a row of spots on
each flank, which are always the same in number, though very variable
in distinctness. From this condition there is but a very small step to
the complete absence of spots in the adults at all seasons; and,
lastly, to their absence at all ages and seasons, as occurs with
certain species. From the existence of this perfect series, and more
especially from the fawns of so many species being spotted, we may
conclude that the now living members of the deer family are the
descendants of some ancient species which, like the axis deer, was
spotted at all ages and seasons. A still more ancient progenitor
probably somewhat resembled the Hyomoschus aquaticus—for this animal is
spotted, and the hornless males have large exserted canine teeth, of
which some few true deer still retain rudiments. Hyomoschus, also,
offers one of those interesting cases of a form linking together two
groups, for it is intermediate in certain osteological characters
between the pachyderms and ruminants, which were formerly thought to be
quite distinct. (42. Falconer and Cautley, ‘Proc. Geolog. Soc.’ 1843;
and Falconer’s ‘Pal. Memoirs,’ vol. i. p. 196.)

A curious difficulty here arises. If we admit that coloured spots and
stripes were first acquired as ornaments, how comes it that so many
existing deer, the descendants of an aboriginally spotted animal, and
all the species of pigs and tapirs, the descendants of an aboriginally
striped animal, have lost in their adult state their former ornaments?
I cannot satisfactorily answer this question. We may feel almost sure
that the spots and stripes disappeared at or near maturity in the
progenitors of our existing species, so that they were still retained
by the young; and, owing to the law of inheritance at corresponding
ages, were transmitted to the young of all succeeding generations. It
may have been a great advantage to the lion and puma, from the open
nature of their usual haunts, to have lost their stripes, and to have
been thus rendered less conspicuous to their prey; and if the
successive variations, by which this end was gained, occurred rather
late in life, the young would have retained their stripes, as is now
the case. As to deer, pigs, and tapirs, Fritz Müller has suggested to
me that these animals, by the removal of their spots or stripes through
natural selection, would have been less easily seen by their enemies;
and that they would have especially required this protection, as soon
as the carnivora increased in size and number during the tertiary
periods. This may be the true explanation, but it is rather strange
that the young should not have been thus protected, and still more so
that the adults of some species should have retained their spots,
either partially or completely, during part of the year. We know that,
when the domestic ass varies and becomes reddish-brown, grey, or black,
the stripes on the shoulders and even on the spine frequently
disappear, though we cannot explain the cause. Very few horses, except
dun-coloured kinds, have stripes on any part of their bodies, yet we
have good reason to believe that the aboriginal horse was striped on
the legs and spine, and probably on the shoulders. (43. The ‘Variation
of Animals and Plants under Domestication,’ 1868, vol. i. pp. 61-64.)
Hence the disappearance of the spots and stripes in our adult existing
deer, pigs, and tapirs, may be due to a change in the general colour of
their coats; but whether this change was effected through sexual or
natural selection, or was due to the direct action of the conditions of
life, or to some other unknown cause, it is impossible to decide. An
observation made by Mr. Sclater well illustrates our ignorance of the
laws which regulate the appearance and disappearance of stripes; the
species of Asinus which inhabit the Asiatic continent are destitute of
stripes, not having even the cross shoulder-stripe, whilst those which
inhabit Africa are conspicuously striped, with the partial exception of
A. taeniopus, which has only the cross shoulder-stripe and generally
some faint bars on the legs; and this species inhabits the almost
intermediate region of Upper Egypt and Abyssinia. (44. ‘Proc. Zool.
Soc.’ 1862, p. 164. See, also, Dr. Hartmann, ‘Ann. d. Landw.’ Bd.
xliii. s. 222.)

QUADRUMANA.

[Fig. 72. Head of Semnopithecus rubicundus. This and the following
figures (from Prof. Gervais) are given to shew the odd arrangement and
development of the hair on the head.

Fig. 73. Head of Semnopithecus comatus.

Fig. 74. Head of Cebus capucinus.

Fig. 75. Head of Ateles marginatus.

Fig. 76. Head of Cebus vellerosus.]

Before we conclude, it will be well to add a few remarks on the
ornaments of monkeys. In most of the species the sexes resemble each
other in colour, but in some, as we have seen, the males differ from
the females, especially in the colour of the naked parts of the skin,
in the development of the beard, whiskers, and mane. Many species are
coloured either in so extraordinary or so beautiful a manner, and are
furnished with such curious and elegant crests of hair, that we can
hardly avoid looking at these characters as having been gained for the
sake of ornament. The accompanying figures (Figs. 72 to 76) serve to
shew the arrangement of the hair on the face and head in several
species. It is scarcely conceivable that these crests of hair, and the
strongly contrasted colours of the fur and skin, can be the result of
mere variability without the aid of selection; and it is inconceivable
that they can be of use in any ordinary way to these animals. If so,
they have probably been gained through sexual selection, though
transmitted equally, or almost equally, to both sexes. With many of the
Quadrumana, we have additional evidence of the action of sexual
selection in the greater size and strength of the males, and in the
greater development of their canine teeth, in comparison with the
females.

[Fig. 77. Cercopithecus petaurista (from Brehm).]

A few instances will suffice of the strange manner in which both sexes
of some species are coloured, and of the beauty of others. The face of
the Cercopithecus petaurista (Fig. 77) is black, the whiskers and beard
being white, with a defined, round, white spot on the nose, covered
with short white hair, which gives to the animal an almost ludicrous
aspect. The Semnopithecus frontatus likewise has a blackish face with a
long black beard, and a large naked spot on the forehead of a
bluish-white colour. The face of Macacus lasiotus is dirty
flesh-coloured, with a defined red spot on each cheek. The appearance
of Cercocebus aethiops is grotesque, with its black face, white
whiskers and collar, chestnut head, and a large naked white spot over
each eyelid. In very many species, the beard, whiskers, and crests of
hair round the face are of a different colour from the rest of the
head, and when different, are always of a lighter tint (45. I observed
this fact in the Zoological Gardens; and many cases may be seen in the
coloured plates in Geoffroy St.-Hilaire and F. Cuvier, ‘Histoire Nat.
des Mammifères,’ tom. i. 1824.), being often pure white, sometimes
bright yellow, or reddish. The whole face of the South American
Brachyurus calvus is of a “glowing scarlet hue”; but this colour does
not appear until the animal is nearly mature. (46. Bates, ‘The
Naturalist on the Amazons,’ 1863, vol. ii. p. 310.) The naked skin of
the face differs wonderfully in colour in the various species. It is
often brown or flesh-colour, with parts perfectly white, and often as
black as that of the most sooty negro. In the Brachyurus the scarlet
tint is brighter than that of the most blushing Caucasian damsel. It is
sometimes more distinctly orange than in any Mongolian, and in several
species it is blue, passing into violet or grey. In all the species
known to Mr. Bartlett, in which the adults of both sexes have
strongly-coloured faces, the colours are dull or absent during early
youth. This likewise holds good with the mandrill and Rhesus, in which
the face and the posterior parts of the body are brilliantly coloured
in one sex alone. In these latter cases we have reason to believe that
the colours were acquired through sexual selection; and we are
naturally led to extend the same view to the foregoing species, though
both sexes when adult have their faces coloured in the same manner.

[Fig. 78. Cercopithecus diana (from Brehm).]

Although many kinds of monkeys are far from beautiful according to our
taste, other species are universally admired for their elegant
appearance and bright colours. The Semnopithecus nemaeus, though
peculiarly coloured, is described as extremely pretty; the
orange-tinted face is surrounded by long whiskers of glossy whiteness,
with a line of chestnut-red over the eyebrows; the fur on the back is
of a delicate grey, with a square patch on the loins, the tail and the
fore-arms being of a pure white; a gorget of chestnut surmounts the
chest; the thighs are black, with the legs chestnut-red. I will mention
only two other monkeys for their beauty; and I have selected these as
presenting slight sexual differences in colour, which renders it in
some degree probable that both sexes owe their elegant appearance to
sexual selection. In the moustache-monkey (Cercopithecus cephus) the
general colour of the fur is mottled-greenish with the throat white; in
the male the end of the tail is chestnut, but the face is the most
ornamented part, the skin being chiefly bluish-grey, shading into a
blackish tint beneath the eyes, with the upper lip of a delicate blue,
clothed on the lower edge with a thin black moustache; the whiskers are
orange-coloured, with the upper part black, forming a band which
extends backwards to the ears, the latter being clothed with whitish
hairs. In the Zoological Society’s Gardens I have often overheard
visitors admiring the beauty of another monkey, deservedly called
Cercopithecus diana (Fig. 78); the general colour of the fur is grey;
the chest and inner surface of the forelegs are white; a large
triangular defined space on the hinder part of the back is rich
chestnut; in the male the inner sides of the thighs and the abdomen are
delicate fawn-coloured, and the top of the head is black; the face and
ears are intensely black, contrasting finely with a white transverse
crest over the eyebrows and a long white peaked beard, of which the
basal portion is black. (47. I have seen most of the above monkeys in
the Zoological Society’s Gardens. The description of the Semnopithecus
nemaeus is taken from Mr. W.C. Martin’s ‘Natural History of Mammalia,’
1841, p. 460; see also pp. 475, 523.)

In these and many other monkeys, the beauty and singular arrangement of
their colours, and still more the diversified and elegant arrangement
of the crests and tufts of hair on their heads, force the conviction on
my mind that these characters have been acquired through sexual
selection exclusively as ornaments.

A SUMMARY.

The law of battle for the possession of the female appears to prevail
throughout the whole great class of mammals. Most naturalists will
admit that the greater size, strength, courage, and pugnacity of the
male, his special weapons of offence, as well as his special means of
defence, have been acquired or modified through that form of selection
which I have called sexual. This does not depend on any superiority in
the general struggle for life, but on certain individuals of one sex,
generally the male, being successful in conquering other males, and
leaving a larger number of offspring to inherit their superiority than
do the less successful males.

There is another and more peaceful kind of contest, in which the males
endeavour to excite or allure the females by various charms. This is
probably carried on in some cases by the powerful odours emitted by the
males during the breeding-season; the odoriferous glands having been
acquired through sexual selection. Whether the same view can be
extended to the voice is doubtful, for the vocal organs of the males
must have been strengthened by use during maturity, under the powerful
excitements of love, jealousy or rage, and will consequently have been
transmitted to the same sex. Various crests, tufts, and mantles of
hair, which are either confined to the male, or are more developed in
this sex than in the female, seem in most cases to be merely
ornamental, though they sometimes serve as a defence against rival
males. There is even reason to suspect that the branching horns of
stags, and the elegant horns of certain antelopes, though properly
serving as weapons of offence or defence, have been partly modified for
ornament.

When the male differs in colour from the female, he generally exhibits
darker and more strongly-contrasted tints. We do not in this class meet
with the splendid red, blue, yellow, and green tints, so common with
male birds and many other animals. The naked parts, however, of certain
Quadrumana must be excepted; for such parts, often oddly situated, are
brilliantly coloured in some species. The colours of the male in other
cases may be due to simple variation, without the aid of selection. But
when the colours are diversified and strongly pronounced, when they are
not developed until near maturity, and when they are lost after
emasculation, we can hardly avoid the conclusion that they have been
acquired through sexual selection for the sake of ornament, and have
been transmitted exclusively, or almost exclusively, to the same sex.
When both sexes are coloured in the same manner, and the colours are
conspicuous or curiously arranged, without being of the least apparent
use as a protection, and especially when they are associated with
various other ornamental appendages, we are led by analogy to the same
conclusion, namely, that they have been acquired through sexual
selection, although transmitted to both sexes. That conspicuous and
diversified colours, whether confined to the males or common to both
sexes, are as a general rule associated in the same groups and
sub-groups with other secondary sexual characters serving for war or
for ornament, will be found to hold good, if we look back to the
various cases given in this and the last chapter.

The law of the equal transmission of characters to both sexes, as far
as colour and other ornaments are concerned, has prevailed far more
extensively with mammals than with birds; but weapons, such as horns
and tusks, have often been transmitted either exclusively or much more
perfectly to the males than to the females. This is surprising, for, as
the males generally use their weapons for defence against enemies of
all kinds, their weapons would have been of service to the females. As
far as we can see, their absence in this sex can be accounted for only
by the form of inheritance which has prevailed. Finally, with
quadrupeds the contest between the individuals of the same sex, whether
peaceful or bloody, has, with the rarest exceptions, been confined to
the males; so that the latter have been modified through sexual
selection, far more commonly than the females, either for fighting with
each other or for alluring the opposite sex.




PART III.
SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.




CHAPTER XIX.
SECONDARY SEXUAL CHARACTERS OF MAN.


Differences between man and woman—Causes of such differences and of
certain characters common to both sexes—Law of battle—Differences in
mental powers, and voice—On the influence of beauty in determining the
marriages of mankind—Attention paid by savages to ornaments—Their ideas
of beauty in woman—The tendency to exaggerate each natural peculiarity.

With mankind the differences between the sexes are greater than in most
of the Quadrumana, but not so great as in some, for instance, the
mandrill. Man on an average is considerably taller, heavier, and
stronger than woman, with squarer shoulders and more plainly-pronounced
muscles. Owing to the relation which exists between muscular
development and the projection of the brows (1. Schaaffhausen,
translation in ‘Anthropological Review,’ Oct. 1868, pp. 419, 420,
427.), the superciliary ridge is generally more marked in man than in
woman. His body, and especially his face, is more hairy, and his voice
has a different and more powerful tone. In certain races the women are
said to differ slightly in tint from the men. For instance,
Schweinfurth, in speaking of a negress belonging to the Monbuttoos, who
inhabit the interior of Africa a few degrees north of the equator,
says, “Like all her race, she had a skin several shades lighter than
her husband’s, being something of the colour of half-roasted coffee.”
(2. ‘The Heart of Africa,’ English transl. 1873, vol i. p. 544.) As the
women labour in the fields and are quite unclothed, it is not likely
that they differ in colour from the men owing to less exposure to the
weather. European women are perhaps the brighter coloured of the two
sexes, as may be seen when both have been equally exposed.

Man is more courageous, pugnacious and energetic than woman, and has a
more inventive genius. His brain is absolutely larger, but whether or
not proportionately to his larger body, has not, I believe, been fully
ascertained. In woman the face is rounder; the jaws and the base of the
skull smaller; the outlines of the body rounder, in parts more
prominent; and her pelvis is broader than in man (3. Ecker,
translation, in ‘Anthropological Review,’ Oct. 1868, pp. 351-356. The
comparison of the form of the skull in men and women has been followed
out with much care by Welcker.); but this latter character may perhaps
be considered rather as a primary than a secondary sexual character.
She comes to maturity at an earlier age than man.

As with animals of all classes, so with man, the distinctive characters
of the male sex are not fully developed until he is nearly mature; and
if emasculated they never appear. The beard, for instance, is a
secondary

sexual character, and male children are beardless, though at an early
age they have abundant hair on the head. It is probably due to the
rather late appearance in life of the successive variations whereby man
has acquired his masculine characters, that they are transmitted to the
male sex alone. Male and female children resemble each other closely,
like the young of so many other animals in which the adult sexes differ
widely; they likewise resemble the mature female much more closely than
the mature male. The female, however, ultimately assumes certain
distinctive characters, and in the formation of her skull, is said to
be intermediate between the child and the man. (4. Ecker and Welcker,
ibid. pp. 352, 355; Vogt, ‘Lectures on Man,’ Eng. translat. p. 81.)
Again, as the young of closely allied though distinct species do not
differ nearly so much from each other as do the adults, so it is with
the children of the different races of man. Some have even maintained
that race-differences cannot be detected in the infantile skull. (5.
Schaaffhausen, ‘Anthropolog. Review,’ ibid. p. 429.) In regard to
colour, the new-born negro child is reddish nut-brown, which soon
becomes slaty-grey; the black colour being fully developed within a
year in the Soudan, but not until three years in Egypt. The eyes of the
negro are at first blue, and the hair chestnut-brown rather than black,
being curled only at the ends. The children of the Australians
immediately after birth are yellowish-brown, and become dark at a later
age. Those of the Guaranys of Paraguay are whitish-yellow, but they
acquire in the course of a few weeks the yellowish-brown tint of their
parents. Similar observations have been made in other parts of America.
(6. Pruner-Bey, on negro infants as quoted by Vogt, ‘Lectures on Man,’
Eng. translat. 1864, p. 189: for further facts on negro infants, as
quoted from Winterbottom and Camper, see Lawrence, ‘Lectures on
Physiology,’ etc. 1822, p. 451. For the infants of the Guaranys, see
Rengger, ‘Säugethiere,’ etc. s. 3. See also Godron, ‘De l’Espèce,’ tom.
ii. 1859, p. 253. For the Australians, Waitz, ‘Introduction to
Anthropology,’ Eng. translat. 1863, p. 99.)

I have specified the foregoing differences between the male and female
sex in mankind, because they are curiously like those of the
Quadrumana. With these animals the female is mature at an earlier age
than the male; at least this is certainly the case in Cebus azarae. (7.
Rengger, ‘Säugethiere,’ etc., 1830, s. 49.) The males of most species
are larger and stronger than the females, of which fact the gorilla
affords a well-known instance. Even in so trifling a character as the
greater prominence of the superciliary ridge, the males of certain
monkeys differ from the females (8. As in Macacus cynomolgus
(Desmarest, ‘Mammalogie,’ p. 65), and in Hylobates agilis (Geoffroy
St.-Hilaire and F. Cuvier, ‘Histoire Nat. des Mammifères,’ 1824, tom.
i. p. 2)., and agree in this respect with mankind. In the gorilla and
certain other monkeys, the cranium of the adult male presents a
strongly-marked sagittal crest, which is absent in the female; and
Ecker found a trace of a similar difference between the two sexes in
the Australians. (9. ‘Anthropological Review,’ Oct. 1868, p. 353.) With
monkeys when there is any difference in the voice, that of the male is
the more powerful. We have seen that certain male monkeys have a
well-developed beard, which is quite deficient, or much less developed
in the female. No instance is known of the beard, whiskers, or
moustache being larger in the female than in the male monkey. Even in
the colour of the beard there is a curious parallelism between man and
the Quadrumana, for with man when the beard differs in colour from the
hair of the head, as is commonly the case, it is, I believe, almost
always of a lighter tint, being often reddish. I have repeatedly
observed this fact in England; but two gentlemen have lately written to
me, saying that they form an exception to the rule. One of these
gentlemen accounts for the fact by the wide difference in colour of the
hair on the paternal and maternal sides of his family. Both had been
long aware of this peculiarity (one of them having often been accused
of dyeing his beard), and had been thus led to observe other men, and
were convinced that the exceptions were very rare. Dr. Hooker attended
to this little point for me in Russia, and found no exception to the
rule. In Calcutta, Mr. J. Scott, of the Botanic Gardens, was so kind as
to observe the many races of men to be seen there, as well as in some
other parts of India, namely, two races of Sikhim, the Bhoteas,
Hindoos, Burmese, and Chinese, most of which races have very little
hair on the face; and he always found that when there was any
difference in colour between the hair of the head and the beard, the
latter was invariably lighter. Now with monkeys, as has already been
stated, the beard frequently differs strikingly in colour from the hair
of the head, and in such cases it is always of a lighter hue, being
often pure white, sometimes yellow or reddish. (10. Mr. Blyth informs
me that he has only seen one instance of the beard, whiskers, etc., in
a monkey becoming white with old age, as is so commonly the case with
us. This, however, occurred in an aged Macacus cynomolgus, kept in
confinement whose moustaches were “remarkably long and human-like.”
Altogether this old monkey presented a ludicrous resemblance to one of
the reigning monarchs of Europe, after whom he was universally
nick-named. In certain races of man the hair on the head hardly ever
becomes grey; thus Mr. D. Forbes has never, as he informs me, seen an
instance with the Aymaras and Quichuas of South America.)

In regard to the general hairiness of the body, the women in all races
are less hairy than the men; and in some few Quadrumana the under side
of the body of the female is less hairy than that of the male. (11.
This is the case with the females of several species of Hylobates; see
Geoffroy St.-Hilaire and F. Cuvier, ‘Hist. Nat. des Mamm.’ tom. i. See
also, on H. lar, ‘Penny Cyclopedia,’ vol. ii. pp. 149, 150.) Lastly,
male monkeys, like men, are bolder and fiercer than the females. They
lead the troop, and when there is danger, come to the front. We thus
see how close is the parallelism between the sexual differences of man
and the Quadrumana. With some few species, however, as with certain
baboons, the orang and the gorilla, there is a considerably greater
difference between the sexes, as in the size of the canine teeth, in
the development and colour of the hair, and especially in the colour of
the naked parts of the skin, than in mankind.

All the secondary sexual characters of man are highly variable, even
within the limits of the same race; and they differ much in the several
races. These two rules hold good generally throughout the animal
kingdom. In the excellent observations made on board the Novara (12.
The results were deduced by Dr. Weisbach from the measurements made by
Drs. K. Scherzer and Schwarz, see ‘Reise der Novara: Anthropolog.
Theil,’ 1867, ss. 216, 231, 234, 236, 239, 269.), the male Australians
were found to exceed the females by only 65 millim. in height, whilst
with the Javans the average excess was 218 millim.; so that in this
latter race the difference in height between the sexes is more than
thrice as great as with the Australians. Numerous measurements were
carefully made of the stature, the circumference of the neck and chest,
the length of the back-bone and of the arms, in various races; and
nearly all these measurements shew that the males differ much more from
one another than do the females. This fact indicates that, as far as
these characters are concerned, it is the male which has been chiefly
modified, since the several races diverged from their common stock.

The development of the beard and the hairiness of the body differ
remarkably in the men of distinct races, and even in different tribes
or families of the same race. We Europeans see this amongst ourselves.
In the Island of St. Kilda, according to Martin (13. ‘Voyage to St.
Kilda’ (3rd ed. 1753), p. 37.), the men do not acquire beards until the
age of thirty or upwards, and even then the beards are very thin. On
the Europaeo-Asiatic continent, beards prevail until we pass beyond
India; though with the natives of Ceylon they are often absent, as was
noticed in ancient times by Diodorus. (14. Sir J.E. Tennent, ‘Ceylon,’
vol. ii. 1859, p. 107.) Eastward of India beards disappear, as with the
Siamese, Malays, Kalmucks, Chinese, and Japanese; nevertheless, the
Ainos (15. Quatrefages, ‘Revue des Cours Scientifiques,’ Aug. 29, 1868,
p. 630; Vogt, ‘Lectures on Man,’ Eng. trans. p. 127.), who inhabit the
northernmost islands of the Japan Archipelago, are the hairiest men in
the world. With negroes the beard is scanty or wanting, and they rarely
have whiskers; in both sexes the body is frequently almost destitute of
fine down. (16. On the beards of negroes, Vogt, ‘Lectures,’ etc. p.
127; Waitz, ‘Introduct. to Anthropology,’ Engl. translat. 1863, vol. i.
p. 96. It is remarkable that in the United States (‘Investigations in
Military and Anthropological Statistics of American Soldiers,’ 1869, p.
569) the pure negroes and their crossed offspring seem to have bodies
almost as hairy as Europeans.) On the other hand, the Papuans of the
Malay Archipelago, who are nearly as black as negroes, possess
well-developed beards. (17. Wallace, ‘The Malay Arch.’ vol. ii. 1869,
p. 178.) In the Pacific Ocean the inhabitants of the Fiji Archipelago
have large bushy beards, whilst those of the not distant archipelagoes
of Tonga and Samoa are beardless; but these men belong to distinct
races. In the Ellice group all the inhabitants belong to the same race;
yet on one island alone, namely Nunemaya, “the men have splendid
beards”; whilst on the other islands “they have, as a rule, a dozen
straggling hairs for a beard.” (18. Dr. J. Barnard Davis on Oceanic
Races, in ‘Anthropological Review,’ April 1870, pp. 185, 191.)

Throughout the great American continent the men may be said to be
beardless; but in almost all the tribes a few short hairs are apt to
appear on the face, especially in old age. With the tribes of North
America, Catlin estimates that eighteen out of twenty men are
completely destitute by nature of a beard; but occasionally there may
be seen a man, who has neglected to pluck out the hairs at puberty,
with a soft beard an inch or two in length. The Guaranys of Paraguay
differ from all the surrounding tribes in having a small beard, and
even some hair on the body, but no whiskers. (19. Catlin, ‘North
American Indians,’ 3rd. ed. 1842, vol. ii. p. 227. On the Guaranys, see
Azara, ‘Voyages dans l’Amérique Merid.’ tom. ii. 1809, p. 85; also
Rengger, ‘Säugethiere von Paraguay,’ s. 3.) I am informed by Mr. D.
Forbes, who particularly attended to this point, that the Aymaras and
Quichuas of the Cordillera are remarkably hairless, yet in old age a
few straggling hairs occasionally appear on the chin. The men of these
two tribes have very little hair on the various parts of the body where
hair grows abundantly in Europeans, and the women have none on the
corresponding parts. The hair on the head, however, attains an
extraordinary length in both sexes, often reaching almost to the
ground; and this is likewise the case with some of the N. American
tribes. In the amount of hair, and in the general shape of the body,
the sexes of the American aborigines do not differ so much from each
other, as in most other races. (20. Prof. and Mrs. Agassiz (‘Journey in
Brazil,’ p. 530) remark that the sexes of the American Indians differ
less than those of the negroes and of the higher races. See also
Rengger, ibid. p. 3, on the Guaranys.) This fact is analogous with what
occurs with some closely allied monkeys; thus the sexes of the
chimpanzee are not as different as those of the orang or gorilla. (21.
Rutimeyer, ‘Die Grenzen der Thierwelt; eine Betrachtung zu Darwin’s
Lehre,’ 1868, s. 54.)

In the previous chapters we have seen that with mammals, birds, fishes,
insects, etc., many characters, which there is every reason to believe
were primarily gained through sexual selection by one sex, have been
transferred to the other. As this same form of transmission has
apparently prevailed much with mankind, it will save useless repetition
if we discuss the origin of characters peculiar to the male sex
together with certain other characters common to both sexes.

LAW OF BATTLE.

With savages, for instance, the Australians, the women are the constant
cause of war both between members of the same tribe and between
distinct tribes. So no doubt it was in ancient times; “nam fuit ante
Helenam mulier teterrima belli causa.” With some of the North American
Indians, the contest is reduced to a system. That excellent observer,
Hearne (22. ‘A Journey from Prince of Wales Fort,’ 8vo. ed. Dublin,
1796, p. 104. Sir J. Lubbock (‘Origin of Civilisation,’ 1870, p. 69)
gives other and similar cases in North America. For the Guanas of South
America see Azara, ‘Voyages,’ etc. tom. ii. p. 94.), says:—“It has ever
been the custom among these people for the men to wrestle for any woman
to whom they are attached; and, of course, the strongest party always
carries off the prize. A weak man, unless he be a good hunter, and
well-beloved, is seldom permitted to keep a wife that a stronger man
thinks worth his notice. This custom prevails throughout all the
tribes, and causes a great spirit of emulation among their youth, who
are upon all occasions, from their childhood, trying their strength and
skill in wrestling.” With the Guanas of South America, Azara states
that the men rarely marry till twenty years old or more, as before that
age they cannot conquer their rivals.

Other similar facts could be given; but even if we had no evidence on
this head, we might feel almost sure, from the analogy of the higher
Quadrumana (23. On the fighting of the male gorillas, see Dr. Savage,
in ‘Boston Journal of Natural History,’ vol. v. 1847, p. 423. On
Presbytis entellus, see the ‘Indian Field,’ 1859, p. 146.), that the
law of battle had prevailed with man during the early stages of his
development. The occasional appearance at the present day of canine
teeth which project above the others, with traces of a diastema or open
space for the reception of the opposite canines, is in all probability
a case of reversion to a former state, when the progenitors of man were
provided with these weapons, like so many existing male Quadrumana. It
was remarked in a former chapter that as man gradually became erect,
and continually used his hands and arms for fighting with sticks and
stones, as well as for the other purposes of life, he would have used
his jaws and teeth less and less. The jaws, together with their
muscles, would then have been reduced through disuse, as would the
teeth through the not well understood principles of correlation and
economy of growth; for we everywhere see that parts, which are no
longer of service, are reduced in size. By such steps the original
inequality between the jaws and teeth in the two sexes of mankind would
ultimately have been obliterated. The case is almost parallel with that
of many male Ruminants, in which the canine teeth have been reduced to
mere rudiments, or have disappeared, apparently in consequence of the
development of horns. As the prodigious difference between the skulls
of the two sexes in the orang and gorilla stands in close relation with
the development of the immense canine teeth in the males, we may infer
that the reduction of the jaws and teeth in the early male progenitors
of man must have led to a most striking and favourable change in his
appearance.

There can be little doubt that the greater size and strength of man, in
comparison with woman, together with his broader shoulders, more
developed muscles, rugged outline of body, his greater courage and
pugnacity, are all due in chief part to inheritance from his half-human
male ancestors. These characters would, however, have been preserved or
even augmented during the long ages of man’s savagery, by the success
of the strongest and boldest men, both in the general struggle for life
and in their contests for wives; a success which would have ensured
their leaving a more numerous progeny than their less favoured
brethren. It is not probable that the greater strength of man was
primarily acquired through the inherited effects of his having worked
harder than woman for his own subsistence and that of his family; for
the women in all barbarous nations are compelled to work at least as
hard as the men. With civilised people the arbitrament of battle for
the possession of the women has long ceased; on the other hand, the
men, as a general rule, have to work harder than the women for their
joint subsistence, and thus their greater strength will have been kept
up.

DIFFERENCE IN THE MENTAL POWERS OF THE TWO SEXES.

With respect to differences of this nature between man and woman, it is
probable that sexual selection has played a highly important part. I am
aware that some writers doubt whether there is any such inherent
difference; but this is at least probable from the analogy of the lower
animals which present other secondary sexual characters. No one
disputes that the bull differs in disposition from the cow, the
wild-boar from the sow, the stallion from the mare, and, as is well
known to the keepers of menageries, the males of the larger apes from
the females. Woman seems to differ from man in mental disposition,
chiefly in her greater tenderness and less selfishness; and this holds
good even with savages, as shewn by a well-known passage in Mungo
Park’s Travels, and by statements made by many other travellers. Woman,
owing to her maternal instincts, displays these qualities towards her
infants in an eminent degree; therefore it is likely that she would
often extend them towards her fellow-creatures. Man is the rival of
other men; he delights in competition, and this leads to ambition which
passes too easily into selfishness. These latter qualities seem to be
his natural and unfortunate birthright. It is generally admitted that
with woman the powers of intuition, of rapid perception, and perhaps of
imitation, are more strongly marked than in man; but some, at least, of
these faculties are characteristic of the lower races, and therefore of
a past and lower state of civilisation.

The chief distinction in the intellectual powers of the two sexes is
shewn by man’s attaining to a higher eminence, in whatever he takes up,
than can woman—whether requiring deep thought, reason, or imagination,
or merely the use of the senses and hands. If two lists were made of
the most eminent men and women in poetry, painting, sculpture, music
(inclusive both of composition and performance), history, science, and
philosophy, with half-a-dozen names under each subject, the two lists
would not bear comparison. We may also infer, from the law of the
deviation from averages, so well illustrated by Mr. Galton, in his work
on ‘Hereditary Genius,’ that if men are capable of a decided
pre-eminence over women in many subjects, the average of mental power
in man must be above that of woman.

Amongst the half-human progenitors of man, and amongst savages, there
have been struggles between the males during many generations for the
possession of the females. But mere bodily strength and size would do
little for victory, unless associated with courage, perseverance, and
determined energy. With social animals, the young males have to pass
through many a contest before they win a female, and the older males
have to retain their females by renewed battles. They have, also, in
the case of mankind, to defend their females, as well as their young,
from enemies of all kinds, and to hunt for their joint subsistence. But
to avoid enemies or to attack them with success, to capture wild
animals, and to fashion weapons, requires the aid of the higher mental
faculties, namely, observation, reason, invention, or imagination.
These various faculties will thus have been continually put to the test
and selected during manhood; they will, moreover, have been
strengthened by use during this same period of life. Consequently in
accordance with the principle often alluded to, we might expect that
they would at least tend to be transmitted chiefly to the male
offspring at the corresponding period of manhood.

Now, when two men are put into competition, or a man with a woman, both
possessed of every mental quality in equal perfection, save that one
has higher energy, perseverance, and courage, the latter will generally
become more eminent in every pursuit, and will gain the ascendancy.
(24. J. Stuart Mill remarks (‘The Subjection of Women,’ 1869, p. 122),
“The things in which man most excels woman are those which require most
plodding, and long hammering at single thoughts.” What is this but
energy and perseverance?) He may be said to possess genius—for genius
has been declared by a great authority to be patience; and patience, in
this sense, means unflinching, undaunted perseverance. But this view of
genius is perhaps deficient; for without the higher powers of the
imagination and reason, no eminent success can be gained in many
subjects. These latter faculties, as well as the former, will have been
developed in man, partly through sexual selection,—that is, through the
contest of rival males, and partly through natural selection, that is,
from success in the general struggle for life; and as in both cases the
struggle will have been during maturity, the characters gained will
have been transmitted more fully to the male than to the female
offspring. It accords in a striking manner with this view of the
modification and re-inforcement of many of our mental faculties by
sexual selection, that, firstly, they notoriously undergo a
considerable change at puberty (25. Maudsley, ‘Mind and Body,’ p. 31.),
and, secondly, that eunuchs remain throughout life inferior in these
same qualities. Thus, man has ultimately become superior to woman. It
is, indeed, fortunate that the law of the equal transmission of
characters to both sexes prevails with mammals; otherwise, it is
probable that man would have become as superior in mental endowment to
woman, as the peacock is in ornamental plumage to the peahen.

It must be borne in mind that the tendency in characters acquired by
either sex late in life, to be transmitted to the same sex at the same
age, and of early acquired characters to be transmitted to both sexes,
are rules which, though general, do not always hold. If they always
held good, we might conclude (but I here exceed my proper bounds) that
the inherited effects of the early education of boys and girls would be
transmitted equally to both sexes; so that the present inequality in
mental power between the sexes would not be effaced by a similar course
of early training; nor can it have been caused by their dissimilar
early training. In order that woman should reach the same standard as
man, she ought, when nearly adult, to be trained to energy and
perseverance, and to have her reason and imagination exercised to the
highest point; and then she would probably transmit these qualities
chiefly to her adult daughters. All women, however, could not be thus
raised, unless during many generations those who excelled in the above
robust virtues were married, and produced offspring in larger numbers
than other women. As before remarked of bodily strength, although men
do not now fight for their wives, and this form of selection has passed
away, yet during manhood, they generally undergo a severe struggle in
order to maintain themselves and their families; and this will tend to
keep up or even increase their mental powers, and, as a consequence,
the present inequality between the sexes. (26. An observation by Vogt
bears on this subject: he says, “It is a remarkable circumstance, that
the difference between the sexes, as regards the cranial cavity,
increases with the development of the race, so that the male European
excels much more the female, than the negro the negress. Welcker
confirms this statement of Huschke from his measurements of negro and
German skulls.” But Vogt admits (‘Lectures on Man,’ Eng. translat.
1864, p. 81) that more observations are requisite on this point.

VOICE AND MUSICAL POWERS.

In some species of Quadrumana there is a great difference between the
adult sexes, in the power of their voices and in the development of the
vocal organs; and man appears to have inherited this difference from
his early progenitors. His vocal cords are about one-third longer than
in woman, or than in boys; and emasculation produces the same effect on
him as on the lower animals, for it “arrests that prominent growth of
the thyroid, etc., which accompanies the elongation of the cords.” (27.
Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 603.) With respect to the
cause of this difference between the sexes, I have nothing to add to
the remarks in the last chapter on the probable effects of the
long-continued use of the vocal organs by the male under the excitement
of love, rage and jealousy. According to Sir Duncan Gibb (28. ‘Journal
of the Anthropological Society,’ April 1869, p. lvii. and lxvi.), the
voice and the form of the larynx differ in the different races of
mankind; but with the Tartars, Chinese, etc., the voice of the male is
said not to differ so much from that of the female, as in most other
races.

The capacity and love for singing or music, though not a sexual
character in man, must not here be passed over. Although the sounds
emitted by animals of all kinds serve many purposes, a strong case can
be made out, that the vocal organs were primarily used and perfected in
relation to the propagation of the species. Insects and some few
spiders are the lowest animals which voluntarily produce any sound; and
this is generally effected by the aid of beautifully constructed
stridulating organs, which are often confined to the males. The sounds
thus produced consist, I believe in all cases, of the same note,
repeated rhythmically (29. Dr. Scudder, ‘Notes on Stridulation,’ in
‘Proc. Boston Soc. of Nat. Hist.’ vol. xi. April 1868.); and this is
sometimes pleasing even to the ears of man. The chief and, in some
cases, exclusive purpose appears to be either to call or charm the
opposite sex.

The sounds produced by fishes are said in some cases to be made only by
the males during the breeding-season. All the air-breathing Vertebrata
necessarily possess an apparatus for inhaling and expelling air, with a
pipe capable of being closed at one end. Hence when the primeval
members of this class were strongly excited and their muscles violently
contracted, purposeless sounds would almost certainly have been
produced; and these, if they proved in any way serviceable, might
readily have been modified or intensified by the preservation of
properly adapted variations. The lowest Vertebrates which breathe air
are Amphibians; and of these, frogs and toads possess vocal organs,
which are incessantly used during the breeding-season, and which are
often more highly developed in the male than in the female. The male
alone of the tortoise utters a noise, and this only during the season
of love. Male alligators roar or bellow during the same season. Every
one knows how much birds use their vocal organs as a means of
courtship; and some species likewise perform what may be called
instrumental music.

In the class of Mammals, with which we are here more particularly
concerned, the males of almost all the species use their voices during
the breeding-season much more than at any other time; and some are
absolutely mute excepting at this season. With other species both
sexes, or only the females, use their voices as a love-call.
Considering these facts, and that the vocal organs of some quadrupeds
are much more largely developed in the male than in the female, either
permanently or temporarily during the breeding-season; and considering
that in most of the lower classes the sounds produced by the males,
serve not only to call but to excite or allure the female, it is a
surprising fact that we have not as yet any good evidence that these
organs are used by male mammals to charm the females. The American
Mycetes caraya perhaps forms an exception, as does the Hylobates
agilis, an ape allied to man. This gibbon has an extremely loud but
musical voice. Mr. Waterhouse states (30. Given in W.C.L. Martin’s
‘General Introduction to Natural History of Mamm. Animals,’ 1841, p.
432; Owen, ‘Anatomy of Vertebrates,’ vol. iii, p. 600.), “It appeared
to me that in ascending and descending the scale, the intervals were
always exactly half-tones; and I am sure that the highest note was the
exact octave to the lowest. The quality of the notes is very musical;
and I do not doubt that a good violinist would be able to give a
correct idea of the gibbon’s composition, excepting as regards its
loudness.” Mr. Waterhouse then gives the notes. Professor Owen, who is
a musician, confirms the foregoing statement, and remarks, though
erroneously, that this gibbon “alone of brute mammals may be said to
sing.” It appears to be much excited after its performance.
Unfortunately, its habits have never been closely observed in a state
of nature; but from the analogy of other animals, it is probable that
it uses its musical powers more especially during the season of
courtship.

This gibbon is not the only species in the genus which sings, for my
son, Francis Darwin, attentively listened in the Zoological Gardens to
H. leuciscus whilst singing a cadence of three notes, in true musical
intervals and with a clear musical tone. It is a more surprising fact
that certain rodents utter musical sounds. Singing mice have often been
mentioned and exhibited, but imposture has commonly been suspected. We
have, however, at last a clear account by a well-known observer, the
Rev. S. Lockwood (31. The ‘American Naturalist,’ 1871, p. 761.), of the
musical powers of an American species, the Hesperomys cognatus,
belonging to a genus distinct from that of the English mouse. This
little animal was kept in confinement, and the performance was
repeatedly heard. In one of the two chief songs, “the last bar would
frequently be prolonged to two or three; and she would sometimes change
from C sharp and D, to C natural and D, then warble on these two notes
awhile, and wind up with a quick chirp on C sharp and D. The
distinctness between the semitones was very marked, and easily
appreciable to a good ear.” Mr. Lockwood gives both songs in musical
notation; and adds that though this little mouse “had no ear for time,
yet she would keep to the key of B (two flats) and strictly in a major
key.”...”Her soft clear voice falls an octave with all the precision
possible; then at the wind up, it rises again into a very quick trill
on C sharp and D.”

A critic has asked how the ears of man, and he ought to have added of
other animals, could have been adapted by selection so as to
distinguish musical notes. But this question shews some confusion on
the subject; a noise is the sensation resulting from the co-existence
of several aerial “simple vibrations” of various periods, each of which
intermits so frequently that its separate existence cannot be
perceived. It is only in the want of continuity of such vibrations, and
in their want of harmony inter se, that a noise differs from a musical
note. Thus an ear to be capable of discriminating noises—and the high
importance of this power to all animals is admitted by every one—must
be sensitive to musical notes. We have evidence of this capacity even
low down in the animal scale: thus Crustaceans are provided with
auditory hairs of different lengths, which have been seen to vibrate
when the proper musical notes are struck. (32. Helmholtz, ‘Theorie
Phys. de la Musique,’ 1868, p. 187.) As stated in a previous chapter,
similar observations have been made on the hairs of the antennae of
gnats. It has been positively asserted by good observers that spiders
are attracted by music. It is also well known that some dogs howl when
hearing particular tones. (33. Several accounts have been published to
this effect. Mr. Peach writes to me that an old dog of his howls when B
flat is sounded on the flute, and to no other note. I may add another
instance of a dog always whining, when one note on a concertina, which
was out of tune, was played.) Seals apparently appreciate music, and
their fondness for it “was well known to the ancients, and is often
taken advantage of by the hunters at the present day.” (34. Mr. R.
Brown, in ‘Proc. Zool. Soc.’ 1868, p. 410.)

Therefore, as far as the mere perception of musical notes is concerned,
there seems no special difficulty in the case of man or of any other
animal. Helmholtz has explained on physiological principles why
concords are agreeable, and discords disagreeable to the human ear; but
we are little concerned with these, as music in harmony is a late
invention. We are more concerned with melody, and here again, according
to Helmholtz, it is intelligible why the notes of our musical scale are
used. The ear analyses all sounds into their component “simple
vibrations,” although we are not conscious of this analysis. In a
musical note the lowest in pitch of these is generally predominant, and
the others which are less marked are the octave, the twelfth, the
second octave, etc., all harmonies of the fundamental predominant note;
any two notes of our scale have many of these harmonic over-tones in
common. It seems pretty clear then, that if an animal always wished to
sing precisely the same song, he would guide himself by sounding those
notes in succession, which possess many over-tones in common—that is,
he would choose for his song, notes which belong to our musical scale.

But if it be further asked why musical tones in a certain order and
rhythm give man and other animals pleasure, we can no more give the
reason than for the pleasantness of certain tastes and smells. That
they do give pleasure of some kind to animals, we may infer from their
being produced during the season of courtship by many insects, spiders,
fishes, amphibians, and birds; for unless the females were able to
appreciate such sounds and were excited or charmed by them, the
persevering efforts of the males, and the complex structures often
possessed by them alone, would be useless; and this it is impossible to
believe.

Human song is generally admitted to be the basis or origin of
instrumental music. As neither the enjoyment nor the capacity of
producing musical notes are faculties of the least use to man in
reference to his daily habits of life, they must be ranked amongst the
most mysterious with which he is endowed. They are present, though in a
very rude condition, in men of all races, even the most savage; but so
different is the taste of the several races, that our music gives no
pleasure to savages, and their music is to us in most cases hideous and
unmeaning. Dr. Seemann, in some interesting remarks on this subject
(35. ‘Journal of Anthropological Society,’ Oct. 1870, p. clv. See also
the several later chapters in Sir John Lubbock’s ‘Prehistoric Times,’
2nd ed. 1869, which contain an admirable account of the habits of
savages.), “doubts whether even amongst the nations of Western Europe,
intimately connected as they are by close and frequent intercourse, the
music of the one is interpreted in the same sense by the others. By
travelling eastwards we find that there is certainly a different
language of music. Songs of joy and dance-accompaniments are no longer,
as with us, in the major keys, but always in the minor.” Whether or not
the half-human progenitors of man possessed, like the singing gibbons,
the capacity of producing, and therefore no doubt of appreciating,
musical notes, we know that man possessed these faculties at a very
remote period. M. Lartet has described two flutes made out of the bones
and horns of the reindeer, found in caves together with flint tools and
the remains of extinct animals. The arts of singing and of dancing are
also very ancient, and are now practised by all or nearly all the
lowest races of man. Poetry, which may be considered as the offspring
of song, is likewise so ancient, that many persons have felt astonished
that it should have arisen during the earliest ages of which we have
any record.

We see that the musical faculties, which are not wholly deficient in
any race, are capable of prompt and high development, for Hottentots
and Negroes have become excellent musicians, although in their native
countries they rarely practise anything that we should consider music.
Schweinfurth, however, was pleased with some of the simple melodies
which he heard in the interior of Africa. But there is nothing
anomalous in the musical faculties lying dormant in man: some species
of birds which never naturally sing, can without much difficulty be
taught to do so; thus a house-sparrow has learnt the song of a linnet.
As these two species are closely allied, and belong to the order of
Insessores, which includes nearly all the singing-birds in the world,
it is possible that a progenitor of the sparrow may have been a
songster. It is more remarkable that parrots, belonging to a group
distinct from the Insessores, and having differently constructed vocal
organs, can be taught not only to speak, but to pipe or whistle tunes
invented by man, so that they must have some musical capacity.
Nevertheless it would be very rash to assume that parrots are descended
from some ancient form which was a songster. Many cases could be
advanced of organs and instincts originally adapted for one purpose,
having been utilised for some distinct purpose. (36. Since this chapter
was printed, I have seen a valuable article by Mr. Chauncey Wright
(‘North American Review,’ Oct. 1870, page 293), who, in discussing the
above subject, remarks, “There are many consequences of the ultimate
laws or uniformities of nature, through which the acquisition of one
useful power will bring with it many resulting advantages as well as
limiting disadvantages, actual or possible, which the principle of
utility may not have comprehended in its action.” As I have attempted
to shew in an early chapter of this work, this principle has an
important bearing on the acquisition by man of some of his mental
characteristics.) Hence the capacity for high musical development which
the savage races of man possess, may be due either to the practice by
our semi-human progenitors of some rude form of music, or simply to
their having acquired the proper vocal organs for a different purpose.
But in this latter case we must assume, as in the above instance of
parrots, and as seems to occur with many animals, that they already
possessed some sense of melody.

Music arouses in us various emotions, but not the more terrible ones of
horror, fear, rage, etc. It awakens the gentler feelings of tenderness
and love, which readily pass into devotion. In the Chinese annals it is
said, “Music hath the power of making heaven descend upon earth.” It
likewise stirs up in us the sense of triumph and the glorious ardour
for war. These powerful and mingled feelings may well give rise to the
sense of sublimity. We can concentrate, as Dr. Seemann observes,
greater intensity of feeling in a single musical note than in pages of
writing. It is probable that nearly the same emotions, but much weaker
and far less complex, are felt by birds when the male pours forth his
full volume of song, in rivalry with other males, to captivate the
female. Love is still the commonest theme of our songs. As Herbert
Spencer remarks, “music arouses dormant sentiments of which we had not
conceived the possibility, and do not know the meaning; or, as Richter
says, tells us of things we have not seen and shall not see.”
Conversely, when vivid emotions are felt and expressed by the orator,
or even in common speech, musical cadences and rhythm are instinctively
used. The negro in Africa when excited often bursts forth in song;
“another will reply in song, whilst the company, as if touched by a
musical wave, murmur a chorus in perfect unison.” (37. Winwood Reade,
‘The Martyrdom of Man,’ 1872, p. 441, and ‘African Sketch Book,’ 1873,
vol. ii. p. 313.) Even monkeys express strong feelings in different
tones—anger and impatience by low,—fear and pain by high notes. (38.
Rengger, ‘Säugethiere von Paraguay,’ s. 49.) The sensations and ideas
thus excited in us by music, or expressed by the cadences of oratory,
appear from their vagueness, yet depth, like mental reversions to the
emotions and thoughts of a long-past age.

All these facts with respect to music and impassioned speech become
intelligible to a certain extent, if we may assume that musical tones
and rhythm were used by our half-human ancestors, during the season of
courtship, when animals of all kinds are excited not only by love, but
by the strong passions of jealousy, rivalry, and triumph. From the
deeply-laid principle of inherited associations, musical tones in this
case would be likely to call up vaguely and indefinitely the strong
emotions of a long-past age. As we have every reason to suppose that
articulate speech is one of the latest, as it certainly is the highest,
of the arts acquired by man, and as the instinctive power of producing
musical notes and rhythms is developed low down in the animal series,
it would be altogether opposed to the principle of evolution, if we
were to admit that man’s musical capacity has been developed from the
tones used in impassioned speech. We must suppose that the rhythms and
cadences of oratory are derived from previously developed musical
powers. (39. See the very interesting discussion on the ‘Origin and
Function of Music,’ by Mr. Herbert Spencer, in his collected ‘Essays,’
1858, p. 359. Mr. Spencer comes to an exactly opposite conclusion to
that at which I have arrived. He concludes, as did Diderot formerly,
that the cadences used in emotional speech afford the foundation from
which music has been developed; whilst I conclude that musical notes
and rhythm were first acquired by the male or female progenitors of
mankind for the sake of charming the opposite sex. Thus musical tones
became firmly associated with some of the strongest passions an animal
is capable of feeling, and are consequently used instinctively, or
through association when strong emotions are expressed in speech. Mr.
Spencer does not offer any satisfactory explanation, nor can I, why
high or deep notes should be expressive, both with man and the lower
animals, of certain emotions. Mr. Spencer gives also an interesting
discussion on the relations between poetry, recitative and song.) We
can thus understand how it is that music, dancing, song, and poetry are
such very ancient arts. We may go even further than this, and, as
remarked in a former chapter, believe that musical sounds afforded one
of the bases for the development of language. (40. I find in Lord
Monboddo’s ‘Origin of Language,’ vol. i. 1774, p. 469, that Dr.
Blacklock likewise thought “that the first language among men was
music, and that before our ideas were expressed by articulate sounds,
they were communicated by tones varied according to different degrees
of gravity and acuteness.”)

As the males of several quadrumanous animals have their vocal organs
much more developed than in the females, and as a gibbon, one of the
anthropomorphous apes, pours forth a whole octave of musical notes and
may be said to sing, it appears probable that the progenitors of man,
either the males or females or both sexes, before acquiring the power
of expressing their mutual love in articulate language, endeavoured to
charm each other with musical notes and rhythm. So little is known
about the use of the voice by the Quadrumana during the season of love,
that we have no means of judging whether the habit of singing was first
acquired by our male or female ancestors. Women are generally thought
to possess sweeter voices than men, and as far as this serves as any
guide, we may infer that they first acquired musical powers in order to
attract the other sex. (41. See an interesting discussion on this
subject by Haeckel, ‘Generelle Morphologie,’ B. ii. 1866, s. 246.) But
if so, this must have occurred long ago, before our ancestors had
become sufficiently human to treat and value their women merely as
useful slaves. The impassioned orator, bard, or musician, when with his
varied tones and cadences he excites the strongest emotions in his
hearers, little suspects that he uses the same means by which his
half-human ancestors long ago aroused each other’s ardent passions,
during their courtship and rivalry.

THE INFLUENCE OF BEAUTY IN DETERMINING THE MARRIAGES OF MANKIND.

In civilised life man is largely, but by no means exclusively,
influenced in the choice of his wife by external appearance; but we are
chiefly concerned with primeval times, and our only means of forming a
judgment on this subject is to study the habits of existing
semi-civilised and savage nations. If it can be shewn that the men of
different races prefer women having various characteristics, or
conversely with the women, we have then to enquire whether such choice,
continued during many generations, would produce any sensible effect on
the race, either on one sex or both according to the form of
inheritance which has prevailed.

It will be well first to shew in some detail that savages pay the
greatest attention to their personal appearance. (42. A full and
excellent account of the manner in which savages in all parts of the
world ornament themselves, is given by the Italian traveller, Professor
Mantegazza, ‘Rio de la Plata, Viaggi e Studi,’ 1867, pp. 525-545; all
the following statements, when other references are not given, are
taken from this work. See, also, Waitz, ‘Introduction to Anthropology,’
Eng. translat. vol. i. 1863, p. 275, et passim. Lawrence also gives
very full details in his ‘Lectures on Physiology,’ 1822. Since this
chapter was written Sir J. Lubbock has published his ‘Origin of
Civilisation,’ 1870, in which there is an interesting chapter on the
present subject, and from which (pp. 42, 48) I have taken some facts
about savages dyeing their teeth and hair, and piercing their teeth.)
That they have a passion for ornament is notorious; and an English
philosopher goes so far as to maintain, that clothes were first made
for ornament and not for warmth. As Professor Waitz remarks, “however
poor and miserable man is, he finds a pleasure in adorning himself.”
The extravagance of the naked Indians of South America in decorating
themselves is shewn “by a man of large stature gaining with difficulty
enough by the labour of a fortnight to procure in exchange the chica
necessary to paint himself red.” (43. Humboldt, ‘Personal Narrative,’
Eng. translat. vol. iv. p. 515; on the imagination shewn in painting
the body, p. 522; on modifying the form of the calf of the leg, p.
466.) The ancient barbarians of Europe during the Reindeer period
brought to their caves any brilliant or singular objects which they
happened to find. Savages at the present day everywhere deck themselves
with plumes, necklaces, armlets, ear-rings, etc. They paint themselves
in the most diversified manner. “If painted nations,” as Humboldt
observes, “had been examined with the same attention as clothed
nations, it would have been perceived that the most fertile imagination
and the most mutable caprice have created the fashions of painting, as
well as those of garments.”

In one part of Africa the eyelids are coloured black; in another the
nails are coloured yellow or purple. In many places the hair is dyed of
various tints. In different countries the teeth are stained black, red,
blue, etc., and in the Malay Archipelago it is thought shameful to have
white teeth “like those of a dog.” Not one great country can be named,
from the polar regions in the north to New Zealand in the south, in
which the aborigines do not tattoo themselves. This practice was
followed by the Jews of old, and by the ancient Britons. In Africa some
of the natives tattoo themselves, but it is a much more common practice
to raise protuberances by rubbing salt into incisions made in various
parts of the body; and these are considered by the inhabitants of
Kordofan and Darfur “to be great personal attractions.” In the Arab
countries no beauty can be perfect until the cheeks “or temples have
been gashed.” (44. ‘The Nile Tributaries,’ 1867; ‘The Albert N’yanza,’
1866, vol. i. p. 218.) In South America, as Humboldt remarks, “a mother
would be accused of culpable indifference towards her children, if she
did not employ artificial means to shape the calf of the leg after the
fashion of the country.” In the Old and New Worlds the shape of the
skull was formerly modified during infancy in the most extraordinary
manner, as is still the case in many places, and such deformities are
considered ornamental. For instance, the savages of Colombia (45.
Quoted by Prichard, ‘Physical History of Mankind,’ 4th ed. vol. i.
1851, p. 321.) deem a much flattened head “an essential point of
beauty.”

The hair is treated with especial care in various countries; it is
allowed to grow to full length, so as to reach to the ground, or is
combed into “a compact frizzled mop, which is the Papuan’s pride and
glory.” (46. On the Papuans, Wallace, ‘The Malay Archipelago,’ vol. ii.
p. 445. On the coiffure of the Africans, Sir S. Baker, ‘The Albert
N’yanza,’ vol. i. p. 210.) In northern Africa “a man requires a period
of from eight to ten years to perfect his coiffure.” With other nations
the head is shaved, and in parts of South America and Africa even the
eyebrows and eyelashes are eradicated. The natives of the Upper Nile
knock out the four front teeth, saying that they do not wish to
resemble brutes. Further south, the Batokas knock out only the two
upper incisors, which, as Livingstone (47. ‘Travels,’ p. 533.) remarks,
gives the face a hideous appearance, owing to the prominence of the
lower jaw; but these people think the presence of the incisors most
unsightly, and on beholding some Europeans, cried out, “Look at the
great teeth!” The chief Sebituani tried in vain to alter this fashion.
In various parts of Africa and in the Malay Archipelago the natives
file the incisors into points like those of a saw, or pierce them with
holes, into which they insert studs.

As the face with us is chiefly admired for its beauty, so with savages
it is the chief seat of mutilation. In all quarters of the world the
septum, and more rarely the wings of the nose are pierced; rings,
sticks, feathers, and other ornaments being inserted into the holes.
The ears are everywhere pierced and similarly ornamented, and with the
Botocudos and Lenguas of South America the hole is gradually so much
enlarged that the lower edge touches the shoulder. In North and South
America and in Africa either the upper or lower lip is pierced; and
with the Botocudos the hole in the lower lip is so large that a disc of
wood, four inches in diameter, is placed in it. Mantegazza gives a
curious account of the shame felt by a South American native, and of
the ridicule which he excited, when he sold his tembeta,—the large
coloured piece of wood which is passed through the hole. In Central
Africa the women perforate the lower lip and wear a crystal, which,
from the movement of the tongue, has “a wriggling motion, indescribably
ludicrous during conversation.” The wife of the chief of Latooka told
Sir S. Baker (49. ‘The Albert N’yanza,’ 1866, vol. i. p. 217.) that
Lady Baker “would be much improved if she would extract her four front
teeth from the lower jaw, and wear the long pointed polished crystal in
her under lip.” Further south with the Makalolo, the upper lip is
perforated, and a large metal and bamboo ring, called a pelele, is worn
in the hole. “This caused the lip in one case to project two inches
beyond the tip of the nose; and when the lady smiled, the contraction
of the muscles elevated it over the eyes. ‘Why do the women wear these
things?’ the venerable chief, Chinsurdi, was asked. Evidently surprised
at such a stupid question, he replied, ‘For beauty! They are the only
beautiful things women have; men have beards, women have none. What
kind of a person would she be without the pelele? She would not be a
woman at all with a mouth like a man, but no beard.’” (49. Livingstone,
‘British Association,’ 1860; report given in the ‘Athenaeum,’ July 7,
1860, p. 29.)

Hardly any part of the body, which can be unnaturally modified, has
escaped. The amount of suffering thus caused must have been extreme,
for many of the operations require several years for their completion,
so that the idea of their necessity must be imperative. The motives are
various; the men paint their bodies to make themselves appear terrible
in battle; certain mutilations are connected with religious rites, or
they mark the age of puberty, or the rank of the man, or they serve to
distinguish the tribes. Amongst savages the same fashions prevail for
long periods (50. Sir S. Baker (ibid. vol. i. p. 210) speaking of the
natives of Central Africa says, “every tribe has a distinct and
unchanging fashion for dressing the hair.” See Agassiz (‘Journey in
Brazil,’ 1868, p. 318) on invariability of the tattooing of Amazonian
Indians.), and thus mutilations, from whatever cause first made, soon
come to be valued as distinctive marks. But self-adornment, vanity, and
the admiration of others, seem to be the commonest motives. In regard
to tattooing, I was told by the missionaries in New Zealand that when
they tried to persuade some girls to give up the practice, they
answered, “We must just have a few lines on our lips; else when we grow
old we shall be so very ugly.” With the men of New Zealand, a most
capable judge (51. Rev. R. Taylor, ‘New Zealand and its Inhabitants,’
1855, p. 152.) says, “to have fine tattooed faces was the great
ambition of the young, both to render themselves attractive to the
ladies, and conspicuous in war.” A star tattooed on the forehead and a
spot on the chin are thought by the women in one part of Africa to be
irresistible attractions. (52. Mantegazza, ‘Viaggi e Studi,’ p. 542.)
In most, but not all parts of the world, the men are more ornamented
than the women, and often in a different manner; sometimes, though
rarely, the women are hardly at all ornamented. As the women are made
by savages to perform the greatest share of the work, and as they are
not allowed to eat the best kinds of food, so it accords with the
characteristic selfishness of man that they should not be allowed to
obtain, or use the finest ornaments. Lastly, it is a remarkable fact,
as proved by the foregoing quotations, that the same fashions in
modifying the shape of the head, in ornamenting the hair, in painting,
tattooing, in perforating the nose, lips, or ears, in removing or
filing the teeth, etc., now prevail, and have long prevailed, in the
most distant quarters of the world. It is extremely improbable that
these practices, followed by so many distinct nations, should be due to
tradition from any common source. They indicate the close similarity of
the mind of man, to whatever race he may belong, just as do the almost
universal habits of dancing, masquerading, and making rude pictures.

Having made these preliminary remarks on the admiration felt by savages
for various ornaments, and for deformities most unsightly in our eyes,
let us see how far the men are attracted by the appearance of their
women, and what are their ideas of beauty. I have heard it maintained
that savages are quite indifferent about the beauty of their women,
valuing them solely as slaves; it may therefore be well to observe that
this conclusion does not at all agree with the care which the women
take in ornamenting themselves, or with their vanity. Burchell (53.
‘Travels in South Africa,’ 1824, vol. i. p. 414.) gives an amusing
account of a Bush-woman who used as much grease, red ochre, and shining
powder “as would have ruined any but a very rich husband.” She
displayed also “much vanity and too evident a consciousness of her
superiority.” Mr. Winwood Reade informs me that the negroes of the West
Coast often discuss the beauty of their women. Some competent observers
have attributed the fearfully common practice of infanticide partly to
the desire felt by the women to retain their good looks. (54. See, for
references, Gerland, ‘Ueber das Aussterben der Naturvölker,’ 1868, ss.
51, 53, 55; also Azara, ‘Voyages,’ etc., tom. ii. p. 116.) In several
regions the women wear charms and use love-philters to gain the
affections of the men; and Mr. Brown enumerates four plants used for
this purpose by the women of North-Western America. (55. On the
vegetable productions used by the North-Western American Indians, see
‘Pharmaceutical Journal,’ vol. x.)

Hearne (56. ‘A Journey from Prince of Wales Fort,’ 8vo. ed. 1796, p.
89.), an excellent observer, who lived many years with the American
Indians, says, in speaking of the women, “Ask a Northern Indian what is
beauty, and he will answer, a broad flat face, small eyes, high
cheek-bones, three or four broad black lines across each cheek, a low
forehead, a large broad chin, a clumsy hook nose, a tawny hide, and
breasts hanging down to the belt.” Pallas, who visited the northern
parts of the Chinese empire, says, “those women are preferred who have
the Mandschu form; that is to say, a broad face, high cheek-bones, very
broad noses, and enormous ears”(57. Quoted by Prichard, ‘Physical
History of Mankind,’ 3rd ed. vol. iv. 1844, p. 519; Vogt, ‘Lectures on
Man,’ Eng. translat. p. 129. On the opinion of the Chinese on the
Cingalese, E. Tennent, ‘Ceylon,’ 1859, vol. ii. p. 107.); and Vogt
remarks that the obliquity of the eye, which is proper to the Chinese
and Japanese, is exaggerated in their pictures for the purpose, as it
“seems, of exhibiting its beauty, as contrasted with the eye of the
red-haired barbarians.” It is well known, as Huc repeatedly remarks,
that the Chinese of the interior think Europeans hideous, with their
white skins and prominent noses. The nose is far from being too
prominent, according to our ideas, in the natives of Ceylon; yet “the
Chinese in the seventh century, accustomed to the flat features of the
Mongol races, were surprised at the prominent noses of the Cingalese;
and Thsang described them as having ‘the beak of a bird, with the body
of a man.’”

Finlayson, after minutely describing the people of Cochin China, says
that their rounded heads and faces are their chief characteristics;
and, he adds, “the roundness of the whole countenance is more striking
in the women, who are reckoned beautiful in proportion as they display
this form of face.” The Siamese have small noses with divergent
nostrils, a wide mouth, rather thick lips, a remarkably large face,
with very high and broad cheek-bones. It is, therefore, not wonderful
that “beauty, according to our notion, is a stranger to them. Yet they
consider their own females to be much more beautiful than those of
Europe.” (58. Prichard, as taken from Crawfurd and Finlayson, ‘Phys.
Hist. of Mankind,’ vol. iv. pp. 534, 535.)

It is well known that with many Hottentot women the posterior part of
the body projects in a wonderful manner; they are steatopygous; and Sir
Andrew Smith is certain that this peculiarity is greatly admired by the
men. (59. Idem illustrissimus viator dixit mihi praecinctorium vel
tabulam foeminae, quod nobis teterrimum est, quondam permagno aestimari
ab hominibus in hac gente. Nunc res mutata est, et censent talem
conformationem minime optandam esse.) He once saw a woman who was
considered a beauty, and she was so immensely developed behind, that
when seated on level ground she could not rise, and had to push herself
along until she came to a slope. Some of the women in various negro
tribes have the same peculiarity; and, according to Burton, the Somal
men are said to choose their wives by ranging them in a line, and by
picking her out who projects farthest a tergo. Nothing can be more
hateful to a negro than the opposite form.” (60. The ‘Anthropological
Review,’ November 1864, p. 237. For additional references, see Waitz,
‘Introduction to Anthropology,’ Eng. translat., 1863, vol. i. p. 105.)

With respect to colour, the negroes rallied Mungo Park on the whiteness
of his skin and the prominence of his nose, both of which they
considered as “unsightly and unnatural conformations.” He in return
praised the glossy jet of their skins and the lovely depression of
their noses; this they said was “honeymouth,” nevertheless they gave
him food. The African Moors, also, “knitted their brows and seemed to
shudder” at the whiteness of his skin. On the eastern coast, the negro
boys when they saw Burton, cried out, “Look at the white man; does he
not look like a white ape?” On the western coast, as Mr. Winwood Reade
informs me, the negroes admire a very black skin more than one of a
lighter tint. But their horror of whiteness may be attributed,
according to this same traveller, partly to the belief held by most
negroes that demons and spirits are white, and partly to their thinking
it a sign of ill-health.

The Banyai of the more southern part of the continent are negroes, but
“a great many of them are of a light coffee-and-milk colour, and,
indeed, this colour is considered handsome throughout the whole
country”; so that here we have a different standard of taste. With the
Kaffirs, who differ much from negroes, “the skin, except among the
tribes near Delagoa Bay, is not usually black, the prevailing colour
being a mixture of black and red, the most common shade being
chocolate. Dark complexions, as being most common, are naturally held
in the highest esteem. To be told that he is light-coloured, or like a
white man, would be deemed a very poor compliment by a Kaffir. I have
heard of one unfortunate man who was so very fair that no girl would
marry him.” One of the titles of the Zulu king is, “You who are black.”
(61. Mungo Park’s ‘Travels in Africa,’ 4to. 1816, pp. 53, 131. Burton’s
statement is quoted by Schaaffhausen, ‘Archiv. fur Anthropologie,’
1866, s. 163. On the Banyai, Livingstone, ‘Travels,’ p. 64. On the
Kaffirs, the Rev. J. Shooter, ‘The Kafirs of Natal and the Zulu
Country,’ 1857, p. 1.) Mr. Galton, in speaking to me about the natives
of S. Africa, remarked that their ideas of beauty seem very different
from ours; for in one tribe two slim, slight, and pretty girls were not
admired by the natives.

Turning to other quarters of the world; in Java, a yellow, not a white
girl, is considered, according to Madame Pfeiffer, a beauty. A man of
Cochin China “spoke with contempt of the wife of the English
Ambassador, that she had white teeth like a dog, and a rosy colour like
that of potato-flowers.” We have seen that the Chinese dislike our
white skin, and that the N. Americans admire “a tawny hide.” In S.
America, the Yuracaras, who inhabit the wooded, damp slopes of the
eastern Cordillera, are remarkably pale-coloured, as their name in
their own language expresses; nevertheless they consider European women
as very inferior to their own. (62. For the Javans and Cochin-Chinese,
see Waitz, ‘Introduct. to Anthropology,’ Eng. translat. vol. i. p. 305.
On the Yuracaras, A. d’Orbigny, as quoted in Prichard, ‘Physical
History of Mankind,’ vol. v. 3rd ed. p. 476.)

In several of the tribes of North America the hair on the head grows to
a wonderful length; and Catlin gives a curious proof how much this is
esteemed, for the chief of the Crows was elected to this office from
having the longest hair of any man in the tribe, namely ten feet and
seven inches. The Aymaras and Quichuas of S. America, likewise have
very long hair; and this, as Mr. D. Forbes informs me, is so much
valued as a beauty, that cutting it off was the severest punishment
which he could inflict on them. In both the Northern and Southern
halves of the continent the natives sometimes increase the apparent
length of their hair by weaving into it fibrous substances. Although
the hair on the head is thus cherished, that on the face is considered
by the North American Indians “as very vulgar,” and every hair is
carefully eradicated. This practice prevails throughout the American
continent from Vancouver’s Island in the north to Tierra del Fuego in
the south. When York Minster, a Fuegian on board the “Beagle,” was
taken back to his country, the natives told him he ought to pull out
the few short hairs on his face. They also threatened a young
missionary, who was left for a time with them, to strip him naked, and
pluck the hair from his face and body, yet he was far from being a
hairy man. This fashion is carried so far that the Indians of Paraguay
eradicate their eyebrows and eyelashes, saying that they do not wish to
be like horses. (63. ‘North American Indians,’ by G. Catlin, 3rd ed.,
1842, vol. i. p. 49; vol. ii, p. 227. On the natives of Vancouver’s
Island, see Sproat, ‘Scenes and Studies of Savage Life,’ 1868, p. 25.
On the Indians of Paraguay, Azara, ‘Voyages,’ tom. ii. p. 105.)

It is remarkable that throughout the world the races which are almost
completely destitute of a beard dislike hairs on the face and body, and
take pains to eradicate them. The Kalmucks are beardless, and they are
well known, like the Americans, to pluck out all straggling hairs; and
so it is with the Polynesians, some of the Malays, and the Siamese. Mr.
Veitch states that the Japanese ladies “all objected to our whiskers,
considering them very ugly, and told us to cut them off, and be like
Japanese men.” The New Zealanders have short, curled beards; yet they
formerly plucked out the hairs on the face. They had a saying that
“there is no woman for a hairy man;” but it would appear that the
fashion has changed in New Zealand, perhaps owing to the presence of
Europeans, and I am assured that beards are now admired by the Maories.
(64. On the Siamese, Prichard, ibid. vol. iv. p. 533. On the Japanese,
Veitch in ‘Gardeners’ Chronicle,’ 1860, p. 1104. On the New Zealanders,
Mantegazza, ‘Viaggi e Studi,’ 1867, p. 526. For the other nations
mentioned, see references in Lawrence, ‘Lectures on Physiology,’ etc.,
1822, p. 272.)

On the other hand, bearded races admire and greatly value their beards;
among the Anglo-Saxons every part of the body had a recognised value;
“the loss of the beard being estimated at twenty shillings, while the
breaking of a thigh was fixed at only twelve.” (65. Lubbock, ‘Origin of
Civilisation,’ 1870, p. 321.) In the East men swear solemnly by their
beards. We have seen that Chinsurdi, the chief of the Makalolo in
Africa, thought that beards were a great ornament. In the Pacific the
Fijian’s beard is “profuse and bushy, and is his greatest pride”;
whilst the inhabitants of the adjacent archipelagoes of Tonga and Samoa
are “beardless, and abhor a rough chin.” In one island alone of the
Ellice group “the men are heavily bearded, and not a little proud
thereof.” (66. Dr. Barnard Davis quotes Mr. Prichard and others for
these facts in regard to the Polynesians, in ‘Anthropolog. Review,’
April 1870, pp. 185, 191.)

We thus see how widely the different races of man differ in their taste
for the beautiful. In every nation sufficiently advanced to have made
effigies of their gods or of their deified rulers, the sculptors no
doubt have endeavoured to express their highest ideal of beauty and
grandeur. (67. Ch. Comte has remarks to this effect in his ‘Traité de
Législation,’ 3rd ed. 1837, p. 136.) Under this point of view it is
well to compare in our mind the Jupiter or Apollo of the Greeks with
the Egyptian or Assyrian statues; and these with the hideous
bas-reliefs on the ruined buildings of Central America.

I have met with very few statements opposed to this conclusion. Mr.
Winwood Reade, however, who has had ample opportunities for
observation, not only with the negroes of the West Coast of Africa, but
with those of the interior who have never associated with Europeans, is
convinced that their ideas of beauty are ON THE WHOLE the same as ours;
and Dr. Rohlfs writes to me to the same effect with respect to Bornu
and the countries inhabited by the Pullo tribes. Mr. Reade found that
he agreed with the negroes in their estimation of the beauty of the
native girls; and that their appreciation of the beauty of European
women corresponded with ours. They admire long hair, and use artificial
means to make it appear abundant; they admire also a beard, though
themselves very scantily provided. Mr. Reade feels doubtful what kind
of nose is most appreciated; a girl has been heard to say, “I do not
want to marry him, he has got no nose”; and this shews that a very flat
nose is not admired. We should, however, bear in mind that the
depressed, broad noses and projecting jaws of the negroes of the West
Coast are exceptional types with the inhabitants of Africa.
Notwithstanding the foregoing statements, Mr. Reade admits that negroes
“do not like the colour of our skin; they look on blue eyes with
aversion, and they think our noses too long and our lips too thin.” He
does not think it probable that negroes would ever prefer the most
beautiful European woman, on the mere grounds of physical admiration,
to a good-looking negress. (68. The ‘African Sketch Book,’ vol. ii.
1873, pp. 253, 394, 521. The Fuegians, as I have been informed by a
missionary who long resided with them, consider European women as
extremely beautiful; but from what we have seen of the judgment of the
other aborigines of America, I cannot but think that this must be a
mistake, unless indeed the statement refers to the few Fuegians who
have lived for some time with Europeans, and who must consider us as
superior beings. I should add that a most experienced observer, Capt.
Burton, believes that a woman whom we consider beautiful is admired
throughout the world. ‘Anthropological Review,’ March, 1864, p. 245.)

The general truth of the principle, long ago insisted on by Humboldt
(69. ‘Personal Narrative,’ Eng. translat. vol. iv. p. 518, and
elsewhere. Mantegazza, in his ‘Viaggi e Studi,’ strongly insists on
this same principle.), that man admires and often tries to exaggerate
whatever characters nature may have given him, is shewn in many ways.
The practice of beardless races extirpating every trace of a beard, and
often all the hairs on the body affords one illustration. The skull has
been greatly modified during ancient and modern times by many nations;
and there can be little doubt that this has been practised, especially
in N. and S. America, in order to exaggerate some natural and admired
peculiarity. Many American Indians are known to admire a head so
extremely flattened as to appear to us idiotic. The natives on the
north-western coast compress the head into a pointed cone; and it is
their constant practice to gather the hair into a knot on the top of
the head, for the sake, as Dr. Wilson remarks, “of increasing the
apparent elevation of the favourite conoid form.” The inhabitants of
Arakhan admire a broad, smooth forehead, and in order to produce it,
they fasten a plate of lead on the heads of the new-born children. On
the other hand, “a broad, well-rounded occiput is considered a great
beauty” by the natives of the Fiji Islands. (70. On the skulls of the
American tribes, see Nott and Gliddon, ‘Types of Mankind,’ 1854, p.
440; Prichard, ‘Physical History of Mankind,’ vol. i. 3rd ed. p. 321;
on the natives of Arakhan, ibid. vol. iv. p. 537. Wilson, ‘Physical
Ethnology,’ Smithsonian Institution, 1863, p. 288; on the Fijians, p.
290. Sir J. Lubbock (‘Prehistoric Times,’ 2nd ed. 1869, p. 506) gives
an excellent resume on this subject.)

As with the skull, so with the nose; the ancient Huns during the age of
Attila were accustomed to flatten the noses of their infants with
bandages, “for the sake of exaggerating a natural conformation.” With
the Tahitians, to be called LONG-NOSE is considered as an insult, and
they compress the noses and foreheads of their children for the sake of
beauty. The same holds with the Malays of Sumatra, the Hottentots,
certain Negroes, and the natives of Brazil. (71. On the Huns, Godron,
‘De l’Espèce,’ tom. ii. 1859, p. 300. On the Tahitians, Waitz,
‘Anthropology,’ Eng. translat. vol. i. p. 305. Marsden, quoted by
Prichard, ‘Phys. Hist. of Mankind,’ 3rd edit. vol. v. p. 67. Lawrence,
‘Lectures on Physiology,’ p. 337.) The Chinese have by nature unusually
small feet (72. This fact was ascertained in the ‘Reise der Novara:
Anthropolog. Theil.’ Dr. Weisbach, 1867, s. 265.); and it is well known
that the women of the upper classes distort their feet to make them
still smaller. Lastly, Humboldt thinks that the American Indians prefer
colouring their bodies with red paint in order to exaggerate their
natural tint; and until recently European women added to their
naturally bright colours by rouge and white cosmetics; but it may be
doubted whether barbarous nations have generally had any such intention
in painting themselves.

In the fashions of our own dress we see exactly the same principle and
the same desire to carry every point to an extreme; we exhibit, also,
the same spirit of emulation. But the fashions of savages are far more
permanent than ours; and whenever their bodies are artificially
modified, this is necessarily the case. The Arab women of the Upper
Nile occupy about three days in dressing their hair; they never imitate
other tribes, “but simply vie with each other in the superlativeness of
their own style.” Dr. Wilson, in speaking of the compressed skulls of
various American races, adds, “such usages are among the least
eradicable, and long survive the shock of revolutions that change
dynasties and efface more important national peculiarities.” (73.
‘Smithsonian Institution,’ 1863, p. 289. On the fashions of Arab women,
Sir S. Baker, ‘The Nile Tributaries,’ 1867, p. 121.) The same principle
comes into play in the art of breeding; and we can thus understand, as
I have elsewhere explained (74. The ‘Variation of Animals and Plants
under Domestication,’ vol. i. p. 214; vol. ii. p. 240.), the wonderful
development of the many races of animals and plants, which have been
kept merely for ornament. Fanciers always wish each character to be
somewhat increased; they do not admire a medium standard; they
certainly do not desire any great and abrupt change in the character of
their breeds; they admire solely what they are accustomed to, but they
ardently desire to see each characteristic feature a little more
developed.

The senses of man and of the lower animals seem to be so constituted
that brilliant colours and certain forms, as well as harmonious and
rhythmical sounds, give pleasure and are called beautiful; but why this
should be so we know not. It is certainly not true that there is in the
mind of man any universal standard of beauty with respect to the human
body. It is, however, possible that certain tastes may in the course of
time become inherited, though there is no evidence in favour of this
belief: and if so, each race would possess its own innate ideal
standard of beauty. It has been argued (75. Schaaffhausen, ‘Archiv. für
Anthropologie,’ 1866, s. 164.) that ugliness consists in an approach to
the structure of the lower animals, and no doubt this is partly true
with the more civilised nations, in which intellect is highly
appreciated; but this explanation will hardly apply to all forms of
ugliness. The men of each race prefer what they are accustomed to; they
cannot endure any great change; but they like variety, and admire each
characteristic carried to a moderate extreme. (76. Mr. Bain has
collected (‘Mental and Moral Science,’ 1868, pp. 304-314) about a dozen
more or less different theories of the idea of beauty; but none is
quite the same as that here given.) Men accustomed to a nearly oval
face, to straight and regular features, and to bright colours, admire,
as we Europeans know, these points when strongly developed. On the
other hand, men accustomed to a broad face, with high cheek-bones, a
depressed nose, and a black skin, admire these peculiarities when
strongly marked. No doubt characters of all kinds may be too much
developed for beauty. Hence a perfect beauty, which implies many
characters modified in a particular manner, will be in every race a
prodigy. As the great anatomist Bichat long ago said, if every one were
cast in the same mould, there would be no such thing as beauty. If all
our women were to become as beautiful as the Venus de’ Medici, we
should for a time be charmed; but we should soon wish for variety; and
as soon as we had obtained variety, we should wish to see certain
characters a little exaggerated beyond the then existing common
standard.




CHAPTER XX.
SECONDARY SEXUAL CHARACTERS OF MAN—continued.


On the effects of the continued selection of women according to a
different standard of beauty in each race—On the causes which interfere
with sexual selection in civilised and savage nations—Conditions
favourable to sexual selection during primeval times—On the manner of
action of sexual selection with mankind—On the women in savage tribes
having some power to choose their husbands—Absence of hair on the body,
and development of the beard—Colour of the skin—Summary.

We have seen in the last chapter that with all barbarous races
ornaments, dress, and external appearance are highly valued; and that
the men judge of the beauty of their women by widely different
standards. We must next inquire whether this preference and the
consequent selection during many generations of those women, which
appear to the men of each race the most attractive, has altered the
character either of the females alone, or of both sexes. With mammals
the general rule appears to be that characters of all kinds are
inherited equally by the males and females; we might therefore expect
that with mankind any characters gained by the females or by the males
through sexual selection would commonly be transferred to the offspring
of both sexes. If any change has thus been effected, it is almost
certain that the different races would be differently modified, as each
has its own standard of beauty.

With mankind, especially with savages, many causes interfere with the
action of sexual selection as far as the bodily frame is concerned.
Civilised men are largely attracted by the mental charms of women, by
their wealth, and especially by their social position; for men rarely
marry into a much lower rank. The men who succeed in obtaining the more
beautiful women will not have a better chance of leaving a long line of
descendants than other men with plainer wives, save the few who
bequeath their fortunes according to primogeniture. With respect to the
opposite form of selection, namely, of the more attractive men by the
women, although in civilised nations women have free or almost free
choice, which is not the case with barbarous races, yet their choice is
largely influenced by the social position and wealth of the men; and
the success of the latter in life depends much on their intellectual
powers and energy, or on the fruits of these same powers in their
forefathers. No excuse is needed for treating this subject in some
detail; for, as the German philosopher Schopenhauer remarks, “the final
aim of all love intrigues, be they comic or tragic, is really of more
importance than all other ends in human life. What it all turns upon is
nothing less than the composition of the next generation...It is not
the weal or woe of any one individual, but that of the human race to
come, which is here at stake.” (1. ‘Schopenhauer and Darwinism,’ in
‘Journal of Anthropology,’ Jan. 1871, p. 323.

There is, however, reason to believe that in certain civilised and
semi-civilised nations sexual selection has effected something in
modifying the bodily frame of some of the members. Many persons are
convinced, as it appears to me with justice, that our aristocracy,
including under this term all wealthy families in which primogeniture
has long prevailed, from having chosen during many generations from all
classes the more beautiful women as their wives, have become handsomer,
according to the European standard, than the middle classes; yet the
middle classes are placed under equally favourable conditions of life
for the perfect development of the body. Cook remarks that the
superiority in personal appearance “which is observable in the erees or
nobles in all the other islands (of the Pacific) is found in the
Sandwich Islands”; but this may be chiefly due to their better food and
manner of life.

The old traveller Chardin, in describing the Persians, says their
“blood is now highly refined by frequent intermixtures with the
Georgians and Circassians, two nations which surpass all the world in
personal beauty. There is hardly a man of rank in Persia who is not
born of a Georgian or Circassian mother.” He adds that they inherit
their beauty, “not from their ancestors, for without the above mixture,
the men of rank in Persia, who are descendants of the Tartars, would be
extremely ugly.” (2. These quotations are taken from Lawrence
(‘Lectures on Physiology,’ etc., 1822, p. 393), who attributes the
beauty of the upper classes in England to the men having long selected
the more beautiful women.) Here is a more curious case; the priestesses
who attended the temple of Venus Erycina at San-Giuliano in Sicily,
were selected for their beauty out of the whole of Greece; they were
not vestal virgins, and Quatrefages (3. ‘Anthropologie,’ ‘Revue des
Cours Scientifiques,’ Oct. 1868, p. 721.), who states the foregoing
fact, says that the women of San-Giuliano are now famous as the most
beautiful in the island, and are sought by artists as models. But it is
obvious that the evidence in all the above cases is doubtful.

The following case, though relating to savages, is well worth giving
for its curiosity. Mr. Winwood Reade informs me that the Jollofs, a
tribe of negroes on the west coast of Africa, “are remarkable for their
uniformly fine appearance.” A friend of his asked one of these men,
“How is it that every one whom I meet is so fine looking, not only your
men but your women?” The Jollof answered, “It is very easily explained:
it has always been our custom to pick out our worst-looking slaves and
to sell them.” It need hardly be added that with all savages, female
slaves serve as concubines. That this negro should have attributed,
whether rightly or wrongly, the fine appearance of his tribe to the
long-continued elimination of the ugly women is not so surprising as it
may at first appear; for I have elsewhere shewn (4. ‘Variation of
Animals and Plants under Domestication,’ vol. i. p. 207.) that negroes
fully appreciate the importance of selection in the breeding of their
domestic animals, and I could give from Mr. Reade additional evidence
on this head.

THE CAUSES WHICH PREVENT OR CHECK THE ACTION OF SEXUAL SELECTION WITH
SAVAGES.

The chief causes are, first, so-called communal marriages or
promiscuous intercourse; secondly, the consequences of female
infanticide; thirdly, early betrothals; and lastly, the low estimation
in which women are held, as mere slaves. These four points must be
considered in some detail.

It is obvious that as long as the pairing of man, or of any other
animal, is left to mere chance, with no choice exerted by either sex,
there can be no sexual selection; and no effect will be produced on the
offspring by certain individuals having had an advantage over others in
their courtship. Now it is asserted that there exist at the present day
tribes which practise what Sir J. Lubbock by courtesy calls communal
marriages; that is, all the men and women in the tribe are husbands and
wives to one another. The licentiousness of many savages is no doubt
astonishing, but it seems to me that more evidence is requisite, before
we fully admit that their intercourse is in any case promiscuous.
Nevertheless all those who have most closely studied the subject (5.
Sir J. Lubbock, ‘The Origin of Civilisation,’ 1870, chap. iii.
especially pp. 60-67. Mr. M’Lennan, in his extremely valuable work on
‘Primitive Marriage,’ 1865, p. 163, speaks of the union of the sexes
“in the earliest times as loose, transitory, and in some degree
promiscuous.” Mr. M’Lennan and Sir J. Lubbock have collected much
evidence on the extreme licentiousness of savages at the present time.
Mr. L.H. Morgan, in his interesting memoir of the classificatory system
of relationship. (‘Proceedings of the American Academy of Sciences,’
vol. vii. Feb. 1868, p. 475), concludes that polygamy and all forms of
marriage during primeval times were essentially unknown. It appears
also, from Sir J. Lubbock’s work, that Bachofen likewise believes that
communal intercourse originally prevailed.), and whose judgment is
worth much more than mine, believe that communal marriage (this
expression being variously guarded) was the original and universal form
throughout the world, including therein the intermarriage of brothers
and sisters. The late Sir A. Smith, who had travelled widely in S.
Africa, and knew much about the habits of savages there and elsewhere,
expressed to me the strongest opinion that no race exists in which
woman is considered as the property of the community. I believe that
his judgment was largely determined by what is implied by the term
marriage. Throughout the following discussion I use the term in the
same sense as when naturalists speak of animals as monogamous, meaning
thereby that the male is accepted by or chooses a single female, and
lives with her either during the breeding-season or for the whole year,
keeping possession of her by the law of might; or, as when they speak
of a polygamous species, meaning that the male lives with several
females. This kind of marriage is all that concerns us here, as it
suffices for the work of sexual selection. But I know that some of the
writers above referred to imply by the term marriage a recognised right
protected by the tribe.

The indirect evidence in favour of the belief of the former prevalence
of communal marriages is strong, and rests chiefly on the terms of
relationship which are employed between the members of the same tribe,
implying a connection with the tribe, and not with either parent. But
the subject is too large and complex for even an abstract to be here
given, and I will confine myself to a few remarks. It is evident in the
case of such marriages, or where the marriage tie is very loose, that
the relationship of the child to its father cannot be known. But it
seems almost incredible that the relationship of the child to its
mother should ever be completely ignored, especially as the women in
most savage tribes nurse their infants for a long time. Accordingly, in
many cases the lines of descent are traced through the mother alone, to
the exclusion of the father. But in other cases the terms employed
express a connection with the tribe alone, to the exclusion even of the
mother. It seems possible that the connection between the related
members of the same barbarous tribe, exposed to all sorts of danger,
might be so much more important, owing to the need of mutual protection
and aid, than that between the mother and her child, as to lead to the
sole use of terms expressive of the former relationships; but Mr.
Morgan is convinced that this view is by no means sufficient.

The terms of relationship used in different parts of the world may be
divided, according to the author just quoted, into two great classes,
the classificatory and descriptive, the latter being employed by us. It
is the classificatory system which so strongly leads to the belief that
communal and other extremely loose forms of marriage were originally
universal. But as far as I can see, there is no necessity on this
ground for believing in absolutely promiscuous intercourse; and I am
glad to find that this is Sir J. Lubbock’s view. Men and women, like
many of the lower animals, might formerly have entered into strict
though temporary unions for each birth, and in this case nearly as much
confusion would have arisen in the terms of relationship as in the case
of promiscuous intercourse. As far as sexual selection is concerned,
all that is required is that choice should be exerted before the
parents unite, and it signifies little whether the unions last for life
or only for a season.

Besides the evidence derived from the terms of relationship, other
lines of reasoning indicate the former wide prevalence of communal
marriage. Sir J. Lubbock accounts for the strange and widely-extended
habit of exogamy—that is, the men of one tribe taking wives from a
distinct tribe,—by communism having been the original form of
intercourse; so that a man never obtained a wife for himself unless he
captured her from a neighbouring and hostile tribe, and then she would
naturally have become his sole and valuable property. Thus the practice
of capturing wives might have arisen; and from the honour so gained it
might ultimately have become the universal habit. According to Sir J.
Lubbock (6. ‘Address to British Association On the Social and Religious
Condition of the Lower Races of Man,’ 1870, p. 20.), we can also thus
understand “the necessity of expiation for marriage as an infringement
of tribal rites, since according to old ideas, a man had no right to
appropriate to himself that which belonged to the whole tribe.” Sir J.
Lubbock further gives a curious body of facts shewing that in old times
high honour was bestowed on women who were utterly licentious; and
this, as he explains, is intelligible, if we admit that promiscuous
intercourse was the aboriginal, and therefore long revered custom of
the tribe. (7. ‘Origin of Civilisation,’ 1870, p. 86. In the several
works above quoted, there will be found copious evidence on
relationship through the females alone, or with the tribe alone.)

Although the manner of development of the marriage tie is an obscure
subject, as we may infer from the divergent opinions on several points
between the three authors who have studied it most closely, namely, Mr.
Morgan, Mr. M’Lennan, and Sir J. Lubbock, yet from the foregoing and
several other lines of evidence it seems probable (8. Mr. C. Staniland
Wake argues strongly (‘Anthropologia,’ March, 1874, p. 197) against the
views held by these three writers on the former prevalence of almost
promiscuous intercourse; and he thinks that the classificatory system
of relationship can be otherwise explained.) that the habit of
marriage, in any strict sense of the word, has been gradually
developed; and that almost promiscuous or very loose intercourse was
once extremely common throughout the world. Nevertheless, from the
strength of the feeling of jealousy all through the animal kingdom, as
well as from the analogy of the lower animals, more particularly of
those which come nearest to man, I cannot believe that absolutely
promiscuous intercourse prevailed in times past, shortly before man
attained to his present rank in the zoological scale. Man, as I have
attempted to shew, is certainly descended from some ape-like creature.
With the existing Quadrumana, as far as their habits are known, the
males of some species are monogamous, but live during only a part of
the year with the females: of this the orang seems to afford an
instance. Several kinds, for example some of the Indian and American
monkeys, are strictly monogamous, and associate all the year round with
their wives. Others are polygamous, for example the gorilla and several
American species, and each family lives separate. Even when this
occurs, the families inhabiting the same district are probably somewhat
social; the chimpanzee, for instance, is occasionally met with in large
bands. Again, other species are polygamous, but several males, each
with his own females, live associated in a body, as with several
species of baboons. (9. Brehm (‘Thierleben,’ B. i. p. 77) says
Cynocephalus hamadryas lives in great troops containing twice as many
adult females as adult males. See Rengger on American polygamous
species, and Owen (‘Anatomy of Vertebrates,’ vol. iii. p. 746) on
American monogamous species. Other references might be added.) We may
indeed conclude from what we know of the jealousy of all male
quadrupeds, armed, as many of them are, with special weapons for
battling with their rivals, that promiscuous intercourse in a state of
nature is extremely improbable. The pairing may not last for life, but
only for each birth; yet if the males which are the strongest and best
able to defend or otherwise assist their females and young, were to
select the more attractive females, this would suffice for sexual
selection.

Therefore, looking far enough back in the stream of time, and judging
from the social habits of man as he now exists, the most probable view
is that he aboriginally lived in small communities, each with a single
wife, or if powerful with several, whom he jealously guarded against
all other men. Or he may not have been a social animal, and yet have
lived with several wives, like the gorilla; for all the natives “agree
that but one adult male is seen in a band; when the young male grows
up, a contest takes place for mastery, and the strongest, by killing
and driving out the others, establishes himself as the head of the
community.” (10. Dr. Savage, in ‘Boston Journal of Natural History,’
vol. v. 1845-47, p. 423.) The younger males, being thus expelled and
wandering about, would, when at last successful in finding a partner,
prevent too close interbreeding within the limits of the same family.

Although savages are now extremely licentious, and although communal
marriages may formerly have largely prevailed, yet many tribes practise
some form of marriage, but of a far more lax nature than that of
civilised nations. Polygamy, as just stated, is almost universally
followed by the leading men in every tribe. Nevertheless there are
tribes, standing almost at the bottom of the scale, which are strictly
monogamous. This is the case with the Veddahs of Ceylon: they have a
saying, according to Sir J. Lubbock (11. ‘Prehistoric Times,’ 1869, p.
424.), “that death alone can separate husband and wife.” An intelligent
Kandyan chief, of course a polygamist, “was perfectly scandalised at
the utter barbarism of living with only one wife, and never parting
until separated by death.” It was, he said, “just like the Wanderoo
monkeys.” Whether savages who now enter into some form of marriage,
either polygamous or monogamous, have retained this habit from primeval
times, or whether they have returned to some form of marriage, after
passing through a stage of promiscuous intercourse, I will not pretend
to conjecture.

INFANTICIDE.

This practice is now very common throughout the world, and there is
reason to believe that it prevailed much more extensively during former
times. (12. Mr. M’Lennan, ‘Primitive Marriage,’ 1865. See especially on
exogamy and infanticide, pp. 130, 138, 165.) Barbarians find it
difficult to support themselves and their children, and it is a simple
plan to kill their infants. In South America some tribes, according to
Azara, formerly destroyed so many infants of both sexes that they were
on the point of extinction. In the Polynesian Islands women have been
known to kill from four or five, to even ten of their children; and
Ellis could not find a single woman who had not killed at least one. In
a village on the eastern frontier of India Colonel MacCulloch found not
a single female child. Wherever infanticide (13. Dr. Gerland (‘Ueber
das Aussterben der Naturvölker,’ 1868) has collected much information
on infanticide, see especially ss. 27, 51, 54. Azara (‘Voyages,’ etc.,
tom. ii. pp. 94, 116) enters in detail on the motives. See also
M’Lennan (ibid. p. 139) for cases in India. In the former reprints of
the 2nd edition of this book an incorrect quotation from Sir G. Grey
was unfortunately given in the above passage and has now been removed
from the text.) prevails the struggle for existence will be in so far
less severe, and all the members of the tribe will have an almost
equally good chance of rearing their few surviving children. In most
cases a larger number of female than of male infants are destroyed, for
it is obvious that the latter are of more value to the tribe, as they
will, when grown up, aid in defending it, and can support themselves.
But the trouble experienced by the women in rearing children, their
consequent loss of beauty, the higher estimation set on them when few,
and their happier fate, are assigned by the women themselves, and by
various observers, as additional motives for infanticide.

When, owing to female infanticide, the women of a tribe were few, the
habit of capturing wives from neighbouring tribes would naturally
arise. Sir J. Lubbock, however, as we have seen, attributes the
practice in chief part to the former existence of communal marriage,
and to the men having consequently captured women from other tribes to
hold as their sole property. Additional causes might be assigned, such
as the communities being very small, in which case, marriageable women
would often be deficient. That the habit was most extensively practised
during former times, even by the ancestors of civilised nations, is
clearly shewn by the preservation of many curious customs and
ceremonies, of which Mr. M’Lennan has given an interesting account. In
our own marriages the “best man” seems originally to have been the
chief abettor of the bridegroom in the act of capture. Now as long as
men habitually procured their wives through violence and craft, they
would have been glad to seize on any woman, and would not have selected
the more attractive ones. But as soon as the practice of procuring
wives from a distinct tribe was effected through barter, as now occurs
in many places, the more attractive women would generally have been
purchased. The incessant crossing, however, between tribe and tribe,
which necessarily follows from any form of this habit, would tend to
keep all the people inhabiting the same country nearly uniform in
character; and this would interfere with the power of sexual selection
in differentiating the tribes.

The scarcity of women, consequent on female infanticide, leads, also,
to another practice, that of polyandry, still common in several parts
of the world, and which formerly, as Mr. M’Lennan believes, prevailed
almost universally: but this latter conclusion is doubted by Mr. Morgan
and Sir J. Lubbock. (14. ‘Primitive Marriage,’ p. 208; Sir J. Lubbock,
‘Origin of Civilisation,’ p. 100. See also Mr. Morgan, loc. cit., on
the former prevalence of polyandry.) Whenever two or more men are
compelled to marry one woman, it is certain that all the women of the
tribe will get married, and there will be no selection by the men of
the more attractive women. But under these circumstances the women no
doubt will have the power of choice, and will prefer the more
attractive men. Azara, for instance, describes how carefully a Guana
woman bargains for all sorts of privileges, before accepting some one
or more husbands; and the men in consequence take unusual care of their
personal appearance. So amongst the Todas of India, who practise
polyandry, the girls can accept or refuse any man. (15. Azara,
‘Voyages,’ etc., tom. ii. pp. 92-95; Colonel Marshall, ‘Amongst the
Todas,’ p. 212.) A very ugly man in these cases would perhaps
altogether fail in getting a wife, or get one later in life; but the
handsomer men, although more successful in obtaining wives, would not,
as far as we can see, leave more offspring to inherit their beauty than
the less handsome husbands of the same women.

EARLY BETROTHALS AND SLAVERY OF WOMEN.

With many savages it is the custom to betroth the females whilst mere
infants; and this would effectually prevent preference being exerted on
either side according to personal appearance. But it would not prevent
the more attractive women from being afterwards stolen or taken by
force from their husbands by the more powerful men; and this often
happens in Australia, America, and elsewhere. The same consequences
with reference to sexual selection would to a certain extent follow,
when women are valued almost solely as slaves or beasts of burden, as
is the case with many savages. The men, however, at all times would
prefer the handsomest slaves according to their standard of beauty.

We thus see that several customs prevail with savages which must
greatly interfere with, or completely stop, the action of sexual
selection. On the other hand, the conditions of life to which savages
are exposed, and some of their habits, are favourable to natural
selection; and this comes into play at the same time with sexual
selection. Savages are known to suffer severely from recurrent famines;
they do not increase their food by artificial means; they rarely
refrain from marriage (16. Burchell says (‘Travels in S. Africa,’ vol.
ii. 1824, p. 58), that among the wild nations of Southern Africa,
neither men nor women ever pass their lives in a state of celibacy.
Azara (‘Voyages dans l’Amérique Merid.’ tom. ii. 1809, p. 21) makes
precisely the same remark in regard to the wild Indians of South
America.), and generally marry whilst young. Consequently they must be
subjected to occasional hard struggles for existence, and the favoured
individuals will alone survive.

At a very early period, before man attained to his present rank in the
scale, many of his conditions would be different from what now obtains
amongst savages. Judging from the analogy of the lower animals, he
would then either live with a single female, or be a polygamist. The
most powerful and able males would succeed best in obtaining attractive
females. They would also succeed best in the general struggle for life,
and in defending their females, as well as their offspring, from
enemies of all kinds. At this early period the ancestors of man would
not be sufficiently advanced in intellect to look forward to distant
contingencies; they would not foresee that the rearing of all their
children, especially their female children, would make the struggle for
life severer for the tribe. They would be governed more by their
instincts and less by their reason than are savages at the present day.
They would not at that period have partially lost one of the strongest
of all instincts, common to all the lower animals, namely the love of
their young offspring; and consequently they would not have practised
female infanticide. Women would not have been thus rendered scarce, and
polyandry would not have been practised; for hardly any other cause,
except the scarcity of women seems sufficient to break down the natural
and widely prevalent feeling of jealousy, and the desire of each male
to possess a female for himself. Polyandry would be a natural
stepping-stone to communal marriages or almost promiscuous intercourse;
though the best authorities believe that this latter habit preceded
polyandry. During primordial times there would be no early betrothals,
for this implies foresight. Nor would women be valued merely as useful
slaves or beasts of burthen. Both sexes, if the females as well as the
males were permitted to exert any choice, would choose their partners
not for mental charms, or property, or social position, but almost
solely from external appearance. All the adults would marry or pair,
and all the offspring, as far as that was possible, would be reared; so
that the struggle for existence would be periodically excessively
severe. Thus during these times all the conditions for sexual selection
would have been more favourable than at a later period, when man had
advanced in his intellectual powers but had retrograded in his
instincts. Therefore, whatever influence sexual selection may have had
in producing the differences between the races of man, and between man
and the higher Quadrumana, this influence would have been more powerful
at a remote period than at the present day, though probably not yet
wholly lost.

THE MANNER OF ACTION OF SEXUAL SELECTION WITH MANKIND.

With primeval man under the favourable conditions just stated, and with
those savages who at the present time enter into any marriage tie,
sexual selection has probably acted in the following manner, subject to
greater or less interference from female infanticide, early betrothals,
etc. The strongest and most vigorous men—those who could best defend
and hunt for their families, who were provided with the best weapons
and possessed the most property, such as a large number of dogs or
other animals,—would succeed in rearing a greater average number of
offspring than the weaker and poorer members of the same tribes. There
can, also, be no doubt that such men would generally be able to select
the more attractive women. At present the chiefs of nearly every tribe
throughout the world succeed in obtaining more than one wife. I hear
from Mr. Mantell that, until recently, almost every girl in New Zealand
who was pretty, or promised to be pretty, was tapu to some chief. With
the Kafirs, as Mr. C. Hamilton states (17. ‘Anthropological Review,’
Jan. 1870, p. xvi.), “the chiefs generally have the pick of the women
for many miles round, and are most persevering in establishing or
confirming their privilege.” We have seen that each race has its own
style of beauty, and we know that it is natural to man to admire each
characteristic point in his domestic animals, dress, ornaments, and
personal appearance, when carried a little beyond the average. If then
the several foregoing propositions be admitted, and I cannot see that
they are doubtful, it would be an inexplicable circumstance if the
selection of the more attractive women by the more powerful men of each
tribe, who would rear on an average a greater number of children, did
not after the lapse of many generations somewhat modify the character
of the tribe.

When a foreign breed of our domestic animals is introduced into a new
country, or when a native breed is long and carefully attended to,
either for use or ornament, it is found after several generations to
have undergone a greater or less amount of change whenever the means of
comparison exist. This follows from unconscious selection during a long
series of generations—that is, the preservation of the most approved
individuals—without any wish or expectation of such a result on the
part of the breeder. So again, if during many years two careful
breeders rear animals of the same family, and do not compare them
together or with a common standard, the animals are found to have
become, to the surprise of their owners, slightly different. (18. The
‘Variation of Animals and Plants under Domestication,’ vol. ii. pp.
210-217.) Each breeder has impressed, as von Nathusius well expresses
it, the character of his own mind—his own taste and judgment—on his
animals. What reason, then, can be assigned why similar results should
not follow from the long-continued selection of the most admired women
by those men of each tribe who were able to rear the greatest number of
children? This would be unconscious selection, for an effect would be
produced, independently of any wish or expectation on the part of the
men who preferred certain women to others.

Let us suppose the members of a tribe, practising some form of
marriage, to spread over an unoccupied continent, they would soon split
up into distinct hordes, separated from each other by various barriers,
and still more effectually by the incessant wars between all barbarous
nations. The hordes would thus be exposed to slightly different
conditions and habits of life, and would sooner or later come to differ
in some small degree. As soon as this occurred, each isolated tribe
would form for itself a slightly different standard of beauty (19. An
ingenious writer argues, from a comparison of the pictures of Raphael,
Rubens, and modern French artists, that the idea of beauty is not
absolutely the same even throughout Europe: see the ‘Lives of Haydn and
Mozart,’ by Bombet (otherwise M. Beyle), English translation, p. 278.);
and then unconscious selection would come into action through the more
powerful and leading men preferring certain women to others. Thus the
differences between the tribes, at first very slight, would gradually
and inevitably be more or less increased.

With animals in a state of nature, many characters proper to the males,
such as size, strength, special weapons, courage and pugnacity, have
been acquired through the law of battle. The semi-human progenitors of
man, like their allies the Quadrumana, will almost certainly have been
thus modified; and, as savages still fight for the possession of their
women, a similar process of selection has probably gone on in a greater
or less degree to the present day. Other characters proper to the males
of the lower animals, such as bright colours and various ornaments,
have been acquired by the more attractive males having been preferred
by the females. There are, however, exceptional cases in which the
males are the selectors, instead of having been the selected. We
recognise such cases by the females being more highly ornamented than
the males,—their ornamental characters having been transmitted
exclusively or chiefly to their female offspring. One such case has
been described in the order to which man belongs, that of the Rhesus
monkey.

Man is more powerful in body and mind than woman, and in the savage
state he keeps her in a far more abject state of bondage than does the
male of any other animal; therefore it is not surprising that he should
have gained the power of selection. Women are everywhere conscious of
the value of their own beauty; and when they have the means, they take
more delight in decorating themselves with all sorts of ornaments than
do men. They borrow the plumes of male birds, with which nature has
decked this sex, in order to charm the females. As women have long been
selected for beauty, it is not surprising that some of their successive
variations should have been transmitted exclusively to the same sex;
consequently that they should have transmitted beauty in a somewhat
higher degree to their female than to their male offspring, and thus
have become more beautiful, according to general opinion, than men.
Women, however, certainly transmit most of their characters, including
some beauty, to their offspring of both sexes; so that the continued
preference by the men of each race for the more attractive women,
according to their standard of taste, will have tended to modify in the
same manner all the individuals of both sexes belonging to the race.

With respect to the other form of sexual selection (which with the
lower animals is much the more common), namely, when the females are
the selectors, and accept only those males which excite or charm them
most, we have reason to believe that it formerly acted on our
progenitors. Man in all probability owes his beard, and perhaps some
other characters, to inheritance from an ancient progenitor who thus
gained his ornaments. But this form of selection may have occasionally
acted during later times; for in utterly barbarous tribes the women
have more power in choosing, rejecting, and tempting their lovers, or
of afterwards changing their husbands, than might have been expected.
As this is a point of some importance, I will give in detail such
evidence as I have been able to collect.

Hearne describes how a woman in one of the tribes of Arctic America
repeatedly ran away from her husband and joined her lover; and with the
Charruas of S. America, according to Azara, divorce is quite optional.
Amongst the Abipones, a man on choosing a wife bargains with the
parents about the price. But “it frequently happens that the girl
rescinds what has been agreed upon between the parents and the
bridegroom, obstinately rejecting the very mention of marriage.” She
often runs away, hides herself, and thus eludes the bridegroom. Captain
Musters who lived with the Patagonians, says that their marriages are
always settled by inclination; “if the parents make a match contrary to
the daughter’s will, she refuses and is never compelled to comply.” In
Tierra del Fuego a young man first obtains the consent of the parents
by doing them some service, and then he attempts to carry off the girl;
“but if she is unwilling, she hides herself in the woods until her
admirer is heartily tired of looking for her, and gives up the pursuit;
but this seldom happens.” In the Fiji Islands the man seizes on the
woman whom he wishes for his wife by actual or pretended force; but “on
reaching the home of her abductor, should she not approve of the match,
she runs to some one who can protect her; if, however, she is
satisfied, the matter is settled forthwith.” With the Kalmucks there is
a regular race between the bride and bridegroom, the former having a
fair start; and Clarke “was assured that no instance occurs of a girl
being caught, unless she has a partiality to the pursuer.” Amongst the
wild tribes of the Malay Archipelago there is also a racing match; and
it appears from M. Bourien’s account, as Sir J. Lubbock remarks, that
“the race, ‘is not to the swift, nor the battle to the strong,’ but to
the young man who has the good fortune to please his intended bride.” A
similar custom, with the same result, prevails with the Koraks of
North-Eastern Asia.

Turning to Africa: the Kafirs buy their wives, and girls are severely
beaten by their fathers if they will not accept a chosen husband; but
it is manifest from many facts given by the Rev. Mr. Shooter, that they
have considerable power of choice. Thus very ugly, though rich men,
have been known to fail in getting wives. The girls, before consenting
to be betrothed, compel the men to shew themselves off first in front
and then behind, and “exhibit their paces.” They have been known to
propose to a man, and they not rarely run away with a favoured lover.
So again, Mr. Leslie, who was intimately acquainted with the Kafirs,
says, “it is a mistake to imagine that a girl is sold by her father in
the same manner, and with the same authority, with which he would
dispose of a cow.” Amongst the degraded Bushmen of S. Africa, “when a
girl has grown up to womanhood without having been betrothed, which,
however, does not often happen, her lover must gain her approbation, as
well as that of the parents.” (20. Azara, ‘Voyages,’ etc., tom. ii. p.
23. Dobrizhoffer, ‘An Account of the Abipones,’ vol. ii. 1822, p. 207.
Capt. Musters, in ‘Proc. R. Geograph. Soc.’ vol. xv. p. 47. Williams on
the Fiji Islanders, as quoted by Lubbock, ‘Origin of Civilisation,’
1870, p. 79. On the Fuegians, King and Fitzroy, ‘Voyages of the
“Adventure” and “Beagle,”’ vol. ii. 1839, p. 182. On the Kalmucks,
quoted by M’Lennan, ‘Primitive Marriage,’ 1865, p. 32. On the Malays,
Lubbock, ibid. p. 76. The Rev. J. Shooter, ‘On the Kafirs of Natal,’
1857, pp. 52-60. Mr. D. Leslie, ‘Kafir Character and Customs,’ 1871, p.
4. On the Bush-men, Burchell, ‘Travels in S. Africa,’ ii. 1824, p. 59.
On the Koraks by McKennan, as quoted by Mr. Wake, in ‘Anthropologia,’
Oct. 1873, p. 75.) Mr. Winwood Reade made inquiries for me with respect
to the negroes of Western Africa, and he informs me that “the women, at
least among the more intelligent Pagan tribes, have no difficulty in
getting the husbands whom they may desire, although it is considered
unwomanly to ask a man to marry them. They are quite capable of falling
in love, and of forming tender, passionate, and faithful attachments.”
Additional cases could be given.

We thus see that with savages the women are not in quite so abject a
state in relation to marriage as has often been supposed. They can
tempt the men whom they prefer, and can sometimes reject those whom
they dislike, either before or after marriage. Preference on the part
of the women, steadily acting in any one direction, would ultimately
affect the character of the tribe; for the women would generally choose
not merely the handsomest men, according to their standard of taste,
but those who were at the same time best able to defend and support
them. Such well-endowed pairs would commonly rear a larger number of
offspring than the less favoured. The same result would obviously
follow in a still more marked manner if there was selection on both
sides; that is, if the more attractive, and at the same time more
powerful men were to prefer, and were preferred by, the more attractive
women. And this double form of selection seems actually to have
occurred, especially during the earlier periods of our long history.

We will now examine a little more closely some of the characters which
distinguish the several races of man from one another and from the
lower animals, namely, the greater or less deficiency of hair on the
body, and the colour of the skin. We need say nothing about the great
diversity in the shape of the features and of the skull between the
different races, as we have seen in the last chapter how different is
the standard of beauty in these respects. These characters will
therefore probably have been acted on through sexual selection; but we
have no means of judging whether they have been acted on chiefly from
the male or female side. The musical faculties of man have likewise
been already discussed.

ABSENCE OF HAIR ON THE BODY, AND ITS DEVELOPMENT ON THE FACE AND HEAD.

From the presence of the woolly hair or lanugo on the human foetus, and
of rudimentary hairs scattered over the body during maturity, we may
infer that man is descended from some animal which was born hairy and
remained so during life. The loss of hair is an inconvenience and
probably an injury to man, even in a hot climate, for he is thus
exposed to the scorching of the sun, and to sudden chills, especially
during wet weather. As Mr. Wallace remarks, the natives in all
countries are glad to protect their naked backs and shoulders with some
slight covering. No one supposes that the nakedness of the skin is any
direct advantage to man; his body therefore cannot have been divested
of hair through natural selection. (21. ‘Contributions to the Theory of
Natural Selection,’ 1870, p. 346. Mr. Wallace believes (p. 350) “that
some intelligent power has guided or determined the development of
man”; and he considers the hairless condition of the skin as coming
under this head. The Rev. T.R. Stebbing, in commenting on this view
(‘Transactions of Devonshire Association for Science,’ 1870) remarks,
that had Mr. Wallace “employed his usual ingenuity on the question of
man’s hairless skin, he might have seen the possibility of its
selection through its superior beauty or the health attaching to
superior cleanliness.”) Nor, as shewn in a former chapter, have we any
evidence that this can be due to the direct action of climate, or that
it is the result of correlated development.

The absence of hair on the body is to a certain extent a secondary
sexual character; for in all parts of the world women are less hairy
than men. Therefore we may reasonably suspect that this character has
been gained through sexual selection. We know that the faces of several
species of monkeys, and large surfaces at the posterior end of the body
of other species, have been denuded of hair; and this we may safely
attribute to sexual selection, for these surfaces are not only vividly
coloured, but sometimes, as with the male mandrill and female rhesus,
much more vividly in the one sex than in the other, especially during
the breeding-season. I am informed by Mr. Bartlett that, as these
animals gradually reach maturity, the naked surfaces grow larger
compared with the size of their bodies. The hair, however, appears to
have been removed, not for the sake of nudity, but that the colour of
the skin may be more fully displayed. So again with many birds, it
appears as if the head and neck had been divested of feathers through
sexual selection, to exhibit the brightly-coloured skin.

As the body in woman is less hairy than in man, and as this character
is common to all races, we may conclude that it was our female
semi-human ancestors who were first divested of hair, and that this
occurred at an extremely remote period before the several races had
diverged from a common stock. Whilst our female ancestors were
gradually acquiring this new character of nudity, they must have
transmitted it almost equally to their offspring of both sexes whilst
young; so that its transmission, as with the ornaments of many mammals
and birds, has not been limited either by sex or age. There is nothing
surprising in a partial loss of hair having been esteemed as an
ornament by our ape-like progenitors, for we have seen that innumerable
strange characters have been thus esteemed by animals of all kinds, and
have consequently been gained through sexual selection. Nor is it
surprising that a slightly injurious character should have been thus
acquired; for we know that this is the case with the plumes of certain
birds, and with the horns of certain stags.

The females of some of the anthropoid apes, as stated in a former
chapter, are somewhat less hairy on the under surface than the males;
and here we have what might have afforded a commencement for the
process of denudation. With respect to the completion of the process
through sexual selection, it is well to bear in mind the New Zealand
proverb, “There is no woman for a hairy man.” All who have seen
photographs of the Siamese hairy family will admit how ludicrously
hideous is the opposite extreme of excessive hairiness. And the king of
Siam had to bribe a man to marry the first hairy woman in the family;
and she transmitted this character to her young offspring of both
sexes. (22. The ‘Variation of Animals and Plants under Domestication,’
vol. ii. 1868, p. 237.)

Some races are much more hairy than others, especially the males; but
it must not be assumed that the more hairy races, such as the European,
have retained their primordial condition more completely than the naked
races, such as the Kalmucks or Americans. It is more probable that the
hairiness of the former is due to partial reversion; for characters
which have been at some former period long inherited are always apt to
return. We have seen that idiots are often very hairy, and they are apt
to revert in other characters to a lower animal type. It does not
appear that a cold climate has been influential in leading to this kind
of reversion; excepting perhaps with the negroes, who have been reared
during several generations in the United States (23. ‘Investigations
into Military and Anthropological Statistics of American Soldiers,’ by
B.A. Gould, 1869, p. 568:—Observations were carefully made on the
hairiness of 2129 black and coloured soldiers, whilst they were
bathing; and by looking to the published table, “it is manifest at a
glance that there is but little, if any, difference between the white
and the black races in this respect.” It is, however, certain that
negroes in their native and much hotter land of Africa, have remarkably
smooth bodies. It should be particularly observed, that both pure
blacks and mulattoes were included in the above enumeration; and this
is an unfortunate circumstance, as in accordance with a principle, the
truth of which I have elsewhere proved, crossed races of man would be
eminently liable to revert to the primordial hairy character of their
early ape-like progenitors.), and possibly with the Ainos, who inhabit
the northern islands of the Japan archipelago. But the laws of
inheritance are so complex that we can seldom understand their action.
If the greater hairiness of certain races be the result of reversion,
unchecked by any form of selection, its extreme variability, even
within the limits of the same race, ceases to be remarkable. (24.
Hardly any view advanced in this work has met with so much disfavour
(see for instance, Sprengel, ‘Die Fortschritte des Darwinismus,’ 1874,
p. 80) as the above explanation of the loss of hair in mankind through
sexual selection; but none of the opposed arguments seem to me of much
weight, in comparison with the facts shewing that the nudity of the
skin is to a certain extent a secondary sexual character in man and in
some of the Quadrumana.)

With respect to the beard in man, if we turn to our best guide, the
Quadrumana, we find beards equally developed in both sexes of many
species, but in some, either confined to the males, or more developed
in them than in the females. From this fact and from the curious
arrangement, as well as the bright colours of the hair about the heads
of many monkeys, it is highly probable, as before explained, that the
males first acquired their beards through sexual selection as an
ornament, transmitting them in most cases, equally or nearly so, to
their offspring of both sexes. We know from Eschricht (25. ‘Ueber die
Richtung der Haare am Menschlichen Körper,’ in Müller’s ‘Archiv. für
Anat. und Phys.’ 1837, s. 40.) that with mankind the female as well as
the male foetus is furnished with much hair on the face, especially
round the mouth; and this indicates that we are descended from
progenitors of whom both sexes were bearded. It appears therefore at
first sight probable that man has retained his beard from a very early
period, whilst woman lost her beard at the same time that her body
became almost completely divested of hair. Even the colour of our
beards seems to have been inherited from an ape-like progenitor; for
when there is any difference in tint between the hair of the head and
the beard, the latter is lighter coloured in all monkeys and in man. In
those Quadrumana in which the male has a larger beard than that of the
female, it is fully developed only at maturity, just as with mankind;
and it is possible that only the later stages of development have been
retained by man. In opposition to this view of the retention of the
beard from an early period is the fact of its great variability in
different races, and even within the same race; for this indicates
reversion,—long lost characters being very apt to vary on
re-appearance.

Nor must we overlook the part which sexual selection may have played in
later times; for we know that with savages the men of the beardless
races take infinite pains in eradicating every hair from their faces as
something odious, whilst the men of the bearded races feel the greatest
pride in their beards. The women, no doubt, participate in these
feelings, and if so sexual selection can hardly have failed to have
effected something in the course of later times. It is also possible
that the long-continued habit of eradicating the hair may have produced
an inherited effect. Dr. Brown-Sequard has shewn that if certain
animals are operated on in a particular manner, their offspring are
affected. Further evidence could be given of the inheritance of the
effects of mutilations; but a fact lately ascertained by Mr. Salvin
(26. On the tail-feathers of Motmots, ‘Proceedings of the Zoological
Society,’ 1873, p. 429.) has a more direct bearing on the present
question; for he has shewn that the motmots, which are known habitually
to bite off the barbs of the two central tail-feathers, have the barbs
of these feathers naturally somewhat reduced. (27. Mr. Sproat has
suggested (‘Scenes and Studies of Savage Life,’ 1868, p. 25) this same
view. Some distinguished ethnologists, amongst others M. Gosse of
Geneva, believe that artificial modifications of the skull tend to be
inherited.) Nevertheless, with mankind the habit of eradicating the
beard and the hairs on the body would probably not have arisen until
these had already become by some means reduced.

It is difficult to form any judgment as to how the hair on the head
became developed to its present great length in many races. Eschricht
(28. ‘Ueber die Richtung,’ ibid. s. 40.) states that in the human
foetus the hair on the face during the fifth month is longer than that
on the head; and this indicates that our semi-human progenitors were
not furnished with long tresses, which must therefore have been a late
acquisition. This is likewise indicated by the extraordinary difference
in the length of the hair in the different races; in the negro the hair
forms a mere curly mat; with us it is of great length, and with the
American natives it not rarely reaches to the ground. Some species of
Semnopithecus have their heads covered with moderately long hair, and
this probably serves as an ornament and was acquired through sexual
selection. The same view may perhaps be extended to mankind, for we
know that long tresses are now and were formerly much admired, as may
be observed in the works of almost every poet; St. Paul says, “if a
woman have long hair, it is a glory to her;” and we have seen that in
North America a chief was elected solely from the length of his hair.

COLOUR OF THE SKIN.

The best kind of evidence that in man the colour of the skin has been
modified through sexual selection is scanty; for in most races the
sexes do not differ in this respect, and only slightly, as we have
seen, in others. We know, however, from the many facts already given
that the colour of the skin is regarded by the men of all races as a
highly important element in their beauty; so that it is a character
which would be likely to have been modified through selection, as has
occurred in innumerable instances with the lower animals. It seems at
first sight a monstrous supposition that the jet-blackness of the negro
should have been gained through sexual selection; but this view is
supported by various analogies, and we know that negroes admire their
own colour. With mammals, when the sexes differ in colour, the male is
often black or much darker than the female; and it depends merely on
the form of inheritance whether this or any other tint is transmitted
to both sexes or to one alone. The resemblance to a negro in miniature
of Pithecia satanas with his jet black skin, white rolling eyeballs,
and hair parted on the top of the head, is almost ludicrous.

The colour of the face differs much more widely in the various kinds of
monkeys than it does in the races of man; and we have some reason to
believe that the red, blue, orange, almost white and black tints of
their skin, even when common to both sexes, as well as the bright
colours of their fur, and the ornamental tufts about the head, have all
been acquired through sexual selection. As the order of development
during growth, generally indicates the order in which the characters of
a species have been developed and modified during previous generations;
and as the newly-born infants of the various races of man do not differ
nearly as much in colour as do the adults, although their bodies are as
completely destitute of hair, we have some slight evidence that the
tints of the different races were acquired at a period subsequent to
the removal of the hair, which must have occurred at a very early
period in the history of man.

A SUMMARY.

We may conclude that the greater size, strength, courage, pugnacity,
and energy of man, in comparison with woman, were acquired during
primeval times, and have subsequently been augmented, chiefly through
the contests of rival males for the possession of the females. The
greater intellectual vigour and power of invention in man is probably
due to natural selection, combined with the inherited effects of habit,
for the most able men will have succeeded best in defending and
providing for themselves and for their wives and offspring. As far as
the extreme intricacy of the subject permits us to judge, it appears
that our male ape-like progenitors acquired their beards as an ornament
to charm or excite the opposite sex, and transmitted them only to their
male offspring. The females apparently first had their bodies denuded
of hair, also as a sexual ornament; but they transmitted this character
almost equally to both sexes. It is not improbable that the females
were modified in other respects for the same purpose and by the same
means; so that women have acquired sweeter voices and become more
beautiful than men.

It deserves attention that with mankind the conditions were in many
respects much more favourable for sexual selection, during a very early
period, when man had only just attained to the rank of manhood, than
during later times. For he would then, as we may safely conclude, have
been guided more by his instinctive passions, and less by foresight or
reason. He would have jealously guarded his wife or wives. He would not
have practised infanticide; nor valued his wives merely as useful
slaves; nor have been betrothed to them during infancy. Hence we may
infer that the races of men were differentiated, as far as sexual
selection is concerned, in chief part at a very remote epoch; and this
conclusion throws light on the remarkable fact that at the most ancient
period, of which we have not as yet any record, the races of man had
already come to differ nearly or quite as much as they do at the
present day.

The views here advanced, on the part which sexual selection has played
in the history of man, want scientific precision. He who does not admit
this agency in the case of the lower animals, will disregard all that I
have written in the later chapters on man. We cannot positively say
that this character, but not that, has been thus modified; it has,
however, been shewn that the races of man differ from each other and
from their nearest allies, in certain characters which are of no
service to them in their daily habits of life, and which it is
extremely probable would have been modified through sexual selection.
We have seen that with the lowest savages the people of each tribe
admire their own characteristic qualities,—the shape of the head and
face, the squareness of the cheek-bones, the prominence or depression
of the nose, the colour of the skin, the length of the hair on the
head, the absence of hair on the face and body, or the presence of a
great beard, and so forth. Hence these and other such points could
hardly fail to be slowly and gradually exaggerated, from the more
powerful and able men in each tribe, who would succeed in rearing the
largest number of offspring, having selected during many generations
for their wives the most strongly characterised and therefore most
attractive women. For my own part I conclude that of all the causes
which have led to the differences in external appearance between the
races of man, and to a certain extent between man and the lower
animals, sexual selection has been the most efficient.




CHAPTER XXI.
GENERAL A SUMMARY AND CONCLUSION.


Main conclusion that man is descended from some lower form—Manner of
development—Genealogy of man—Intellectual and moral faculties—Sexual
Selection—Concluding remarks.

A brief summary will be sufficient to recall to the reader’s mind the
more salient points in this work. Many of the views which have been
advanced are highly speculative, and some no doubt will prove
erroneous; but I have in every case given the reasons which have led me
to one view rather than to another. It seemed worth while to try how
far the principle of evolution would throw light on some of the more
complex problems in the natural history of man. False facts are highly
injurious to the progress of science, for they often endure long; but
false views, if supported by some evidence, do little harm, for every
one takes a salutary pleasure in proving their falseness: and when this
is done, one path towards error is closed and the road to truth is
often at the same time opened.

The main conclusion here arrived at, and now held by many naturalists
who are well competent to form a sound judgment, is that man is
descended from some less highly organised form. The grounds upon which
this conclusion rests will never be shaken, for the close similarity
between man and the lower animals in embryonic development, as well as
in innumerable points of structure and constitution, both of high and
of the most trifling importance,—the rudiments which he retains, and
the abnormal reversions to which he is occasionally liable,—are facts
which cannot be disputed. They have long been known, but until recently
they told us nothing with respect to the origin of man. Now when viewed
by the light of our knowledge of the whole organic world, their meaning
is unmistakable. The great principle of evolution stands up clear and
firm, when these groups or facts are considered in connection with
others, such as the mutual affinities of the members of the same group,
their geographical distribution in past and present times, and their
geological succession. It is incredible that all these facts should
speak falsely. He who is not content to look, like a savage, at the
phenomena of nature as disconnected, cannot any longer believe that man
is the work of a separate act of creation. He will be forced to admit
that the close resemblance of the embryo of man to that, for instance,
of a dog—the construction of his skull, limbs and whole frame on the
same plan with that of other mammals, independently of the uses to
which the parts may be put—the occasional re-appearance of various
structures, for instance of several muscles, which man does not
normally possess, but which are common to the Quadrumana—and a crowd of
analogous facts—all point in the plainest manner to the conclusion that
man is the co-descendant with other mammals of a common progenitor.

We have seen that man incessantly presents individual differences in
all parts of his body and in his mental faculties. These differences or
variations seem to be induced by the same general causes, and to obey
the same laws as with the lower animals. In both cases similar laws of
inheritance prevail. Man tends to increase at a greater rate than his
means of subsistence; consequently he is occasionally subjected to a
severe struggle for existence, and natural selection will have effected
whatever lies within its scope. A succession of strongly-marked
variations of a similar nature is by no means requisite; slight
fluctuating differences in the individual suffice for the work of
natural selection; not that we have any reason to suppose that in the
same species, all parts of the organisation tend to vary to the same
degree. We may feel assured that the inherited effects of the
long-continued use or disuse of parts will have done much in the same
direction with natural selection. Modifications formerly of importance,
though no longer of any special use, are long-inherited. When one part
is modified, other parts change through the principle of correlation,
of which we have instances in many curious cases of correlated
monstrosities. Something may be attributed to the direct and definite
action of the surrounding conditions of life, such as abundant food,
heat or moisture; and lastly, many characters of slight physiological
importance, some indeed of considerable importance, have been gained
through sexual selection.

No doubt man, as well as every other animal, presents structures, which
seem to our limited knowledge, not to be now of any service to him, nor
to have been so formerly, either for the general conditions of life, or
in the relations of one sex to the other. Such structures cannot be
accounted for by any form of selection, or by the inherited effects of
the use and disuse of parts. We know, however, that many strange and
strongly-marked peculiarities of structure occasionally appear in our
domesticated productions, and if their unknown causes were to act more
uniformly, they would probably become common to all the individuals of
the species. We may hope hereafter to understand something about the
causes of such occasional modifications, especially through the study
of monstrosities: hence the labours of experimentalists, such as those
of M. Camille Dareste, are full of promise for the future. In general
we can only say that the cause of each slight variation and of each
monstrosity lies much more in the constitution of the organism, than in
the nature of the surrounding conditions; though new and changed
conditions certainly play an important part in exciting organic changes
of many kinds.

Through the means just specified, aided perhaps by others as yet
undiscovered, man has been raised to his present state. But since he
attained to the rank of manhood, he has diverged into distinct races,
or as they may be more fitly called, sub-species. Some of these, such
as the Negro and European, are so distinct that, if specimens had been
brought to a naturalist without any further information, they would
undoubtedly have been considered by him as good and true species.
Nevertheless all the races agree in so many unimportant details of
structure and in so many mental peculiarities that these can be
accounted for only by inheritance from a common progenitor; and a
progenitor thus characterised would probably deserve to rank as man.

It must not be supposed that the divergence of each race from the other
races, and of all from a common stock, can be traced back to any one
pair of progenitors. On the contrary, at every stage in the process of
modification, all the individuals which were in any way better fitted
for their conditions of life, though in different degrees, would have
survived in greater numbers than the less well-fitted. The process
would have been like that followed by man, when he does not
intentionally select particular individuals, but breeds from all the
superior individuals, and neglects the inferior. He thus slowly but
surely modifies his stock, and unconsciously forms a new strain. So
with respect to modifications acquired independently of selection, and
due to variations arising from the nature of the organism and the
action of the surrounding conditions, or from changed habits of life,
no single pair will have been modified much more than the other pairs
inhabiting the same country, for all will have been continually blended
through free intercrossing.

By considering the embryological structure of man,—the homologies which
he presents with the lower animals,—the rudiments which he retains,—and
the reversions to which he is liable, we can partly recall in
imagination the former condition of our early progenitors; and can
approximately place them in their proper place in the zoological
series. We thus learn that man is descended from a hairy, tailed
quadruped, probably arboreal in its habits, and an inhabitant of the
Old World. This creature, if its whole structure had been examined by a
naturalist, would have been classed amongst the Quadrumana, as surely
as the still more ancient progenitor of the Old and New World monkeys.
The Quadrumana and all the higher mammals are probably derived from an
ancient marsupial animal, and this through a long line of diversified
forms, from some amphibian-like creature, and this again from some
fish-like animal. In the dim obscurity of the past we can see that the
early progenitor of all the Vertebrata must have been an aquatic
animal, provided with branchiae, with the two sexes united in the same
individual, and with the most important organs of the body (such as the
brain and heart) imperfectly or not at all developed. This animal seems
to have been more like the larvae of the existing marine Ascidians than
any other known form.

The high standard of our intellectual powers and moral disposition is
the greatest difficulty which presents itself, after we have been
driven to this conclusion on the origin of man. But every one who
admits the principle of evolution, must see that the mental powers of
the higher animals, which are the same in kind with those of man,
though so different in degree, are capable of advancement. Thus the
interval between the mental powers of one of the higher apes and of a
fish, or between those of an ant and scale-insect, is immense; yet
their development does not offer any special difficulty; for with our
domesticated animals, the mental faculties are certainly variable, and
the variations are inherited. No one doubts that they are of the utmost
importance to animals in a state of nature. Therefore the conditions
are favourable for their development through natural selection. The
same conclusion may be extended to man; the intellect must have been
all-important to him, even at a very remote period, as enabling him to
invent and use language, to make weapons, tools, traps, etc., whereby
with the aid of his social habits, he long ago became the most dominant
of all living creatures.

A great stride in the development of the intellect will have followed,
as soon as the half-art and half-instinct of language came into use;
for the continued use of language will have reacted on the brain and
produced an inherited effect; and this again will have reacted on the
improvement of language. As Mr. Chauncey Wright (1. ‘On the Limits of
Natural Selection,’ in the ‘North American Review,’ Oct. 1870, p. 295.)
has well remarked, the largeness of the brain in man relatively to his
body, compared with the lower animals, may be attributed in chief part
to the early use of some simple form of language,—that wonderful engine
which affixes signs to all sorts of objects and qualities, and excites
trains of thought which would never arise from the mere impression of
the senses, or if they did arise could not be followed out. The higher
intellectual powers of man, such as those of ratiocination,
abstraction, self-consciousness, etc., probably follow from the
continued improvement and exercise of the other mental faculties.

The development of the moral qualities is a more interesting problem.
The foundation lies in the social instincts, including under this term
the family ties. These instincts are highly complex, and in the case of
the lower animals give special tendencies towards certain definite
actions; but the more important elements are love, and the distinct
emotion of sympathy. Animals endowed with the social instincts take
pleasure in one another’s company, warn one another of danger, defend
and aid one another in many ways. These instincts do not extend to all
the individuals of the species, but only to those of the same
community. As they are highly beneficial to the species, they have in
all probability been acquired through natural selection.

A moral being is one who is capable of reflecting on his past actions
and their motives—of approving of some and disapproving of others; and
the fact that man is the one being who certainly deserves this
designation, is the greatest of all distinctions between him and the
lower animals. But in the fourth chapter I have endeavoured to shew
that the moral sense follows, firstly, from the enduring and
ever-present nature of the social instincts; secondly, from man’s
appreciation of the approbation and disapprobation of his fellows; and
thirdly, from the high activity of his mental faculties, with past
impressions extremely vivid; and in these latter respects he differs
from the lower animals. Owing to this condition of mind, man cannot
avoid looking both backwards and forwards, and comparing past
impressions. Hence after some temporary desire or passion has mastered
his social instincts, he reflects and compares the now weakened
impression of such past impulses with the ever-present social
instincts; and he then feels that sense of dissatisfaction which all
unsatisfied instincts leave behind them, he therefore resolves to act
differently for the future,—and this is conscience. Any instinct,
permanently stronger or more enduring than another, gives rise to a
feeling which we express by saying that it ought to be obeyed. A
pointer dog, if able to reflect on his past conduct, would say to
himself, I ought (as indeed we say of him) to have pointed at that hare
and not have yielded to the passing temptation of hunting it.

Social animals are impelled partly by a wish to aid the members of
their community in a general manner, but more commonly to perform
certain definite actions. Man is impelled by the same general wish to
aid his fellows; but has few or no special instincts. He differs also
from the lower animals in the power of expressing his desires by words,
which thus become a guide to the aid required and bestowed. The motive
to give aid is likewise much modified in man: it no longer consists
solely of a blind instinctive impulse, but is much influenced by the
praise or blame of his fellows. The appreciation and the bestowal of
praise and blame both rest on sympathy; and this emotion, as we have
seen, is one of the most important elements of the social instincts.
Sympathy, though gained as an instinct, is also much strengthened by
exercise or habit. As all men desire their own happiness, praise or
blame is bestowed on actions and motives, according as they lead to
this end; and as happiness is an essential part of the general good,
the greatest-happiness principle indirectly serves as a nearly safe
standard of right and wrong. As the reasoning powers advance and
experience is gained, the remoter effects of certain lines of conduct
on the character of the individual, and on the general good, are
perceived; and then the self-regarding virtues come within the scope of
public opinion, and receive praise, and their opposites blame. But with
the less civilised nations reason often errs, and many bad customs and
base superstitions come within the same scope, and are then esteemed as
high virtues, and their breach as heavy crimes.

The moral faculties are generally and justly esteemed as of higher
value than the intellectual powers. But we should bear in mind that the
activity of the mind in vividly recalling past impressions is one of
the fundamental though secondary bases of conscience. This affords the
strongest argument for educating and stimulating in all possible ways
the intellectual faculties of every human being. No doubt a man with a
torpid mind, if his social affections and sympathies are well
developed, will be led to good actions, and may have a fairly sensitive
conscience. But whatever renders the imagination more vivid and
strengthens the habit of recalling and comparing past impressions, will
make the conscience more sensitive, and may even somewhat compensate
for weak social affections and sympathies.

The moral nature of man has reached its present standard, partly
through the advancement of his reasoning powers and consequently of a
just public opinion, but especially from his sympathies having been
rendered more tender and widely diffused through the effects of habit,
example, instruction, and reflection. It is not improbable that after
long practice virtuous tendencies may be inherited. With the more
civilised races, the conviction of the existence of an all-seeing Deity
has had a potent influence on the advance of morality. Ultimately man
does not accept the praise or blame of his fellows as his sole guide,
though few escape this influence, but his habitual convictions,
controlled by reason, afford him the safest rule. His conscience then
becomes the supreme judge and monitor. Nevertheless the first
foundation or origin of the moral sense lies in the social instincts,
including sympathy; and these instincts no doubt were primarily gained,
as in the case of the lower animals, through natural selection.

The belief in God has often been advanced as not only the greatest, but
the most complete of all the distinctions between man and the lower
animals. It is however impossible, as we have seen, to maintain that
this belief is innate or instinctive in man. On the other hand a belief
in all-pervading spiritual agencies seems to be universal; and
apparently follows from a considerable advance in man’s reason, and
from a still greater advance in his faculties of imagination, curiosity
and wonder. I am aware that the assumed instinctive belief in God has
been used by many persons as an argument for His existence. But this is
a rash argument, as we should thus be compelled to believe in the
existence of many cruel and malignant spirits, only a little more
powerful than man; for the belief in them is far more general than in a
beneficent Deity. The idea of a universal and beneficent Creator does
not seem to arise in the mind of man, until he has been elevated by
long-continued culture.

He who believes in the advancement of man from some low organised form,
will naturally ask how does this bear on the belief in the immortality
of the soul. The barbarous races of man, as Sir J. Lubbock has shewn,
possess no clear belief of this kind; but arguments derived from the
primeval beliefs of savages are, as we have just seen, of little or no
avail. Few persons feel any anxiety from the impossibility of
determining at what precise period in the development of the
individual, from the first trace of a minute germinal vesicle, man
becomes an immortal being; and there is no greater cause for anxiety
because the period cannot possibly be determined in the gradually
ascending organic scale. (2. The Rev. J.A. Picton gives a discussion to
this effect in his ‘New Theories and the Old Faith,’ 1870.)

I am aware that the conclusions arrived at in this work will be
denounced by some as highly irreligious; but he who denounces them is
bound to shew why it is more irreligious to explain the origin of man
as a distinct species by descent from some lower form, through the laws
of variation and natural selection, than to explain the birth of the
individual through the laws of ordinary reproduction. The birth both of
the species and of the individual are equally parts of that grand
sequence of events, which our minds refuse to accept as the result of
blind chance. The understanding revolts at such a conclusion, whether
or not we are able to believe that every slight variation of
structure,—the union of each pair in marriage, the dissemination of
each seed,—and other such events, have all been ordained for some
special purpose.

Sexual selection has been treated at great length in this work; for, as
I have attempted to shew, it has played an important part in the
history of the organic world. I am aware that much remains doubtful,
but I have endeavoured to give a fair view of the whole case. In the
lower divisions of the animal kingdom, sexual selection seems to have
done nothing: such animals are often affixed for life to the same spot,
or have the sexes combined in the same individual, or what is still
more important, their perceptive and intellectual faculties are not
sufficiently advanced to allow of the feelings of love and jealousy, or
of the exertion of choice. When, however, we come to the Arthropoda and
Vertebrata, even to the lowest classes in these two great Sub-Kingdoms,
sexual selection has effected much.

In the several great classes of the animal kingdom,—in mammals, birds,
reptiles, fishes, insects, and even crustaceans,—the differences
between the sexes follow nearly the same rules. The males are almost
always the wooers; and they alone are armed with special weapons for
fighting with their rivals. They are generally stronger and larger than
the females, and are endowed with the requisite qualities of courage
and pugnacity. They are provided, either exclusively or in a much
higher degree than the females, with organs for vocal or instrumental
music, and with odoriferous glands. They are ornamented with infinitely
diversified appendages, and with the most brilliant or conspicuous
colours, often arranged in elegant patterns, whilst the females are
unadorned. When the sexes differ in more important structures, it is
the male which is provided with special sense-organs for discovering
the female, with locomotive organs for reaching her, and often with
prehensile organs for holding her. These various structures for
charming or securing the female are often developed in the male during
only part of the year, namely the breeding-season. They have in many
cases been more or less transferred to the females; and in the latter
case they often appear in her as mere rudiments. They are lost or never
gained by the males after emasculation. Generally they are not
developed in the male during early youth, but appear a short time
before the age for reproduction. Hence in most cases the young of both
sexes resemble each other; and the female somewhat resembles her young
offspring throughout life. In almost every great class a few anomalous
cases occur, where there has been an almost complete transposition of
the characters proper to the two sexes; the females assuming characters
which properly belong to the males. This surprising uniformity in the
laws regulating the differences between the sexes in so many and such
widely separated classes, is intelligible if we admit the action of one
common cause, namely sexual selection.

Sexual selection depends on the success of certain individuals over
others of the same sex, in relation to the propagation of the species;
whilst natural selection depends on the success of both sexes, at all
ages, in relation to the general conditions of life. The sexual
struggle is of two kinds; in the one it is between individuals of the
same sex, generally the males, in order to drive away or kill their
rivals, the females remaining passive; whilst in the other, the
struggle is likewise between the individuals of the same sex, in order
to excite or charm those of the opposite sex, generally the females,
which no longer remain passive, but select the more agreeable partners.
This latter kind of selection is closely analogous to that which man
unintentionally, yet effectually, brings to bear on his domesticated
productions, when he preserves during a long period the most pleasing
or useful individuals, without any wish to modify the breed.

The laws of inheritance determine whether characters gained through
sexual selection by either sex shall be transmitted to the same sex, or
to both; as well as the age at which they shall be developed. It
appears that variations arising late in life are commonly transmitted
to one and the same sex. Variability is the necessary basis for the
action of selection, and is wholly independent of it. It follows from
this, that variations of the same general nature have often been taken
advantage of and accumulated through sexual selection in relation to
the propagation of the species, as well as through natural selection in
relation to the general purposes of life. Hence secondary sexual
characters, when equally transmitted to both sexes can be distinguished
from ordinary specific characters only by the light of analogy. The
modifications acquired through sexual selection are often so strongly
pronounced that the two sexes have frequently been ranked as distinct
species, or even as distinct genera. Such strongly-marked differences
must be in some manner highly important; and we know that they have
been acquired in some instances at the cost not only of inconvenience,
but of exposure to actual danger.

The belief in the power of sexual selection rests chiefly on the
following considerations. Certain characters are confined to one sex;
and this alone renders it probable that in most cases they are
connected with the act of reproduction. In innumerable instances these
characters are fully developed only at maturity, and often during only
a part of the year, which is always the breeding-season. The males
(passing over a few exceptional cases) are the more active in
courtship; they are the better armed, and are rendered the more
attractive in various ways. It is to be especially observed that the
males display their attractions with elaborate care in the presence of
the females; and that they rarely or never display them excepting
during the season of love. It is incredible that all this should be
purposeless. Lastly we have distinct evidence with some quadrupeds and
birds, that the individuals of one sex are capable of feeling a strong
antipathy or preference for certain individuals of the other sex.

Bearing in mind these facts, and the marked results of man’s
unconscious selection, when applied to domesticated animals and
cultivated plants, it seems to me almost certain that if the
individuals of one sex were during a long series of generations to
prefer pairing with certain individuals of the other sex, characterised
in some peculiar manner, the offspring would slowly but surely become
modified in this same manner. I have not attempted to conceal that,
excepting when the males are more numerous than the females, or when
polygamy prevails, it is doubtful how the more attractive males succeed
in leaving a large number of offspring to inherit their superiority in
ornaments or other charms than the less attractive males; but I have
shewn that this would probably follow from the females,—especially the
more vigorous ones, which would be the first to breed,—preferring not
only the more attractive but at the same time the more vigorous and
victorious males.

Although we have some positive evidence that birds appreciate bright
and beautiful objects, as with the bower-birds of Australia, and
although they certainly appreciate the power of song, yet I fully admit
that it is astonishing that the females of many birds and some mammals
should be endowed with sufficient taste to appreciate ornaments, which
we have reason to attribute to sexual selection; and this is even more
astonishing in the case of reptiles, fish, and insects. But we really
know little about the minds of the lower animals. It cannot be
supposed, for instance, that male birds of paradise or peacocks should
take such pains in erecting, spreading, and vibrating their beautiful
plumes before the females for no purpose. We should remember the fact
given on excellent authority in a former chapter, that several peahens,
when debarred from an admired male, remained widows during a whole
season rather than pair with another bird.

Nevertheless I know of no fact in natural history more wonderful than
that the female Argus pheasant should appreciate the exquisite shading
of the ball-and-socket ornaments and the elegant patterns on the
wing-feather of the male. He who thinks that the male was created as he
now exists must admit that the great plumes, which prevent the wings
from being used for flight, and which are displayed during courtship
and at no other time in a manner quite peculiar to this one species,
were given to him as an ornament. If so, he must likewise admit that
the female was created and endowed with the capacity of appreciating
such ornaments. I differ only in the conviction that the male Argus
pheasant acquired his beauty gradually, through the preference of the
females during many generations for the more highly ornamented males;
the aesthetic capacity of the females having been advanced through
exercise or habit, just as our own taste is gradually improved. In the
male through the fortunate chance of a few feathers being left
unchanged, we can distinctly trace how simple spots with a little
fulvous shading on one side may have been developed by small steps into
the wonderful ball-and-socket ornaments; and it is probable that they
were actually thus developed.

Everyone who admits the principle of evolution, and yet feels great
difficulty in admitting that female mammals, birds, reptiles, and fish,
could have acquired the high taste implied by the beauty of the males,
and which generally coincides with our own standard, should reflect
that the nerve-cells of the brain in the highest as well as in the
lowest members of the Vertebrate series, are derived from those of the
common progenitor of this great Kingdom. For we can thus see how it has
come to pass that certain mental faculties, in various and widely
distinct groups of animals, have been developed in nearly the same
manner and to nearly the same degree.

The reader who has taken the trouble to go through the several chapters
devoted to sexual selection, will be able to judge how far the
conclusions at which I have arrived are supported by sufficient
evidence. If he accepts these conclusions he may, I think, safely
extend them to mankind; but it would be superfluous here to repeat what
I have so lately said on the manner in which sexual selection
apparently has acted on man, both on the male and female side, causing
the two sexes to differ in body and mind, and the several races to
differ from each other in various characters, as well as from their
ancient and lowly-organised progenitors.

He who admits the principle of sexual selection will be led to the
remarkable conclusion that the nervous system not only regulates most
of the existing functions of the body, but has indirectly influenced
the progressive development of various bodily structures and of certain
mental qualities. Courage, pugnacity, perseverance, strength and size
of body, weapons of all kinds, musical organs, both vocal and
instrumental, bright colours and ornamental appendages, have all been
indirectly gained by the one sex or the other, through the exertion of
choice, the influence of love and jealousy, and the appreciation of the
beautiful in sound, colour or form; and these powers of the mind
manifestly depend on the development of the brain.

Man scans with scrupulous care the character and pedigree of his
horses, cattle, and dogs before he matches them; but when he comes to
his own marriage he rarely, or never, takes any such care. He is
impelled by nearly the same motives as the lower animals, when they are
left to their own free choice, though he is in so far superior to them
that he highly values mental charms and virtues. On the other hand he
is strongly attracted by mere wealth or rank. Yet he might by selection
do something not only for the bodily constitution and frame of his
offspring, but for their intellectual and moral qualities. Both sexes
ought to refrain from marriage if they are in any marked degree
inferior in body or mind; but such hopes are Utopian and will never be
even partially realised until the laws of inheritance are thoroughly
known. Everyone does good service, who aids towards this end. When the
principles of breeding and inheritance are better understood, we shall
not hear ignorant members of our legislature rejecting with scorn a
plan for ascertaining whether or not consanguineous marriages are
injurious to man.

The advancement of the welfare of mankind is a most intricate problem:
all ought to refrain from marriage who cannot avoid abject poverty for
their children; for poverty is not only a great evil, but tends to its
own increase by leading to recklessness in marriage. On the other hand,
as Mr. Galton has remarked, if the prudent avoid marriage, whilst the
reckless marry, the inferior members tend to supplant the better
members of society. Man, like every other animal, has no doubt advanced
to his present high condition through a struggle for existence
consequent on his rapid multiplication; and if he is to advance still
higher, it is to be feared that he must remain subject to a severe
struggle. Otherwise he would sink into indolence, and the more gifted
men would not be more successful in the battle of life than the less
gifted. Hence our natural rate of increase, though leading to many and
obvious evils, must not be greatly diminished by any means. There
should be open competition for all men; and the most able should not be
prevented by laws or customs from succeeding best and rearing the
largest number of offspring. Important as the struggle for existence
has been and even still is, yet as far as the highest part of man’s
nature is concerned there are other agencies more important. For the
moral qualities are advanced, either directly or indirectly, much more
through the effects of habit, the reasoning powers, instruction,
religion, etc., than through natural selection; though to this latter
agency may be safely attributed the social instincts, which afforded
the basis for the development of the moral sense.

The main conclusion arrived at in this work, namely, that man is
descended from some lowly organised form, will, I regret to think, be
highly distasteful to many. But there can hardly be a doubt that we are
descended from barbarians. The astonishment which I felt on first
seeing a party of Fuegians on a wild and broken shore will never be
forgotten by me, for the reflection at once rushed into my mind—such
were our ancestors. These men were absolutely naked and bedaubed with
paint, their long hair was tangled, their mouths frothed with
excitement, and their expression was wild, startled, and distrustful.
They possessed hardly any arts, and like wild animals lived on what
they could catch; they had no government, and were merciless to every
one not of their own small tribe. He who has seen a savage in his
native land will not feel much shame, if forced to acknowledge that the
blood of some more humble creature flows in his veins. For my own part
I would as soon be descended from that heroic little monkey, who braved
his dreaded enemy in order to save the life of his keeper, or from that
old baboon, who descending from the mountains, carried away in triumph
his young comrade from a crowd of astonished dogs—as from a savage who
delights to torture his enemies, offers up bloody sacrifices, practices
infanticide without remorse, treats his wives like slaves, knows no
decency, and is haunted by the grossest superstitions.

Man may be excused for feeling some pride at having risen, though not
through his own exertions, to the very summit of the organic scale; and
the fact of his having thus risen, instead of having been aboriginally
placed there, may give him hope for a still higher destiny in the
distant future. But we are not here concerned with hopes or fears, only
with the truth as far as our reason permits us to discover it; and I
have given the evidence to the best of my ability. We must, however,
acknowledge, as it seems to me, that man with all his noble qualities,
with sympathy which feels for the most debased, with benevolence which
extends not only to other men but to the humblest living creature, with
his god-like intellect which has penetrated into the movements and
constitution of the solar system—with all these exalted powers—Man
still bears in his bodily frame the indelible stamp of his lowly
origin.

SUPPLEMENTAL NOTE.
ON SEXUAL SELECTION IN RELATION TO MONKEYS.

Reprinted from NATURE, November 2, 1876, p. 18.

In the discussion on Sexual Selection in my ‘Descent of Man,’ no case
interested and perplexed me so much as the brightly-coloured hinder
ends and adjoining parts of certain monkeys. As these parts are more
brightly coloured in one sex than the other, and as they become more
brilliant during the season of love, I concluded that the colours had
been gained as a sexual attraction. I was well aware that I thus laid
myself open to ridicule; though in fact it is not more surprising that
a monkey should display his bright-red hinder end than that a peacock
should display his magnificent tail. I had, however, at that time no
evidence of monkeys exhibiting this part of their bodies during their
courtship; and such display in the case of birds affords the best
evidence that the ornaments of the males are of service to them by
attracting or exciting the females. I have lately read an article by
Joh. von Fischer, of Gotha, published in ‘Der Zoologische Garten,’
April 1876, on the expression of monkeys under various emotions, which
is well worthy of study by any one interested in the subject, and which
shews that the author is a careful and acute observer. In this article
there is an account of the behaviour of a young male mandrill when he
first beheld himself in a looking-glass, and it is added, that after a
time he turned round and presented his red hinder end to the glass.
Accordingly I wrote to Herr J. von Fischer to ask what he supposed was
the meaning of this strange action, and he has sent me two long letters
full of new and curious details, which will, I hope, be hereafter
published. He says that he was himself at first perplexed by the above
action, and was thus led carefully to observe several individuals of
various other species of monkeys, which he has long kept in his house.
He finds that not only the mandrill (Cynocephalus mormon) but the drill
(C. leucophaeus) and three other kinds of baboons (C. hamadryas,
sphinx, and babouin), also Cynopithecus niger, and Macacus rhesus and
nemestrinus, turn this part of their bodies, which in all these species
is more or less brightly coloured, to him when they are pleased, and to
other persons as a sort of greeting. He took pains to cure a Macacus
rhesus, which he had kept for five years, of this indecorous habit, and
at last succeeded. These monkeys are particularly apt to act in this
manner, grinning at the same time, when first introduced to a new
monkey, but often also to their old monkey friends; and after this
mutual display they begin to play together. The young mandrill ceased
spontaneously after a time to act in this manner towards his master,
von Fischer, but continued to do so towards persons who were strangers
and to new monkeys. A young Cynopithecus niger never acted, excepting
on one occasion, in this way towards his master, but frequently towards
strangers, and continues to do so up to the present time. From these
facts Von Fischer concludes that the monkeys which behaved in this
manner before a looking-glass (viz., the mandrill, drill, Cynopithecus
niger, Macacus rhesus and nemestrinus) acted as if their reflection
were a new acquaintance. The mandrill and drill, which have their
hinder ends especially ornamented, display it even whilst quite young,
more frequently and more ostentatiously than do the other kinds. Next
in order comes Cynocephalus hamadryas, whilst the other species act in
this manner seldomer. The individuals, however, of the same species
vary in this respect, and some which were very shy never displayed
their hinder ends. It deserves especial attention that Von Fischer has
never seen any species purposely exhibit the hinder part of its body,
if not at all coloured. This remark applies to many individuals of
Macacus cynomolgus and Cercocebus radiatus (which is closely allied to
M. rhesus), to three species of Cercopithecus and several American
monkeys. The habit of turning the hinder ends as a greeting to an old
friend or new acquaintance, which seems to us so odd, is not really
more so than the habits of many savages, for instance that of rubbing
their bellies with their hands, or rubbing noses together. The habit
with the mandrill and drill seems to be instinctive or inherited, as it
was followed by very young animals; but it is modified or guided, like
so many other instincts, by observation, for Von Fischer says that they
take pains to make their display fully; and if made before two
observers, they turn to him who seems to pay the most attention.

With respect to the origin of the habit, Von Fischer remarks that his
monkeys like to have their naked hinder ends patted or stroked, and
that they then grunt with pleasure. They often also turn this part of
their bodies to other monkeys to have bits of dirt picked off, and so
no doubt it would be with respect to thorns. But the habit with adult
animals is connected to a certain extent with sexual feelings, for Von
Fischer watched through a glass door a female Cynopithecus niger, and
she during several days, “umdrehte und dem Männchen mit gurgelnden
Tönen die stark geröthete Sitzflache zeigte, was ich früher nie an
diesem Thier bemerkt hatte. Beim Anblick dieses Gegenstandes erregte
sich das Männchen sichtlich, denn es polterte heftig an den Stäben,
ebenfalls gurgelnde Laute ausstossend.” As all the monkeys which have
the hinder parts of their bodies more or less brightly coloured live,
according to Von Fischer, in open rocky places, he thinks that these
colours serve to render one sex conspicuous at a distance to the other;
but, as monkeys are such gregarious animals, I should have thought that
there was no need for the sexes to recognise each other at a distance.
It seems to me more probable that the bright colours, whether on the
face or hinder end, or, as in the mandrill, on both, serve as a sexual
ornament and attraction. Anyhow, as we now know that monkeys have the
habit of turning their hinder ends towards other monkeys, it ceases to
be at all surprising that it should have been this part of their bodies
which has been more or less decorated. The fact that it is only the
monkeys thus characterised which, as far as at present known, act in
this manner as a greeting towards other monkeys renders it doubtful
whether the habit was first acquired from some independent cause, and
that afterwards the parts in question were coloured as a sexual
ornament; or whether the colouring and the habit of turning round were
first acquired through variation and sexual selection, and that
afterwards the habit was retained as a sign of pleasure or as a
greeting, through the principle of inherited association. This
principle apparently comes into play on many occasions: thus it is
generally admitted that the songs of birds serve mainly as an
attraction during the season of love, and that the leks, or great
congregations of the black-grouse, are connected with their courtship;
but the habit of singing has been retained by some birds when they feel
happy, for instance by the common robin, and the habit of congregating
has been retained by the black-grouse during other seasons of the year.

I beg leave to refer to one other point in relation to sexual
selection. It has been objected that this form of selection, as far as
the ornaments of the males are concerned, implies that all females
within the same district must possess and exercise exactly the same
taste. It should, however, be observed, in the first place, that
although the range of variation of a species may be very large, it is
by no means indefinite. I have elsewhere given a good instance of this
fact in the pigeon, of which there are at least a hundred varieties
differing widely in their colours, and at least a score of varieties of
the fowl differing in the same kind of way; but the range of colour in
these two species is extremely distinct. Therefore the females of
natural species cannot have an unlimited scope for their taste. In the
second place, I presume that no supporter of the principle of sexual
selection believes that the females select particular points of beauty
in the males; they are merely excited or attracted in a greater degree
by one male than by another, and this seems often to depend, especially
with birds, on brilliant colouring. Even man, excepting perhaps an
artist, does not analyse the slight differences in the features of the
woman whom he may admire, on which her beauty depends. The male
mandrill has not only the hinder end of his body, but his face
gorgeously coloured and marked with oblique ridges, a yellow beard, and
other ornaments. We may infer from what we see of the variation of
animals under domestication, that the above several ornaments of the
mandrill were gradually acquired by one individual varying a little in
one way, and another individual in another way. The males which were
the handsomest or the most attractive in any manner to the females
would pair oftenest, and would leave rather more offspring than other
males. The offspring of the former, although variously intercrossed,
would either inherit the peculiarities of their fathers or transmit an
increased tendency to vary in the same manner. Consequently the whole
body of males inhabiting the same country would tend from the effects
of constant intercrossing to become modified almost uniformly, but
sometimes a little more in one character and sometimes in another,
though at an extremely slow rate; all ultimately being thus rendered
more attractive to the females. The process is like that which I have
called unconscious selection by man, and of which I have given several
instances. In one country the inhabitants value a fleet or light dog or
horse, and in another country a heavier and more powerful one; in
neither country is there any selection of individual animals with
lighter or stronger bodies and limbs; nevertheless after a considerable
lapse of time the individuals are found to have been modified in the
desired manner almost uniformly, though differently in each country. In
two absolutely distinct countries inhabited by the same species, the
individuals of which can never during long ages have intermigrated and
intercrossed, and where, moreover, the variations will probably not
have been identically the same, sexual selection might cause the males
to differ. Nor does the belief appear to me altogether fanciful that
two sets of females, surrounded by a very different environment, would
be apt to acquire somewhat different tastes with respect to form,
sound, or colour. However this may be, I have given in my ‘Descent of
Man’ instances of closely-allied birds inhabiting distinct countries,
of which the young and the females cannot be distinguished, whilst the
adult males differ considerably, and this may be attributed with much
probability to the action of sexual selection.

INDEX. — Abbot, C., on the battles of seals.

Abductor of the fifth metatarsal, presence of, in man.

Abercrombie, Dr., on disease of the brain affecting speech.

Abipones, marriage customs of the.

Abortion, prevalence of the practice of.

Abou-Simbel, caves of.

Abramis brama.

Abstraction, power of, in animals.

Acalles, stridulation of.

Acanthodactylus capensis, sexual differences of colour in.

Accentor Modularis.

Acclimatisation, difference of, in different races of men.

Achetidae, stridulation of the; rudimentary stridulating organs in
female.

Acilius sulcatus, elytra of the female.

Acomus, development of spurs in the female of.

Acridiidae, stridulation of the; rudimentary stridulating organs in
female.

Acromio-basilar muscle, and quadrupedal gait.

Acting.

Actiniae, bright colours of.

Adams, Mr., migration of birds; intelligence of nut-hatch; on the
Bombycilla carolinensis.

Admiral butterfly.

Adoption of the young of other animals by female monkeys.

Advancement in the organic scale, Von Baer’s definition of.

Aeby, on the difference between the skulls of man and the quadrumana.

Aesthetic faculty, not highly developed in savages.

Affection, maternal; manifestation of, by animals; parental and filial,
partly the result of natural selection; mutual, of birds; shewn by
birds in confinement, for certain persons.

Africa, probably the birthplace of man; South, crossed population of;
South, retention of colour by the Dutch in; South, proportion of the
sexes in the butterflies of; tattooing practised in; Northern, coiffure
of natives of.

Agassiz, L., on conscience in dogs; on the coincidence of the races of
man with zoological provinces; on the number of species of man; on the
courtship of the land-snails; on the brightness of the colours of male
fishes during the breeding season; on the frontal protuberance of the
males of Geophagus and Cichla; male fishes hatching ova in their
mouths; sexual differences in colour of chromids; on the slight sexual
differences of the South Americans; on the tattooing of the Amazonian
Indians.

Age, in relation to the transmission of characters in birds; variation
in accordance with, in birds.

Agelaeus phoeniceus.

Ageronia feronia, noise produced by.

Agrion, dimorphism in.

Agrion Ramburii, sexes of.

Agrionidae, difference in the sexes of.

Agrotis exclamationis.

Ague, tertian, dog suffering from.

Ainos, hairiness of the.

Aitchison, Mr., on sheep.

Aithurus polytmus, young of.

Albino birds.

Alca torda, young of.

Alces palmata.

Alder and Hancock, MM., on the nudi-branch mollusca.

Allen, J.A., vigour of birds earliest hatched; effect of difference of
temperature, light, etc., on birds; colours of birds; on the relative
size of the sexes of Callorhinus ursinus; on the name of Otaria jubata;
on the pairing of seals; on sexual differences in the colour of bats.

Allen, S., on the habits of Hoplopterus; on the plumes of herons; on
the vernal moult of Herodius bubulcus.

Alligator, courtship of the male; roaring of the male.

Amadavat, pugnacity of male.

Amadina Lathami, display of plumage by the male.

Amadina castanotis, display of plumage by the male.

Amazons, butterflies of the; fishes of the.

America, variation in the skulls of aborigines of; wide range of
aborigines of; lice of the natives of; general beardlessness of the
natives of.

America, North, butterflies of; Indians of, women a cause of strife
among the; Indians of, their notions of female beauty.

America, South, character of the natives of; population of parts of;
piles of stones in; extinction of the fossil horse of; desert-birds of;
slight sexual difference of the aborigines of; prevalence of
infanticide in.

American languages, often highly artificial.

Americans, wide geographical range of; native, variability of; and
negroes, difference of; aversion of, to hair on the face.

Ammophila, on the jaws of.

Ammotragus tragelaphus, hairy forelegs of.

Amphibia, affinity of, to the ganoid fishes; vocal organs of the.

Amphibians, breeding whilst immature.

Amphioxus.

Amphipoda, males sexually mature while young.

Amunoph III., negro character of, features of.

Anal appendages of insects.

Analogous variation in the plumage of birds.

Anas.

Anas acuta, male plumage of.

Anas boschas, male plumage of.

Anas histrionica.

Anas punctata.

Anastomus oscitans, sexes and young of; white nuptial plumage of.

Anatidae, voices of.

Anax junius, differences in the sexes of.

Andaman islanders, susceptible to change of climate.

Anderson, Dr., on the tail of Macacus brunneus; the Bufo sikimmensis;
sounds of Echis carinata.

Andreana fulva.

Anglo-Saxons, estimation of the beard among the.

Animals, domesticated, more fertile than wild; cruelty of savages to;
characters common to man and; domestic, change of breeds of.

Annelida, colours of.

Anobium tessellatum, sounds produced by.

Anolis cristatellus, male, crest of; pugnacity of the male;
throat-pouch of.

Anser canadensis.

Anset cygnoides; knob at the base of the beak of.

Anser hyperboreus, whiteness of.

Antelope, prong-horned, horns of.

Antelopes, generally polygamous; horns of; canine teeth of some male;
use of horns of; dorsal crests in; dewlaps of; winter change of two
species of; peculiar markings of.

Antennae, furnished with cushions in the male of Penthe.

Anthidium manicatum, large male of.

Anthocharis cardamines; sexual difference of colour in.

Anthocharis genutia.

Anthocharis sara.

Anthophora acervorum, large male of.

Anthophora retusa, difference of the sexes in.

Anthropidae.

Anthus, moulting of.

Antics of birds.

Antigua, Dr. Nicholson’s observations on yellow fever in.

Antilocapra americana, horns of.

Antilope bezoartica, horned females of; sexual difference in the colour
of.

Antilope Dorcas and euchore.

Antilope euchore, horns of.

Antilope montana, rudimentary canines in the young male of.

Antilope niger, sing-sing, caama, and gorgon, sexual differences in the
colours of.

Antilope oreas, horns of.

Antilope saiga, polygamous habits of.

Antilope strepsiceros, horns of.

Antilope subgutturosa, absence of suborbital pits in.

Antipathy, shewn by birds in confinement, to certain persons.

Ants, large size of the cerebral ganglia in; soldier, large jaws of;
playing together; memory in; intercommunication of, by means of the
antennae; habits of; difference of the sexes in; recognition of each
other by, after separation.

Ants White, habits of.

Anura.

Apatania muliebris, male unknown.

Apathus, difference of the sexes in.

Apatura Iris.

Apes, difference of the young, from the adult; semi-erect attitude of
some; mastoid processes of; influences of the jaw-muscles on the
physiognomy of; female, destitute of large canines; building platforms;
imitative faculties of; anthropomorphous; probable speedy extermination
of the; Gratiolet on the evolution of; canine teeth of male; females of
some, less hairy beneath than the males.

Apes, long-armed, their mode of progression.

Aphasia, Dr. Bateman on.

Apis mellifica, large male of.

Apollo, Greek statues of.

Apoplexy in Cebus Azarae.

Appendages, anal, of insects.

Approbation, influence of the love of.

Aprosmictus scapulatus.

Apus, proportion of sexes.

Aquatic birds, frequency of white plumage in.

Aquila chrysaetos.

Arab women, elaborate and peculiar coiffure of.

Arabs, fertility of crosses with other races; gashing of cheeks and
temples among the.

Arachnida.

Arakhan, artificial widening of the forehead by the natives of.

Arboricola, young of.

Archeopteryx.

Arctiidae, coloration of the.

Ardea asha, rufescens, and coerulea, change of colour in.

Ardea coerulea, breeding in immature plumage.

Ardea gularis, change of plumage in.

Ardea herodias, love-gestures of the male.

Ardea ludoviciana, age of mature plumage in; continued growth of crest
and plumes in the male of.

Ardea nycticorax, cries of.

Ardeola, young of.

Ardetta, changes of plumage in.

Argenteuil.

Argus pheasant, display of plumage by the male; ocellated spots of the;
gradation of characters in the.

Argyll, Duke of, on the physical weakness of man; the fashioning of
implements peculiar to man; on the contest in man between right and
wrong; on the primitive civilisation of man; on the plumage of the male
Argus pheasant; on Urosticte Benjamini; on the nests of birds.

Argynnis, colouring of the lower surface of.

Aricoris epitus, sexual differences in the wings of.

Aristocracy, increased beauty of the.

Arms, proportions of, in soldiers and sailors; direction of the hair on
the.

Arms and hands, free use of, indirectly correlated with diminution of
canines.

Arrest of development.

Arrow-heads, stone, general resemblance of.

Arrows, use of.

Arteries, variations in the course of the.

Artery, effect of tying, upon the lateral channels.

Arthropoda.

Arts practised by savages.

Ascension, coloured incrustation on the rocks of.

Ascidia, affinity of the lancelet to; tad-pole like larvae of.

Ascidians, bright colours of some.

Asinus, Asiatic and African species of.

Asinus taeniopus.

Ass, colour-variations of the.

Ateles, effects of brandy on an; absence of the thumb in.

Ateles beelzebuth, ears of.

Ateles marginatus, colour of the ruff of; hair on the head of.

Ateuchus cicatricosus, habits of.

Ateuchus, stridulation of.

Athalia, proportions of the sexes in.

Atropus pulsatorius.

Attention, manifestations of, in animals.

Audouin, V., on a hymenopterous parasite with a sedentary male.

Audubon, J.J., on the pinioned goose; on the speculum of Mergus
cucullatus; on the pugnacity of male birds; on courtship of
Caprimulgus; on Tetrao cupido; on Ardea nycticorax; on Sturnella
ludoviciana; on the vocal organs of Tetra cupido; on the drumming of
the male Tetrao umbellus; on sounds produced by the nightjar; on Ardea
herodias and Cathartes jota; on Mimus polyglottus; on display in male
birds; on the spring change of colour in some finches; on migration of
mocking thrushes; recognition of a dog by a turkey; selection of mate
by female birds; on the turkey; on variation in the male scarlet
tanager; on the musk-rat; on the habits of Pyranga aestiva; on local
differences in the nests of the same species of birds; on the habits of
woodpeckers; on Bombycilla carolinensis; on young females of Pyranga
aestiva acquiring male characters; on the immature plumage of thrushes;
on the immature plumage of birds; on birds breeding in immature
plumage; on the growth of the crest and plume in the male Ardea
ludoviciana; on the change of colour in some species of Ardea.

Audobon and Bachman, MM., on squirrels fighting; on the Canadian lynx.

Aughey, Prof., on rattlesnakes.

Austen, N.L., on Anolis cristatellus.

Australia, not the birthplace of man; half-castes killed by the natives
of; lice of the natives of.

Australia, South, variation in the skulls of aborigines of.

Australians, colour of new-born children of; relative height of the
sexes of; women a cause of war among the.

Axis deer, sexual difference in the colour of the.

Aymaras, measurements of the; no grey hair among the; hairlessness of
the face in the; long hair of the.

Azara, on the proportion of men and women among the Guaranys; on
Palamedea cornuta; on the beards of the Guaranys; on strife for women
among the Guanas; on infanticide; on the eradication of the eyebrows
and eyelashes by the Indians of Paraguay; on polyandry among the
Guanas; celibacy unknown among the savages of South America; on the
freedom of divorce among the Charruas.

Babbage C., on the greater proportion of illegitimate female births.

Babirusa, tusks of the.

Baboon, revenge in a; rage excited in, by reading; manifestation of
memory by a; employing a mat for shelter against the sun; protected
from punishment by its companions.

Baboon, Cape, mane of the male; Hamadryas, mane of the male.

Baboon, effects of intoxicating liquors on; ears of; diversity of the
mental faculties in; hands of; habits of; variability of the tail in;
manifestation of maternal affection by; using stones and sticks as
weapons; co-operation of; silence of, on plundering expeditions;
apparent polygamy of; polygamous and social habits of.

Baboons, courtship of.

Bachman, Dr., on the fertility of mulattoes.

Baer, K.E. von, on embryonic development; definition of advancement in
the organic scale.

Bagehot, W., on the social virtues among primitive men; slavery
formerly beneficial; on the value of obedience; on human progress; on
the persistence of savage tribes in classical times.

Bailly, E.M., on the mode of fighting of the Italian buffalo; on the
fighting of stags.

Bain, A., on the sense of duty; aid springing from sympathy; on the
basis of sympathy; on the love of approbation etc.; on the idea of
beauty.

Baird, W., on a difference in colour between the males and females of
some Entozoa.

Baker, Mr., observation on the proportion of the sexes in
pheasant-chicks.

Baker, Sir S., on the fondness of the Arabs for discordant music; on
sexual difference in the colours of an antelope; on the elephant and
rhinoceros attacking white or grey horses; on the disfigurements
practised by the negroes; on the gashing of the cheeks and temples
practised in Arab countries; on the coiffure of the North Africans; on
the perforation of the lower lip by the women of Latooka; on the
distinctive characters of the coiffure of central African tribes; on
the coiffure of Arab women.

“Balz” of the Black-cock.

Bantam, Sebright.

Banteng, horns of; sexual differences in the colours of the.

Banyai, colour of the.

Barbarism, primitive, of civilised nations.

Barbs, filamentous, of the feathers, in certain birds.

Barr, Mr., on sexual preference in dogs.

Barrago, F., on the Simian resemblances of man.

Barrington, Daines, on the language of birds; on the clucking of the
hen; on the object of the song of birds; on the singing of female
birds; on birds acquiring the songs of other birds; on the muscles of
the larynx in song-birds; on the want of the power of song by female
birds.

Barrow, on the widow-bird.

Bartels, Dr., supernumerary mammae in men.

Bartlett, A.D., period of hatching of bird’s eggs; on the tragopan; on
the development of the spurs in Crossoptilon auritum; on the fighting
of the males of Plectopterus gambensis; on the Knot; on display in male
birds; on the display of plumage by the male Polyplectron; on
Crossoptilon auritum and Phasianus Wallichii; on the habits of
Lophophorus; on the colour of the mouth in Buceros bicornis; on the
incubation of the cassowary; on the Cape Buffalo; on the use of the
horns of antelopes; on the fighting of male wart-hogs; on Ammotragus
tragelaphus; on the colours of Cercopithecus cephus; on the colours of
the faces of monkeys; on the naked surfaces of monkeys.

Bartlett, on courting of Argus pheasant.

Bartram, on the courtship of the male alligator.

Basque language, highly artificial.

Bate, C.S., on the superior activity of male crustacea; on the
proportions of the sexes in crabs; on the chelae of crustacea; on the
relative size of the sexes in crustacea; on the colours of crustacea.

Bateman, Dr., tendency to imitation in certain diseased states; on
Aphasia.

Bates, H.W., on variation in the form of the head of Amazonian Indians;
on the proportion of the sexes among Amazonian butterflies; on sexual
differences in the wings of butterflies; on the field-cricket; on
Pyrodes pulcherrimus; on the horns of Lamellicorn beetles; on the
colours of Epicaliae, etc.; on the coloration of tropical butterflies;
on the variability of Papilio Sesostris and Childrenae; on male and
female butterflies inhabiting different stations; on mimicry; on the
caterpillar of a Sphinx; on the vocal organs of the umbrella-bird; on
the toucans; on Brackyurus calvus.

Batokas, knocking out two upper incisors.

Batrachia, eagerness of male.

Bats, scent-glands; sexual differences in the colour of; fur of male
frugivorous.

Battle, law of; among beetles; among birds; among mammals; in man.

Beak, sexual difference in the forms of the; in the colour of the.

Beaks, of birds, bright colours of.

Beard, development of, in man; analogy of the, in man and the
quadrumana; variation of the development of the, in different races of
men; estimation of, among bearded nations; probable origin of the.

Beard, in monkeys; of mammals.

Beautiful, taste for the, in birds; in the quadrumana.

Beauty, sense of, in animals; appreciation of, by birds; influence of;
variability of the standard of.

Beauty, sense of, sufficiently permanent for action of sexual
selection.

Beaven, Lieut., on the development of the horns in Cervus Eldi.

Beaver, instinct and intelligence of the; voice of the; castoreum of
the.

Beavers, battles of male.

Bechstein, on female birds choosing the best singers among the males;
on rivalry in song-birds; on the singing of female birds; on birds
acquiring the songs of other birds; on pairing the canary and siskin;
on a sub-variety of the monk pigeon; on spurred hens.

Beddoe, Dr., on causes of difference in stature.

Bee-eater.

Bees, pollen-baskets and stings of; destruction of drones and queens
by; female, secondary sexual characters of; proportion of sexes;
difference of the sexes in colour and sexual selection.

Beetle, luminous larva of a.

Beetles, size of the cerebral ganglia in; dilatation of the foretarsi
in male; blind; stridulation of.

Belgium, ancient inhabitants of.

Bell, Sir C., on emotional muscles in man; “snarling muscles;” on the
hand.

Bell, T., on the numerical proportion of the sexes in moles; on the
newts; on the croaking of the frog; on the difference in the coloration
of the sexes in Zootoca vivipara; on moles fighting.

Bell-bird, sexual difference in the colour of the.

Bell-birds, colours of.

Belt, Mr., on the nakedness of tropical mankind; on a spider-monkey and
eagle; habits of ants; Lampridae distasteful to mammals; mimicry of
Leptalides; colours of Nicaraguan frogs; display of humming-birds; on
the toucans; protective colouring of skunk.

Benevolence, manifested by birds.

Bennett, A.W., attachment of mated birds; on the habits of Dromaeus
irroratus.

Bennett, Dr., on birds of paradise.

Berbers, fertility of crosses with other races.

Bernicla antarctica, colours of.

Bernicle gander pairing with a Canada goose.

Bert, M., crustaceans distinguish colours.

Bettoni, E., on local differences in the nests of Italian birds.

Beyle, M., see Bombet.

Bhoteas, colour of the beard in.

Bhringa, disc-formed tail-feathers of.

Bianconi, Prof., on structures as explained through mechanical
principles.

Bibio, sexual differences in the genus.

Bichat, on beauty.

Bickes, proportion of sexes in man.

Bile, coloured, in many animals.

Bimana.

Birds, imitations of the songs of other birds by; dreaming; killed by
telegraph wires; language of; sense of beauty in; pleasure of, in
incubation; male, incubation by; and reptiles, alliance of; sexual
differences in the beak of some; migratory, arrival of the male before
the female; apparent relation between polygamy and marked sexual
differences in; monogamous, becoming polygamous under domestication;
eagerness of male in pursuit of the female; wild, numerical proportion
of the sexes in; secondary sexual characters of; difference of size in
the sexes of; fights of male, witnessed by females; display of male, to
captivate the females; close attention of, to the songs of others;
acquiring the song of their foster-parents; brilliant, rarely good
songsters; love-antics and dances of; coloration of; moulting of;
unpaired; male, singing out of season; mutual affection of; in
confinement, distinguish persons; hybrid, production of; Albino;
European, number of species of; variability of; geographical
distribution of colouring; gradation of secondary sexual characters in;
obscurely coloured, building concealed nests; young female, acquiring
male characters; breeding in immature plumage; moulting of; aquatic,
frequency of white plumage in; vocal courtship of; naked skin of the
head and neck in.

Birgus latro, habits of.

Birkbeck, Mr., on the finding of new mates by golden eagles.

Birthplace of man.

Births, numerical proportions of the sexes in, in animals and man; male
and female, numerical proportion of, in England.

Bischoff, Prof., on the agreement between the brains of man and of the
orang; figure of the embryo of the dog; on the convolutions of the
brain in the human foetus; on the difference between the skulls of man
and the quadrumana; resemblance between the ape’s and man’s.

Bishop, J., on the vocal organs of frogs; on the vocal organs of
cervine birds; on the trachea of the Merganser.

Bison, American, co-operation of; mane of the male.

Bitterns, dwarf, coloration of the sexes of.

Biziura lobata, musky odour of the male; large size of male.

Blackbird, sexual differences in the; proportion of the sexes in the;
acquisition of a song by; colour of the beak in the sexes of the;
pairing with a thrush; colours and nidification of the; young of the;
sexual difference in coloration of the.

Black-buck, Indian, sexual difference in the colour of the.

Blackcap, arrival of the male, before the female; young of the.

Black-cock, polygamous; proportion of the sexes in the; pugnacity and
love-dance of the; call of the; moulting of the; duration of the
courtship of the; and pheasant, hybrids of; sexual difference in
coloration of the; crimson eye-cere of the.

Black-grouse, characters of young.

Blacklock, Dr., on music.

Blackwall, J., on the speaking of the magpie; on the desertion of their
young by swallows; on the superior activity of male spiders; on the
proportion of the sexes in spiders; on sexual variation of colour in
spiders; on male spiders.

Bladder-nose Seal, hood of the.

Blaine, on the affections of dogs.

Blair, Dr., on the relative liability of Europeans to yellow fever.

Blake, C.C., on the jaw from La Naulette.

Blakiston, Captain, on the American snipe; on the dances of Tetrao
phasianellus.

Blasius, Dr., on the species of European birds.

Bledius taurus, hornlike processes of male.

Bleeding, tendency to profuse.

Blenkiron, Mr., on sexual preference in horses.

Blennies, crest developed on the head of male, during the breeding
season.

Blethisa multipunctata, stridulation of.

Bloch, on the proportions of the sexes in fishes.

Blood, arterial, red colour of.

Blood pheasant, number of spurs in.

Blow-fly, sounds made by.

Bluebreast, red-throated, sexual differences of the.

Blumenbach, on Man; on the large size of the nasal cavities in American
aborigines; on the position of man; on the number of species of man.

Blyth, E., on the structure of the hand in the species of Hylobates;
observations on Indian crows; on the development of the horns in the
Koodoo and Eland antelopes; on the pugnacity of the males of Gallicrex
cristatus; on the presence of spurs in the female Euplocamus
erythrophthalmus; on the pugnacity of the amadavat; on the spoonbill;
on the moulting of Anthus; on the moulting of bustards, plovers, and
Gallus bankiva; on the Indian honey-buzzard; on sexual differences in
the colour of the eyes of hornbills; on Oriolus melanocephalus; on
Palaeornis javanicus; on the genus Ardetta; on the peregrine falcon; on
young female birds acquiring male characters; on the immature plumage
of birds; on representative species of birds; on the young of Turnix;
on anomalous young of Lanius rufus and Colymbus glacialis; on the sexes
and young of the sparrows; on dimorphism in some herons; on the
ascertainment of the sex of nestling bullfinches by pulling out
breast-feathers; on orioles breeding in immature plumage; on the sexes
and young of Buphus and Anastomus; on the young of the blackcap and
blackbird; on the young of the stonechat; on the white plumage of
Anastomus; on the horns of Bovine animals; on the horns of Antilope
bezoartica; on the mode of fighting of Ovis cycloceros; on the voice of
the Gibbons; on the crest of the male wild goat; on the colours of
Portax picta; on the colours of Antilope bezoartica; on the colour of
the Axis deer; on sexual difference of colour in Hylobates hoolock; on
the hog-deer; on the beard and whiskers in a monkey, becoming white
with age.

Boar, wild, polygamous in India; use of the tusks by the; fighting of.

Boardman, Mr., Albino birds in U.S.

Boitard and Corbie, MM., on the transmission of sexual peculiarities in
pigeons; on the antipathy shewn by some female pigeons to certain
males.

Bold, Mr., on the singing of a sterile hybrid canary.

Bombet, on the variability of the standard of beauty in Europe.

Bombus, difference of the sexes in.

Bombycidae, coloration of; pairing of the; colours of.

Bombycilla carolinensis, red appendages of.

Bombyx cynthia, proportion of the sexes in; pairing of.

Bombyx mori, difference of size of the male and female cocoons of;
pairing of.

Bombyx Pernyi, proportion of sexes of.

Bombyx Yamamai, M. Personnat on; proportion of sexes of.

Bonaparte, C.L., on the call-notes of the wild turkey.

Bond, F., on the finding of new mates by crows.

Bone, implements of, skill displayed in making.

Boner, C., on the transfer of male characters to an old female chamois;
on the habits of stags; on the pairing of red deer.

Bones, increase of, in length and thickness, when carrying a greater
weight.

Bonizzi, P., difference of colour in sexes of pigeons.

Bonnet monkey.

Bonwick, J., extinction of Tasmanians.

Boomerang.

Boreus hyemalis, scarcity of the male.

Bory St. Vincent, on the number of species of man; on the colours of
Labrus pavo.

Bos etruscus.

Bos gaurus, horns of.

Bos moschatus.

Bos primigenius.

Bos sondaicus, horns of, colours of.

Botocudos, mode of life of; disfigurement of the ears and lower lip of
the.

Boucher de Perthes, J.C. de, on the antiquity of man.

Bourbon, proportion of the sexes in a species of Papilio from.

Bourien on the marriage-customs of the savages of the Malay
Archipelago.

Bovidae, dewlaps of.

Bower-birds, habits of the; ornamented playing-places of.

Bows, use of.

Brachycephalic structure, possible explanation of.

Brachyura.

Brachyurus calvus, scarlet face of.

Bradley, Mr., abductor ossis metatarsi quinti in man.

Brain, of man, agreement of the, with that of lower animals;
convolutions of, in the human foetus; influence of development of
mental faculties upon the size of the; influence of the development of
on the spinal column and skull; larger in some existing mammals than in
their tertiary prototypes; relation of the development of the, to the
progress of language; disease of the, affecting speech; difference in
the convolutions of, in different races of men; supplement on, by Prof.
Huxley; development of the gyri and sulci.

Brakenridge, Dr., on the influence of climate.

Brandt, A., on hairy men.

Braubach, Prof., on the quasi-religious feeling of a dog towards his
master; on the self-restraint of dogs.

Brauer, F., on dimorphism in Neurothemis.

Brazil, skulls found in caves of; population of; compression of the
nose by the natives of.

Break between man and the apes.

Bream, proportion of the sexes in the.

Breeding, age of, in birds.

Breeding season, sexual characters making their appearance in the, in
birds.

Brehm, on the effects of intoxicating liquors on monkeys; on the
recognition of women by male Cynocephali; on the diversity of the
mental faculties of monkeys; on the habits of baboons; on revenge taken
by monkeys; on manifestations of maternal affection by monkeys and
baboons; on the instinctive dread of monkeys for serpents; on the use
of stones as missiles by baboons; on a baboon using a mat for shelter
from the sun; on the signal-cries of monkeys; on sentinels posted by
monkeys; on co-operation of animals; on an eagle attacking a young
Cercopithecus; on baboons in confinement protecting one of their number
from punishment; on the habits of baboons when plundering; on polygamy
in Cynocephalus and Cebus; on the numerical proportion of the sexes in
birds; on the love-dance of the blackcock; Palamedea cornuta; on the
habits of the Black-grouse; on sounds produced by birds of paradise; on
assemblages of grouse; on the finding of new mates by birds; on the
fighting of wild boars; on sexual differences in Mycetes; on the habits
of Cynocephalus hamadryas.

Brent, Mr., on the courtship of fowls.

Breslau, numerical proportion of male and female births in.

Bridgeman, Laura.

Brimstone butterfly, sexual difference of colour in the.

British, ancient, tattooing practised by.

Broca, Prof., on the occurrence of the supra-condyloid foramen in the
human humerus; anthropomorphous apes more bipedal than quadrupedal; on
the capacity of Parisian skulls at different periods; comparison of
modern and mediaeval skulls; on tails of quadrupeds; on the influence
of natural selection; on hybridity in man; on human remains from Les
Eyzies; on the cause of the difference between Europeans and Hindoos.

Brodie, Sir B., on the origin of the moral sense in man.

Bronn, H.G., on the copulation of insects of distinct species.

Bronze period, men of, in Europe.

Brown, R., sentinels of seals generally females; on the battles of
seals; on the narwhal; on the occasional absence of the tusks in the
female walrus; on the bladder-nose seal; on the colours of the sexes in
Phoca Groenlandica; on the appreciation of music by seals; on plants
used as love-philters, by North American women.

Browne, Dr. Crichton, injury to infants during parturition.

Brown-Sequard, Dr., on the inheritance of the effects of operations by
guinea-pig.

Bruce, on the use of the elephant’s tusks.

Brulerie, P. de la, on the habits of Ateuchus cicatricosus; on the
stridulation of Ateuchus.

Brunnich, on the pied ravens of the Feroe islands.

Bryant, Dr., preference of tame pigeon for wild mate.

Bryant, Captain, on the courtship of Callorhinus ursinus.

Bubas bison, thoracic projection of.

Bubalus caffer, use of horns.

Bucephalus capensis, difference of the sexes of, in colour.

Buceros, nidification and incubation of.

Buceros bicornis, sexual differences in the colouring of the casque,
beak, and mouth in.

Buceros corrugatus, sexual differences in the beak of.

Buchner, L., on the origin of man; on the use of the human foot as a
prehensile organ; on the mode of progression of the apes; on want of
self-consciousness, etc., in savages.

Bucholz, Dr., quarrels of chamaeleons.

Buckinghamshire, numerical proportion of male and female births in.

Buckland, F., on the numerical proportion of the sexes in rats; on the
proportion of the sexes in the trout; on Chimaera monstrosa.

Buckland, W., on the complexity of crinoids.

Buckler, W., proportion of sexes of Lepidoptera reared by.

Bucorax abyssinicus, inflation of the neck-wattle of the male during
courtship.

Budytes Raii.

Buffalo, Cape.

Buffalo, Indian, horns of the.

Buffalo, Italian, mode of fighting of the.

Buffon, on the number of species of man.

Bufo sikimmensis.

Bugs.

Buist, R., on the proportion of the sexes in salmon; on the pugnacity
of the male salmon.

Bulbul, pugnacity of the male; display of under tail-coverts by the
male.

Bull, mode of fighting of the; curled frontal hair of the.

Buller, Dr., on the Huia; the attachment of birds.

Bullfinch, sexual differences in the; piping; female, singing of the;
courtship of the; widowed, finding a new mate; attacking a
reed-bunting; nestling, sex ascertained by pulling out breast feathers.

Bullfinches, distinguishing persons; rivalry of female.

Bulls, two young, attacking an old one; wild, battles of.

Bull-trout, male, colouring of, during the breeding season.

Bunting, reed, head feathers of the male; attacked by a bullfinch.

Buntings, characters of young.

Buphus coromandus, sexes and young of; change of colour in.

Burchell, Dr., on the zebra; on the extravagance of a Bushwoman in
adorning herself; celibacy unknown among the savages of South Africa;
on the marriage-customs of the Bushwomen.

Burke, on the number of species of man.

Burmese, colour of the beard in.

Burton, Captain, on negro ideas of female beauty; on a universal ideal
of beauty.

Bushmen, marriage among.

Bushwoman, extravagant ornamentation of a.

Bushwomen, hair of; marriage-customs of.

Bustard, throat-pouch of the male; humming noise produced by a male;
Indian, ear-tufts of.

Bustards, occurrence of sexual differences and of polygamy among the;
love-gestures of the male; double moult in.

Butler, A.G., on sexual differences in the wings of Aricoris epitus;
courtship of butterflies; on the colouring of the sexes in species of
Thecla; on the resemblance of Iphias glaucippe to a leaf; on the
rejection of certain moths and caterpillars by lizards and frogs.

Butterfly, noise produced by a; Emperor; meadow brown, instability of
the ocellated spots of.

Butterflies, proportion of the sexes in; forelegs atrophied in some
males; sexual difference in the neuration of the wings of; pugnacity of
male; protective resemblances of the lower surface of; display of the
wings by; white, alighting upon bits of paper; attracted by a dead
specimen of the same species; courtship of; male and female, inhabiting
different stations.

Buxton, C., observations on macaws; on an instance of benevolence in a
parrot.

Buzzard, Indian honey-; variation in the crest of.

Cabbage butterflies.

Cachalot, large head of the male.

Cadences, musical, perception of, by animals.

Caecum, large, in the early progenitors of man.

Cairina moschata, pugnacity of the male.

Californian Indians, decrease of.

Callianassa, chelae of, figured.

Callidryas, colours of sexes.

Callionymus lyra, characters of the male.

Callorhinus ursinus, relative size of the sexes of; courtship of.

Calotes maria.

Calotes nigrilabris, sexual difference in the colour of.

Cambridge, O. Pickard, on the sexes of spiders; on the size of male
Nephila.

Camel, canine teeth of male.

Campbell, J., on the Indian elephant; on the proportion of male and
female births in the harems of Siam.

Campylopterus hemileucurus.

Canaries distinguishing persons.

Canary, polygamy of the; change of plumage in, after moulting; female,
selecting the best singing male; sterile hybrid, singing of a; female,
singing of the; selecting a greenfinch; and siskin, pairing of.

Cancer pagurus.

Canestrini, G., on rudimentary characters and the origin of man; on
rudimentary characters; on the movement of the ear in man; of the
variability of the vermiform appendage in man; on the abnormal division
of the malar bone in man; on abnormal conditions of the human uterus;
on the persistence of the frontal suture in man; on the proportion of
the sexes in silk-moths; secondary sexual characters of spiders.

Canfield, Dr., on the horns of the Antilocapra.

Canine teeth in man, diminution of, in man; diminution of, in horses;
disappearance of, in male ruminants; large in the early progenitors of
man.

Canines, and horns, inverse development of.

Canoes, use of.

Cantharis, difference of colour in the sexes of a species of.

Cantharus lineatus.

Capercailzie, polygamous; proportion of the sexes in the; pugnacity of
the male; pairing of the; autumn meetings of the; call of the; duration
of the courtship of; behaviour of the female; inconvenience of black
colour to the female; sexual difference in the coloration of the;
crimson eye-cere of the male.

Capitonidae, colours and nidification of the.

Capra aegagrus, crest of the male; sexual difference in the colour of.

Capreolus Sibiricus subecaudatus.

Caprice, common to man and animals.

Caprimulgus, noise made by the males of some species of, with their
wings.

Caprimulgus virginianus, pairing of.

Carabidae.

Carbonnier, on the natural history of the pike; on the relative size of
the sexes in fishes; courtship of Chinese Macropus.

Carcineutes, sexual difference of colour in.

Carcinus moenas.

Cardinalis virginianus.

Carduelis elegans, sexual differences of the beak in.

Carnivora, marine, polygamous habits of; sexual differences in the
colours of.

Carp, numerical proportion of the sexes in the.

Carr, R., on the peewit.

Carrier pigeon, late development of the wattle in the.

Carrion beetles, stridulation of.

Carrion-hawk, bright coloured female of.

Carus, Prof. V., on the development of the horns in merino sheep; on
antlers of red deer.

Cassowary, sexes and incubation of the.

Castnia, mode of holding wings.

Castoreum.

Castration, effects of.

Casuarius galeatus.

Cat, convoluted body in the extremity of the tail of a; sick, sympathy
of a dog with a.

Cataract in Cebus Azarae.

Catarrh, liability of Cebus Azarae to.

Catarrhine monkeys.

Caterpillars, bright colours of.

Cathartes aura.

Cathartes jota, love-gestures of the male.

Catlin, G., correlation of colour and texture of hair in the Mandans;
on the development of the beard among the North American Indians; on
the great length of the hair in some North American tribes.

Caton, J.D., on the development of the horns in Cervus virginianus and
strongyloceros; on the wild turkey; on the presence of traces of horns
in the female wapiti; on the fighting of deer; on the crest of the male
wapiti; on the colours of the Virginian deer; on sexual differences of
colour in the wapiti; on the spots of the Virginian deer.

Cats, dreaming; tortoise-shell; enticed by valerian; colours of.

Cattle, rapid increase of, in South America; domestic, lighter in
winter in Siberia; horns of; domestic, sexual differences of, late
developed; numerical proportion of the sexes in.

Caudal vertebrae, number of, in macaques and baboons; basal, of
monkeys, imbedded in the body.

Cavolini, observations on Serranus.

Cebus, maternal affection in a; gradation of species of.

Cebus Apella.

Cebus Azarae, liability of, to the same diseases as man; distinct
sounds produced by; early maturity of the female.

Cebus capucinus, polygamous; sexual differences of colour in; hair on
the head of.

Cebus vellerosus, hair on the head of.

Cecidomyiidae, proportions of the sexes in.

Celibacy, unknown among the savages of South Africa and South America.

Centipedes.

Cephalopoda, absence of secondary sexual characters in.

Cephalopterus ornatus.

Cephalopterus penduliger.

Cerambyx heros, stridulant organ of.

Ceratodus, paddle of.

Ceratophora aspera, nasal appendages of.

Ceratophora Stoddartii, nasal horn of.

Cerceris, habits of.

Cercocebus aethiops, whiskers, etc., of.

Cercopithecus, young, seized by an eagle and rescued by the troop;
definition of species of.

Cercopithecus cephus, sexual difference of colour in.

Cercopithecus cynosurus and griseo-viridis, colour of the scrotum in.

Cercopithecus Diana, sexual differences of colour in.

Cercopithecus griseo-viridis.

Cercopithecus petaurista, whiskers, etc., of.

Ceres, of birds, bright colours of.

Ceriornis Temminckii, swelling of the wattles of the male during
courtship.

Cervulus, weapons of.

Cervulus moschatus, rudimentary horns of the female.

Cervus alces.

Cervus campestris, odour of.

Cervus canadensis, traces of horns in the female; attacking a man;
sexual difference in the colour of.

Cervus elaphus, battles of male; horns of, with numerous points; long
hairs on the throat of.

Cervus Eldi.

Cervus mantchuricus.

Cervus paludosus, colours of.

Cervus strongyloceros.

Cervus virginianus, horns of, in course of modification.

Ceryle, male black-belted in some species of.

Cetacea, nakedness of.

Ceylon, frequent absence of beard in the natives of.

Chaffinch, proportion of the sexes in the; courtship of the.

Chaffinches, new mates found by.

Chalcophaps indicus, characters of young.

Chalcosoma atlas, sexual differences of.

Chamaeleo, sexual differences in the genus; combats of.

Chamaeleo bifurcus.

Chamaeleo Owenii.

Chamaeleo pumilus.

Chamaepetes unicolor, modified wing-feather in the male.

Chameleons.

Chamois, danger-signals of; transfer of male characters to an old
female.

Champneys, Mr., acromio-basilar muscle and quadrupedal gait.

Chapman, Dr., on stridulation in Scolytus.

Chapuis, Dr., on the transmission of sexual peculiarities in pigeons;
on streaked Belgian pigeons.

Char, male, colouring of, during the breeding season.

Characters, male, developed in females; secondary sexual, transmitted
through both sexes; natural, artificial, exaggeration of, by man.

Charadrus hiaticula and pluvialis, sexes and young of.

Chardin on the Persians.

Charms, worn by women.

Charruas, freedom of divorce among the.

Chasmorhynchus, difference of colour in the sexes of; colours of.

Chasmorhynchus niveus.

Chasmorhynchus nudicollis.

Chasmorhynchus tricarunculatus.

Chastity, early estimation of.

Chatterers, sexual differences in.

Cheever, Rev. H.T., census of the Sandwich Islands.

Cheiroptera, absence of secondary sexual characters in.

Chelae of crustacea.

Chelonia, sexual differences in.

Chenalopex aegyptiacus, wing-knobs of.

Chera progne.

Chest, proportions of, in soldiers and sailors; large, of the Quechua
and Aymara Indians.

Chevrotains, canine teeth of.

Chiasognathus, stridulation of.

Chiasognathus Grantii, mandibles of.

Children, legitimate and illegitimate, proportion of the sexes in.

Chiloe, lice of the natives of; population of.

Chimaera monstrosa, bony process on the head of the male.

Chimaeroid fishes, prehensile organs of male.

Chimpanzee, ears of the; representatives of the eyebrows in the; hands
of the; absence of mastoid processes in the; platforms built by the;
cracking nuts with a stone; direction of the hair on the arms of the;
supposed evolution of the; polygamous and social habits of the.

China, North, idea of female beauty in.

China, Southern, inhabitants of.

Chinese, use of flint tools by the; difficulty of distinguishing the
races of the; colour of the beard in; general beardlessness of the;
opinions of the, on the appearance of Europeans and Cingalese;
compression of the feet of.

Chinsurdi, his opinion of beards.

Chlamydera maculata.

Chloeon, pedunculated eyes of the male of.

Chloephaga, coloration of the sexes in.

Chlorocoelus Tanana.

Chorda dorsalis.

Chough, red beak of the.

Chromidae, frontal protuberance in male; sexual differences in colour
of.

Chrysemys picta, long claws of the male.

Chrysococcyx, characters of young of.

Chrysomelidae, stridulation of.

Cicada pruinosa.

Cicada septendecim.

Cicadae, songs of the; rudimentary sound-organs in females of.

Cicatrix of a burn, causing modification of the facial bones.

Cichla, frontal protuberance of male.

Cimetiere du Sud, Paris.

Cincloramphus cruralis, large size of male.

Cinclus aquaticus.

Cingalese, Chinese opinion of the appearance of the.

Cirripedes, complemental males of.

Civilisation, effects of, upon natural selection; influence of, in the
competition of nations.

Clanging of geese, etc.

Claparede, E., on natural selection applied to man.

Clarke, on the marriage-customs of Kalmucks.

Classification.

Claus, C., on the sexes of Saphirina.

Cleft-palate, inherited.

Climacteris erythrops, sexes of.

Climate, cool, favourable to human progress; power of supporting
extremes of, by man; want of connexion of, with colour; direct action
of, on colours of birds.

Cloaca, existence of a, in the early progenitors of man.

Cloacal passage existing in the human embryo.

Clubs, used as weapons before dispersion of mankind.

Clucking of fowls.

Clythra 4-punctata, stridulation of.

Coan, Mr., Sandwich-islanders.

Cobbe, Miss, on morality in hypothetical bee-community.

Cobra, ingenuity of a.

Coccus.

Coccyx, in the human embryo; convoluted body at the extremity of the;
imbedded in the body.

Cochin-China, notions of beauty of the inhabitants of.

Cock, blind, fed by its companion; game, killing a kite; comb and
wattles of the; preference shewn by the, for young hens; game,
transparent zone in the hackles of a.

Cock of the rock.

Cockatoos, nestling; black, immature plumage of.

Coelenterata, absence of secondary sexual characters in.

Coffee, fondness of monkeys for.

Cold, supposed effects of; power of supporting, by man.

Coleoptera, stridulation of; stridulant organs of, discussed.

Colias edusa and hyale.

Collingwood, C., on the pugnacity of the butterflies of Borneo; on
butterflies being attracted by a dead specimen of the same species.

Colobus, absence of the thumb.

Colombia, flattened heads of savages of.

Colonists, success of the English as.

Coloration, protective, in birds.

Colour, supposed to be dependent on light and heat; correlation of,
with immunity from certain poisons and parasites; purpose of, in
lepidoptera; relation of, to sexual functions, in fishes; difference
of, in the sexes of snakes; sexual differences of, in lizards;
influence of, in the pairing of birds of different species; relation
of, to nidification; sexual differences of, in mammals; recognition of,
by quadrupeds; of children, in different races of man; of the skin in
man.

Colours, admired alike by man and animals; bright, due to sexual
selection; bright, among the lower animals; bright, protective to
butterflies and moths; bright, in male fishes; transmission of, in
birds.

Colquhoun, example of reasoning in a retriever.

Columba passerina, young of.

Colymbus glacialis, anomalous young of.

Comb, development of, in fowls.

Combs and wattles in male birds.

Community, preservation of variations useful to the, by natural
selection.

Complexion, different in men and women, in an African tribe.

Compositae, gradation of species among the.

Comte, C., on the expression of the ideal of beauty by sculpture.

Conditions of life, action of changed, upon man; influence of, on
plumage of birds.

Condor, eyes and comb of the.

Conjugations, origin of.

Conscience, absence of, in some criminals.

Constitution, difference of, in different races of men.

Consumption, liability of Cebus Azarae to; connection between
complexion and.

Convergence of characters.

Cooing of pigeons and doves.

Cook, Captain, on the nobles of the Sandwich Islands.

Cope, E.D., on the Dinosauria.

Cophotis ceylanica, sexual differences of.

Copris.

Copris Isidis, sexual differences of.

Copris lunaris, stridulation of.

Corals, bright colours of.

Coral-snakes.

Cordylus, sexual difference of colour in a species of.

Corfu, habits of the Chaffinch in.

Cornelius, on the proportions of the sexes in Lucanus Cervus.

Corpora Wolffiana, agreement of, with the kidneys of fishes.

Correlated variation.

Correlation, influence of, in the production of races.

Corse, on the mode of fighting of the elephant.

Corvus corone.

Corvus graculus, red beak of.

Corvus pica, nuptial assembly of.

Corydalis cornutus, large jaws of the male.

Cosmetornis.

Cosmetornis vexillarius, elongation of wing-feathers in.

Cotingidae, sexual differences in; coloration of the sexes of;
resemblance of the females of distinct species of.

Cottus scorpius, sexual differences in.

Coulter, Dr., on the Californian Indians.

Counting, origin of; limited power of, in primeval man.

Courage, variability of, in the same species; universal high
appreciation of; importance of; characteristic of men.

Courtship, greater eagerness of males in; of fishes; of birds.

Cow, winter change of colour.

Crab, devil.

Crab, shore, habits of.

Crabro cribrarius, dilated tibiae of the male.

Crabs, proportions of the sexes in.

Cranz, on the inheritance of dexterity in seal-catching.

Crawfurd, on the number of species of man.

Crenilabrus massa and C. melops, nests, built by.

Crest, origin of, in Polish fowls.

Crests, of birds, difference of, in the sexes; dorsal hairy, of
mammals.

Cricket, field-, stridulation of the; pugnacity of male.

Cricket, house-, stridulation of the.

Crickets, sexual differences in.

Crinoids, complexity of.

Crioceridae, stridulation of the.

Croaking of frogs.

Crocodiles, musky odour of, during the breeding season.

Crocodilia.

Crossbills, characters of young.

Crosses in man.

Crossing of races, effects of the.

Crossoptilon auritum, adornment of both sexes of; sexes alike in.

Crotch, G.R., on the stridulation of beetles; on the stridulation of
Heliopathes; on the stridulation of Acalles; habit of female deer at
breeding time.

Crow, Indians, long hair of the.

Crow, young of the.

Crows, vocal organs of the; living in triplets.

Crows, carrion, new mates found by.

Crows, Indian, feeding their blind companions.

Cruelty of savages to animals.

Crustacea, parasitic, loss of limbs by female; prehensile feet and
antennae of; male, more active than female; parthenogenesis in;
secondary sexual characters of; amphipod, males sexually mature while
young; auditory hairs of.

Crystal worn in the lower lip by some Central African women.

Cuckoo fowls.

Culicidae, attracted by each other’s humming.

Cullen, Dr., on the throat-pouch of the male bustard.

Cultivation of plants, probable origin of.

Cupples, Mr., on the numerical proportion of the sexes in dogs, sheep,
and cattle; on the Scotch deerhound; on sexual preference in dogs.

Curculionidae, sexual difference in length of snout in some; hornlike
processes in male; musical.

Curiosity, manifestations of, by animals.

Curlews, double moult in.

Cursores, comparative absence of sexual differences among the.

Curtis, J., on the proportion of the sexes in Athalia.

Cuvier, F., on the recognition of women by male quadrumana.

Cuvier, G., on the number of caudal vertebrae in the mandrill; on
instinct and intelligence; views of, as to the position of man; on the
position of the seals; on Hectocotyle.

Cyanalcyon, sexual difference in colours of; immature plumage of.

Cyanecula suecica, sexual differences of.

Cychrus, sounds produced by.

Cycnia mendica, sexual difference of, in colour.

Cygnus ferus, trachea of.

Cygnus immutabilis.

Cygnus olor, white young of.

Cyllo Leda, instability of the ocellated spots of.

Cynanthus, variation in the genus.

Cynipidae, proportion of the sexes in.

Cynocephalus, difference of the young from the adult; male, recognition
of women by; polygamous habits of species of.

Cynocephalus babouin.

Cynocephalus chacma.

Cynocephalus gelada.

Cynocephalus hamadryas, sexual difference of colour in.

Cynocephalus leucophaeus, colours of the sexes of.

Cynocephalus mormon, colours of the male.

Cynocephalus porcarius, mane of the male.

Cynocephalus sphinx.

Cynopithecus niger, ear of.

Cypridina, proportions of the sexes in.

Cyprinidae, proportion of the sexes in the.

Cyprinidae, Indian.

Cyprinodontidae, sexual differences in the.

Cyprinus auratus.

Cypris, relation of the sexes in.

Cyrtodactylus rubidus.

Cystophora cristata, hood of.

Dacelo, sexual difference of colour in.

Dacelo Gaudichaudi, young male of.

Dal-ripa, a kind of ptarmigan.

Damalis albifrons, peculiar markings of.

Damalis pygarga, peculiar markings of.

Dampness of climate, supposed influence of, on the colour of the skin.

Danaidae.

Dances of birds.

Dancing, universality of.

Danger-signals of animals.

Daniell, Dr., his experience of residence in West Africa.

Darfur, protuberances artificially produced by natives of.

Darwin, F., on the stridulation of Dermestes murinus.

Dasychira pudibunda, sexual difference of colour in.

Davis, A.H., on the pugnacity of the male stag-beetle.

Davis, J.B., on the capacity of the skull in various races of men; on
the beards of the Polynesians.

Death’s Head Sphinx.

Death-rate higher in towns than in rural districts.

Death-tick.

De Candolle, Alph., on a case of inherited power of moving the scalp.

Declensions, origin of.

Decoration in birds.

Decticus.

Deer, development of the horns in; spots of young; horns of; use of
horns of; horns of a, in course of modification; size of the horns of;
female, pairing with one male whilst others are fighting for her; male,
attracted by the voice of the female; male, odour emitted by.

Deer, Axis, sexual difference in the colour of the.

Deer, fallow, different coloured herds of.

Deer, Mantchurian.

Deer, Virginian, colour of the, not affected by castration; colours of.

Deerhound, Scotch, greater size of the male.

Defensive orders of mammals.

De Geer, C., on a female spider destroying a male.

Dekay, Dr., on the bladder-nose seal.

Delorenzi, G., division of malar bone.

Demerara, yellow fever in.

Dendrocygna.

Dendrophila frontalis, young of.

Denison, Sir W., manner of ridding themselves of vermin among the
Australians; extinction of Tasmanians.

Denny, H., on the lice of domestic animals.

Dermestes murinus, stridulation of.

Descent traced through the mother alone.

Deserts, protective colouring of animals inhabiting.

Desmarest, on the absence of suborbital pits in Antilope subgutturosa;
on the whiskers of Macacus; on the colour of the opossum; on the
colours of the sexes of Mus minutus; on the colouring of the ocelot; on
the colours of seals; on Antilope caama; on the colours of goats; on
sexual difference of colour in Ateles marginatus; on the mandrill; on
Macacus cynomolgus.

Desmoulins, on the number of species of man; on the muskdeer.

Desor, on the imitation of man by monkeys.

Despine, P., on criminals destitute of conscience.

Development, embryonic of man; correlated.

Devil, not believed in by the Fuegians.

Devil-crab.

Devonian, fossil-insect from the.

Dewlaps, of Cattle and antelopes.

Diadema, sexual differences of colouring in the species of.

Diamond-beetles, bright colours of.

Diastema, occurrence of, in man.

Diastylidae, proportion of the sexes in.

Dicrurus, racket-shaped feathers in; nidification of.

Dicrurus macrocercus, change of plumage in.

Didelphis opossum, sexual difference in the colour of.

Differences, comparative, between different species of birds of the
same sex.

Digits, supernumerary, more frequent in men than in women;
supernumerary, inheritance of; supernumerary, early development of.

Dimorphism, in females of water-beetles; in Neurothemis and Agrion.

Diodorus, on the absence of beard in the natives of Ceylon.

Dipelicus Cantori, sexual differences of.

Diplopoda, prehensile limbs of the male.

Dipsas cynodon, sexual difference in the colour of.

Diptera.

Disease, generated by the contact of distinct peoples.

Diseases, common to man and the lower animals; difference of liability
to, in different races of men; new, effects of, upon savages; sexually
limited.

Display, coloration of Lepidoptera for; of plumage by male birds.

Distribution, wide, of man; geographical, as evidence of specific
distinctness in man.

Disuse, effects of, in producing rudimentary organs; and use of parts,
effects of; of parts, influence of, on the races of men.

Divorce, freedom of, among the Charruas.

Dixon, E.S., on the pairing of different species of geese; on the
courtship of peafowl.

Dobrizhoffer, on the marriage-customs of the Abipones.

Dobson, Dr., on the Cheiroptera; scent-glands of bats; frugivorous
bats.

Dogs, suffering from tertian ague; memory of; dreaming; diverging when
drawing sledges over thin ice; exercise of reasoning faculties by;
domestic, progress of, in moral qualities; distinct tones uttered by;
parallelism between his affection for his master and religious feeling;
sociability of the; sympathy of, with a sick cat; sympathy of, with his
master; their possession of conscience; possible use of the hair on the
fore-legs of the; races of the; numerical proportion of male and female
births in; sexual affection between individuals of; howling at certain
notes; rolling in carrion.

Dolichocephalic structure, possible cause of.

Dolphins, nakedness of.

Domestic animals, races of; change of breeds of.

Domestication, influence of, in removing the sterility of hybrids.

D’Orbigny, A., on the influence of dampness and dryness on the colour
of the skin; on the Yuracaras.

Dotterel.

Doubleday, E., on sexual differences in the wings of butterflies.

Doubleday, H., on the proportion of the sexes in the smaller moths;
males of Lasiocampa quercus and on the attraction of the Saturnia
carpini by the female; on the proportion of the sexes in the
Lepidoptera; on the ticking of Anobium tesselatum; on the structure of
Ageronia feronia; on white butterflies alighting upon paper.

Douglas, J.W., on the sexual differences of the Hemiptera; colours of
British Homoptera.

Down, of birds.

Draco, gular appendages of.

Dragonet, Gemmeous.

Dragon-flies, caudal appendages of male; relative size of the sexes of;
difference in the sexes of; want of pugnacity by the male.

Drake, breeding plumage of the.

Dreams, possible source of the belief in spiritual agencies.

Drill, sexual difference of colour in the.

Dromaeus irroratus.

Dromolaea, Saharan species of.

Drongo shrike.

Drongos, racket-shaped feathers in the tails of.

Dryness of climate, supposed influence of, on the colour of the skin.

Dryopithecus.

Duck, harlequin, age of mature plumage in the; breeding in immature
plumage.

Duck, long-tailed, preference of male, for certain females.

Duck, pintail, pairing with a widgeon.

Duck, voice of the; pairing with a shield-drake; immature plumage of
the.

Duck, wild, sexual differences in the; speculum and male characters of;
pairing with a pin-tail drake.

Ducks, wild, becoming polygamous under partial domestication; dogs and
cats recognised by.

Dufosse, Dr., sounds produced by fish.

Dugong, nakedness of; tusks of.

Dujardin, on the relative size of the cerebral ganglia, in insects.

Duncan, Dr., on the fertility of early marriages; comparative health of
married and single.

Dupont, M., on the occurrence of the supra-condyloid foramen in the
humerus of man.

Durand, J.P., on causes of variation.

Dureau de la Malle, on the songs of birds; on the acquisition of an air
by blackbirds.

Dutch, retention of their colour by the, in South Africa.

Duty, sense of.

Duvaucel, female Hylobates washing her young.

Dyaks, pride of, in mere homicide.

Dynastes, large size of males of.

Dynastini, stridulation of.

Dytiscus, dimorphism of females of; grooved elytra of the female.

Eagle, young Cercopithecus rescued from, by the troop.

Eagle, white-headed, breeding in immature plumage.

Eagles, golden, new mates found by.

Ear, motion of the; external shell of the, useless in man; rudimentary
point of the, in man.

Ears, more variable in men than women; piercing and ornamentation of
the.

Earwigs, parental feeling in.

Echidna.

Echini, bright colours of some.

Echinodermata, absence of secondary sexual characters in.

Echis carinata.

Ecker, figure of the human embryo; on the development of the gyri and
sulci of the brain; on the sexual differences in the pelvis in man; on
the presence of a sagittal crest in Australians.

Edentata, former wide range of, in America; absence of secondary sexual
characters in.

Edolius, racket-shaped feathers in.

Edwards, Mr., on the proportion of the sexes in North American species
of Papilio.

Eels, hermaphroditism of.

Egerton, Sir P., on the use of the antlers of deer; on the pairing of
red deer; on the bellowing of stags.

Eggs, hatched by male fishes.

Egret, Indian, sexes and young of.

Egrets, breeding plumage of; white.

Ehrenberg, on the mane of the male Hamadryas baboon.

Ekstrom, M., on Harelda glacialis.

Elachista rufocinerea, habits of male.

Eland, development of the horns of the.

Elands, sexual differences of colour in.

Elaphomyia, sexual differences in.

Elaphrus uliginosus, stridulation of.

Elaps.

Elateridae, proportion of the sexes in.

Elaters, luminous.

Elephant, rate of increase of the; nakedness of the; using a fan;
Indian, forbearance to his keeper; polygamous habits of the; pugnacity
of the male; tusks of; Indian, mode of fighting of the; male, odour
emitted by the; attacking white or grey horses.

Elevation of abode, modifying influence of.

Elimination of inferior individuals.

Elk, winter change of the.

Elk, Irish, horns of the.

Ellice Islands, beards of the natives.

Elliot, D.G., on Pelecanus erythrorhynchus.

Elliot, R., on the numerical proportion of the sexes in young rats; on
the proportion of the sexes in sheep.

Elliot, Sir W., on the polygamous habits of the Indian wild boar.

Ellis, on the prevalence of infanticide in Polynesia.

Elphinstone, Mr., on local difference of stature among the Hindoos; on
the difficulty of distinguishing the native races of India.

Elytra, of the females of Dytiscus Acilius, Hydroporus.

Emberiza, characters of young.

Emberiza miliaria.

Emberiza schoeniclus, head-feathers of the male.

Embryo of man; of the dog.

Embryos of mammals, resemblance of the.

Emigration.

Emotions experienced by the lower animals in common with man;
manifested by animals.

Emperor butterfly.

Emperor moth.

Emu, sexes and incubation of.

Emulation of singing birds.

Endurance, estimation of.

Energy, a characteristic of men.

England, numerical proportion of male and female births in.

Engleheart, Mr., on the finding of new mates by starlings.

English, success of, as colonists.

Engravers, short-sighted.

Entomostraca.

Entozoa, difference of colour between the males and females of some.

Environment, direct action of the, in causing differences between the
sexes.

Envy, persistence of.

Eocene period, possible divergence of men during the.

Eolidae, colours of, produced by the biliary glands.

Epeira nigra, small size of the male of.

Ephemerae.

Ephemeridae.

Ephippiger vitium, stridulating organs of.

Epicalia, sexual differences of colouring in the species of.

Equus hemionus, winter change of.

Erateina, coloration of.

Ercolani, Prof., hermaphroditism in eels.

Erect attitude of man.

Eristalis, courting of.

Eschricht, on the development of hair in man; on a languinous moustache
in a female foetus; on the want of definition between the scalp and the
forehead in some children; on the arrangement of the hair in the human
foetus; on the hairiness of the face in the human foetus of both sexes.

Esmeralda, difference of colour in the sexes of.

Esox lucius.

Esox reticulatus.

Esquimaux, their belief in the inheritance of dexterity in
seal-catching; mode of life of.

Estrelda amandava, pugnacity of the male.

Eubagis, sexual differences of colouring in the species of.

Euchirus longimanus, sound produced by.

Eudromias morinellus.

Eulampis jugularis, colours of the female.

Euler, on the rate of increase in the United States.

Eunomota superciliaris, racket-shaped feathers in the tail of.

Eupetomena macroura, colours of the female.

Euphema splendida.

Euplocamus erythrophthalmus, possession of spurs by the female.

Europe, ancient inhabitants of.

Europeans, difference of, from Hindoos; hairiness of, probably due to
reversion.

Eurostopodus, sexes of.

Eurygnathus, different proportions of the head in the sexes of.

Eustephanus, sexual differences of species of; young of.

Exaggeration of natural characters by man.

Exogamy.

Experience, acquisition of, by animals.

Expression, resemblances in, between man and the apes.

Extinction of races, causes of.

Eye, destruction of the; change of position in; obliquity of, regarded
as a beauty by the Chinese and Japanese.

Eyebrows, elevation of; development of long hairs in; in monkeys;
eradicated in parts of South America and Africa; eradication of, by the
Indians of Paraguay.

Eyelashes, eradication of, by the Indians of Paraguay.

Eyelids, coloured black, in part of Africa.

Eyes, pillared, of the male of Chloeon; difference in the colour of, in
the sexes of birds.

Eyton, T.C., observations on the development of the horns in the fallow
deer.

Eyzies, Les, human remains from.

Fabre, M., on the habits of Cerceris.

Facial bones, causes of modification of the.

Faculties, diversity of, in the same race of men; inheritance of;
diversity of, in animals of the same species; mental variation of, in
the same species; of birds.

Fakirs, Indian, tortures undergone by.

Falco leucocephalus.

Falco peregrinus.

Falco tinnunclus.

Falcon, peregrine, new mate found by.

Falconer, H., on the mode of fighting of the Indian elephant; on
canines in a female deer; on Hyomoschus aquaticus.

Falkland Islands, horses of.

Fallow-deer, different coloured herds of.

Famines, frequency of, among savages.

Farr, Dr., on the effects of profligacy; on the influence of marriage
on mortality.

Farrar, F.W., on the origin of language; on the crossing or blending of
languages; on the absence of the idea of God in certain races of men;
on early marriages of the poor; on the middle ages.

Farre, Dr., on the structure of the uterus.

Fashions, long prevalence of, among savages.

Faye, Prof., on the numerical proportion of male and female births in
Norway and Russia; on the greater mortality of male children at and
before birth.

Feathers, modified, producing sounds; elongated, in male birds;
racket-shaped; barbless and with filamentous barbs in certain birds;
shedding of margins of.

Feeding, high, probable influence of, in the pairing of birds of
different species.

Feet, thickening of the skin on the soles of the; modification of, in
man.

Felis canadensis, throat-ruff of.

Felis pardalis and F. mitis, sexual difference in the colouring of.

Female, behaviour of the, during courtship.

Female birds, differences of.

Females, presence of rudimentary male organs in; preference of, for
certain males; pursuit of, by males; occurrence of secondary sexual
characters in; development of male character by.

Females and males, comparative numbers of; comparative mortality of,
while young.

Femur and tibia, proportions of, in the Aymara Indians.

Fenton, Mr., decrease of Maories; infanticide amongst the Maories.

Ferguson, Mr., on the courtship of fowls.

Fertilisation, phenomena of, in plants; in the lower animals.

Fertility lessened under changed conditions.

Fevers, immunity of Negroes and Mulattoes from.

Fiber zibethicus, protective colouring of it.

Fick, H., effect of conscription for military service.

Fidelity, in the elephant; of savages to one another; importance of.

Field-slaves, difference of, from house-slaves.

Fiji Archipelago, population of the.

Fiji Islands, beards of the natives; marriage-customs of the.

Fijians, burying their old and sick parents alive; estimation of the
beard among the; admiration of, for a broad occiput.

Filial affection, partly the result of natural selection.

Filum terminale.

Finch, racket-shaped feathers in the tail of a.

Finches, spring change of colour in; British, females of the.

Fingers, partially coherent, in species of Hylobates.

Finlayson, on the Cochin Chinese.

Fire, use of.

Fischer, on the pugnacity of the male of Lethrus cephalotes.

Fischer, F. Von, on display of brightly coloured parts by monkeys in
courtship.

Fish, eagerness of male; proportion of the sexes in; sounds produced
by.

Fishes, kidneys of, represented by Corpora Wolffiana in the human
embryo; male, hatching ova in their mouths; receptacles for ova
possessed by; relative size of the sexes in; fresh-water, of the
tropics; protective resemblances in; change of colour in;
nest-building; spawning of; sounds produced by; continued growth of.

Flamingo, age of mature plumage.

Flexor pollicis longus, similar variation of, in man.

Flies, humming of.

Flint tools.

Flints, difficulty of chipping into form.

Florida, Quiscalus major in.

Florisuga mellivora.

Flounder, coloration of the.

Flower, W.H., on the abductor of the fifth metatarsal in apes; on the
position of the Seals; on the Pithecia monachu; on the throat-pouch of
the male bustard.

Fly-catchers, colours and nidification of.

Foetus, human, woolly covering of the; arrangement of the hair on.

Food, influence of, upon stature.

Foot, prehensile power of the, retained in some savages; prehensile, in
the early progenitors of man.

Foramen, supra-condyloid, exceptional occurrence of in the humerus of
man; in the early progenitors of man.

Forbes, D., on the Aymara Indians; on local variation of colour in the
Quichuas; on the hairlessness of the Aymaras and Quichuas; on the long
hair of the Aymaras and Quichaus.

Forel, F., on white young swans.

Forester, Hon. O.W., on an orphan hawk.

Formica rufa, size of the cerebral ganglia in.

Fossils, absence of, connecting man with the apes.

Fowl, occurrence of spurs in the female; game, early pugnacity of;
Polish, early development of cranial peculiarities of; variations in
plumage of; examples of correlated development in the; domestic, breeds
and sub-breeds of.

Fowls, spangled Hamburg; inheritance of changes of plumage by; sexual
peculiarities in, transmitted only to the same sex; loss of secondary
sexual characters by male; Polish, origin of the crest in; period of
inheritance of characters by; cuckoo-; development of the comb in;
numerical proportion of the sexes in; courtship of; mongrel, between a
black Spanish cock and different hens; pencilled Hamburg, difference of
the sexes in; Spanish, sexual differences of the comb in; spurred, in
both sexes.

Fox, W.D., on some half-tamed wild ducks becoming polygamous, and on
polygamy in the guinea-fowl and canary-bird; on the proportion of the
sexes in cattle; on the pugnacity of the peacock; on a nuptial assembly
of magpies; on the finding of new mates by crows; on partridges living
in triplets; on the pairing of a goose with a Chinese gander.

Foxes, wariness of young, in hunting districts; black.

Fraser, C., on the different colours of the sexes in a species of
Squilla.

Fraser, G., colours of Thecla.

Frere, Hookham, quoting Theognis on selection in mankind.

Fringilla cannabina.

Fringilla ciris, age of mature plumage in.

Fringilla cyanea, age of mature plumage in.

Fringilla leucophrys, young of.

Fringilla spinus.

Fringilla tristis, change of colour in, in spring; young of.

Fringillidae, resemblance of the females of distinct species of.

Frog, bright coloured and distasteful to birds.

Frogs, male; temporary receptacles for ova possessed by; ready to breed
before the females; fighting of; vocal organs of.

Frontal bone, persistence of the suture in.

Fruits, poisonous, avoided by animals.

Fuegians, difference of stature among the; power of sight in the; skill
of, in stone-throwing; resistance of the, to their severe climate;
mental capacity of the; quasi-religious sentiments of the; resemblance
of, in mental characters, to Europeans; mode of life of the; aversion
of, to hair on the face; said to admire European women.

Fulgoridae, songs of the.

Fur, whiteness of, in Arctic animals in winter.

Fur-bearing animals, acquired sagacity of.

Gallicrex, sexual difference in the colour of the irides in.

Gallicrex cristatus, pugnacity of male; red carbuncle occurring in the
male during the breeding-season.

Gallinaceae, frequency of polygamous habits and of sexual differences
in the; love-gestures of; decomposed feathers in; stripes of young;
comparative sexual differences between the species of; plumage of.

Gallinaceous birds, weapons of the male; racket-shaped feathers on the
heads of.

Gallinula chloropus, pugnacity of the male.

Galloperdix, spurs of; development of spurs in the female.

Gallophasis, young of.

Galls.

Gallus bankiva, neck-hackles of.

Gallus Stanleyi, pugnacity of the male.

Galton, Mr., on hereditary genius; gregariousness and independence in
animals; on the struggle between the social and personal impulses; on
the effects of natural selection on civilised nations; on the sterility
of sole daughters; on the degree of fertility of people of genius; on
the early marriages of the poor; on the ancient Greeks; on the Middle
Ages; on the progress of the United States; on South African notions of
beauty.

Gammarus, use of the chelae of.

Gammarus marinus.

Gannets, white only when mature.

Ganoid fishes.

Gaour, horns of the.

Gap between man and the apes.

Gaper, sexes and young of.

Gardner, on an example of rationality in a Gelasimus.

Garrulus glandarius.

Gartner, on sterility of hybrid plants.

Gasteropoda, pulmoniferous, courtship of.

Gasterosteus, nidification of.

Gasterosteus leiurus.

Gasterosteus trachurus.

Gastrophora, wings of, brightly coloured beneath.

Gauchos, want of humanity among the.

Gaudry, M., on a fossil monkey.

Gavia, seasonal change of plumage in.

Geese, clanging noise made by; pairing of different species of; Canada,
selection of mates by.

Gegenbaur, C., on the number of digits in the Ichthyopterygia; on the
hermaphroditism of the remote progenitors of the vertebrata; two types
of nipple in mammals.

Gelasimus, proportions of the sexes in a species of; use of the
enlarged chelae of the male; pugnacity of males of; rational actions of
a; difference of colour in the sexes of a species of.

Gemmules, dormant in one sex.

Genius, hereditary.

Genius, fertility of men and women of.

Geoffroy St.-Hilaire, Isid., on the recognition of women by male
quadrumana; on monstrosities; coincidences of arrested development with
polydactylism; on animal-like anomalies in the human structure; on the
correlation of monstrosities; on the distribution of hair in man and
monkeys; on the caudal vertebrae of monkeys; on correlated variability;
on the classification of man; on the long hair on the heads of species
of Semnopithecus; on the hair in monkeys; on the development of horns
in female deer; and F. Cuvier, on the mandrill; on Hylobates.

Geographical distribution, as evidence of specific distinctions in man.

Geometrae, brightly coloured beneath.

Geophagus, frontal protuberance of, male; eggs hatched by the male, in
the mouth or branchial cavity.

Georgia, change of colour in Germans settled in.

Geotrupes, stridulation of.

Gerbe, M., on the nest-building of Crenilabus massa and C. Melops.

Gerland, Dr., on the prevalence of infanticide; on the extinction of
races.

Gervais, P., on the hairiness of the gorilla; on the mandrill.

Gesture-language.

Ghost-moth, sexual difference of colour in the.

Giard, M., disputes descent of vertebrates from Ascidians; colour of
sponges and Ascidians; musky odour of Sphinx.

Gibbon, voice of.

Gibbon, Hoolock, nose of.

Gibbs, Sir D., on differences of the voice in different races of men.

Gill, Dr., male seals larger than females; sexual differences in seals.

Giraffe, its mode of using the horns; mute, except in the rutting
season.

Giraud-Teulon, on the cause of short sight.

Glanders, communicable to man from the lower animals.

Glands, odoriferous, in mammals.

Glareola, double moult in.

Glomeris limbata, difference of colour in the sexes of.

Glow-worm, female, apterous; luminosity of the.

Gnats, dances of; auditory powers of.

Gnu, skeletons of, found locked together; sexual differences in colour
of the.

Goat, male, wild, falling on his horns; male, odour emitted by; male,
wild, crest of the; Berbura, mane, dewlap, etc., of the male; Kemas,
sexual difference in the colour of the.

Goats, sexual differences in the horns of; horns of; mode of fighting
of; domestic, sexual differences of, late developed; beards of.

Goatsucker, Virginian, pairing of the.

Gobies, nidification of.

God, want of the idea of, in some races of men.

Godron, M., on variability; on difference of stature; on the want of
connexion between climate and the colour of the skin; on the colour of
the skin; on the colour of infants.

Goldfinch, proportion of the sexes in the; sexual differences of the
beak in the; courtship of the.

Goldfinch, North American, young of.

Goldfish.

Gomphus, proportions of the sexes in; difference in the sexes of.

Gonepteryx Rhamni, sexual difference of colour in.

Goodsir, Prof., on the affinity of the lancelet to the ascidians.

Goosander, young of.

Goose, Antarctic, colours of the.

Goose, Canada, pairing with a Bernicle gander.

Goose, Chinese, knob on the beak of the.

Goose, Egyptian.

Goose, Sebastopol, plumage of.

Goose, Snow-, whiteness of the.

Goose, Spur-winged.

Gorilla, semi-erect attitude of the; mastoid processes of the;
protecting himself from rain with his hands; manner of sitting;
supposed to be a kind of mandrill; polygamy of the; voice of the;
cranium of; fighting of male.

Gosse, P.H., on the pugnacity of the male Humming-bird.

Gosse, M., on the inheritance of artificial modifications of the skull.

Gould, B.A., on variation in the length of the legs in man;
measurements of American soldiers; on the proportions of the body and
capacity of the lungs in different races of men; on the inferior
vitality of mulattoes.

Gould, J., on migration of swifts; on the arrival of male snipes before
the females; on the numerical proportion of the sexes in birds; on
Neomorpha Grypus; on the species of Eustephanus; on the Australian
musk-duck; on the relative size of the sexes in Briziura lobata and
Cincloramphus cruralis; on Lobivanellus lobatus; on habits of Menura
Alberti; on the rarity of song in brilliant birds; on Selasphorus
platycerus; on the Bower-birds; on the ornamental plumage of the
Humming-birds; on the moulting of the ptarmigan; on the display of
plumage by the male Humming-birds; on the shyness of adorned male
birds; on the decoration of the bowers of Bower-birds; on the
decoration of their nest by Humming-birds; on variation in the genus
Cynanthus; on the colour of the thighs in a male parrakeet; on
Urosticte Benjamini; on the nidification of the Orioles; on
obscurely-coloured birds building concealed nests; on trogons and
king-fishers; on Australian parrots; on Australian pigeons; on the
moulting of the ptarmigan; on the immature plumage of birds; on the
Australian species of Turnix; on the young of Aithurus polytmus; on the
colours of the bills of toucans; on the relative size of the sexes in
the marsupials of Australia; on the colours of the Marsupials.

Goureaux, on the stridulation of Mutilla europaea.

Gout, sexually transmitted.

Graba, on the Pied Ravens of the Feroe Islands; variety of the
Guillemot.

Gradation of secondary sexual characters in birds.

Grallatores, absence of secondary sexual characters in; double moult in
some.

Grallina, nidification of.

Grasshoppers, stridulation of the.

Gratiolet, Prof., on the anthropomorphous apes; on the evolution of the
anthropomorphous apes; on the difference in the development of the
brains of apes and of man.

Gray, Asa, on the gradation of species among the Compositae.

Gray, J.E., on the caudal vertebrae of monkeys; on the presence of
rudiments of horns in the female of Cervulus moschatus; on the horns of
goats and sheep; on crests of male antelopes; on the beard of the ibex;
on the Berbura goat; on sexual differences in the coloration of
Rodents; ornaments of male sloth; on the colours of the Elands; on the
Sing-sing antelope; on the colours of goats; on Lemur Macaco; on the
hog-deer.

“Greatest happiness principle.”

Greeks, ancient.

Green, A.H., on beavers fighting; on the voice of the beaver.

Greenfinch, selected by a female canary.

Greg, W.R., on the effects of natural selection on civilised nations;
on the early marriages of the poor; on the Ancient Greeks.

Grenadiers, Prussian.

Greyhounds, numerical proportion of the sexes in; numerical proportion
of male and female births in.

Grouse, red, monogamous; pugnacity of young male; producing a sound by
beating their wings together; duration of courtship of; colours and
nidification of.

Gruber, Dr., on the occurrence of the supra-condyloid foramen in the
humerus of man; on division of malar bone; stridulation of locust; on
ephippiger.

Grus americanus, age of mature plumage in; breeding in immature
plumage.

Grus virgo, trachea of.

Gryllus campestris, pugnacity of male.

Gryllus domesticus.

Grypus, sexual differences in the beak in.

Guanacoes, battles of; canine teeth of.

Guanas, strife for women among the; polyandry among the.

Guanche skeletons, occurrence of the supra-condyloid foramen in the
humerus of.

Guaranys, proportion of men and women among; colour of new-born
children of the; beards of the.

Guenee, A., on the sexes of Hyperythra.

Guilding, L., on the stridulation of the Locustidae.

Guillemot, variety of the.

Guinea, sheep of, with males only horned.

Guinea-fowl, monogamous; occasional polygamy of the; markings of the.

Guinea-pigs, inheritance of the effects of operations by.

Gulls, seasonal change of plumage in; white.

Gunther, Dr., on paddle of Ceradotus; on hermaphroditism in Serranus;
on male fishes hatching ova in their mouths; on mistaking infertile
female fishes for males; on the prehensile organs of male Plagiostomous
fishes; spines and brushes on fishes; on the pugnacity of the male
salmon and trout; on the relative size of the sexes in fishes; on
sexual differences in fishes; on the genus Callionymus; on a protective
resemblance of a pipe-fish; on the genus Solenostoma; on the coloration
of frogs and toads; combat of Testudo elegans; on the sexual
differences in the Ophidia; on differences of the sexes of lizards.

Gynanisa Isis, ocellated spots of.

Gypsies, uniformity of, in various parts of the world.

Habits, bad, facilitated by familiarity; variability of the force of.

Haeckel, E., on the origin of man; on rudimentary characters; on death
caused by inflammation of the vermiform appendage; on the canine teeth
in man; on the steps by which man became a biped; on man as a member of
the Catarrhine group; on the position of the Lemuridae; on the
genealogy of the Mammalia; on the lancelet; on the transparency of
pelagic animals; on the musical powers of women.

Hagen, H., and Walsh, B.D., on American Neuroptera.

Hair, development of, in man; character of, supposed to be determined
by light and heat; distribution of, in man; possibly removed for
ornamental purposes; arrangement and direction of; of the early
progenitors of man; different texture of, in distinct races; and skin,
correlation of colour of; development of, in mammals; management of,
among different peoples; great length of, in some North American
tribes; elongation of the, on the human head; possible inherited effect
of plucking out.

Hairiness, difference of, in the sexes in man; variation of, in races
of men.

Hairs and excretory pores, numerical relation of, in sheep.

Hairy family, Siamese.

Halbertsma, Prof., hermaphroditism in Serranus.

Hamadryas baboon, turning over stones; mane of the male.

Hamilton, C., on the cruelty of the Kaffirs to animals; on the
engrossment of the women by the Kaffir chiefs.

Hammering, difficulty of.

Hancock, A., on the colours of the nudibranch Mollusca.

Hands, larger at birth, in the children of labourers; structure of, in
the quadrumana; and arms, freedom of, indirectly correlated with
diminution of canines.

Handwriting, inherited.

Handyside, Dr., supernumerary mammae in men.

Harcourt, E. Vernon, on Fringilla cannabina.

Hare, protective colouring of the.

Harelda glacialis.

Hares, battles of male.

Harlan, Dr., on the difference between field-and house-slaves.

Harris, J.M., on the relation of complexion to climate.

Harris, T.W., on the Katy-did locust; on the stridulation of the
grasshoppers; on Oecanthus nivalis; on the colouring of Lepidoptera; on
the colouring of Saturnia Io.

Harting, spur of the Ornithorhynchus.

Hartman, Dr., on the singing of Cicada septendecim.

Hatred, persistence of.

Haughton, S., on a variation of the flexor pollicis longus in man.

Hawks, feeding orphan nestling.

Hayes, Dr., on the diverging of sledge-dogs on thin ice.

Haymond, R., on the drumming of the male Tetrao umbellus; on the
drumming of birds.

Head, altered position of, to suit the erect attitude of man; hairiness
of, in man; processes of, in male beetles; artificial alterations of
the form of the.

Hearne, on strife for women among the North American Indians; on the
North American Indians’ notion of female beauty; repeated elopements of
a North American woman.

Heart, in the human embryo.

Heat, supposed effects of.

Hectocotyle.

Hedge-warbler, young of the.

Heel, small projection of, in the Aymara Indians.

Hegt, M., on the development of the spurs in peacocks.

Heliconidae, mimicry of, by other butterflies.

Heliopathes, stridulation peculiar to the male.

Heliothrix auriculata, young of.

Helix pomatia, example of individual attachment in.

Hellins, J., proportions of sexes of Lepidoptera reared by.

Helmholtz, on pleasure derived from harmonies; on the human eye; on the
vibration of the auditory hairs of crustacea; the physiology of
harmony.

Hemiptera.

Hemitragus, beardless in both sexes.

Hemsbach, M. von, on medial mamma in man.

Hen, clucking of.

Hepburn, Mr., on the autumn song of the water-ouzel.

Hepialus humuli, sexual difference of colour in the.

Herbs, poisonous, avoided by animals.

Hermaphroditism, of embryos; in fishes.

Herodias bubulcus, vernal moult of.

Heron, Sir R., on the habits of peafowl.

Herons, love-gestures of; decomposed feathers in; breeding plumage of;
young of the; sometimes dimorphic; continued growth of crest and plumes
in the males of some; change of colour in some.

Hesperomys cognatus.

Hetaerina, proportion of the sexes in; difference in the sexes of.

Heterocerus, stridulation of.

Hewitt, Mr., on a game-cock killing a kite; on the recognition of dogs
and cats by ducks; on the pairing of a wild duck with a pintail drake;
on the courtship of fowls; on the coupling of pheasants with common
hens.

Hilgendorf, sounds produced by crustaceans.

Hindoo, his horror of breaking his caste.

Hindoos, local difference of stature among; difference of, from
Europeans; colour of the beard in.

Hipparchia Janira, instability of the ocellated spots of.

Hippocampus, development of; marsupial receptacles of the male.

Hippocampus minor.

Hippopotamus, nakedness of.

Hips, proportions of, in soldiers and sailors.

Hodgson, S., on the sense of duty.

Hoffberg, on the horns of the reindeer; on sexual preferences shewn by
reindeer.

Hoffman, Prof., protective colours; fighting of frogs.

Hog, wart-; river-.

Hog-deer.

Holland, Sir H., on the effects of new diseases.

Homologous structures, correlated variation of.

Homoptera, stridulation of the, and Orthoptera, discussed.

Honduras, Quiscalus major in.

Honey-buzzard of India, variation in the crest of.

Honey-sucker, females and young of.

Honey-suckers, moulting of the; Australian, nidification of.

Honour, law of.

Hooker, Dr., forbearance of elephant to his keeper; on the colour of
the beard in man.

Hookham, Mr., on mental concepts in animals.

Hoolock Gibbon, nose of.

Hoopoe, sounds produced by male.

Hoplopterus armatus, wing-spurs of.

Hornbill, African, inflation of the neck-wattle of the male during
courtship.

Hornbills, sexual difference in the colour of the eyes in; nidification
and incubation of.

Horne, C., on the rejection of a brightly-coloured locust by lizards
and birds.

Horns, sexual differences of, in sheep and goats; loss of, in female
merino sheep; development of, in deer; development in antelopes; from
the head and thorax, in male beetles; of deer; originally a masculine
character in sheep; and canine teeth, inverse development of.

Horse, fossil, extinction of the, in South America; polygamous; canine
teeth of male; winter change of colour.

Horses, rapid increase of, in South America; diminution of canine teeth
in; dreaming; of the Falkland Islands and Pampas; numerical proportion
of the sexes, in; lighter in winter in Siberia; sexual preferences in;
pairing preferently with those of the same colour; numerical proportion
of male and female births in; formerly striped.

Hottentot women, peculiarities of.

Hottentots, lice of; readily become musicians; notions of female beauty
of the; compression of nose by.

Hough, Dr. S., men’s temperature more variable than women’s; proportion
of sexes in man.

House-slaves, difference of, from field-slaves.

Houzeau, on the baying of the dog; on reason in dogs; birds killed by
telegraph wires; on the cries of domestic fowls and parrots; animals
feel no pity; suicide in the Aleutian Islands.

Howorth, H.H., extinction of savages.

Huber, P., on ants playing together; on memory in ants; on the
intercommunication of ants; on the recognition of each other by ants
after separation.

Huc, on Chinese opinions of the appearance of Europeans.

Huia, the, of New Zealand.

Human, man, classed alone in a kingdom.

Human sacrifices.

Humanity, unknown among some savages; deficiency of, among savages.

Humboldt, A. von, on the rationality of mules; on a parrot preserving
the language of a lost tribe; on the cosmetic arts of savages; on the
exaggeration of natural characters by man; on the red painting of
American Indians.

Hume, D., on sympathetic feelings.

Humming-bird, racket-shaped feathers in the tail of a; display of
plumage by the male.

Humming-birds, ornament their nests; polygamous; proportion of the
sexes in; sexual differences in; pugnacity of male; modified primaries
of male; coloration of the sexes of; display by; nidification of the;
colours of female; young of.

Humour, sense of, in dogs.

Humphreys, H.N., on the habits of the stickleback.

Hunger, instinct of.

Huns, ancient, flattening of the nose by the.

Hunter, J., on the number of species of man; on secondary sexual
characters; on the general behaviour of female animals during
courtship; on the muscles of the larynx in song-birds; on strength of
males; on the curled frontal hair of the bull; on the rejection of an
ass by a female zebra.

Hunter, W.W., on the recent rapid increase of the Santali; on the
Santali.

Huss, Dr. Max, on mammary glands.

Hussey, Mr., on a partridge distinguishing persons.

Hutchinson, Col., example of reasoning in a retriever.

Hutton, Captain, on the male wild goat falling on his horns.

Huxley, T.H., on the structural agreement of man with the apes; on the
agreement of the brain in man with that of lower animals; on the adult
age of the orang; on the embryonic development of man; on the origin of
man; on variation in the skulls of the natives of Australia; on the
abductor of the fifth metatarsal in apes; on the nature of the
reasoning power; on the position of man; on the suborders of primates;
on the Lemuridae; on the Dinosauria; on the amphibian affinities of the
Ichthyosaurians; on variability of the skull in certain races of man;
on the races of man; Supplement on the brain.

Hybrid birds, production of.

Hydrophobia, communicable between man and the lower animals.

Hydroporus, dimorphism of females of.

Hyelaphus porcinus.

Hygrogonus.

Hyla, singing species of.

Hylobates, absence of the thumb in; upright progression of some species
of; maternal affection in a; direction of the hair on the arms of
species of; females of, less hairy below than males.

Hylobates agilis, hair on the arms of; musical voice of the;
superciliary ridge of; voice of.

Hylobates hoolock, sexual difference of colour in.

Hylobates lar, hair on the arms of; female less hairy.

Hylobates leuciscus, song of.

Hylobates syndactylus, laryngeal sac of.

Hylophila prasinana.

Hymenoptera, large size of the cerebral ganglia in; classification of;
sexual differences in the wings of; aculeate, relative size of the
sexes of.

Hymenopteron, parasitic, with a sedentary male.

Hyomoschus aquaticus.

Hyperythra, proportion of the sexes in.

Hypogymna dispar, sexual difference of colour in.

Hypopyra, coloration of.

Ibex, male, falling on his horns; beard of the.

Ibis, white, change of colour of naked skin in, during the breeding
season; scarlet, young of the.

Ibis tantalus, age of mature plumage in; breeding in immature plumage.

Ibises, decomposed feathers in; white; and black.

Ichneumonidae, difference of the sexes in.

Ichthyopterygia.

Ichthyosaurians.

Idiots, microcephalous, their characters and habits; hairiness and
animal nature of their actions; microcephalous, imitative faculties of.

Iguana tuberculata.

Iguanas.

Illegitimate and legitimate children, proportion of the sexes in.

Imagination, existence of, in animals.

Imitation, of man by monkeys; tendency to, in monkeys, microcephalous
idiots and savages; influence of.

Immature plumage of birds.

Implacentata.

Implements, employed by monkeys; fashioning of, peculiar to man.

Impregnation, period of, influence of, upon sex.

Improvement, progressive, man alone supposed to be capable of.

Incisor teeth, knocked out or filed by some savages.

Increase, rate of; necessity of checks in.

Indecency, hatred of, a modern virtue.

India, difficulty of distinguishing the native races of; Cyprinidae of;
colour of the beard in races of men of.

Indian, North American, honoured for scalping a man of another tribe.

Individuality, in animals.

Indolence of man, when free from a struggle for existence.

Indopicus carlotta, colours of the sexes of.

Infanticide, prevalence of; supposed cause of; prevalence and causes
of.

Inferiority, supposed physical, of man.

Inflammation of the bowels, occurrence of, in Cebus Azarae.

Inheritance, of long and short sight; of effects of use of vocal and
mental organs; of moral tendencies; laws of; sexual; sexually limited.

Inquisition, influence of the.

Insanity, hereditary.

insect, fossil, from the Devonian.

Insectivora, absence of secondary sexual characters in.

Insects, relative size of the cerebral ganglia in; male, appearance of,
before the females; pursuit of female, by the males; period of
development of sexual characters in; secondary sexual characters of;
kept in cages; stridulation.

Insessores, vocal organs of.

Instep, depth of, in soldiers and sailors.

Instinct and intelligence.

Instinct, migratory, vanquishing the maternal.

Instinctive actions, the result of inheritance.

Instinctive impulses, difference of the force; and moral impulses,
alliance of.

Instincts, complex origin of, through natural selection; possible
origin of some; acquired, of domestic animals; variability of the force
of; difference of force between the social and other; utilised for new
purposes.

Instrumental music of birds.

Intellect, influence of, in natural selection in civilised society.

Intellectual faculties, their influence on natural selection in man;
probably perfected through natural selection.

Intelligence, Mr. H. Spencer on the dawn of.

Intemperance, no reproach among savages; its destructiveness.

Intoxication in monkeys.

Iphias glaucippe.

Iris, sexual difference in the colour of the, in birds.

Ischio-pubic muscle.

Ithaginis cruentus, number of spurs in.

Iulus, tarsal suckers of the males of.

Jackals learning from dogs to bark.

Jack-snipe, coloration of the.

Jacquinot, on the number of species of man.

Jaeger, Dr., length of bones increased from carrying weights; on the
difficulty of approaching herds of wild animals; male Silver-pheasant,
rejected when his plumage was spoilt.

Jaguars, black.

Janson, E.W., on the proportions of the sexes in Tomicus villosus; on
stridulant beetles.

Japan, encouragement of licentiousness in.

Japanese, general beardlessness of the; aversion of the, to whiskers.

Jardine, Sir W., on the Argus pheasant.

Jarrold, Dr., on modifications of the skull induced by unnatural
position.

Jarves, Mr., on infanticide in the Sandwich Islands.

Javans, relative height of the sexes of; notions of female beauty.

Jaw, influence of the muscles of the, upon the physiognomy of the apes.

Jaws, smaller proportionately to the extremities; influence of food
upon the size of; diminution of, in man; in man, reduced by
correlation.

Jay, young of the; Canada, young of the.

Jays, new mates found by; distinguishing persons.

Jeffreys, J. Gwyn, on the form of the shell in the sexes of the
Gasteropoda; on the influence of light upon the colours of shells.

Jelly-fish, bright colours of some.

Jenner, Dr., on the voice of the rook; on the finding of new mates by
magpies; on retardation of the generative functions in birds.

Jenyns, L., on the desertion of their young by swallows; on male birds
singing after the proper season.

Jerdon, Dr., on birds dreaming; on the pugnacity of the male bulbul; on
the pugnacity of the male Ortygornis gularis; on the spurs of
Galloperdix; on the habits of Lobivanellus; on the spoonbill; on the
drumming of the Kalij-pheasant; on Indian bustards; on Otis
bengalensis; on the ear-tufts of Sypheotides auritus; on the double
moults of certain birds; on the moulting of the honeysuckers; on the
moulting of bustards, plovers, and drongos; on the spring change of
colour in some finches; on display in male birds; on the display of the
under-tail coverts by the male bulbul; on the Indian honey-buzzard; on
sexual differences in the colour of the eyes of hornbills; on the
markings of the Tragopan pheasant; on the nidification of the Orioles;
on the nidification of the hornbills; on the Sultan yellow-tit; on
Palaeornis javanicus; on the immature plumage of birds; on
representative species of birds; on the habits of Turnix; on the
continued increase of beauty of the peacock; on coloration in the genus
Palaeornis.

Jevons, W.S., on the migrations of man.

Jews, ancient use of flint tools by the; uniformity of, in various
parts of the world; numerical proportion of male and female births
among the; ancient, tattooing practised by.

Johnstone, Lieut., on the Indian elephant.

Jollofs, fine appearance of the.

Jones, Albert, proportion of sexes of Lepidoptera, reared by.

Juan Fernandez, humming-birds of.

Junonia, sexual differences of colouring in species of.

Jupiter, comparison with Assyrian effigies.

Kaffir skull, occurrence of the diastema in a.

Kaffirs, their cruelty to animals; lice of the; colour of the;
engrossment of the handsomest women by the chiefs of the;
marriage-customs of the.

Kalij-pheasant, drumming of the male; young of.

Kallima, resemblance of, to a withered leaf.

Kulmucks, general beardlessness of; aversion of, to hairs on the face;
marriage-customs of the.

Kangaroo, great red, sexual difference in the colour of.

Kant, Imm., on duty; on self-restraint; on the number of species of
man.

Katy-did, stridulation of the.

Keen, Dr., on the mental powers of snakes.

Keller, Dr., on the difficulty of fashioning stone implements.

Kent, W.S., elongation of dorsal fin of Callionymus lyra; courtship of
Labrus mixtus; colours and courtship of Cantharus lineatus.

Kestrels, new mates found by.

Kidney, one, doing double work in disease.

King, W.R., on the vocal organs of Tetrao cupido; on the drumming of
grouse; on the reindeer; on the attraction of male deer by the voice of
the female.

King and Fitzroy, on the marriage-customs of the Fuegians.

King-crows, nidification of.

Kingfisher, racket-shaped feathers in the tail of a.

Kingfishers, colours and nidification of the; immature plumage of the;
young of the.

King Lory, immature plumage of the.

Kingsley, C., on the sounds produced by the Umbrina.

Kirby and Spence, on sexual differences in the length of the snout in
Curculionidae; on the courtship of insects; on the elytra of Dytiscus;
on peculiarities in the legs of male insects; on the relative size of
the sexes in insects; on the Fulgoridae; on the habits of the Termites;
on difference of colour in the sexes of beetles; on the horns of the
male lamellicorn beetles; on hornlike processes in male Curculionidae;
on the pugnacity of the male stag-beetle.

Kite, killed by a game-cock.

Knot, retention of winter plumage by the.

Knox, R., on the semilunar fold; on the occurrence of the
supra-condyloid foramen in the humerus of man; on the features of the
young Memmon.

Koala, length of the caecum in.

Kobus ellipsiprymnus, proportion of the sexes in.

Kolreuter, on the sterility of hybrid plants.

Koodoo, development of the horns of the; markings of the.

Koppen, F.T., on the migratory locust.

Koraks, marriage customs of.

Kordofan, protuberances artificially produced by natives of.

Korte, on the proportion of sexes in locusts; Russian locusts.

Kovalevsky, A., on the affinity of the Ascidia to the Vertebrata.

Kovalevsky, W., on the pugnacity of the male capercailzie; on the
pairing of the capercailzie.

Krause, on a convoluted body at the extremity of the tail in a Macacus
and a cat.

Kupffer, Prof., on the affinity of the Ascidia to the Vertebrata.

Labidocera Darwinii, prehensile organs of the male.

Labrus, splendid colours of the species of.

Labrus mixtus, sexual differences in.

Labrus pavo.

Lacertilia, sexual differences of.

Lafresnaye, M. de, on birds of paradise.

Lamarck, on the origin of man.

Lamellibranchiata.

Lamellicorn beetles, horn-like processes from the head and thorax of;
influence of sexual selection on.

Lamellicornia, stridulation of.

Lamont, Mr., on the tusks of the walrus; on the use of its tusks by the
walrus; on the bladder-nose seal.

Lampornis porphyrurus, colours of the female.

Lampyridae, distasteful to mammals.

Lancelet.

Landois, H., gnats attracted by sound; on the production of sound by
the Cicadae; on the stridulating organ of the crickets; on Decticus; on
the stridulating organs of the Acridiidae; stridulating apparatus, in
Orthoptera; on the stridulation of Necrophorus; on the stridulant organ
of Cerambyx heros; on the stridulant organ of Geotrupes; on the
stridulating organs in the Coleoptera; on the ticking of Anobium.

Landor, Dr., on remorse for not obeying tribal custom.

Language, an art; articulate, origin of; relation of the progress of,
to the development of the brain; effects of inheritance in production
of; complex structure of, among barbarous nations; natural selection
in; gesture; primeval; of a lost tribe preserved by a parrot.

Languages, presence of rudiments in; classification of; variability of;
crossing or blending of; complexity of, no test of perfection or proof
of special creation; resemblance of, evidence of community of origin.

Languages and species, identity of evidence of their gradual
development.

Lanius, characters of young.

Lanius rufus, anomalous young of.

Lankester, E.R., on comparative longevity; on the destructive effects
of intemperance.

Lanugo of the human foetus.

Lapponian language, highly artificial.

Lark, proportion of the sexes in the; female, singing of the.

Larks, attracted by a mirror.

Lartet, E., comparison of cranial capacities of skulls of recent and
tertiary mammals; on the size of the brain in mammals; on Dryopithecus;
on pre-historic flutes.

Larus, seasonal change of plumage in.

Larva, luminous, of a Brazilian beetle.

Larynx, muscles of the, in songbirds.

Lasiocampa quercus, attraction of males by the female; sexual
difference of colour in.

Latham, R.G., on the migrations of man.

Latooka, perforation of the lower lip by the women of.

Laurillard, on the abnormal division of the malar bone in man.

Lawrence, W., on the superiority of savages to Europeans in power of
sight; on the colour of negro infants; on the fondness of savages for
ornaments; on beardless races; on the beauty of the English
aristocracy.

Layard, E.L., on the instance of rationality in a cobra; on the
pugnacity of Gallus Stanleyi.

Laycock, Dr., on vital periodicity; theroid nature of idiots.

Leaves, autumn, tints useless.

Lecky, Mr., on the sense of duty; on suicide; on the practice of
celibacy; his view of the crimes of savages; on the gradual rise of
morality.

Leconte, J.L., on the stridulant organ in the Coprini and Dynastini.

Lee, H., on the numerical proportion of the sexes in the trout.

Leg, calf of the, artificially modified.

Legitimate and illegitimate children, proportion of the sexes in.

Legs, variation of the length of the, in man; proportions of, in
soldiers and sailors; front, atrophied in some male butterflies;
peculiarities of, in male insects.

Leguay, on the occurrence of the supra-condyloid foramen in the humerus
of man.

Lek of the black-cock and capercailzie.

Lemoine, Albert, on the origin of language.

Lemur macaco, sexual difference of colour in.

Lemuridae, ears of the; variability of the muscles in the; position and
derivation of the; their origin.

Lemurs, uterus in the.

Lenguas, disfigurement of the ears of the.

Leopards, black.

Lepidoptera, numerical proportions of the sexes in the; colouring of;
ocellated spots of.

Lepidosiren.

Leptalides, mimicry of.

Leptorhynchus angustatus, pugnacity of male.

Leptura testacea, difference of colour in the sexes.

Leroy, on the wariness of young foxes in hunting-districts; on the
desertion of their young by swallows.

Leslie, D., marriage customs of Kaffirs.

Lesse, valley of the.

Lesson, on the birds of paradise; on the sea-elephant.

Lessona, M., observations on Serranus.

Lethrus cephalotes, pugnacity of the males of.

Leuciscus phoxinus.

Leuckart, R., on the vesicula prostatica; on the influence of the age
of parents on the sex of offspring.

Levator claviculae muscle.

Libellula depressa, colour of the male.

Libellulidae, relative size of the sexes of; difference in the sexes
of.

Lice of domestic animals and man.

Licentiousness a check upon population; prevalence of, among savages.

Lichtenstein, on Chera progne.

Life, inheritance at corresponding periods of.

Light, effects on complexion; influence of, upon the colours of shells.

Lilford, Lord, the ruff attracted by bright objects.

Limosa lapponica.

Linaria.

Linaria montana.

Lindsay, Dr. W.L., diseases communicated from animals to man; madness
in animals; the dog considers his master his God.

Linnaeus, views of, as to the position of man.

Linnet, numerical proportion of the sexes in the; crimson forehead and
breast of the; courtship of the.

Lion, polygamous; mane of the, defensive; roaring of the.

Lions, stripes of young.

Lips, piercing of the, by savages.

Lithobius, prehensile appendages of the female.

Lithosia, coloration in.

Littorina littorea.

Livingstone, Dr., manner of sitting of gorilla; on the influence of
dampness and dryness on the colour of the skin; on the liability of
negroes to tropical fevers after residence in a cold climate; on the
spur-winged goose; on weaverbirds; on an African night-jar; on the
battle-scars of South African male mammals; on the removal of the upper
incisors by the Batokas; on the perforation of the upper lip by the
Makalolo; on the Banyai.

Livonia, numerical proportion of male and female births in.

Lizards, relative size of the sexes of; gular pouches of.

Lloyd, L., on the polygamy of the capercailzie and bustard; on the
numerical proportion of the sexes in the capercailzie and blackcock; on
the salmon; on the colours of the sea-scorpion; on the pugnacity of
male grouse; on the capercailzie and blackcock; on the call of the
capercailzie; on assemblages of grouse and snipes; on the pairing of a
shield-drake with a common duck; on the battles of seals; on the elk.

Lobivanellus, wing-spurs in.

Local influences, effect of, upon stature.

Lockwood, Mr., on the development of Hippocampus.

Lockwood, Rev. S., musical mouse.

Locust, bright-coloured, rejected by lizards and birds.

Locust, migratory; selection by female.

Locustidae, stridulation of the; descent of the.

Locusts, proportion of sexes in; stridulation of.

Longicorn beetles, difference of the sexes of, in colour; stridulation
of.

Lonsdale, Mr., on an example of personal attachment in Helix pomatia.

Lophobranchii, marsupial receptacles of the male.

Lophophorus, habits of.

Lophorina atra, sexual difference in coloration of.

Lophornis ornatus.

Lord, J.K., on Salmo lycaodon.

Lory, King; immature plumage of the.

Lory, King, constancy of.

Love-antics and dances of birds.

Lowne, B.T., on Musca vomitoria.

Loxia, characters of young of.

Lubbock, Sir J., on the antiquity of man; on the origin of man; on the
mental capacity of savages; on the origin of implements; on the
simplification of languages; on the absence of the idea of God among
certain races of men; on the origin of the belief in spiritual
agencies; on superstitions; on the sense of duty; on the practice of
burying the old and sick among the Fijians; on the immorality of
savages; on Mr. Wallace’s claim to the origination of the idea of
natural selection; on the former barbarism of civilised nations; on
improvements in the arts among savages; on resemblances of the mental
characters in different races of men; on the arts practised by savages;
on the power of counting in primeval man; on the prehensile organs of
the male Labidocera Darwinii; on Chloeon; on Smynthurus luteus; finding
of new mates by jays; on strife for women among the North American
Indians; on music; on the ornamental practices of savages; on the
estimation of the beard among the Anglo-Saxons; on artificial
deformation of the skull; on “communal marriages;” on exogamy; on the
Veddahs; on polyandry.

Lucanidae, variability of the mandibles in the male.

Lucanus, large size of males of.

Lucanus cervus, numerical proportion of sexes of; weapons of the male.

Lucanus elaphus, use of mandibles of; large jaws of male.

Lucas, Prosper, on pigeons; on sexual preference in horses and bulls.

Luminosity in insects.

Lunar periods.

Lund, Dr., on skulls found in Brazilian caves.

Lungs, enlargement of, in the Quichua and Aymara Indians; a modified
swim-bladder; different capacity of, in races of man.

Luschka, Prof., on the termination of the coccyx.

Luxury, expectation of life uninfluenced by.

Lycaena, sexual differences of colour in species of.

Lycaenae, colours of.

Lyell, Sir C., on the antiquity of man; on the origin of man; on the
parallelism of the development of species and languages; on the
extinction of languages; on the Inquisition; on the fossil remains of
vertebrata; on the fertility of mulattoes.

Lynx, Canadian throat-ruff of the.

Lyre-bird, assemblies of.

Macacus, ears of; convoluted body in the extremity of the tail of;
variability of the tail in species of; whiskers of species of.

Macacus brunneus.

Macacus cynomolgus, superciliary ridge of; beard and whiskers of;
becoming white with age.

Macacus ecaudatus.

Macacus lasiotus, facial spots of.

Macacus nemestrinus.

Macacus radiatus.

Macacus rhesus, sexual difference in the colour of.

Macalister, Prof., on variations of the palmaris accessorius muscle; on
muscular abnormalities in man; on the greater variability of the
muscles in men than in women.

Macaws, Mr. Buxton’s observations on.

McCann, J., on mental individuality.

McClelland, J., on the Indian Cyprinidae.

Macculloch, Col., on an Indian village without any female children.

Macculloch, Dr., on tertian ague in a dog.

Macgillivray, W., on the vocal organs of birds; on the Egyptian goose;
on the habits of woodpeckers; on the habits of the snipe; on the
whitethroat; on the moulting of the snipes; on the moulting of the
Anatidae; on the finding of new mates by magpies; on the pairing of a
blackbird and thrush; on pied ravens; on the guillemots; on the colours
of the tits; on the immature plumage of birds.

Machetes, sexes and young of.

Machetes pugnax, supposed to be polygamous; numerical proportion of the
sexes in; pugnacity of the male; double moult in.

McIntosh, Dr., colours of the Nemertians.

McKennan, marriage customs of Koraks.

Mackintosh, on the moral sense.

MacLachlan, R., on Apatania muliebris and Boreus hyemalis; on the anal
appendages of male insects; on the pairing of dragon-flies; on
dragon-flies; on dimorphism in Agrion; on the want of pugnacity in male
dragon-flies; colour of ghost-moth in the Shetland Islands.

M’Lennan, Mr., on infanticide; on the origin of the belief in spiritual
agencies; on the prevalence of licentiousness among savages; on the
primitive barbarism of civilised nations; on traces of the custom of
the forcible capture of wives; on polyandry.

Macnamara, Mr., susceptibility of Andaman islanders and Nepalese to
change.

M’Neill, Mr., on the use of the antlers of deer; on the Scotch
deerhound; on the long hairs on the throat of the stag; on the
bellowing of stags.

Macropus, courtship of.

Macrorhinus proboscideus, structure of the nose of.

Magpie, power of speech of; vocal organs of the; nuptial assemblies of;
new mates found by; stealing bright objects; young of the; coloration
of the.

Maillard, M., on the proportion of the sexes in a species of Papilio
from Bourbon.

Maine, Sir Henry, on the absorption of one tribe by another; a desire
for improvement not general.

Major, Dr. C. Forsyth, on fossil Italian apes; skull of Bos etruscus;
tusks of miocene pigs.

Makalolo, perforation of the upper lip by the.

Malar bone, abnormal division of, in man.

Malay Archipelago, marriage-customs of the savages of the.

Malays, line of separation between the Papuans and the; general
beardlessness of the; staining of the teeth among; aversion of some, to
hairs on the face.

Malays and Papuans, contrasted characters of.

Male animals, struggles of, for the possession of the females;
eagerness of, in courtship; generally more modified than female; differ
in the same way from females and young.

Male characters, developed in females; transfer of, to female birds.

Male, sedentary, of a hymenopterous parasite.

Malefactors.

Males, presence of rudimentary female organs in.

Males and females, comparative numbers of; comparative mortality of,
while young.

Malherbe, on the woodpeckers.

Mallotus Peronii.

Mallotus villosus.

Malthus, T., on the rate of increase of population.

Maluridae, nidification of the.

Malurus, young of.

Mammae, rudimentary, in male mammals; supernumerary, in women; of male
human subject.

Mammalia, Prof. Owen’s classification of; genealogy of the.

Mammals, recent and tertiary, comparison of cranial capacity of;
nipples of; pursuit of female, by the males; secondary sexual
characters of; weapons of; relative size of the sexes of; parallelism
of, with birds in secondary sexual characters; voices of, used
especially during the breeding season.

Man, variability of; erroneously regarded as more domesticated than
other animals; migrations of; wide distribution of; causes of the
nakedness of; supposed physical inferiority of; a member of the
Catarrhine group; early progenitors of; transition from ape indefinite;
numerical proportions of the sexes in; difference between the sexes;
proportion of sexes amongst the illegitimate; different complexion of
male and female negroes; secondary sexual characters of; primeval
condition of.

Mandans, correlation of colour and texture of hair in the.

Mandible, left, enlarged in the male of Taphroderes distortus.

Mandibles, use of the, in Ammophila; large, of Corydalis cornutus;
large, of male Lucanus elaphus.

Mandrill, number of caudal vertebrae in the; colours of the male.

Mantegazza, Prof., on last molar teeth of man; bright colours in male
animals; on the ornaments of savages; on the beardlessness of the New
Zealanders; on the exaggeration of natural characters by man.

Mantell, W., on the engrossment of pretty girls by the New Zealand
chiefs.

Mantis, pugnacity of species of.

Maories, mortality of; infanticide and proportion of sexes; distaste
for hairiness amongst men.

Marcus Aurelius, on the origin of the moral sense; on the influence of
habitual thoughts.

Mareca penelope.

Marks, retained throughout groups of birds.

Marriage, restraints upon, among savages; influence of, upon morals;
influence of, on mortality; development of.

Marriages, early; communal.

Marshall, Dr. W., protuberances on birds’ heads; on the moulting of
birds; advantage to older birds of paradise.

Marshall, Col., interbreeding amongst Todas; infanticide and proportion
of sexes with Todas; choice of husband amongst Todas.

Marshall, Mr., on the brain of a Bushwoman.

Marsupials, development of the nictitating membrane in; uterus of;
possession of nipples by; their origin from Monotremata; abdominal sacs
of; relative size of the sexes of; colours of.

Marsupium, rudimentary in male marsupials.

Martin, W.C.L., on alarm manifested by an orang at the sight of a
turtle; on the hair in Hylobates; on a female American deer; on the
voice of Hylobates agilis; on Semnopithecus nemaeus.

Martin, on the beards of the inhabitants of St. Kilda.

Martins deserting their young.

Martins, C., on death caused by inflammation of the vermiform
appendage.

Mastoid processes in man and apes.

Maudsley, Dr., on the influence of the sense of smell in man; on idiots
smelling their food; on Laura Bridgman; on the development of the vocal
organs; moral sense failing in incipient madness; change of mental
faculties at puberty in man.

Mayers, W.F., on the domestication of the goldfish in China.

Mayhew, E., on the affection between individuals of different sexes in
the dog.

Maynard, C.J., on the sexes of Chrysemys picta.

Meckel, on correlated variation of the muscles of the arm and leg.

Medicines, effect produced by, the same in man and in monkeys.

Medusae, bright colours of some.

Megalithic structures, prevalence of.

Megapicus validus, sexual difference of colour in.

Megasoma, large size of males of.

Meigs, Dr. A., on variation in the skulls of the natives of America.

Meinecke, on the numerical proportion of the sexes in butterflies.

Melanesians, decrease of.

Meldola, Mr., colours and marriage flight of Colias and Pieris.

Meliphagidae, Australian, nidification of.

Melita, secondary sexual characters of.

Meloe, difference of colour in the sexes of a species of.

Memnon, young.

Memory, manifestations of, in animals.

Mental characters, difference of, in different races of men.

Mental faculties, diversity of, in the same race of men; inheritance
of; variation of, in the same species; similarity of the, in different
races of man; of birds.

Mental powers, difference of, in the two sexes in man.

Menura Alberti, song of.

Menura superba, long tails of both sexes of.

Merganser, trachea of the male.

Merganser serrator, male plumage of.

Mergus cucullatus, speculum of.

Mergus merganser, young of.

Metallura, splendid tail-feathers of.

Methoca ichneumonides, large male of.

Meves, M., on the drumming of the snipe.

Mexicans, civilisation of the, not foreign.

Meyer, on a convoluted body at the extremity of the tail in a Macacus
and a cat.

Meyer, Dr. A., on the copulation of Phryganidae of distinct species.

Meyer, Prof. L., on development of helix of ear; men’s ears more
variable than women’s; antennae serving as ears.

Migrations of man, effects of.

Migratory instinct of birds; vanquishing the maternal.

Mill, J.S., on the origin of the moral sense; on the “greatest
happiness principle;” on the difference of the mental powers in the
sexes of man.

Millipedes.

Milne-Edwards, H., on the use of enlarged chelae of the male Gelasimus.

Milvago leucurus, sexes and young of.

Mimicry.

Mimus polyglottus.

Mind, difference of, in man and the highest animals; similarity of the,
in different races.

Minnow, proportion of the sexes in the.

Mirror, behaviour of monkeys before.

Mirrors, larks attracted by.

Mitchell, Dr., interbreeding in the Hebrides.

Mitford, selection of children in Sparta.

Mivart, St. George, on the reduction of organs; on the ears of the
lemuroidea; on variability of the muscles in lemuroidea; on the caudal
vertebrae of monkeys; on the classification of the primates; on the
orang and on man; on differences in the lemuroidea; on the crest of the
male newt.

Mobius, Prof., on reasoning powers in a pike.

Mocking-thrush, partial migration of; young of the.

Modifications, unserviceable.

Moggridge, J.T., on habits of spiders; on habits of ants.

Moles, numerical proportion of the sexes in; battles of male.

Mollienesia petenensis, sexual difference in.

Mollusca, beautiful colours and shapes of; absence of secondary sexual
characters in the.

Molluscoida.

Monacanthus scopas and M. Peronii.

Monboddo, Lord, on music.

Mongolians, perfection of the senses in.

Monkey, protecting his keeper from a baboon; bonnet-; rhesus-, sexual
difference in colour of the; moustache-, colours of the.

Monkeys, liability of, to the same diseases as man; male, recognition
of women by; diversity of the mental faculties in; breaking hard fruits
with stones; hands of the; basal caudal vertebrae of, imbedded in the
body; revenge taken by; maternal affection in; variability of the
faculty of attention in; American, manifestation of reason in; using
stones and sticks; imitative faculties of; signal-cries of; mutual
kindnesses of; sentinels posted by; human characters of; American,
direction of the hair on the arms of some; gradation of species of;
beards of; ornamental characters of; analogy of sexual differences of,
with those of man; different degrees of difference in the sexes of;
expression of emotions by; generally monogamous habits of; polygamous
habits of some; naked surfaces of; courtship of.

Monogamy, not primitive.

Monogenists.

Mononychus pseudacori, stridulation of.

Monotremata, development of the nictitating membrane in; lactiferous
glands of; connecting mammals with reptiles.

Monstrosities, analogous, in man and lower animals; caused by arrest of
development; correlation of; transmission of.

Montagu, G., on the habits of the black and red grouse; on the
pugnacity of the ruff; on the singing of birds; on the double moult of
the male pintail.

Monteiro, Mr., on Bucorax abyssinicus.

Montes de Oca, M., on the pugnacity of male Humming-birds.

Monticola cyanea.

Monuments, as traces of extinct tribes.

Moose, battles of; horns of the, an incumbrance.

Moral and instinctive impulses, alliance of.

Moral faculties, their influence on natural selection in man.

Moral rules, distinction between the higher and lower.

Moral sense, so-called, derived from the social instincts; origin of
the.

Moral tendencies, inheritance of.

Morality, supposed to be founded in selfishness; test of, the general
welfare of the community; gradual rise of; influence of a high standard
of.

Morgan, L.H., on the beaver; on the reasoning powers of the beaver; on
the forcible capture of wives; on the castoreum of the beaver; marriage
unknown in primeval times; on polyandry.

Morley, J., on the appreciation of praise and fear of blame.

Morris, F.O., on hawks feeding an orphan nestling.

Morse, Dr., colours of mollusca.

Morselli, E., division of the malar bone.

Mortality, comparative, of female and male.

Morton on the number of species of man.

Moschkau, Dr. A., on a speaking starling.

Moschus moschiferus, odoriferous organs of.

Motacillae, Indian, young of.

Moth, odoriferous.

Moths, absence of mouth in some males; apterous female; male,
prehensile use of the tarsi by; male, attracted by females; sound
produced by; coloration of; sexual differences of colour in.

Motmot, inheritance of mutilation of tail feathers; racket-shaped
feathers in the tail of a.

Moult, double; double annual, in birds.

Moulting of birds.

Moults, partial.

Mouse, song of.

Moustache-monkey, colours of the.

Moustaches, in monkeys.

Mud-turtle, long claws of the male.

Mulattoes, persistent fertility of; immunity of, from yellow fever.

Mule, sterility and strong vitality of the.

Mules, rational.

Muller, Ferd., on the Mexicans and Peruvians.

Muller, Fritz, on astomatous males of Tanais; on the disappearance of
spots and stripes in adult mammals; on the proportions of the sexes in
some Crustacea; on secondary sexual characters in various Crustaceans;
musical contest between male Cicadae; mode of holding wings in Castina;
on birds shewing a preference for certain colours; on the sexual
maturity of young amphipod Crustacea.

Muller, Hermann, emergence of bees, from pupa; pollen-gathering of
bees; proportion of sexes in bees; courting of Eristalis; colour and
sexual selection with bees.

Muller, J., on the nictitating membrane and semilunar fold.

Muller, Max, on the origin of language; language implies power of
general conception; struggle for life among the words, etc., of
languages.

Muller, S., on the banteng; on the colours of Semnopithecus
chrysomelas.

Muntjac-deer, weapons of the.

Murie, J., on the reduction of organs; on the ears of the Lemuroidea;
on variability of the muscles in the Lemuroidea; basal caudal vertebrae
of Macacus brunneus imbedded in the body; on the manner of sitting in
short-tailed apes; on differences in the Lemuroidea; on the
throat-pouch of the male bustard; on the mane of Otaria jubata; on the
sub-orbital pits of Ruminants; on the colours of the sexes in Otaria
nigrescens.

Murray, A., on the Pediculi of different races of men.

Murray, T.A., on the fertility of Australian women with white men.

Mus coninga.

Mus minutus, sexual difference in the colour of.

Musca vomitoria.

Muscicapa grisola.

Muscicapa luctuosa.

Muscicapa ruticilla, breeding in immature plumage.

Muscle, ischio-pubic.

Muscles, rudimentary, occurrence of, in man; variability of the;
effects of use and disuse upon; animal-like abnormalities of, in man;
correlated variation of, in the arm and leg; variability of, in the
hands and feet; of the jaws, influence of, on the physiognomy of the
Apes; habitual spasms of, causing modifications of the facial bones, of
the early progenitors of man; greater variability of the, in men than
in women.

Musculus sternalis, Prof. Turner on the.

Music, of birds; discordant, love of savages for; reason of power of
perception of notes in animals; power of distinguishing notes; its
connection with primeval speech; different appreciation of, by
different peoples; origin of; effects of.

Musical cadences, perception of, by animals; powers of man.

Musk-deer, canine teeth of male; male, odoriferous organs of the;
winter change of the.

Musk-duck, Australian; large size of male; of Guiana, pugnacity of the
male.

Musk-ox, horns of.

Musk-rat, protective resemblance of the, to a clod of earth.

Musophagae, colours and nidification of the; both sexes of, equally
brilliant.

Mussels opened by monkeys.

Mustela, winter change of two species of.

Musters, Captain, on Rhea Darwinii; marriages amongst Patagonians.

Mutilations, healing of; inheritance of.

Mutilla europaea, stridulation of.

Mutillidae, absence of ocelli in female.

Mycetes caraya, polygamous; vocal organs of; beard of; sexual
differences of colour in; voice of.

Mycetes seniculus, sexual differences of colour in.

Myriapoda.

Nageli, on the influence of natural selection on plants; on the
gradation of species of plants.

Nails, coloured yellow or purple in part of Africa.

Narwhal, tusks of the.

Nasal cavities, large size of, in American aborigines.

Nascent organs.

Nathusius, H. von, on the improved breeds of pigs; male domesticated
animals more variable than females; horns of castrated sheep; on the
breeding of domestic animals.

Natural selection, its effects on the early progenitors of man;
influence of, on man; limitation of the principle; influence of, on
social animals; Mr. Wallace on the limitation of, by the influence of
the mental faculties in man; influence of, in the progress of the
United States; in relation to sex.

Natural and sexual selection contrasted.

Naulette, jaw from, large size of the canines in.

Neanderthal skull, capacity of the.

Neck, proportion of, in soldiers and sailors.

Necrophorus, stridulation of.

Nectarinia, young of.

Nectariniae, moulting of the; nidification of.

Negro, resemblance of a, to Europeans in mental characters.

Negro-women, their kindness to Mungo Park.

Negroes, Caucasian features in; character of; lice of; fertility of,
when crossed with other races; blackness of; variability of; immunity
of, from yellow fever; difference of, from Americans; disfigurements of
the; colour of new-born children of; comparative beardlessness of;
readily become musicians; appreciation of beauty of their women by;
idea of beauty among; compression of the nose by some.

Nemertians, colours of.

Neolithic period.

Neomorpha, sexual difference of the beak in.

Nephila, size of male.

Nests, made by fishes; decoration of, by Humming-birds.

Neumeister, on a change of colour in pigeons after several moultings.

Neuration, difference of, in the two sexes of some butterflies and
hymenoptera.

Neuroptera.

Neurothemis, dimorphism in.

New Zealand, expectation by the natives of, of their extinction;
practice of tattooing in; aversion of natives of, to hairs on the face;
pretty girls engrossed by the chiefs in.

Newton, A., on the throat-pouch of the male bustard; on the differences
between the females of two species of Oxynotus; on the habits of the
Phalarope, dotterel, and godwit.

Newts.

Nicholson, Dr., on the non-immunity of dark Europeans from yellow
fever.

Nictitating membrane.

Nidification of fishes; relation of, to colour; of British birds.

Night-heron, cries of the.

Nightingale, arrival of the male before the female; object of the song
of the.

Nightingales, new mates found by.

Nightjar, selection of a mate by the female; Australian, sexes of;
coloration of the.

Nightjars, noise made by some male, with their wings; elongated
feathers in.

Nilghau, sexual differences of colour in the.

Nilsson, Prof., on the resemblance of stone arrow-heads from various
places; on the development of the horns of the reindeer.

Nipples, absence of, in Monotremata.

Nitsche, Dr., ear of foetal orang.

Nitzsch, C.L., on the down of birds.

Noctuae, brightly-coloured beneath.

Noctuidae, coloration of.

Nomadic habits, unfavourable to human progress.

Nordmann, A., on Tetrao urogalloides.

Norfolk Island, half-breeds on.

Norway, numerical proportion of male and female births in.

Nose, resemblance of, in man and the apes; piercing and ornamentation
of the; very flat, not admired in negroes; flattening of the.

Nott and Gliddon, on the features of Rameses II.; on the features of
Amunoph III.; on skulls from Brazilian caves; on the immunity of
negroes and mulattoes from yellow fever; on the deformation of the
skull among American tribes.

Novara, voyage of the, suicide in New Zealand.

Nudibranch Mollusca, bright colours of.

Numerals, Roman.

Nunemaya, natives of, bearded.

Nuthatch, of Japan, intelligence of; Indian.

Obedience, value of.

Observation, powers of, possessed by birds.

Occupations, sometimes a cause of diminished stature; effect of, upon
the proportions of the body.

Ocelli, absence of, in female Mutilidae.

Ocelli of birds, formation and variability of the.

Ocelot, sexual differences in the colouring of the.

Ocyhaps lophotes.

Odonata.

Odonestis potatoria, sexual difference of colour in.

Odour, correlation of, with colour of skin; of moths; emitted by snakes
in the breeding season; of mammals.

Oecanthus nivalis, difference of colour in the sexes of.

Oecanthus pellucidus.

Ogle, Dr. W., relation between colour and power of smell.

Oidemia.

Oliver, on sounds produced by Pimelia striata.

Omaloplia brunnea, stridulation of.

Onitis furcifer, processes of anterior femora of the male, and on the
head and thorax of the female.

Onthophagus.

Onthophagus rangifer, sexual differences of; variations in the horns of
the male.

Ophidia, sexual differences of.

Ophidium.

Opossum, wide range of, in America.

Optic nerve, atrophy of the, caused by destruction of the eye.

Orang-Outan, Bischoff on the agreement of the brain of the, with that
of man; adult age of the; ears of the; vermiform appendage of; hands of
the; absence of mastoid processes in the; platforms built by the;
alarmed at the sight of a turtle; using a stick as a lever; using
missiles; using the leaves of the Pandanus as a night covering;
direction of the hair on the arms of the; its aberrant characters;
supposed evolution of the; voice of the; monogamous habits of the;
male, beard of the.

Oranges, treatment of, by monkeys.

Orange-tip butterfly.

Orchestia Darwinii, dimorphism of males of.

Orchestia Tucuratinga, limbs of.

Ordeal, trial by.

Oreas canna, colours of.

Oreas Derbianus, colours of.

Organs, prehensile; utilised for new purposes.

Organic scale, von Baer’s definition of progress in.

Orioles, nidification of.

Oriolus, species of, breeding in immature plumage.

Oriolus melanocephalus, coloration of the sexes in.

Ornaments, prevalence of similar; of male birds; fondness of savages
for.

Ornamental characters, equal transmission of, to both sexes, in
mammals; of monkeys.

Ornithoptera croesus.

Ornithorhynchus, reptilian tendency of; spur of the male.

Orocetes erythrogastra, young of.

Orrony, Grotto of.

Orsodacna atra, difference of colour in the sexes of.

Orsodacna ruficollis.

Orthoptera, metamorphosis of; stridulating apparatus of; colours of;
rudimentary stridulating organs in female; stridulation of the, and
Homoptera, discussed.

Ortygornis gularis, pugnacity of the male.

Oryctes, stridulation of; sexual differences in the stridulant organs
of.

Oryx leucoryx, use of the horns of.

Osphranter rufus, sexual difference in the colour of.

Ostrich, African, sexes and incubation of the.

Ostriches, stripes of young.

Otaria jubata, mane of the male.

Otaria nigrescens, difference in the coloration of the sexes of.

Otis bengalensis, love-antics of the male.

Otis tarda, throat-pouch of the male; polygamous.

Ouzel, ring-, colours and nidification of the.

Ouzel, water-, singing in the autumn; colours and nidification of the.

Ovibos moschatus, horns of.

Ovipositor of insects.

Ovis cycloceros, mode of fighting of.

Ovule of man.

Owen, Prof., on the Corpora Wolffiana; on the great toe in man; on the
nictitating membrane and semilunar fold; on the development of the
posterior molars in different races of man; on the length of the caecum
in the Koala; on the coccygeal vertebrae; on rudimentary structures
belonging to the reproductive system; on abnormal conditions of the
human uterus; on the number of digits in the Ichthyopterygia; on the
canine teeth in man; on the walking of the chimpanzee and orang; on the
mastoid processes in the higher apes; on the hairiness of elephants in
elevated districts; on the caudal vertebrae of monkeys; classification
of mammalia; on the hair in monkeys; on the piscine affinities of the
Ichthyosaurians; on polygamy and monogamy among the antelopes; on the
horns of Antilocapra Americana; on the musky odour of crocodiles during
the breeding season; on the scent-glands of snakes; on the Dugong,
Cachalot, and Ornithorhynchus; on the antlers of the red deer; on the
dentition of the Camelidae; on the horns of the Irish elk; on the voice
of the giraffe, porcupine, and stag; on the laryngeal sac of the
gorilla and orang; on the odoriferous glands of mammals; on the effects
of emasculation on the vocal organs of men; on the voice of Hylobates
agilis; on American monogamous monkeys.

Owls, white, new mates found by.

Oxynotus, difference of the females of two species of.

Pachydermata.

Pachytylus migratorius.

Paget, on the abnormal development of hairs in man; on the thickness of
the skin on the soles of the feet of infants.

Pagurus, carrying the female.

Painting, pleasure of savages in.

Palaemon, chelae of a species of.

Palaeornis, sexual differences of colour in.

Palaeornis javanicus, colour of beak of.

Palaeornis rosa, young of.

Palamedea cornuta, spurs on the wings.

Paleolithic period.

Palestine, habits of the chaffinch in.

Pallas, on the perfection of the senses in the Mongolians; on the want
of connexion between climate and the colour of the skin; on the
polygamous habits of Antilope Saiga; on the lighter colour of horses
and cattle in winter in Siberia; on the tusks of the musk-deer; on the
odoriferous glands of mammals; on the odoriferous glands of the
musk-deer; on winter changes of colour in mammals; on the ideal of
female beauty in North China.

Palmaris accessorius, muscle variations of the.

Pampas, horses of the.

Pangenesis, hypothesis of.

Panniculus carnosus.

Pansch, on the brain of a foetal Cebus apella.

Papilio, proportion of the sexes in North American species of; sexual
differences of colouring in species of; coloration of the wings in
species of.

Papilio ascanius.

Papilio Sesostris and Childrenae, variability of.

Papilio Turnus.

Papilionidae, variability in the.

Papuans, line of separation between the, and the Malays; beards of the;
teeth of.

Papuans and Malays, contrast in characters of.

Paradise, Birds of; supposed by Lesson to be polygamous; rattling of
their quills by; racket-shaped feathers in; sexual differences in
colour of; decomposed feathers in; display of plumage by the male;
sexual differences in colour of.

Paradisea apoda, barbless feathers in the tail of; plumage of; and P.
papuana; divergence of the females of; increase of beauty with age.

Paradisea papuana, plumage of.

Paraguay, Indians of, eradication of eyebrows and eyelashes by.

Parallelism of development of species and languages.

Parasites, on man and animals; as evidence of specific identity or
distinctness; immunity from, correlated with colour.

Parental feeling in earwigs, starfishes, and spiders; affection, partly
a result of natural selection.

Parents, age of, influence upon sex of offspring.

Parinae, sexual difference of colour in.

Park, Mungo, negro-women teaching their children to love the truth; his
treatment by the negro-women; on negro opinions of the appearance of
white men.

Parker, Mr., no bird or reptile in line of mammalian descent.

Parrakeet, young of; Australian, variation in the colour of the thighs
of a male.

Parrot, racket-shaped feathers in the tail of a; instance of
benevolence in a.

Parrots, change of colour in; imitative faculties of; living in
triplets; affection of; colours and nidification of the; immature
plumage of the; colours of; sexual differences of colour in; musical
powers of.

Parthenogenesis in the Tenthredinae; in Cynipidae; in Crustacea.

Partridge, monogamous; proportion of the sexes in the; Indian; female.

Partridge-“dances.”

Partridges, living in triplets; spring coveys of male; distinguishing
persons.

Parus coeruleus.

Passer, sexes and young of.

Passer brachydactylus.

Passer domesticus.

Passer montanus.

Patagonians, self-sacrifice by; marriages of.

Patterson, Mr., on the Agrionidae.

Patteson, Bishop, decrease of Melanesians.

Paulistas of Brazil.

Pavo cristatus.

Pavo muticus, possession of spurs by the female.

Pavo nigripennis.

Payaguas Indians, thin legs and thick arms of the.

Payan, Mr., on the proportion of the sexes in sheep.

Peacock, polygamous; sexual characters of; pugnacity of the; Javan,
possessing spurs; rattling of the quills by; elongated tail-coverts of
the; love of display of the; ocellated spots of the; inconvenience of
long tail of the, to the female; continued increase of beauty of the.

Peacock-butterfly.

Peafowl, preference of females for a particular male; first advances
made by the female.

Pediculi of domestic animals and man.

Pedigree of man.

Pedionomus torquatus, sexes of.

Peel, J., on horned sheep.

Peewit, wing-tubercles of the male.

Pelagic animals, transparency of.

Pelecanus erythrorhynchus, horny crest on the beak of the male, during
the breeding season.

Pelecanus onocrotalus, spring plumage of.

Pelele, an African ornament.

Pelican, blind, fed by his companions; young, guided by old birds;
pugnacity of the male.

Pelicans, fishing in concert.

Pelobius Hermanni, stridulation of.

Pelvis, alteration of, to suit the erect attitude of man; differences
of the, in the sexes of man.

Penelope nigra, sound produced by the male.

Pennant, on the battles of seals; on the bladder-nose seal.

Penthe, antennal cushions of the male.

Perch, brightness of male, during breeding season.

Peregrine falcon, new mate found by.

Period of variability, relation of, to sexual selection.

Periodicity, vital, Dr. Laycock on.

Periods, lunar, followed by functions in man and animals.

Periods of life, inheritance at corresponding.

Perisoreus canadensis, young of.

Peritrichia, difference of colour in the sexes of a species of.

Periwinkle.

Pernis cristata.

Perrier, M., on sexual selection; on bees.

Perseverance, a characteristic of man.

Persians, said to be improved by intermixture with Georgians and
Circassians.

Personnat, M., on Bombyx Yamamai.

Peruvians, civilisation of the, not foreign.

Petrels, colours of.

Petrocincla cyanea, young of.

Petrocossyphus.

Petronia.

Pfeiffer, Ida, on Javan ideas of beauty.

Phacochoerus aethiopicus, tusks and pads of.

Phalanger, Vulpine, black varieties of the.

Phalaropus fulicarius.

Phalaropus hyperboreus.

Phanaeus.

Phanaeus carnifex, variation of the horns of the male.

Phanaeus faunus, sexual differences of.

Phanaeus lancifer.

Phaseolarctus cinereus, taste for rum and tobacco.

Phasgonura viridissima, stridulation of.

Phasianus Soemmerringii.

Phasianus versicolor.

Phasianus Wallichii.

Pheasant, polygamous; and black grouse, hybrids of; production of
hybrids with the common fowl; immature plumage of the.

Pheasant, Amherst, display of.

Pheasant, Argus, display of plumage by the male; ocellated spots of
the; gradation of characters in the.

Pheasant, Blood- Pheasant, Cheer.

Pheasant, Eared, length of the tail in the; sexes alike in the.

Pheasant, Fire-backed, possessing spurs.

Pheasant, Golden, display of plumage by the male; age of mature plumage
in the; sex of young, ascertained by pulling out head-feathers.

Pheasant, Kalij, drumming of the male.

Pheasant, Reeve’s, length of the tail in.

Pheasant, Silver, triumphant male, deposed on account of spoiled
plumage; sexual coloration of the.

Pheasant, Soemmerring’s.

Pheasant, Tragopan, display of plumage by the male; marking of the
sexes of the.

Pheasants, period of acquisition of male characters in the family of
the; proportion of sexes in chicks of; length of the tail in.

Philters, worn by women.

Phoca groenlandica, sexual difference in the coloration of.

Phoenicura ruticilla.

Phosphorescence of insects.

Phryganidae, copulation of distinct species of.

Phryniscus nigricans.

Physical inferiority, supposed, of man.

Pickering, on the number of species of man.

Picton, J.A., on the soul of man.

Picus auratus.

Picus major.

Pieris.

Pigeon, female, deserting a weakened mate; carrier, late development of
the wattle in; pouter, late development of crop in; domestic, breeds
and sub-breeds of.

Pigeons, nestling, fed by the secretion of the crop of both parents;

changes of plumage in; transmission of sexual peculiarities in;
Belgian, with black-streaked males; changing colour after several
moultings; numerical proportion of the sexes in; cooing of; variations
in plumage of; display of plumage by male; local memory of; antipathy
of female, to certain males; pairing of; profligate male and female;
wing-bars and tail-feathers of; supposititious breed of; pouter and
carrier, peculiarities of, predominant in males; nidification of;
Australian; immature plumage of the.

Pigs, origin of the improved breeds of; numerical proportion of the
sexes in; stripes of young; tusks of miocene; sexual preference shewn
by.

Pike, American, brilliant colours of the male, during the breeding
season.

Pike, reasoning powers of; male, devoured by females.

Pike, L.O., on the psychical elements of religion.

Pimelia striata, sounds produced by the female.

Pinel, hairiness in idiots.

Pintail, drake, plumage of; pairing with a wild duck.

Pintail Duck, pairing with a widgeon.

Pipe-fish, filamentous; marsupial receptacles of the male.

Pipits, moulting of the.

Pipra, modified secondary wing-feathers of male.

Pipra deliciosa.

Pirates stridulus, stridulation of.

Pitcairn island, half-breeds on.

Pithecia leucocephala, sexual differences of colour in.

Pithecia Satanas, beard of; resemblance of, to a negro.

Pits, suborbital, of Ruminants.

Pittidae, nidification of.

Placentata.

Plagiostomous fishes.

Plain-wanderer, Australian.

Planariae, bright colours of some.

Plantain-eaters, colours and nidification of the; both sexes of,
equally brilliant.

Plants, cultivated, more fertile than wild; Nageli, on natural
selection in; male flowers of, mature before the female; phenomena of
fertilisation in.

Platalea, change of plumage in.

Platyblemus.

Platycercus, young of.

Platyphyllum concavum.

Platyrrhine monkeys.

Platysma myoides.

Plecostomus, head-tentacles of the males of a species of.

Plecostomus barbatus, peculiar beard of the male.

Plectropterus gambensis, spurred wings of.

Ploceus.

Plovers, wing-spurs of; double moult in.

Plumage, changes of, inheritance of, by fowls; tendency to analogous
variation in; display of, by male birds; changes of, in relation to
season; immature, of birds; colour of, in relation to protection.

Plumes on the head in birds, difference of, in the sexes.

Pneumora, structure of.

Podica, sexual difference in the colour of the irides.

Poeppig, on the contact of civilised and savage races.

Poison, avoidance of, by animals.

Poisonous fruits and herbs avoided by animals.

Poisons, immunity from, correlated with colour.

Polish fowls, origin of the crest in.

Pollen and van Dam, on the colours of Lemur macaco.

Polyandry, in certain Cyprinidae; among the Elateridae.

Polydactylism in man.

Polygamy, influence of, upon sexual selection; superinduced by
domestication; supposed increase of female births by. In the
stickleback.

Polygenists.

Polynesia, prevalence of infanticide in.

Polynesians, wide geographical range of; difference of stature among
the; crosses of; variability of; heterogeneity of the; aversion of, to
hairs on the face.

Polyplectron, number of spurs in; display of plumage by the male;
gradation of characters in; female of.

Polyplectron chinquis.

Polyplectron Hardwickii.

Polyplectron malaccense.

Polyplectron Napoleonis.

Polyzoa.

Pomotis.

Pontoporeia affinis.

Porcupine, mute, except in the rutting season.

Pores, excretory, numerical relation of, to the hairs in sheep.

Porpitae, bright colours of some.

Portax picta, dorsal crest and throat-tuft of; sexual differences of
colour in.

Portunus puber, pugnacity of.

Potamochoerus pencillatus, tusks and facial knobs of the.

Pouchet, G., the relation of instinct to intelligence; on the instincts
of ants; on the caves of Abou-Simbel; on the immunity of negroes from
yellow fever; change of colour in fishes.

Pouter pigeon, late development of the large crop in.

Powell, Dr., on stridulation.

Power, Dr., on the different colours of the sexes in a species of
Squilla.

Powys, Mr., on the habits of the chaffinch in Corfu.

Pre-eminence of man.

Preference for males by female birds; shewn by mammals, in pairing.

Prehensile organs.

Presbytis entellus, fighting of the male.

Preyer, Dr., on function of shell of ear; on supernumerary mammae in
women.

Prichard, on the difference of stature among the Polynesians; on the
connection between the breadth of the skull in the Mongolians and the
perfection of their senses; on the capacity of British skulls of
different ages; on the flattened heads of the Colombian savages; on
Siamese notions of beauty; on the beardlessness of the Siamese; on the
deformation of the head among American tribes and the natives of
Arakhan.

Primary sexual organs.

Primates, sexual differences of colour in.

Primogeniture, evils of.

Prionidae, difference of the sexes in colour.

Proctotretus multimaculatus.

Proctotretus tenuis, sexual difference in the colour of.

Profligacy.

Progenitors, early, of man.

Progress, not the normal rule in human society; elements of.

Prong-horn antelope, horns of.

Proportions, difference of, in distinct races.

Protective colouring in butterflies; in lizards; in birds; in mammals.

Protective nature of the dull colouring of female Lepidoptera.

Protective resemblances in fishes.

Protozoa, absence of secondary sexual characters in.

Pruner-Bey, on the occurrence of the supra-condyloid foramen in the
humerus of man; on the colour of negro infants.

Prussia, numerical proportion of male and female births in.

Psocus, proportions of the sexes in.

Ptarmigan, monogamous; summer and winter plumage of the; nuptial
assemblages of; triple moult of the; protective coloration of.

Puff-birds, colours and nidification of the.

Pugnacity of fine-plumaged male birds.

Pumas, stripes of young.

Puppies learning from cats to clean their faces.

Pycnonotus haemorrhous, pugnacity of the male; display of under-tail
coverts by the male.

Pyranga aestiva, male aiding in incubation; male characters in female
of.

Pyrodes, difference of the sexes in colour.

Quadrumana, hands of; differences between man and the; sexual
differences of colour in; ornamental characters of; analogy of sexual
differences of, with those of man; fighting of males for the females;
monogamous habits of; beards of the.

Quain, R., on the variation of the muscles in man.

Quatrefages, A. de, on the occurrence of a rudimentary tail in man; on
variability; on the moral sense as a distinction between man and
animals; civilised men stronger than savages; on the fertility of
Australian women with white men; on the Paulistas of Brazil; on the
evolution of the breeds of cattle; on the Jews; on the liability of
negroes to tropical fevers after residence in a cold climate; on the
difference between field-and house-slaves; on the influence of climate
on colour; colours of annelids; on the Ainos; on the women of San
Giuliano.

Quechua, see Quichua.

Querquedula acuta.

Quetelet, proportion of sexes in man; relative size in man and woman.

Quichua Indians; local variation of colour in the; no grey hair among
the; hairlessness of the; long hair of the.

Quiscalus major, proportions of the sexes of, in Florida and Honduras.

Rabbit, white tail of the.

Rabbits, domestic, elongation of the skull in; modification of the
skull in, by the lopping of the ear; danger-signals of; numerical
proportion of the sexes in.

Races, distinctive characters of; or species of man; crossed, fertility
or sterility of; of man, variability of the; of man, resemblance of, in
mental characters; formation of; of man, extinction of; effects of the
crossing of; of man, formation of the; of man, children of the;
beardless, aversion of, to hairs on the face.

Raffles, Sir S., on the banteng.

Rafts, use of.

Rage, manifested by animals.

Raia batis, teeth of.

Raia clavata, female spined on the back; sexual difference in the teeth
of.

Raia maculata, teeth of.

Rails, spur-winged.

Ram, mode of fighting of the; African, mane of an; fat-tailed.

Rameses II., features of.

Ramsay, Mr., on the Australian musk-duck; on the regent-bird; on the
incubation of Menura superba.

Rana esculenta, vocal sacs of.

Rat, common, general dispersion of, a consequence of superior cunning;
supplantation of the native in New Zealand, by the European rat;
common, said to be polygamous; numerical proportion of the sexes in.

Rats, enticed by essential oils.

Rationality of birds.

Rattlesnakes, difference of the sexes in the; rattles as a call.

Raven, vocal organs of the; stealing bright objects; pied, of the Feroe
Islands.

Rays, prehensile organs of male.

Razor-bill, young of the.

Reade, Winwood, suicide among savages in Africa; mulattoes not
prolific; effect of castration of horned sheep; on the Guinea sheep; on
the occurrence of a mane in an African ram; on singing of negroes; on
the negroes’ appreciation of the beauty of their women; on the
admiration of negroes for a black skin; on the idea of beauty among
negroes; on the Jollofs; on the marriage-customs of the negroes.

Reason in animals.

Redstart, American, breeding in immature plumage.

Redstarts, new mates found by.

Reduvidae, stridulation of.

Reed-bunting, head-feathers of the male; attacked by a bullfinch.

Reefs, fishes frequenting.

Reeks, H., retention of horns by breeding deer; cow rejected by a bull;
destruction of piebald rabbits by cats.

Regeneration, partial, of lost parts in man.

Regent bird.

Reindeer, horns of the; battles of; horns of the female; antlers of,
with numerous points; winter change of the; sexual preferences shown
by.

Relationship, terms of.

Religion, deficiency of among certain races; psychical elements of.

Remorse, deficiency of, among savages.

Rengger, on the diseases of Cebus Azarae; on the diversity of the
mental faculties of monkeys; on the Payaguas Indians; on the
inferiority of Europeans to savages in their senses; revenge taken by
monkeys; on maternal affection in a Cebus; on the reasoning powers of
American monkeys; on the use of stones by monkeys for cracking hard
nuts; on the sounds uttered by Cebus Azarae; on the signal-cries of
monkeys; on the polygamous habits of Mycetes caraya; on the voice of
the howling monkeys; on the odour of Cervus campestris; on the beards
of Mycetes caraya and Pithecia Satanas; on the colours of Felis mitis;
on the colours of Cervus paludosus; on sexual differences of colour in
Mycetes; on the colour of the infant Guaranys; on the early maturity of
the female of Cebus Azarae; on the beards of the Guaranys; on the
emotional notes employed by monkeys; on American polygamous monkeys.

Representative species, of birds.

Reproduction, unity of phenomena of, throughout the mammalia; period
of, in birds.

Reproductive system, rudimentary structures in the; accessory parts of.

Reptiles.

Reptiles and birds, alliance of.

Resemblances, small, between man and the apes.

Retrievers, exercise of reasoning faculties by.

Revenge, manifested by animals.

Reversion, perhaps the cause of some bad dispositions.

Rhagium, difference of colour in the sexes of a species of.

Rhamphastos carinatus.

Rhea Darwinii.

Rhinoceros, nakedness of; horns of; horns of, used defensively;
attacking white or grey horses.

Rhynchaea, sexes and young of.

Rhynchaea australis.

Rhynchaea bengalensis.

Rhynchaea capensis.

Rhythm, perception of, by animals.

Richard, M., on rudimentary muscles in man.

Richardson, Sir J., on the pairing of Tetrao umbellus; on Tetrao
urophasianus; on the drumming of grouse; on the dances of Tetrao
phasianellus; on assemblages of grouse; on the battles of male deer; on
the reindeer; on the horns of the musk-ox; on antlers of the reindeer
with numerous points; on the moose; on the Scotch deerhound.

Richter, Jean Paul, on imagination.

Riedel, on profligate female pigeons.

Riley, Mr., on mimicry in butterflies; bird’s disgust at taste of
certain caterpillars.

Ring-ouzel, colours and nidification of the.

Ripa, Father, on the difficulty of distinguishing the races of the
Chinese.

Rivalry, in singing, between male birds.

River-hog, African, tusks and knobs of the.

Rivers, analogy of, to islands.

Roach, brightness of the male during breeding-season.

Robbery, of strangers, considered honourable.

Robertson, Mr., remarks on the development of the horns in the roebuck
and red deer.

Robin, pugnacity of the male; autumn song of the; female singing of
the; attacking other birds with red in their plumage; young of the.

Robinet, on the difference of size of the male and female cocoons of
the silk-moth.

Rodents, uterus in the; absence of secondary sexual characters in;
sexual differences in the colours of.

Roe, winter changes of the.

Rohfs, Dr., Caucasian features in negro; fertility of mixed races in
Sahara; colours of birds in Sahara; ideas of beauty amongst the
Bornuans.

Rolle, F., on the origin of man; on a change in German families settled
in Georgia.

Roller, harsh cry of.

Romans, ancient, gladiatorial exhibitions of the.

Rook, voice of the.

Rossler, Dr., on the resemblance of the lower surface of butterflies to
the bark of trees.

Rostrum, sexual difference in the length of in some weevils.

Royer, Madlle., mammals giving suck.

Rudimentary organs, origin of.

Rudiments, presence of, in languages.

Rudolphi, on the want of connexion between climate and the colour of
the skin.

Ruff, supposed to be polygamous; proportion of the sexes in the;
pugnacity of the; double moult in; duration of dances of; attraction of
the, to bright objects.

Ruminants, male, disappearance of canine teeth in; generally
polygamous; suborbital pits of; sexual differences of colour in.

Rupicola crocea, display of plumage by the male.

Ruppell, on canine teeth in deer and antelopes.

Russia, numerical proportion of male and female births in.

Ruticilla.

Rutimeyer, Prof., on the physiognomy of the apes; on tusks of miocene
boar; on the sexual differences of monkeys.

Rutlandshire, numerical proportion of male and female births in.

Sachs, Prof., on the behaviour of the male and female elements in
fertilisation.

Sacrifices, human.

Sagittal crest, in male apes and Australians.

Sahara, fertility of mixed races in; birds of the; animal inhabitants
of the.

Sailors, growth of, delayed by conditions of life; long-sighted.

Sailors and soldiers, difference in the proportions of.

St. John, Mr., on the attachment of mated birds.

St. Kilda, beards of the inhabitants of.

Salmo eriox, and Salmo umbla, colouring of the male, during the
breeding season.

Salmo lycaodon.

Salmo salar.

Salmon, leaping out of fresh water; male, ready to breed before the
female; proportion of the sexes in; male, pugnacity of the; male,
characters of, during the breeding season; spawning of the; breeding of
immature male.

Salvin, O., inheritance of mutilated feathers; on the Humming-birds; on
the numerical proportion of the sexes in Humming-birds; on Chamaepetes
and Penelope; on Selasphorus platycercus; Pipra deliciosa; on
Chasmorhynchus.

Samoa Islands, beardlessness of the natives of.

Sandhoppers, claspers of male.

Sand-skipper.

Sandwich Islands, variation in the skulls of the natives of the;
decrease of native population; population of; superiority of the nobles
in the.

Sandwich Islanders, lice of.

San-Giuliano, women of.

Santali, recent rapid increase of the; Mr. Hunter on the.

Saphirina, characters of the males of.

Sarkidiornis melanonotus, characters of the young.

Sars, O., on Pontoporeia affinis.

Saturnia carpini, attraction of males by the female.

Saturnia Io, difference of coloration in the sexes of.

Saturniidae, coloration of the.

Savage, Dr., on the fighting of the male gorillas; on the habits of the
gorilla.

Savage and Wyman on the polygamous habits of the gorilla.

Savages, uniformity of, exaggerated; long-sighted; rate of increase
among, usually small; retention of the prehensile power of the feet by;
imitative faculties of; causes of low morality of; tribes of,
supplanting one another; improvements in the arts among; arts of;
fondness of, for rough music; on long-enduring fashions among;
attention paid by, to personal appearance; relation of the sexes among.

Saviotti, Dr., division of malar bone.

Saw-fly, pugnacity of a male.

Saw-flies, proportions of the sexes in.

Saxicola rubicola, young of.

Scalp, motion of the.

Scent-glands in snakes.

Schaaffhausen, Prof., on the development of the posterior molars in
different races of man; on the jaw from La Naulette; on the correlation
between muscularity and prominent supra-orbital ridges; on the mastoid
processes of man; on modifications of the cranial bones; on human
sacrifices; on the probable speedy extermination of the
anthropomorphous apes; on the ancient inhabitants of Europe; on the
effects of use and disuse of parts; on the superciliary ridge in man;
on the absence of race-differences in the infant skull in man; on
ugliness.

Schaum, H., on the elytra of Dytiscus and Hydroporus.

Scherzer and Schwarz, measurements of savages.

Schelver, on dragon-flies.

Schiodte, on the stridulation of Heterocerus.

Schlegel, F. von, on the complexity of the languages of uncivilised
peoples.

Schlegel, Prof., on Tanysiptera.

Schleicher, Prof, on the origin of language.

Schomburgk, Sir R., on the pugnacity of the male musk-duck of Guiana;
on the courtship of Rupicola crocea.

Schoolcraft, Mr., on the difficulty of fashioning stone implements.

Schopenhauer, on importance of courtship to mankind.

Schweinfurth, complexion of negroes.

Sciaena aquila.

Sclater, P.L., on modified secondary wing-feathers in the males of
Pipra; on elongated feathers in nightjars; on the species of
Chasmorhynchus; on the plumage of Pelecanus onocrotalus; on the
plantain-eaters; on the sexes and young of Tadorna variegata; on the
colours of Lemur macaco; on the stripes in asses.

Scolecida, absence of secondary sexual characters in.

Scolopax frenata, tail feathers of;

Scolopax gallinago, drumming of.

Scolopax javensis, tail-feathers of.

Scolopax major, assemblies of.

Scolopax Wilsonii, sound produced by.

Scolytus, stridulation of.

Scoter-duck, black, sexual difference in coloration of the; bright beak
of male.

Scott, Dr., on idiots smelling their food.

Scott, J., on the colour of the beard in man.

Scrope, on the pugnacity of the male salmon; on the battles of stags.

Scudder, S.H., imitation of the stridulation of the Orthoptera; on the
stridulation of the Acridiidae; on a Devonian insect; on stridulation.

Sculpture, expression of the ideal of beauty by.

Sea-anemones, bright colours of.

Sea-bear, polygamous.

Sea-elephant, male, structure of the nose of the; polygamous.

Sea-lion, polygamous.

Seal, bladder-nose.

Seals, their sentinels generally females; evidence furnished by, on
classification; polygamous habits of; battles of male; canine teeth of
male; sexual differences; pairing of; sexual peculiarities of; in the
coloration of; appreciation of music by.

Sea-scorpion, sexual differences in.

Season, changes of colour in birds, in accordance with the; changes of
plumage of birds in relation to.

Seasons, inheritance at corresponding.

Sebituani, African chief, trying to alter a fashion.

Sebright Bantam.

Secondary sexual characters; relations of polygamy to; transmitted
through both sexes; gradation of, in birds.

Sedgwick, W., on hereditary tendency to produce twins.

Seemann, Dr., on the different appreciation of music by different
peoples; on the effects of music.

Seidlitz, on horns of reindeer.

Selasphorus platycercus, acuminate first primary of the male.

Selby, P.J., on the habits of the black and red grouse.

Selection as applied to primeval man.

Selection, double.

Selection, injurious forms of, in civilised nations.

Selection of male by female birds.

Selection, methodical, of Prussian grenadiers.

Selection, sexual, explanation of; influence of, on the colouring of
Lepidoptera.

Selection, sexual and natural, contrasted.

Self-command, habit of, inherited; estimation of.

Self-consciousness, in animals.

Self-preservation, instinct of.

Self-sacrifice, by savages; estimation of.

Semilunar fold.

Semnopithecus, long hair on the heads of species of.

Semnopithecus chrysomelas, sexual differences of colour in.

Semnopithecus comatus, ornamental hair on the head of.

Semnopithecus frontatus, beard etc., of.

Semnopithecus nasica, nose of.

Semnopithecus nemaeus, colouring of.

Semnopithecus rubicundus, ornamental hair on the head of.

Senses, inferiority of Europeans to savages in the.

Sentinels, among animals.

Serpents, instinctively dreaded by apes and monkeys.

Serranus, hermaphroditism in.

Setina, noise produced by.

Sex, inheritance limited by.

Sexes, relative proportions of, in man; proportions of, sometimes
influenced by selection; probable relation of the, in primeval man.

Sexual and natural selection, contrasted.

Sexual characters, effects of the loss of; limitation of.

Sexual characters, secondary; relations of polygamy to; transmitted
through both sexes; gradation of, in birds.

Sexual differences in man.

Sexual selection, explanation of; influence of, on the colouring of
Lepidoptera; objections to; action of, in mankind.

Sexual selection in spiders.

Sexual selection, supplemental note on.

Sexual similarity.

Shaler, Prof., sizes of sexes in whales.

Shame.

Sharks, prehensile organs of male.

Sharpe, Dr., Europeans in the tropics.

Sharpe, R.B., on Tanysiptera sylvia; on Ceryle; on the young male of
Dacelo Gaudi-chaudi.

Shaw, Mr., on the pugnacity of the male salmon.

Shaw, J., on the decorations of birds.

Sheep, danger-signals of; sexual differences in the horns of; horns of;
domestic, sexual differences of, late developed; numerical proportion
of the sexes in; inheritance of horns by one sex; effect of castration;
mode of fighting of; arched foreheads of some.

Sheep, Merino, loss of horns in females of; horns of.

Shells, difference in form of, in male and female Gasteropoda;
beautiful colours and shapes of.

Shield-drake, pairing with a common duck; New Zealand, sexes and young
of.

Shooter, J., on the Kaffirs; on the marriage-customs of the Kaffirs.

Shrew-mice, odour of.

Shrike, Drongo.

Shrikes, characters of young.

Shuckard, W.E., on sexual differences in the wings of Hymenoptera.

Shyness of adorned male birds;

Siagonium, proportions of the sexes in; dimorphism in males of.

Siam, proportion of male and female births in.

Siamese, general beardlessness of the; notions of beauty of the; hairy
family of.

Sidgwick, H., on morality in hypothetical bee community; our actions
not entirely directed by pain and pleasure.

Siebold, C.T., von, on the proportion of sexes in the Apus; on the
auditory apparatus of the stridulent Orthoptera.

Sight, inheritance of long and short.

Signal-cries of monkeys.

Silk-moth, proportion of the sexes in; Ailanthus, Prof. Canestrini, on
the destruction of its larvae by wasps; difference of size of the male
and female cocoons of the; pairing of the.

Simiadae, their origin and divisions.

Similarity, sexual.

Singing of the Cicadae and Fulgoridae; of tree-frogs; of birds, object
of the.

Sirenia, nakedness of.

Sirex juvencus.

Siricidae, difference of the sexes in.

Siskin, pairing with a canary.

Sitana, throat-pouch of the males of.

Size, relative, of the sexes of insects.

Skin, dark colour of, a protection against heat.

Skin, movement of the; nakedness of, in man; colour of the.

Skin and hair, correlation of colour of.

Skull, variation of, in man; cubic contents of, no absolute test of
intellect; Neanderthal, capacity of the; causes of modification of the;
difference of, in form and capacity, in different races of men;
variability of the shape of the; differences of, in the sexes in man;
artificial modification of the shape of.

Skunk, odour emitted by the; white tail of, protective.

Slavery, prevalence of; of women.

Slaves, difference between field-and house-slaves.

Sloth, ornaments of male.

Smell, sense of, in man and animals.

Smith, Adam, on the basis of sympathy.

Smith, Sir A., on the recognition of women by male Cynocephali; on
revenge by a baboon; on an instance of memory in a baboon; on the
retention of their colour by the Dutch in South Africa; on the polygamy
of the South African antelopes; on the polygamy of the lion; on the
proportion of the sexes in Kobus ellipsiprymnus; on Bucephalus
capensis; on South African lizards; on fighting gnus; on the horns of
rhinoceroses; on the fighting of lions; on the colours of the Cape
Eland; on the colours of the gnu; on Hottentot notions of beauty;
disbelief in communistic marriages.

Smith, F., on the Cynipidae and Tenthredinidae; on the relative size of
the sexes of Aculeate Hymenoptera; on the difference between the sexes
of ants and bees; on the stridulation of Trox sabulosus; on the
stridulation of Mononychus pseudacori.

Smynthurus luteus, courtship of.

Snakes, sexual differences of; mental powers of; male, ardency of.

“Snarling muscles.”

Snipe, drumming of the; coloration of the.

Snipe, painted, sexes and young of.

Snipe, solitary, assemblies of.

Snipes, arrival of male before the female; pugnacity of male; double
moult in.

Snow-goose, whiteness of the.

Sociability, the sense of duty connected with; impulse to, in animals;
manifestations of, in man; instinct of, in animals.

Social animals, affection of, for each other; defence of, by the males.

Sociality, probable, of primeval men; influence of, on the development
of the intellectual faculties; origin of, in man.

Soldiers, American, measurements of.

Soldiers and sailors, difference in the proportions of.

Solenostoma, bright colours and marsupial sac of the females of.

Song, of male birds appreciated by their females; want of, in brilliant
plumaged birds; of birds.

Sorex, odour of.

Sounds, admired alike by man and animals; produced by fishes; produced
by male frogs and toads; instrumentally produced by birds.

Spain, decadence of.

Sparassus smaragdulus, difference of colour in the sexes of.

Sparrow, pugnacity of the male; acquisition of the Linnet’s song by a;
coloration of the; immature plumage of the.

Sparrow, white-crowned, young of the.

Sparrows, house-and tree-.

Sparrows, new mates found by.

Sparrows, sexes and young of; learning to sing.

Spathura Underwoodi.

Spawning of fishes.

Spear, used before dispersion of man.

Species, causes of the advancement of; distinctive characters of; or
races of man; sterility and fertility of, when crossed; supposed, of
man; gradation of; difficulty of defining; representative, of birds; of
birds, comparative differences between the sexes of distinct.

Spectrum femoratum, difference of colour in the sexes of.

Speech, connection between the brain and the faculty of; connection of
intonation with music.

Spel, of the black-cock.

Spencer, Herbert, on the influence of food on the size of the jaws; on
the dawn of intelligence; on the origin of the belief in spiritual
agencies; on the origin of the moral sense; on music.

Spengel, disagrees with explanation of man’s hairlessness.

Sperm-whales, battles of male.

Sphingidae, coloration of the.

Sphinx, Humming-bird.

Sphinx, Mr. Bates on the caterpillar of a.

Sphinx moth, musky odour of.

Spiders, parental feeling in; male, more active than female; proportion
of the sexes in; secondary sexual characters of; courtship of male;
attracted by music; male, small size of.

Spilosoma menthastri, rejected by turkeys.

Spine, alteration of, to suit the erect attitude of man.

Spirits, fondness of monkeys for.

Spiritual agencies, belief in, almost universal.

Spiza cyanea and ciris.

Spoonbill, Chinese, change of plumage in.

Spots, retained throughout groups of birds; disappearance of, in adult
mammals.

Sprengel, C.K., on the sexuality of plants.

Springboc, horns of the.

Sproat, Mr., on the extinction of savages in Vancouver Island; on the
eradication of facial hair by the natives of Vancouver Island; on the
eradication of the beard by the Indians of Vancouver Island.

Spurs, occurrence of, in female fowls; development of, in various
species of Phasianidae; of Gallinaceous birds; development of, in
female Gallinaceae.

Squilla, different colours of the sexes of a species of.

Squirrels, battles of male; African, sexual differences in the
colouring of; black.

Stag, long hairs of the throat of; horns of the; battles of; horns of
the, with numerous branches; bellowing of the; crest of the.

Stag-beetle, numerical proportion of sexes of; use of jaws; large size
of male; weapons of the male.

Stainton, H.T., on the numerical proportion of the sexes in the smaller
moths; habits of Elachista rufocinerea; on the coloration of moths; on
the rejection of Spilosoma menthastri by turkeys; on the sexes of
Agrotis exclamationis.

Staley, Bishop, mortality of infant Maories.

Stallion, mane of the.

Stallions, two, attacking a third; fighting; small canine teeth of.

Stansbury, Captain, observations on pelicans.

Staphylinidae, hornlike processes in male.

Starfishes, parental feeling in; bright colours of some.

Stark, Dr., on the death-rate in towns and rural districts; on the
influence of marriage on mortality; on the higher mortality of males in
Scotland.

Starling, American field-, pugnacity of male.

Starling, red-winged, selection of a mate by the female.

Starlings, three, frequenting the same nest; new mates found by.

Statues, Greek, Egyptian, Assyrian, etc., contrasted.

Stature, dependence of, upon local influences.

Staudinger, Dr., on breeding Lepidoptera; his list of Lepidoptera.

Staunton, Sir G., hatred of indecency a modern virtue.

Stealing of bright objects by birds.

Stebbing, T.R., on the nakedness of the human body.

Stemmatopus.

Stendhal, see Bombet.

Stenobothrus pratorum, stridulation.

Stephen, Mr. L., on the difference in the minds of men and animals; on
general concepts in animals; distinction between material and formal
morality.

Sterility, general, of sole daughters; when crossed, a distinctive
character of species; under changed conditions.

Sterna, seasonal change of plumage in.

Stickleback, polygamous; male, courtship of the; male, brilliant
colouring of, during the breeding season; nidification of the.

Sticks used as implements and weapons by monkeys.

Sting in bees.

Stokes, Captain, on the habits of the great bower-bird.

Stoliczka, Dr., on colours in snakes.

Stoliczka, on the pre-anal pores of lizards.

Stonechat, young of the.

Stone implements, difficulty of making; as traces of extinct tribes.

Stones, used by monkeys for breaking hard fruits and as missiles; piles
of.

Stork, black, sexual differences in the bronchi of the; red beak of
the.

Storks, sexual difference in the colour of the eyes of.

Strange, Mr., on the satin bowerbird.

Strepsiceros kudu, horns of; markings of.

Stretch, Mr., on the numerical proportion in the sexes of chickens.

Stridulation, by males of Theridion; of Hemiptera; of the Orthoptera
and Homoptera discussed; of beetles.

Stripes, retained throughout groups of birds; disappearance of, in
adult mammals.

Strix flammea.

Structure, existence of unserviceable modifications of.

Struggle for existence, in man.

Struthers, Dr., on the occurrence of the supra-condyloid foramen in the
humerus of man.

Sturnella ludoviciana, pugnacity of the male.

Sturnus vulgaris.

Sub-species.

Suffering, in strangers, indifference of savages to.

Suicide, formerly not regarded as a crime; rarely practised among the
lowest savages.

Suidae, stripes of the young.

Sulivan, Sir B.J., on speaking of parrots; on two stallions attacking a
third.

Sumatra, compression of the nose by the Malays of.

Sumner, Archb., man alone capable of progressive improvement.

Sun-birds, nidification of.

Superciliary ridge in man.

Supernumerary digits, more frequent in men than in women; inheritance
of; early development of.

Superstitions, prevalence of.

Superstitious customs.

Supra-condyloid foramen in the early progenitors of man.

Suspicion, prevalence of, among animals.

Swallow-tail butterfly.

Swallows deserting their young.

Swan, black, wild, trachea of the; white, young of; red beak of the;
black-necked.

Swans, young.

Swaysland, Mr., on the arrival of migratory birds.

Swifts, migration of.

Swinhoe, R., on the common rat in Formosa and China; behaviour of
lizards when caught; on the sounds produced by the male hoopoe; on
Dicrurus macrocercus and the spoonbill; on the young of Ardeola; on the
habits of Turnix; on the habits of Rhynchaea bengalensis; on Orioles
breeding in immature plumage.

Sylvia atricapilla, young of.

Sylvia cinerea, aerial love-dance of the male.

Sympathy, among animals; its supposed basis.

Sympathies, gradual widening of.

Syngnathous fishes, abdominal pouch in male.

Sypheotides auritus, acuminated primaries of the male; ear-tufts of.

Tabanidae, habits of.

Tadorna variegata, sexes and young of.

Tadorna vulpanser.

Tahitians, compression of the nose by the.

Tail, rudimentary, occurrence of, in man; convoluted body in the
extremity of the; absence of, in man and the higher apes; variability
of, in species of Macacus and in baboons; presence of, in the early
progenitors of man; length of, in pheasants; difference of length of
the, in the two sexes of birds.

Tait, Lawson, on the effects of natural selection on civilised nations.

Tanager, scarlet, variation in the male.

Tanagra aestiva, age of mature plumage in.

Tanagra rubra, young of.

Tanais, absence of mouth in the males of some species of; relations of
the sexes in; dimorphic males of a species of.

Tankerville, Earl, on the battles of wild bulls.

Tanysiptera, races of, determined from adult males.

Tanysiptera sylvia, long tail-feathers of.

Taphroderes distortus, enlarged left mandible of the male.

Tapirs, longitudinal stripes of young.

Tarsi, dilatation of front, in male beetles.

Tarsius.

Tasmania, half-castes killed by the natives of.

Tasmanians, extinction of.

Taste, in the Quadrumana.

Tattooing, universality of.

Taylor, G., on Quiscalus major.

Taylor, Rev. R., on tattooing in New Zealand.

Tea, fondness of monkeys for.

Teal, constancy of.

Tear-sacs, of Ruminants.

Teebay, Mr., on changes of plumage in spangled Hamburg fowls.

Teeth, rudimentary incisor, in Ruminants; posterior molar, in man;
wisdom; diversity of; canine, in the early progenitors of man; canine,
of male mammals; in man, reduced by correlation; staining of the;
front, knocked out or filed by some savages.

Tegetmeier, Mr., on the transmission of colours in pigeons by one sex
alone; numerical proportion of male and female births in dogs; on the
abundance of male pigeons; on the wattles of game-cocks; on the
courtship of fowls; on the loves of pigeons; on dyed pigeons; blue
dragon pigeons.

Tembeta, S. American ornament.

Temper, in dogs and horses, inherited.

Tench, proportions of the sexes in the; brightness of male, during
breeding season.

Tenebrionidae, stridulation of.

Tennent, Sir J.E., on the tusks of the Ceylon Elephant; on the frequent
absence of beard in the natives of Ceylon; on the Chinese opinion of
the aspect of the Cingalese.

Tennyson, A., on the control of thought.

Tenthredinidae, proportions of the sexes in; fighting habits of male;
difference of the sexes in.

Tephrodornis, young of.

Terai, in India.

Termites, habits of.

Terns, white; and black.

Terns, seasonal change of plumage in.

Terror, common action of, upon the lower animals and man.

Testudo elegans.

Testudo nigra.

Tetrao cupido, battles of; sexual difference in the vocal organs of.

Tetrao phasianellus, dances of; duration of dances of.

Tetrao scoticus.

Tetrao tetrix, pugnacity of the male.

Tetrao umbellus, pairing of; battles of; drumming of the male.

Tetrao urogalloides, dances of.

Tetrao urogallus, pugnacity of the male.

Tetrao urophasianus, inflation of the oesophagus in the male.

Thamnobia, young of.

Thecla, sexual differences of colouring in species of.

Thecla rubi, protective colouring of.

Thecophora fovea.

Theognis, selection in mankind.

Theridion, stridulation of males of.

Theridion lineatum.

Thomisus citreus, and Thomisus floricolens, difference of colour in the
sexes of.

Thompson, J.H., on the battles of sperm-whales.

Thompson, W., on the colouring of the male char during the breeding
season; on the pugnacity of the males of Gallinula chloropus; on the
finding of new mates by magpies; on the finding of new mates by
Peregrine falcons.

Thorax, processes of, in male beetles.

Thorell, T., on the proportion of sexes in spiders.

Thornback, difference in the teeth of the two sexes of the.

Thoughts, control of.

Thrush, pairing with a blackbird; colours and nidification of the.

Thrushes, characters of young.

Thug, remorse of a.

Thumb, absence of, in Ateles and Hylobates.

Thury, M., on the numerical proportion of male and female births among
the Jews.

Thylacinus, possession of the marsupial sac by the male.

Thysanura.

Tibia, dilated, of the male Crabro cribrarius.

Tibia and femur, proportions of, in the Aymara Indians.

Tierra del Fuego, marriage-customs of.

Tiger, colours and markings of the.

Tigers, depopulation of districts by, in India.

Tillus elongatus, difference of colour in the sexes of.

Timidity, variability of, in the same species.

Tinca vulgaris.

Tipula, pugnacity of male.

Tits, sexual difference of colour in.

Toads, male, treatment of ova by some; male, ready to breed before the
female.

Todas, infanticide and proportion of sexes; practice polyandry; choice
of husbands amongst.

Toe, great, condition of, in the human embryo.

Tomicus villosus, proportion of the sexes in.

Tomtit, blue, sexual difference of colour in the.

Tonga Islands, beardlessness of the natives of.

Tooke, Horne, on language.

Tools, flint; used by monkeys; use of.

Topknots in birds.

Tortoise, voice of the male.

Tortures, submitted to by American savages.

Totanus, double moult in.

Toucans, colours and nidification of the; beaks and ceres of the.

Towns, residence in, a cause of diminished stature.

Toynbee, J., on the external shell of the ear in man.

Trachea, convoluted and imbedded in the sternum, in some birds;
structure of the, in Rhynchaea.

Trades, affecting the form of the skull.

Tragelaphus, sexual differences of colour in.

Tragelaphus scriptus, dorsal crest of; markings of.

Tragopan, swelling of the wattles of the male, during courtship;
display of plumage by the male; marking of the sexes of the.

Tragops dispar, sexual difference in the colour of.

Training, effect of, on the mental difference between the sexes of man.

Transfer of male characters to female birds.

Transmission, equal, of ornamental characters, to both sexes in
mammals.

Traps, avoidance of, by animals; use of.

Treachery, to comrades, avoidance of, by savages.

Tremex columbae.

Tribes, extinct; extinction of.

Trichius, difference of colour in the sexes of a species of.

Trigla.

Trigonocephalus, noise made by tail of.

Trimen, R., on the proportion of the sexes in South African
butterflies; on the attraction of males by the female Lasiocampa
quercus; on Pneumora; on difference of colour in the sexes of beetles;
on moths brilliantly coloured beneath; on mimicry in butterflies; on
Gynanisa Isis, and on the ocellated spots of Lepidoptera; on Cyllo
Leda.

Tringa, sexes and young of.

Tringa cornuta.

Triphaena, coloration of the species of.

Tristram, H.B., on unhealthy districts in North Africa; on the habits
of the chaffinch in Palestine; on the birds of the Sahara; on the
animals inhabiting the Sahara.

Triton cristatus.

Triton palmipes.

Triton punctatus.

Troglodyte skulls, greater than those of modern Frenchmen.

Troglodytes vulgaris.

Trogons, colours and nidification of the.

Tropic-birds, white only when mature.

Tropics, freshwater fishes of the.

Trout, proportion of the sexes in; male, pugnacity of the.

Trox sabulosus, stridulation of.

Truth, not rare between members of the same tribe; more highly
appreciated by certain tribes.

Tulloch, Major, on the immunity of the negro from certain fevers.

Tumbler, almond, change of plumage in the.

Turdus merula, young of.

Turdus migratorius.

Turdus musicus.

Turdus polyglottus, young of.

Turdus torquatus.

Turkey, wild, pugnacity of young male; wild, notes of the; swelling of
the wattles of the male; variety of, with a top-knot; recognition of a
dog by a; male, wild, acceptable to domesticated females; wild, first
advances made by older females; wild, breast-tuft of bristles of the.

Turkey-cock, scraping of the wings of, upon the ground; wild, display
of plumage by; fighting habits of.

Turner, Prof. W., on muscular fasciculi in man referable to the
panniculus carnosus; on the occurrence of the supra-condyloid foramen
in the human humerus; on muscles attached to the coccyx in man; on the
filum terminale in man; on the variability of the muscles; on abnormal
conditions of the human uterus; on the development of the mammary
glands; on male fishes hatching ova in their mouths; on the external
perpendicular fissure of the brain; on the bridging convolutions in the
brain of a chimpanzee.

Turnix, sexes of some species of.

Turtle-dove, cooing of the.

Tuttle, H., on the number of species of man.

Tylor, E.B., on emotional cries, gestures, etc., of man; on the origin
of the belief in spiritual agencies; remorse for violation of tribal
usage in marrying; on the primitive barbarism of civilised nations; on
the origin of counting; inventions of savages; on resemblances, of the
mental characters in different races of man.

Type of structure, prevalence of.

Typhaeus, stridulating organs of; stridulation of.

Twins, tendency to produce, hereditary.

Twite, proportion of the sexes in.

Ugliness, said to consist in an approach to the lower animals.

Umbrella-bird.

Umbrina, sounds produced by.

United States, rate of increase in; influence of natural selection on
the progress of; change undergone by Europeans in the.

Upupa epops, sounds produced by the male.

Uraniidae, coloration of the.

Uria troile, variety of (=U. lacrymans).

Urodela.

Urosticte Benjamini, sexual differences in.

Use and disuse of parts, effects of; influence of, on the races of man.

Uterus, reversion in the; more or less divided, in the human subject;
double, in the early progenitors of man.

Vaccination, influence of.

Vancouver Island, Mr. Sproat on the savages of; natives of, eradication
of facial hair by the.

Vanellus cristatus, wing tubercles of the male.

Vanessae, resemblance of lower surface of, to bark of trees.

Variability, causes of; in man, analogous to that in the lower animals;
of the races of man; greater in men than in women; period of, relation
of the, to sexual selection; of birds; of secondary sexual characters
in man.

Variation, laws of; correlated; in man; analogous; analogous, in
plumage of birds.

Variations, spontaneous.

Varieties, absence of, between two species, evidence of their
distinctness.

Variety, an object in nature.

Variola, communicable between man and the lower animals.

Vaureal, human bones from.

Veddahs, monogamous habits of.

Veitch, Mr., on the aversion of Japanese ladies to whiskers.

Vengeance, instinct of.

Venus Erycina, priestesses of.

Vermes.

Vermiform appendage.

Verreaux, M., on the attraction of numerous males by the female of an
Australian Bombyx.

Vertebrae, caudal, number of in macaques and baboons; of monkeys,
partly imbedded in the body.

Vertebrata, common origin of the; most ancient progenitors of; origin
of the voice in air-breathing.

Vesicula prostatica, the homologue of the uterus.

Vibrissae, represented by long hairs in the eyebrows.

Vidua.

Vidua axillaris.

Villerme, M., on the influence of plenty upon stature.

Vinson, Aug., courtship of male spider; on the male of Epeira nigra.

Viper, difference of the sexes in the.

Virey, on the number of species of man.

Virtues, originally social only; gradual appreciation of.

Viscera, variability of, in man.

Vlacovich, Prof., on the ischio-pubic muscle.

Vocal music of birds.

Vocal organs of man; of birds; of frogs; of the Insessores; difference
of, in the sexes of birds; primarily used in relation to the
propagation of the species.

Vogt, Karl, on the origin of species; on the origin of man; on the
semilunar fold in man; on microcephalous idiots; on the imitative
faculties of microcephalous idiots; on skulls from Brazilian caves; on
the evolution of the races of man; on the formation of the skull in
women; on the Ainos and negroes; on the increased cranial difference of
the sexes in man with race development; on the obliquity of the eye in
the Chinese and Japanese.

Voice in mammals; in monkeys and man; in man; origin of, in
air-breathing vertebrates.

Von Baer, see Baer.

Vulpian, Prof., on the resemblance between the brains of man and the
higher apes.

Vultures, selection of a mate by the female; colours of.

Waders, young of.

Wagner, R., on the occurrence of the diastema in a Kaffir skull; on the
bronchi of the black stork.

Wagtail, Ray’s, arrival of the male before the female.

Wagtails, Indian, young of.

Waist, proportions of, in soldiers and sailors.

Waitz, Prof., on the number of species of man; on the liability of
negroes to tropical fevers after residence in a cold climate; on the
colour of Australian infants; on the beardlessness of negroes; on the
fondness of mankind for ornaments; on negro ideas of female beauty; on
Javan and Cochin Chinese ideas of beauty.

Waldeyer, M., on the hermaphroditism of the vertebrate embryo.

Wales, North, numerical proportion of male and female births in.

Walkenaer and Gervais, spider attracted by music; on the Myriapoda.

Walker, Alex., on the large size of the hands of labourers’ children.

Walker, F., on sexual differences in the diptera.

Wallace, Dr. A., on the prehensile use of the tarsi in male moths; on
the rearing of the Ailanthus silkmoth; on breeding Lepidoptera;
proportion of sexes of Bombyx cynthia, B. yamamai, and B. Pernyi reared
by; on the development of Bombyx cynthia and B. yamamai; on the pairing
of Bombyx cynthia.

Wallace, A.R., on the origin of man; on the power of imitation in man;
on the use of missiles by the orang; on the varying appreciation of
truth among different tribes; on the limits of natural selection in
man; on the occurrence of remorse among savages; on the effects of
natural selection on civilised nations; on the use of the convergence
of the hair at the elbow in the orang; on the contrast in the
characters of the Malays and Papuans; on the line of separation between
the Papuans and Malays; on the birds of paradise; on the sexes of
Ornithoptera Croesus; on protective resemblances; on the relative sizes
of the sexes of insects; on Elaphomyia; on the pugnacity of the males
of Leptorhynchus angustatus; on sounds produced by Euchirus longimanus;
on the colours of Diadema; on Kallima; on the protective colouring of
moths; on bright coloration as protective in butterflies; on
variability in the Papilionidae; on male and female butterflies,
inhabiting different stations; on the protective nature of the dull
colouring of female butterflies; on mimicry in butterflies; on the
bright colours of caterpillars; on brightly-coloured fishes frequenting
reefs; on the coral snakes; on Paradisea apoda; on the display of
plumage by male birds of paradise; on assemblies of birds of paradise;
on the instability of the ocellated spots in Hipparchia Janira; on
sexually limited inheritance; on the sexual coloration of birds; on the
relation between the colours and nidification of birds; on the
coloration of the Cotingidae; on the females of Paradisea apoda and
papuana; on the incubation of the cassowary; on protective coloration
in birds; on the Babirusa; on the markings of the tiger; on the beards
of the Papuans; on the hair of the Papuans; on the distribution of hair
on the human body.

Walrus, development of the nictitating membrane in the; tusks of the;
use of the tusks by the.

Walsh, B.D., on the proportion of the sexes in Papilio Turnus; on the
Cynipidae and Cecidomyidae; on the jaws of Ammophila; on Corydalis
cornutus; on the prehensile organs of male insects; on the antennae of
Penthe; on the caudal appendages of dragonflies; on Platyphyllum
concavum; on the sexes of the Ephemeridae; on the difference of colour
in the sexes of Spectrum femoratum; on sexes of dragon-flies; on the
difference of the sexes in the Ichneumonidae; on the sexes of Orsodacna
atra; on the variation of the horns of the male Phanaeas carnifex; on
the coloration of the species of Anthocharis.

Wapiti, battles of; traces of horns in the female; attacking a man;
crest of the male; sexual difference in the colour of the.

Warbler, hedge-; young of the.

Warblers, superb, nidification of.

Wariness, acquired by animals.

Warington, R., on the habits of the stickleback; on the brilliant
colours of the male stickleback during the breeding season.

Wart-hog, tusks and pads of the.

Watchmakers, short-sighted.

Waterhen.

Waterhouse, C.O., on blind beetles; on difference of colour in the
sexes of beetles.

Waterhouse, G.R., on the voice of Hylobates agilis.

Water-ouzel, autumn song of the.

Waterton, C., on the Bell-bird; on the pairing of a Canada goose with a
Bernicle gander; on hares fighting.

Wattles, disadvantageous to male birds in fighting.

Weale, J., Mansel, on a South African caterpillar.

Wealth, influence of.

Weapons, used by man; employed by monkeys; offensive, of males; of
mammals.

Weaver-bird.

Weaver-birds, rattling of the wings of; assemblies of.

Webb, Dr., on the wisdom teeth.

Wedderburn, Mr., assembly of black game.

Wedgwood, Hensleigh, on the origin of language.

Weevils, sexual difference in length of snout in some.

Weir, Harrison, on the numerical proportion of the sexes in pigs and
rabbits; on the sexes of young pigeons; on the songs of birds; on
pigeons; on the dislike of blue pigeons to other coloured varieties; on
the desertion of their mates by female pigeons.

Weir, J. Jenner, on the nightingale and blackcap; on the relative
sexual maturity of male birds; on female pigeons deserting a feeble
mate; on three starlings frequenting the same nest; on the proportion
of the sexes in Machetes pugnax and other birds; on the coloration of
the Triphaenae; on the rejection of certain caterpillars by birds; on
sexual differences of the beak in the goldfinch; on a piping bullfinch;
on the object of the nightingale’s song; on song-birds; on the
pugnacity of male fine-plumaged birds; on the courtship of birds; on
the finding of new mates by Peregrine falcons and Kestrels; on the
bullfinch and starling; on the cause of birds remaining unpaired; on
starlings and parrots living in triplets; on recognition of colour by
birds; on hybrid birds; on the selection of a greenfinch by a female
canary; on a case of rivalry of female bullfinches; on the maturity of
the golden pheasant.

Weisbach, Dr., measurement of men of different races; on the greater
variability of men than of women; on the relative proportions of the
body in the sexes of different races of man.

Weismann, Prof., colours of Lycaenae.

Welcker, M., on brachycephaly and dolichocephaly; on sexual differences
in the skull in man.

Wells, Dr., on the immunity of coloured races from certain poisons.

Westring, on the stridulation of males of Theridion; on the
stridulation of Reduvius personatus; on the stridulation of beetles; on
the stridulation of Omaloplia brunnea; on the stridulating organs of
the Coleoptera; on sounds produced by Cychrus.

Westropp, H.M., on reason in a bear; on the prevalence of certain forms
of ornamentation.

Westwood, J.O., on the classification of the Hymenoptera; on the
Culicidae and Tabanidae; on a Hymenopterous parasite with a sedentary
male; on the proportions of the sexes in Lucanus cervus and Siagonium;
on the absence of ocelli in female Mutillidae; on the jaws of
Ammophila; on the copulation of insects of distinct species; on the
male of Crabro cribrarius; on the pugnacity of the male Tipulae; on the
stridulation of Pirates stridulus; on the Cicadae; on the stridulating
organs of the cricket; on Ephippiger vitium; on Pneumora; on the
pugnacity of the Mantides; on Platyblemnus; on difference in the sexes
of the Agrionidae; on the pugnacity of the males of a species of
Tenthredinae; on the pugnacity of the male stag-beetle; on Bledius
taurus and Siagonium; on lamellicorn beetles; on the coloration of
Lithosia.

Whale, Sperm-, battles of male.

Whales, nakedness of.

Whately, Arch., language not peculiar to man; on the primitive
civilisation of man.

Whewell, Prof., on maternal affection.

Whiskers, in monkeys.

White, F.B., noise produced by Hylophila.

White, Gilbert, on the proportion of the sexes in the partridge; on the
house-cricket; on the object of the song of birds; on the finding of
new mates by white owls; on spring coveys of male partridges.

Whiteness, a sexual ornament in some birds; of mammals inhabiting snowy
countries.

White-throat, aerial love-dance of the male.

Whitney, Prof., on the development of language; language not
indispensable for thought.

Widgeon, pairing with a pintail duck.

Widow-bird, polygamous; breeding plumage of the male; female, rejecting
the unadorned male.

Widows and widowers, mortality of.

Wilckens, Dr., on the modification of domestic animals in mountainous
regions; on a numerical relation between the hairs and excretory pores
in sheep.

Wilder, Dr. Burt, on the greater frequency of supernumerary digits in
men than in women.

Williams, on the marriage-customs of the Fijians.

Wilson, Dr., on the conical heads of the natives of North-Western
Africa; on the Fijians; on the persistence of the fashion of
compressing the skull.

Wing-spurs.

Wings, differences of, in the two sexes of butterflies and Hymenoptera;
play of, in the courtship of birds.

Winter, change of colour of mammals in.

Witchcraft.

Wives, traces of the forcible capture of.

Wolf, winter change of the.

Wolff, on the variability of the viscera in man.

Wollaston, T.V., on Eurygnathus; on musical Curculionidae; on the
stridulation of Acalles.

Wolves, learning to bark from dogs; hunting in packs.

Wolves, black.

Wombat, black varieties of the.

Women, distinguished from men by male monkeys; preponderance of, in
numbers; selection of, for beauty; effects of selection of, in
accordance with different standards of beauty; practice of capturing;
early betrothals and slavery of; freedom of selection by, in savage
tribes.

Wonder, manifestations of, by animals.

Wonfor, Mr., on sexual peculiarities, in the wings of butterflies.

Wood, J., on muscular variations in man; on the greater variability of
the muscles in men than in women.

Wood, T.W., on the colouring of the orange-tip butterfly; on the habits
of the Saturniidae; quarrels of chamaeleons; on the habits of Menura
Alberti; on Tetrao cupido; on the display of plumage by male pheasants;
on the ocellated spots of the Argus pheasant; on fighting of Menura
superba; on the habits of the female cassowary.

Woodcock, coloration of the.

Woodpecker, selection of a mate by the female.

Woodpeckers, tapping of; colours and nidification of the; characters of
young.

Woolner, Mr., observations on the ear in man.

Wormald, Mr., on the coloration of Hypopyra.

Wounds, healing of.

Wren, young of the.

Wright, C.A., on the young of Orocetes and Petrocincla.

Wright, Chauncey, great brain-power requisite for language; on
correlative acquisition; on the enlargement of the brain in man.

Wright, Mr., on the Scotch deer-hound; on sexual preference in dogs; on
the rejection of a horse by a mare.

Wright, W. von, on the protective plumage of the Ptarmigan.

Writing.

Wyman, Prof., on the prolongation of the coccyx in the human embryo; on
the condition of the great toe in the human embryo; on the occurrence
of the supra-condyloid foramen in the humerus of man; on variation in
the skulls of the natives of the Sandwich Islands; on the hatching of
the eggs in the mouths and branchial cavities of male fishes.

Xenarchus, on the Cicadae.

Xenophon, selection in mankind advocated by.

Xenorhynchus, sexual difference in the colour of the eyes in.

Xiphophorus Hellerii, peculiar anal fin of the male.

Xylocopa, difference of the sexes in.

Yarrel, W., on the habits of the Cyprinidae; on Raia clavata; on the
characters of the male salmon during the breeding season; on the
characters of the rays; on the gemmeous dragonet; on colours of salmon;
on the spawning of the salmon; on the incubation of the Lophobranchii;
on rivalry in song-birds; on the trachea of the swan; on the moulting
of the Anatidae; on the young of the waders.

Yellow fever, immunity of negroes and mulattoes from.

Youatt, Mr., on the development of the horns in cattle.

Yura-caras, their notions of beauty.

Zebra, rejection of an ass by a female; stripes of the.

Zebus, humps of.

Zigzags, prevalence of, as ornaments.

Zincke, Mr., on European emigration to America.

Zootoca vivipara, sexual difference in the colour of.

Zouteveen, Dr., polydactylism; proportion of sexes at Cape of Good
Hope; spiders attracted by music; on sounds produced by fish.

Zygaenidae, coloration of the.

THE END.