IN RELATION TO SEX***


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

by

CHARLES DARWIN, M.A., F.R.S., &c.

IN TWO VOLUMES.—VOL. II.

With Illustrations.







London:
John Murray, Albemarle Street.
1871.

[The right of Translation is reserved.]


ERRATA.

VOL. I.

  Page                line         _For_                 _read_

   27                  13           kaolo               koala.
   31                   6           prostratica         prostatica.
   59, _note_[86]       2           speech              species.
   74, _note_[107]      —           Browne              Brown.
  118, _note_[167]      —           Vol. I.             Vol. II.
  128, _note_[184]      4          _Before_ vol. xiv.  _insert_ ‘Proc.
                                                          Royal Soc.
  208                   2           prostratica.        prostatica.
  322                   5           Actineæ             Actiniæ.
  324                  30           land-shells         land-snails.
  330                  16           figs. 4 and 5       figs. 4, 5, and 6.
  334                  17           Birgos              Birgus.
  339                   8           attractions         attentions.
  341                   3           dragon-flys         dragon-flies.
  378                  17           Typhæus             Typhœus.
  384                  31           tesselatum          tessellatum.
  397                   9           Hypopira            Hypopyra.
  405                  21           Acrœidæ             Acræidæ.

  VOL. II.

   32                  30           chamelion           chameleon.
  115                   4           mail                male.
  178                  23           Chloehaga           Chloephaga.
  227, _note_[281]      —           Ramphaston          Ramphastos.
  240, _note_[289]      —           Mr. H. Brown        Mr. R. Brown.
   —   _note_[290]      2           elephus             elaphas.
  242                  14           walruses            narwhals.
  339                  27           Durfur              Darfur.


CONTENTS.


PART II.

SEXUAL SELECTION—_continued_.


  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                   Page 1-37


  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                 38-98


  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       99-153


  CHAPTER XV.

  BIRDS—_continued_.

  Discussion why the males alone of some species, and both sexes
  of other species, 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              154-182


  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             183-238


  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                              239-273


  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                           274-315


  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                                                   316-354


  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           355-384


  CHAPTER XXI.

  GENERAL 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           385-405


  INDEX                                                             406


POSTSCRIPT.

Vol. I. pp. 297-299.—I have fallen into a serious and unfortunate
error, in relation to the sexual differences of animals, in attempting
to explain what seemed to me a singular coincidence in the late period
of life at which the necessary variations have arisen in many cases, and
the late period at which sexual selection acts. The explanation given is
wholly erroneous, as I have discovered by working out an illustration in
figures. Moreover, the supposed coincidence of period is far from
general, and is not remarkable; for, as I have elsewhere attempted to
show, variations arising early in life have often been accumulated
through sexual selection, being then commonly transmitted to both sexes.
On the other hand, variations arising late in life cannot fail to
coincide approximately in period with that of the process of sexual
selection. Allusions to these erroneous views reappear in Vol. II. pp.
161 and 237.




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, namely Fishes. The males of
Plagiostomous fishes (sharks, rays) and of Chimæroid fishes are provided
with claspers which serve to retain the female, like the various
structures possessed by so 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 the other parts of their bodies smooth. They are only temporarily
developed during the breeding-season; and Dr. Günther 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]

Owing to the element which fishes inhabit, little is known about their
courtship, and not much about their battles. 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.”[2] The
males are said to be polygamists;[3] 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,[4] “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. Günther. Mr. Shaw saw a violent
contest between two male salmons 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.”[5]
The keeper of the Stormontfield breeding-ponds visited, as Mr. Buist
informs me, in June, 1868, 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.

[Illustration: Fig. 26. Head of male of 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, under the kind
superintendence of Dr. Günther, from specimens in the British Museum.)]

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.”[6] (Figs. 26 and 27.) 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[7] believes, is permanent and best marked in the older males which
have previously ascended the rivers. In these old males the jaws become
developed into immense hook-like projections, and the teeth grow into
regular fangs, often more than half an inch in length. With the European
salmon, according to Mr. Lloyd,[8] 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.

[Illustration: Fig. 27. Head of female salmon.]

The salmon is not the only fish in which the teeth differ in the two
sexes. 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, forming 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_,
possess, when adult, 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 completely adult; the males
acquiring them at an earlier age than the females. We shall hereafter
meet with analogous cases with certain birds, in which the male acquires
the plumage common to both adult sexes, at a somewhat earlier age than
the female. With other species of rays the males even when old never
possess sharp teeth, and consequently both sexes when adult are provided
with broad, flat teeth like those of the young, and of the mature
females of the above-mentioned species.[9] As the rays are bold, strong
and voracious fishes, 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[10] maintains that with almost all
fishes the female is larger than the male; and Dr. Günther 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 the
female. As with many kinds of fishes the males habitually fight
together; it is surprising that they have not generally become through
the effects of sexual selection larger and stronger than the females.
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.

[Illustration: Fig. 28. Callionymus lyra. Upper figure, male; lower
figure, female.]

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 great
kindness of Dr. Günther. 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 freshly taken 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 Linnæus 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;[11] but the most
striking difference is the extraordinary elongation in the male (fig.
28) of the dorsal fin. The young males resemble in structure and colour
the adult females. Throughout the genus Callionymus,[12] the male is
generally much more brightly spotted than the female, and in several
species, not only the dorsal, but the anal fin of the male is much
elongated.

The male of the _Cottus scorpius_, or sea-scorpion, is more slender and
smaller than the female. There is also a great difference in colour
between them. It is difficult, as Mr. Lloyd[13] 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.

In the very distinct family of the Cyprinodontidæ—inhabitants of the
fresh waters of foreign lands—the sexes sometimes differ much in
various characters. In the male of the _Mollienesia petenensis_,[14] 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. 29), the inferior margin
of the anal fin is developed into a long filament, which is striped, as
I hear from Dr. Günther, 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
in colour and structure the adult females. Sexual differences such as
these may be strictly compared with those which are so frequent with
gallinaceous birds.[15]

[Illustration: Fig. 29. Xiphophorus Hellerii. Upper figure, male; lower
figure, female.]

In a siluroid fish, inhabiting the fresh waters of South America, namely
the _Plecostomus barbatus_[16] (fig. 30), the male has its mouth and
interoperculum fringed with a beard of stiff hairs, of which the female
shews 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. The
_Monacanthus scopas_, which was shewn to me in the British Museum by Dr.
Günther, presents a nearly analogous case. The male 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 an inch and a half
in length; the female has on the same place a cluster of bristles, which
may be compared with those of a tooth-brush. In another species, the _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 the same part of 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. In that strange monster,
the _Chimæra monstrosa_, the male has a hook-shaped bone on the top of
the head, directed forwards, with its rounded end covered with sharp
spines; in the female “this crown is altogether absent,” but what its
use may be is utterly unknown.[17]

[Illustration: Fig. 30. Plecostomus barbatus. Upper figure, head of
male; lower figure, female.]

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[18] a crest is developed on the head of the male only during the
breeding-season, and their bodies at the same time become 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 this case and
in that of the Monacanthus, we have good instances to how great an
extent the sexual characters of closely-allied forms may differ. In many
of the Chromidæ, for instance in Geophagus and especially in Cichla, the
males, as I hear from Professor Agassiz,[19] 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 in their
periodical appearance resemble the fleshy caruncles on the heads of
certain birds; but whether they serve as ornaments must remain at
present doubtful.

The males of those fishes, which differ permanently in colour from the
females, often become more brilliant, as I hear from Professor Agassiz
and Dr. Günther, during the breeding-season. This is likewise the case
with a multitude of fishes, the sexes of which at all other seasons of
the year are identical in colour. 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.”[20] 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.[21] 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.[22] Another striking instance out of many is
afforded by the male stickleback (_Gasterosteus leiurus_), which is
described by Mr. Warington,[23] 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.

That with fishes there exists some close relation between their colours
and their sexual functions we can clearly see;—firstly, from the adult
males of certain species being differently coloured from the females,
and often much more brilliantly;—secondly, from these same males,
whilst immature, resembling the mature females;—and, lastly, from the
males, even of those species which at all other times of the year are
identical in colour with the females, often acquiring brilliant tints
during the spawning-season. We know that the males are ardent in their
courtship and sometimes fight desperately together. If we may assume
that the females have the power of exerting a choice and of selecting
the more highly-ornamented males, all the above facts become
intelligible through the principle of sexual selection. On the other
hand, if the females habitually deposited and left their ova to be
fertilised by the first male which chanced to approach, this fact would
be fatal to the efficiency of sexual selection; for there could be no
choice of a partner. But, as far as is known, the female never willingly
spawns except in the close presence of a male, and the male never
fertilises the ova except in the close presence of a female. It is
obviously difficult to obtain direct evidence with respect to female
fishes selecting their partners. An excellent observer,[24] who
carefully watched the spawning of minnows (_Cyprinus phoxinus_), remarks
that owing to the males, which were ten times as numerous as the
females, crowding closely round them, he could “speak only doubtfully on
their operations. When a female came among a number of males they
immediately pursued her; if she was not ready for shedding her spawn,
she made a precipitate retreat; but if she was ready, she came boldly in
among them, and was immediately pressed closely by a male on each side;
and when they had been in that situation a short time, were superseded
by other two, who wedged themselves in between them and the female, who
appeared to treat all her lovers with the same kindness.”
Notwithstanding this last statement, I cannot, from the several previous
considerations, give up the belief that the males which are the most
attractive to the females, from their brighter colours or other
ornaments, are commonly preferred by them; and that the males have thus
been rendered more beautiful in the course of ages.

We have next to inquire whether this view can be extended, through the
law of the equal transmission of characters to both sexes, 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,[25] 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 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
any aid from selection. The goldfish (_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.[26] 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, must we conclude in regard to the many fishes, both sexes of
which are splendidly coloured? Mr. Wallace[27] 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 Cyprinidæ in India are ornamented with “bright
longitudinal lines of various tints.”[28] 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 kingfishers, 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 (as explained when treating of
caterpillars) that they were unpalatable; but it is not, I believe,
known that any fish, at least any freshwater 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 have been acquired by the
males as a sexual ornament, and have been transferred in an equal or
nearly equal degree 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, with the variations inherited only by his male offspring;
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 acquired by many fishes as a protection: no one can behold the
speckled upper surface of a flounder, and overlook its resemblance to
the sandy bed of the sea on which it lives. One of the most striking
instances ever recorded of an animal gaining protection by its colour
(as far as can be judged in preserved specimens) and by its form, is
that given by Dr. Günther[29] 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. Fishes offer valuable evidence on this head. 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 sex; 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 of smaller size, 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 most
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,[30] 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 or the race.

Certain fishes, belonging to several families, make nests; and some of
these fishes take care of their young when hatched. Both sexes of the
brightly-coloured _Crenilabrus massa_ and _melops_ work together in
building their nests with sea-weed, shells, &c.[31] 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,[32] 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 during a long time the duties of a
nurse with exemplary care and vigilance, 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.[33]

The males of certain other fishes inhabiting South America and Ceylon,
and belonging to two distinct orders, have the extraordinary habit of
hatching the eggs laid by the females within their mouths or branchial
cavities.[34] With the Amazonian species which follow this habit, the
males, as I am informed by the kindness of Professor Agassiz, “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 Promotis 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, 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 these 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, &c.) 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.[35] The sexes do not commonly differ much in
colour; but Dr. Günther believes that the male Hippocampi are rather
brighter than the females. The genus Solenostoma, however, offers a
very curious exceptional case,[36] 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 the sex which is the most important of
the two for the welfare of the offspring must serve, in some manner, as
a protection. But from the multitude of fishes, the males of which are
either permanently or periodically brighter than the females, but whose
life is not at all more important than that of the female for the
welfare of the species, this view can hardly be maintained. When we
treat of birds we shall meet with analogous cases in which 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 purpose.

The last point which need be noticed is that in many parts of the world
fishes are known to make peculiar noises, which are described in some
cases as being musical. Very little has been ascertained with respect to
the means by which such sounds are produced, and even less about their
purpose. The drumming of the Umbrinas in the European seas is said to be
audible from a depth of twenty fathoms. 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.”[37] If this
statement is trustworthy, we have an instance in this, the lowest class
of the Vertebrata, of what we shall find prevailing throughout the other
vertebrate classes, and which prevails, as we have already seen, with
insects and spiders; namely, that vocal and instrumental sounds so
commonly serve as a love-call or as a love-charm, that the power of
producing them was probably first developed in connection with the
propagation of the species.


AMPHIBIANS.

[Illustration: Fig. 31. Triton cristatus (half natural size, from Bell’s
‘British Reptiles’). Upper figure, male during the breeding-season;
lower figure, female.]

_Urodela._—First for 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 forelegs 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.[38] This structure no doubt aids the male in his eager
search and pursuit of the female. 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, being
absorbed during the winter. It is not furnished, as Mr. St. George
Mivart informs me, with muscles, and therefore cannot be used for
locomotion. As during the season of courtship it becomes edged with
bright colours, it serves, there can hardly be a doubt, as 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.[39] 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 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, namely the _Phryniscus
nigricans_[40] 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 may be beneficial by
making this toad known to all birds of prey as a nauseous mouthful; for
it is familiar to every one that these animals emit a poisonous
secretion, which causes the mouth of a dog to froth, as if attacked by
hydrophobia. I was the more struck with the conspicuous colours of this
toad, as close by I found a lizard (_Proctotretus multimaculatus_)
which, when frightened, flattened its body, closed its eyes, and then
from its mottled tints could hardly be distinguishable from the
surrounding sand.

With respect to sexual differences of colour, Dr. Günther knows of no
striking instance 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 Dr. Günther 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. The _Megalophrys
montana_[41] (fig. 32) offers the best case of a certain amount of
structural difference between the sexes; for in the male the tip of the
nose and the eyelids are produced into triangular flaps of skin, and
there is a little black tubercle on the back—characters which are
absent, or only feebly developed, in the females. It is surprising that
frogs and toads should not have acquired more strongly-marked sexual
differences; for though cold-blooded, their passions are strong. Dr.
Günther 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.

[Illustration: Fig. 32. Megalophrys montana. The two left-hand figures,
the male; the two right-hand figures, the female.]

These animals, however, 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 de Janeiro I used often to sit in
the evening to listen to a number of little Hylæ, which, perched on
blades of grass close to the water, 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.[42]
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.[43] 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.[44] The vocal organs differ considerably in structure in
the several genera of the family; 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.[45] 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.[46]

_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[47]
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 his head and tail lifted up, he spins 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.[48]

_Ophidia._—I have little to say about Snakes. Dr. Günther 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, Dr. Günther 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 instantly 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.”[49] 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.[50] No doubt the colours of some snakes
serve as a protection, as 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 or viper, serve to conceal them; and this is still more
doubtful with the many foreign species which are coloured with extreme
elegance.

During the breeding-season their anal scent-glands are in active
function;[51] 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.[52] Male snakes, though appearing so
sluggish, are amorous; for many have been observed crowding round the
same female, and even round the dead body of a female. They are not
known to fight together from rivalry. Their intellectual powers are
higher than might have been anticipated. An excellent observer in
Ceylon, Mr. E. Layard,[53] saw a Cobra thrust its head through a narrow
hole and swallow a toad. “With this incumbrance 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.”

It does not, however, follow because snakes have some reasoning power
and strong passions, 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. Günther,[54] 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.

_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, 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;[55] and this, as far as Dr. Günther
has been able to ascertain, is the general rule with lizards of all
kinds.

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 possesses a dorsal crest, though much less
developed than in the male; and so it is, as Dr. Günther 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, though in a rudimental
condition, in the female. Again, in certain other lizards, both sexes
are equally well provided with throat-pouches. Here, as in so many
previous cases, we see with species belonging to the same group, the
same character confined to the males, or more largely developed in the
males than in the females, or 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 in
the male when arrived 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.[56]

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

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 is of quite minute size in the female and in the young.
These appendages, as Dr. Günther has remarked to me, may be compared
with the combs of gallinaceous birds, and apparently serve as ornaments.

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

[Illustration: Fig. 35. Chamæleon bifurcus. Upper figure, male; lower
figure, female.]

In the genus Chamæleon we come to the climax 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 _Chamæleon 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; but Dr. Günther, to whom I am
indebted for the foregoing details, does not believe that such peaceable
creatures would ever become pugnacious. Hence we are driven to infer
that these almost monstrous deviations of structure serve as masculine
ornaments.

[Illustration: Fig. 36. Chamæleon Owenii. Upper figure, male; lower
figure, female.]

With many kinds of 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
previously-mentioned 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 greater difference in colour between the sexes; 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.”[57] 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.[58] I collected in S. America
fourteen species of this genus, and though I neglected to record the
sexes, I observed that certain individuals alone were marked with
emerald-like green spots, whilst others had orange-coloured gorges; and
these in both cases no doubt were the males.

In the foregoing species, the males are more brightly coloured than the
females, but with many lizards both sexes are coloured in the same
elegant or even magnificent manner; and there is no reason to suppose
that such conspicuous colours are protective. With some lizards,
however, the green tints no doubt serve for concealment; and an instance
has already been incidently given of one species of Proctotretus which
closely resembles the sand on which it lives. On the whole we may
conclude with tolerable safety that the beautiful colours of many
lizards, as well as various appendages and other strange modifications
of structure, have been gained by the males through sexual selection for
the sake of ornament, and have been 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. But
the less conspicuous colours of the females in comparison with those of
the males cannot be accounted for, as Mr. Wallace believes to be the
case with birds, by the 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
females by vocal or instrumental music of the most varied kinds. They
are ornamented by all sorts of combs, wattles, protuberances, horns,
air-distended sacs, 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,[59] 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.[60] On the
whole, birds appear to be the most æsthetic 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.

Before treating of the 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 sexes 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 curious Neomorpha of New
Zealand, there is a still wider difference in the form of the beak; and
Mr. Gould has been informed that the male with his “straight and stout
beak” tears off the bark of trees, in order that the female may feed on
the uncovered larvæ with her weaker and more curved beak. Something of
the same kind may be observed with our 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, as an old and trustworthy bird-catcher asserted, are commonly
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
nature as a foundation, we can see how the beaks of the two sexes might
be made to differ greatly through natural selection. In all these cases,
however, especially in that of the quarrelsome humming-birds, it is
possible that the differences in the beaks may have been first acquired
by the males in relation to their battles, and 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[61]
describes a battle, in which a pair of humming-birds 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 of another genus, 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.”[62]
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.[63] The males of an
allied bird (_Gallicrex cristatus_), as Mr. Blyth informs me, are one
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 hæmorrhous_) which “fight
with great spirit.”[64]

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.[65] 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.”[66] Birds which seem ill-adapted for fighting engage in
fierce conflicts; thus with the pelican the stronger males drive away
the weaker ones, snapping with their huge beaks and giving heavy blows
with their wings. Male snipes fight together, “tugging and pushing each
other with their bills in the most curious manner imaginable.” Some few
species are believed never to fight; this is the case, according to
Audubon, with one of the woodpeckers of the United States (_Picus
auratus_), although “the hens are followed by even half a dozen of their
gay suitors.”[67]

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

The males of many birds are larger than the females, and this no doubt
is an advantage to them in their battles with their rivals, and has been
gained through sexual selection. 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.[68] 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[69] 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 following brutal scene, told me that a bird had both
its legs broken by some accident in the cock-pit, 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 and 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.[70] 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.”[71]

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. M. W. Kowalevsky 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-dance and
love-song of the Black-cock is called in Germany. The bird utters almost
continuously the most strange 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.[72]

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 two peacocks became so excited whilst fighting at
some little distance from Chester that they flew over the whole city,
still fighting, 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 (see fig. 51, p. 90) 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
erythropthalmus_) 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.[73] Hence spurs may safely be considered as a masculine character,
though occasionally transferred in a greater or less degree to the
females. Like most other secondary sexual characters, the spurs are
highly variable both in number and development in the same species.

[Illustration: 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 ægyptiacus_) has only “bare obtuse knobs,” and these
probably shew us the first steps by which true spurs have been developed
in other allied birds. 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
driven 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.[74] 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 are
known to 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 a fatal
result. Thus also they drive away other enemies.[75]

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,[76] 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.[77] 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,[78] which
afterwards pair with the victorious combatants. But in some cases the
pairing precedes instead of succeeding the combat: thus, according to
Audubon,[79] several males of the Virginian goat-sucker (_Caprimulgus
Virginianus_) “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 with all their power 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 M. W. Kowalevsky
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.[80]

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[81] goes so far
as to believe that the battles of the males “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.”[82]


_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 with the
hissing noise made by some nestling-birds. Audubon[83] 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;”[84] 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 well
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.”[85] 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.”[86] 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.[87] 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,[88] 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[89] 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 a man, as
Mr. Weir informs me, has caught, in the course of a single day, 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 birds should sing from emulation as well as for the sake of
charming the female, is not at all incompatible; and, indeed, might have
been expected to go together, like decoration 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 the canary,
robin, lark, and bullfinch, especially, as Bechstein remarks, when in a
state of widowhood, 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,[90] for this disturbs all
the usual 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.[91] 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 _balzens_ or _leks_ at the usual place of assemblage during the
autumn.[92] Hence it is not at all surprising that male birds should
continue singing for their own amusement after the season for courtship
is over.

Singing is to a certain extent, as shewn in a previous chapter, 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,[93] and sometimes that of
their neighbours.[94] 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,[95]
though they never sing, and do not naturally modulate their voices to
any great extent. Hunter asserts[96] 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.[97]
It is also remarkable that the birds which sing 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,
&c., utter harsh cries; and the brilliant birds of the tropics are
hardly ever songsters.[98] 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 have to be employed to charm the females; and the
voice being rendered melodious would offer one such means.

[Illustration: Fig. 39. Tetrao cupido; male. (From Brehm.)]

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 a 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.”[99] The male of another kind of
grouse (_Tetrao urophasianus_), whilst courting the female, has his
“bare yellow œsophagus 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 œsophagus of the female is not
in any way remarkable.[100]

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 serve, as was formerly supposed, to hold water, but is connected
with the utterance during the breeding-season of a peculiar sound
resembling “ock.” The bird whilst uttering this sound throws himself
into the most extraordinary attitudes. It is a singular fact that with
the males of the same species the sack is not developed in all the
individuals.[101] A crow-like bird inhabiting South America
(_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.[102]

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

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 female or young
male. In the male Merganser the enlarged portion of the trachea is
furnished with an additional pair of muscles.[103] But the meaning of
these differences between the sexes of many Anatidæ is not at all
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.[104] 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.[105] So that highly important structures have 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 different note from the gobbling noise which he makes,
when with erected feathers, rustling wings and distended wattles, he
puffs and struts before her.[106] 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 already present are thus
charmed.[107] The voice of the common rook is known to alter during the
breeding-season, and is therefore in some way sexual.[108] 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 the
loud voices of many male birds may be the result, without any advantage
being thus gained, of the inherited effects of the continued use of
their vocal organs, when they are 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, and the
vibratory movement apparently serves merely to make a noise, for it can
hardly add to the beauty of their plumage. 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 rapidly with
his “lowered wings on the trunk of a fallen tree,” or, according to
Audubon, against his own body; 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.” In the Himalayas the male of the Kalij pheasant “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 same season the males of
certain nightjars (Caprimulgus) make a most strange 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
cause would never be conjectured by any one who heard 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 saw,
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.” When the male
utters its cry without striking his beak the sound is quite
different.[109]

[Illustration: Fig. 41. Outer tail-feather of Scolopax gallinago (from
Proc. Zool. Soc. 1858).]

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 the sounds. The drumming, or bleating, or neighing, or
thundering noise, as expressed by different observers, which is 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 in a curved line, with outspread tail and quivering
pinions, with surprising velocity to the earth. 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
exactly 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.[110]

[Illustration: Fig. 42. Outer tail-feather of Scolopax frenata.]

[Illustration: Fig. 43. Outer tail-feather of Scolopax javensis.]

In the male of the _Chamæpetes 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.[111] 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.[112] In a
widely different group of birds, namely the 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), excised in this
manner. Whilst flying from flower to flower he makes “a shrill, almost
whistling, noise;”[113] but it did not appear to Mr. Salvin that the
noise was intentionally made.

[Illustration: 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.]

Lastly, in several species of a sub-genus of Pipra or Manakin, the males
have their _secondary_ wing-feathers modified, as described by Mr.
Sclater, 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.”[114]

[Illustration: 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.]

The diversity of the sounds, both vocal and instrumental, made by the
males of many species 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 same conclusion with respect 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. This is somewhat more difficult in the case of the
modified feathers, by which the drumming, whistling, or roaring noises
are produced. But we have seen 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 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,[115] 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 various birds,
especially of the Gallinaceæ, 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
manœuvre several times successively, 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.[116]

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 highly 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[117] the habits of some Satin
Bower-birds, which he kept in his 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, and 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 assemblages, 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.

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


_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.[118] 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 (see fig. 39 ante) are occasionally present. The head is
sometimes covered with velvety down like that of the pheasant; or is
naked and vividly coloured; or supports fleshy appendages, filaments,
and solid protuberances. The throat, also, is sometimes ornamented with
a beard, or with 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 more vivid tints, as in the case
of 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. 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.”[119] 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.”[120]

The males are often ornamented with elongated feathers or plumes
springing 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 of the Argus pheasant. The
body of this latter bird 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.[121] The wing-feathers are not elongated
nearly so often as the tail-feathers; for their elongation would impede
the act of flight. Yet the beautifully ocellated secondary wing-feathers
of the male Argus pheasant are nearly three feet in length; and in a
small African nightjar (_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 nightjars, the shafts of the
elongated wing-feathers are naked, except at the extremity, where there
is a disc.[122] Again, in another genus of nightjars, the tail-feathers
are even still more prodigiously developed; so that we see the same kind
of ornament gained by the males of closely-allied birds, through the
development of widely different feathers.

It is a curious fact that the feathers of birds belonging to distinct
groups have been modified in almost exactly the same peculiar manner.
Thus the wing-feathers in one of the above-mentioned nightjars 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 kingfisher, 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.[123] The barbs of the feathers in various
widely-distinct birds are filamentous or plumose, as with some Herons,
Ibises, Birds of Paradise and Gallinaceæ. In other cases the barbs
disappear, leaving the shafts bare; and these in the tail of the
_Paradisea apoda_ attain a length of thirty-four inches.[124] 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 resembled, to a
certain extent, 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.[125]

[Illustration: Fig. 47. Paradisea rubra, male (from Brehm)]

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

In regard to colour hardly anything need here be said; for every one
knows how splendid are the tints of 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 differences between the sexes, or of the extreme beauty of the
males 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 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_ (see fig. 47 of _P. rubra_, a
much less beautiful species), 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.”[126] In another most beautiful species the head is bald,
“and of a rich cobalt blue, crossed by several lines of black velvety
feathers.”[127]

[Illustration: 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 the
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 belonging to the same species in other
characters; and these have been seized on by man and augmented to an
extreme point—as 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, &c., it is due to sexual selection,—that is 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 who first hears it. The male is pure white, whilst the female
is dusky-green; and the former colour with terrestrial species of
moderate size and inoffensive habits is very rare. 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 most
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 chesnut-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.[128]

The coloured plumage and certain other ornaments of the males when
adult are either retained for life or are periodically renewed during
the summer and breeding-season. At this 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, &c. In the white ibis, the
cheeks, the inflatable skin of the throat, and the basal portion of the
beak, then become crimson.[129] In one of the rails, _Gallicrex
cristatus_ a large red caruncle is developed during this same 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 exuviæ.[130]

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
by very young birds of their down; for the down in most cases arises
from the summits of the first true feathers.[131]

With respect to the birds which annually undergo a double moult, there
are, firstly, some kinds, for instance snipes, swallow-plovers
(Glareolæ), 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, which
seems, when there is no change of colour, the most probable cause of a
double moult. Secondly, there are birds, for instance certain species of
Totanus and other grallatores, the sexes of which resemble each other,
but have a slightly different summer and winter plumage. The difference,
however, in colour in these cases is so slight 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,
sometimes, as with certain bustards, a great change of colour. 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,[132] 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, &c., for they acquire
their beautiful plumes only during the breeding-season. Moreover, such
plumes, top-knots, &c., though possessed by both sexes, are occasionally
a little more highly 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.[133]

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 moulting
twice in the year has not been acquired in order that the male should
assume during the breeding-season an ornamental character; 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 with
closely-allied birds, some 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 black-cock only once:
some of the splendidly-coloured honey-suckers (Nectariniæ) of India and
some sub-genera of obscurely-coloured pipits (Anthus) have a double,
whilst others have only a single annual moult.[134] But the gradations
in the manner of moulting, which are known to occur with various birds,
shew us how species, or whole groups of species, 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 alone 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. A gradation can also be shewn to exist in the length of
time during which either annual plumage is retained; so that the one
might come to be retained for the whole year, the other being completely
lost. Thus the _Machetes pugnax_ retains his ruff in the spring for
barely two months. The male widow-bird (_Chera progne_) acquires in
Natal his fine plumage and long tail-feathers in December or January and
loses them in March; so that they are retained during only 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, with respect to part of the plumage, a double moult
changed under domestication into a single moult.[135]

The common drake (_Anas boschas_) is well known after the
breeding-season to lose his male plumage for a period of three months,
during which time he assumes that of the female. The male pintail-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 he who believes in the gradual modification
of species will be far from feeling surprise at finding gradations of
all kinds. If the male pintail 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.[136]

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. With 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.[137]


_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, or attract, or charm 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 will
shew off his finery, as I have often seen, before poultry or even
pigs.[138] 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 delight to display 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[139] 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.

It must be a grand sight in the forests of India “to come suddenly on
twenty or thirty peafowl, 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
gorged 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.[140] 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 flying about, raising their wings,
elevating their exquisite plumes, and making them vibrate, 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.[141]

[Illustration: Fig. 50. Rupicola crocea, male (from Brehm).]

The gold pheasant (_Thaumalea picta_) during his courtship not only
expands and raises his splendid frill, but turns it, 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.[142] 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 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.

[Illustration: Fig. 51. Polyplectron chinquis, male (from Brehm)]

The case of the Argus pheasant is still more striking. The immensely
developed secondary wing-feathers, which are confined to the male, are
ornamented with a row of from twenty to twenty-three ocelli, each above
an inch in diameter. The feathers are also elegantly marked with oblique
dark stripes and rows of spots, like those on the skin of a tiger and
leopard combined. The ocelli are so beautifully shaded that, as the Duke
of Argyll remarks,[143] they stand out like a ball lying loosely within
a socket. But when I looked at the specimen in the British Museum, which
is mounted with the wings expanded and trailing downwards, I was greatly
disappointed, for the ocelli appeared flat or even concave. Mr. Gould,
however, soon made the case clear to me, for he had made a drawing of a
male whilst he was displaying himself. At such times the long secondary
feathers in both wings are vertically erected and expanded; and these,
together with the enormously elongated tail-feathers, make a grand
semicircular upright fan. Now as soon as the wing-feathers are held in
this position, and the light shines on them from above, the full effect
of the shading comes out, and each ocellus at once resembles the
ornament called a ball and socket. These feathers have been shewn 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 primary wing-feathers, which in most gallinaceous birds are
uniformly coloured, are in the Argus pheasant not less wonderful objects
than the secondary wing-feathers. 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
chesnut, 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 when the long secondary
feathers are erected, though in a widely different manner; for they are
expanded in front like two little fans or shields, one on each side of
the breast near the ground.

The case of the male Argus pheasant is eminently interesting, because it
affords good evidence that the most refined beauty may serve as a charm
for the female, and for no other purpose. We must conclude that this is
the case, as the primary wing-feathers are never displayed, and the
ball-and-socket ornaments are not exhibited in full perfection, except
when the male assumes the attitude of courtship. The Argus pheasant does
not possess brilliant colours, so that his success in courtship appears
to have depended 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, though perhaps she
admires the general effect rather than each separate detail. 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 beautiful 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 identically 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 very 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, selected from a large body of valuable notes, sent to
me by Mr. Jenner Weir, who has long kept birds of many kinds, including
all the British Fringillidæ and Emberizidæ. 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 act thus 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. No other British finch, as Mr. Weir
informs me, turns during his courtship from side to side in this manner;
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
schœniculus_) 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.[144] 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 and scarlet rump and scarlet upper
tail-coverts. I may here add from Dr. Jerdon, that the Indian Bulbul
(_Pycnonotus hæmorrhous_) has crimson _under_ tail-coverts, and the
beauty of these feathers, 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.”[145] 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 showing off
these feathers 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
perpendicularly 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 they have been acquired in some cases at
the expense of greatly impeded powers of flight or of running. The
African nightjar (_Cosmetornis_), which during the pairing-season has
one of its primary wing-feathers developed into a streamer of extreme
length, is thus 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 are 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 a more easy 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 it probably is, as Mr. Gould has remarked, 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.[146]

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 comb 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.”[147]
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, when distended during the
act of 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 male must be of the highest importance to him;
and we further see that beauty in some cases is even 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, in the power of singing, or in
producing what I have called instrumental music, it is almost invariably
the male which excels 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, this is always shortly 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 all 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 equally
excite and attract the female? or does she exert a choice, and prefer
certain males? This question can be answered in the affirmative by much
direct and indirect evidence. It is much 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 the
reiteration of the act of pairing. Thus in Germany and Scandinavia the
balzens 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[148] 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 full-plumaged male Birds of
Paradise 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 not probably 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 the 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.[149]

Some of the above-mentioned birds, namely, the black-cock, capercailzie,
pheasant-grouse, the ruff, the Solitary snipe, and perhaps some others,
are, as it 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 species which are strictly monogamous 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 or _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[150] 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.[151]

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. Whilst they were so numerous, they had the
habit very early in the spring of assembling 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 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 never met with any account of regular assemblages of
black game in Scotland, yet these assemblages are so well known in
Germany and Scandinavia that they have special names.

_Unpaired Birds._—From the facts now given, we may conclude that with
birds belonging to widely-different groups their courtship 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 in consequence 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.[152] The first and
most obvious conjecture is that male magpies must be much more numerous
than the females; and that in the above cases, as well 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 the
male will sit on the eggs, as I hear from Mr. Fox, when the female is
killed.

Sir J. Lubbock’s gamekeeper has repeatedly shot, but how many times he
could not say, one of a pair of jays (_Garrulus glandarius_), and has
never failed shortly afterwards to find the survivor rematched. The Rev.
W. D. 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 to occur
with the peregrine falcons at Beachy Head. The same observer informs me
that three kestrels, all males (_Falco tinnunculus_), were killed one
after the other whilst attending the same nest; two of these were in
mature plumage, and the third in the plumage of the previous year. Even
with the rare golden eagle (_Aquila chrysaëtos_), 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_), it has
been observed that “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 was always soon provided with 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
(_Phœnicura ruticilla_), the writer remarks that it was by no means
common in the neighbourhood, and he expresses much surprise how the
sitting female could so soon give effectual notice that she was a widow.
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
far from 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.[153]

These facts are certainly remarkable. How is it that so many birds are
ready immediately to replace a lost mate? Magpies, jays, carrion-crows,
partridges, and some other birds, are never seen during the spring by
themselves, and these offer at first sight the most perplexing case. 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. 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 either one of a pair, would leave the
other bird 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.[154]
Such contingencies as these probably explain most of the foregoing
cases.[155] 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 inasmuch as the act of courtship appears to be with many birds a
prolonged and tedious affair, 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 discuss any further 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[156] leading to an opposite conclusion. 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 for a long time pines; 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[157] various facts proving the attachment of
mated birds. Starlings, however, as we have seen, may be consoled thrice
in the same day for the loss of their mates. In the Zoological Gardens
parrots have clearly recognised their former masters after an interval
of some months. 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
would naturally remain mated for life be separated for a few weeks
during the winter and 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 even of distinct species, but this perhaps ought to be considered
as a mistaken instinct. They will also 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.”[158]

Birds possess acute powers of observation. Every mated bird, of course,
recognises its fellow. Audubon states that with the mocking-thrushes of
the United States (_Mimus polyglottus_) a certain number remain all the
year round in Louisiana, whilst the 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.”[159] Mr. Hewitt has carefully 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 so
well Mr. Hewitt’s own dogs and cats 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.[160]

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
schœniculus_), which had acquired its black head, 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. Mr. Weir was also obliged to turn out a robin, as it
fiercely attacked all birds 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 into his aviary, fly towards the species which resemble
them most in colour, and settle by their sides.

As male birds display with so much care their fine plumage and other
ornaments in the presence of 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 at
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,[161] attracts the Ruff strongly 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 outside 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
(see fig. 46, p. 70), where the sexes congregate and play strange
antics, are differently constructed, but what most concerns us is, that
they are decorated in a different manner by the several species. 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 rearranged, 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 shewing a decided
taste for the beautiful.” Well may Mr. Gould say “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.[162]


_Preference for 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.[163] Several years ago eighteen cases had been recorded of
the occurrence in Great Britain of hybrids between the black grouse and
pheasant;[164] 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[165] 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.

With the members of the same species the fact of the female preferring
to pair with one male rather than with another is not so likely to
excite attention, as when this occurs between distinct species. Such
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 referred to; 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 everyone 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 (_Agelæus phœniceus_) 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 nightjars
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 or
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.”[166] 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 they have long been kept. Mr. Tegetmeier is convinced
that a game-cock, though disfigured by being dubbed 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.[167]

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.[168] 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 be matched, after
repeated trials, with a black male, but immediately paired with a dun.
Generally colour alone 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 Corbié, 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 chènevis 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.”[169] 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,[170] 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.[171]

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
peacock. 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.”[172] This rival was a japanned or black-winged
peacock, which to our eyes is 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.[173] Here is another striking case; Dr. Jaeger,[174]
director of the Zoological Gardens of Vienna, states that a male
silver pheasant, who had been triumphant over the 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.

Not only does the female exert a choice, but in some few cases she
courts the male, or even fights 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.[175] We have seen that a tame
wild-duck seduced after a long courtship an unwilling Pintail drake. 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, Mr. Weir replaced 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 exceptions to this rule, as we shall hereafter see, apparently occur
in some few groups. With domesticated birds, I have heard of only one
case in which the males shew any preference for particular 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.”[176] From some
inexplicable cause he shews the most determined aversion to certain
hens, which no care on the part of the breeder can overcome. Some hens,
as Mr. Hewitt informs me, 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. Ekström, “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.[177]

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
placing ourselves in imagination in the same position. If an inhabitant
of another planet were to behold a number of young rustics at a fair,
courting and quarrelling over a pretty girl, like birds at one of their
places of assemblage, he would be able to infer that she had the power
of choice only by observing the eagerness of the wooers to please her,
and to display their finery. 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
most highly 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 have been thought, would have
altogether depended 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 the analogy of our own minds; and the mental powers
of birds, if reason be excluded, do not fundamentally differ 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
present individual differences is admitted by every one; and that they
have sometimes been modified into distinct races, is generally
admitted.[178] Variations are of two kinds, which insensibly graduate
into each other, namely, slight differences between all the members of
the same species, and more strongly-marked deviations which occur only
occasionally. These latter are rare with birds in a state of nature, and
it is very doubtful whether they have often been preserved through
selection, and then transmitted to succeeding generations.[179]
Nevertheless, it may be worth while to give the few cases relating
chiefly to colour (simple albinism and melanism being excluded), which I
have been able to collect.

Mr. Gould is well known rarely to admit the existence of varieties, for
he esteems very slight differences as specific; now he states[180] 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.”[181] 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;”[182] but
this variation seems to be somewhat rare, so that its preservation
through sexual selection would follow only under unusually 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.”[183]

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 Brünnich to conclude that it was specifically
distinct; but this is now known to be an error.[184]

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, consists of this variety. It is
characterised[185] 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,[186] 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 great 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 and driven away by their
comrades, had been highly attractive, like the pied peacock before
mentioned, to the common black females, 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.[187] 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 exclusively in most cases, as I
hope to shew in the following chapter, on the form of inheritance which
prevails in the groups in question.

It is sometimes difficult to form any 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 innumerable instances in which the
male displays splendid colours or other ornaments, of which the female
partakes only to a slight degree; for these cases are almost certainly
due to characters primarily acquired by the male, having been
transferred, in a greater or less degree, 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?[188] 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,[189] the males have intense crimson, and the females
white eyes. 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
Chili[190] 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. With many
gallinaceous birds the comb 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 Crève-cœur 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 Golden
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 modified in the
same manner. We are thus enabled without much trouble to rear breeds
with their plumage marked and coloured 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 see feathers becoming 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 large groups of birds it may be observed that the plumage is
differently coloured in each species, yet that certain spots, marks, or
stripes, though likewise differently coloured, are retained by all the
species. 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 almost an exactly reversed manner
to 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 small part black which is white in the
parent-species.[191]

_Formation and variability of the Ocelli or eye-like Spots on the
Plumage of Birds._—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 at
least with insects has probably been a simple one; 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_)
belonging to the same family, the ocelli are even still more variable.
In some specimens (A, fig. 52) 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
(A¹) ocellus, 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).[192] In cases like these, the development of a perfect ocellus
does not require a long course of variation and selection.

[Illustration: Fig. 52. Cyllo leda, Linn., from a drawing by Mr. Trimen,
shewing the extreme range of variation in the ocelli.

A. Specimen, from Mauritius, upper     B. Specimen, from Java, upper
     surface of fore-wing.                   surface of hind-wing.

A¹. Specimen, from Natal, ditto.      B¹. Specimen, from Mauritius,
                                              ditto.]


With birds and many other animals it seems, from the comparison of
allied species, to follow, 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;[193] 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 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
simplest 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 bearing
in mind the zoned feathers of the mongrel offspring from
differently-coloured fowls, and the extraordinary variability of the
ocelli in many Lepidoptera, the formation of these beautiful ornaments
can hardly be a highly complex process, and probably depends on some
slight and graduated change in the nature of the tissues.


_Gradation of Secondary Sexual Characters._—Cases of gradation are
important for us, as they shew that it is at least possible that highly
complex ornaments may have been 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 ancient and extinct progenitors; but this
is obviously impossible. We may, however, generally gain a clue by
comparing all the species of a group, if it be a large one; for some of
them will probably retain, at least in a partial manner, 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 some one or two strongly-characterised
cases, for instance that of the peacock, in order to discover if any
light can thus 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 to form
the oval disc or ocellus, which is certainly one of the most beautiful
objects in the world. This consists of an iridescent, intensely blue,
indented centre, surrounded by a rich green zone, and 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
perhaps deserves notice; the barbs, for a space along one of the
concentric zones are destitute, to a greater or less degree, of their
barbules, so that a part of the disc is surrounded by an almost
transparent zone, which gives to it a highly-finished aspect. But I have
elsewhere described[194] 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. 53), of
indentations, or rather breaks. These indentations are common to the
Indian and Javan peacocks (_Pavo cristatus_ and _P. muticus_); and they
seemed to me 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 of other
birds; and so with all the other characters of the peacock. Let us look
to the allied Gallinaceæ 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, p. 90) 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, somewhat like that of this same kind of peacock. The
ocelli on the wings and tail of the several species of Polyplectron 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 which is edged with cream-colour, so
that the ocellus is here surrounded with differently, though not
brightly, shaded concentric zones. The unusual length of the
tail-coverts is another highly remarkable character in Polyplectron; for
in some of the species they are half as long, and in others two-thirds
of the length of the true tail-feathers. The tail-coverts are ocellated,
as in the peacock. Thus the several species of Polyplectron manifestly
make a graduated approach in the length of their tail-coverts, in the
zoning of the ocelli, and in some other characters, to the peacock.

[Illustration: Fig. 53. Feather of Peacock, about two-thirds of natural
size, carefully drawn by Mr. Ford. The transparent zone is represented
by the outermost white zone, confined to the upper end of the disc.]

Notwithstanding this approach, the first species of Polyplectron which I
happened to examine 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. 54), one on each side of the shaft. Hence I
concluded that the early progenitors of the peacock could not have
resembled in any degree 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 in the tail-coverts of this same species as
well as of _P. malaccense_ (fig. 55) 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.

[Illustration: Fig. 54. Part of a tail-covert of Polyplectron chinquis,
with two oval ocelli of nat. size.]

[Illustration: Fig. 55. Part of a tail-covert of Polyplectron
malaccense, with the two oval ocelli, partially confluent, of nat.
size.]

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 at the lower or basal end alone. 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 be quite obliterated.

The tail-feathers in both species of 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 of Polyplectron in order to discover whether the
ocelli in any of them shewed any tendency to disappear, and, to my great
satisfaction, I was successful. 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 rudimentary
vestige 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
resemble the tail-coverts of the peacock. Now in this species the two
central tail-feathers alone are ornamented, each with two
brightly-coloured ocelli, the ocelli having completely disappeared from
the inner sides of 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 the principle of gradation throws light on the steps by
which the magnificent train of the peacock has been acquired, hardly
anything more is needed. We may 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; and we shall then see in
our mind’s eye, a bird possessing 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; we shall see in short, a Polyplectron. The
indentation of the central disc and surrounding zones of the ocellus in
both species of peacock, seems to me to speak plainly in favour of this
view; and this structure is otherwise inexplicable. The males of
Polyplectron are no doubt very beautiful birds, but their beauty, when
viewed from a little distance, cannot be compared, as I formerly saw in
the Zoological Gardens, 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 of 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 within
sockets, and which 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 various 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.

The wing-feathers, bearing the ocelli, are covered with dark stripes or
rows of dark spots, each stripe or row running obliquely down the outer
side of the shaft to an ocellus. The spots are generally elongated in a
transverse line 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.

[Illustration: Fig. 56. Part of Secondary wing-feather of Argus
pheasant, shewing two, _a_ and _b_, perfect ocelli. A, B, C, &c., 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.)]

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 engraved, but a woodcut cannot
exhibit the exquisite shading of the original. The ring is almost always
slightly broken or interrupted (see fig. 56) 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 browner tint and is indistinctly separated
by a curved oblique line from the upper part, which is yellower and more
leaden; this 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 the tints, which cannot of course be shewn in the woodcut, does not
in the least interfere with the perfect shading of the ball.[195] It
should be particularly observed that each ocellus stands in obvious
connection with a dark stripe, or row of dark spots, for both occur
indifferently on the same feather. Thus in fig. 56 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.

[Illustration: Fig. 57. 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. 57), nearest
to the body, is marked like the other feathers, with oblique,
longitudinal, rather irregular, rows of spots. The lowest spot, or that
nearest the shaft, in the five lower rows (excluding the basal row) is a
little larger than the other spots in 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 quite overlooked. The
next higher spot in each row does not differ at all from the upper ones
in the same row, although in the following series it becomes, as we
shall see, greatly modified. The larger spots occupy exactly the same
relative position on this feather as those occupied by the perfect
ocelli on the longer wing-feathers.

By looking to the next two or three succeeding secondary wing-feathers,
an absolutely insensible gradation can be traced from one of the
above-described lower 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. 58). We here
see several oblique rows, A, B, C, D (see the lettered diagram), &c., 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. 56 runs down to, and is connected with, one of
the ball-and-socket ocelli. Looking to any one row, for instance, B, the
lowest spot or 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. This mark corresponds in every respect
with the larger, shaded spot, described in the last paragraph (fig. 57),
but is more highly developed and more brightly coloured. To the right
and above this spot (_b_), 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_). 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 is unusually
narrow, elongated, and regular. It apparently consists of a lateral and
broken prolongation of the mark (_c_), as I infer from traces of
similar prolongations from the succeeding upper spots; 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 stand in a line parallel to the shaft, and 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.

[Illustration: Fig. 58. 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, &c. 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.]

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. I regret that I have not
given an additional drawing, besides fig. 58, which stands about
half-way in the series between one of the simple spots and a perfect
ocellus. The passage from the elliptic ornament into an ocellus is
effected by the elongation and greater curvature in opposed directions
of the lower black mark (_b_), and more especially of the upper one
(_c_), together with the contraction of the irregular 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, at the same time increasing in diameter.
Traces of the junction of all three elongated spots or marks, especially
of the two upper ones, can still be observed in many of the most perfect
ocelli. The broken state of the black ring on the upper side of the
ocellus in fig. 56 was pointed out. The irregular sub-triangular or
narrow mark (_d_) manifestly forms, by its contraction and equalisation,
the thickened portion of the ring on the left upper side of the perfect
ball-and-socket ocellus. The lower part of the ring is invariably a
little thicker than the other parts (see fig. 56), and this follows
from the lower black mark of the elliptic ornament (_b_) having been
originally 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 (see again fig. 56) 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-leaden
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. 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 was before especially noticed), the line of
separation being oblique, in the same direction with 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. 57) having some dull fulvous
shading on the upper side.

[Illustration: Fig. 59. 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. 59.) 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. Even the oblique stripe belonging to the uppermost ocellus (_b_)
is represented only by a very short irregular black mark with the usual,
curved, transverse base. As this stripe is thus abruptly cut off above,
we can understand, from what has gone before, how it is that the upper
thickened part of the ring is absent in the uppermost ocellus; for, as
before stated, this thickened part is apparently formed by a broken
prolongation of the next higher spot in the same row. 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 ocelli. I should
add that in the secondary wing-feather farthest from the body all the
ocelli are smaller and less perfect than on the other feathers, with
the upper parts of the external black rings 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; on the contrary, they are often broken up
into smaller spots, so that two or three rows run down to each ocellus.

We have now seen that a perfect series can be followed, from two almost
simple spots, at first quite distinct from each other, to one of 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
which have been 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, will deny that a simple dark spot
with some fulvous shading might be converted, through the approximation
and modification of the 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 extremely pretty, some thinking them even more beautiful
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 improvements in
the pattern and shading; and this process has been carried on until the
wonderful ball-and-socket ocelli have been 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 reflected 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 more clearly see) 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
darkness. Mr. Gould several years ago pointed out to me a humming-bird,
the _Urosticte benjamini_, remarkable from the curious differences
presented by the two 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 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,[196] 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
E. 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. 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.”[197] If this be admitted, we can perceive that
the males which 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 consequently have left a larger
number of offspring to inherit their newly-acquired beauty.




CHAPTER XV.

BIRDS—_continued_.


   Discussion why the males alone of some species, and both sexes
   of other species, 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 with many kinds of birds the
female has not received the same ornaments as the male; and why with
many others, both sexes are equally, or almost equally, ornamented? In
the following chapter we shall consider why in some few rare cases the
female is more conspicuously coloured than the male.

In my ‘Origin of Species’[198] 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
appeared. Since my remarks appeared, the subject of sexual coloration
has been discussed in some very interesting papers by Mr. Wallace,[199]
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, by means of
selection, to one sex alone. 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 colour, for the primordial slaty tint
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, of the desired character in
the above case, 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
Sœmmerring’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 Sœmmerring 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 her tail nearly _twice as long_ as that of
the female Sœmmerring 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 Sœmmerring’s pheasant.[200]

Our fancier, in order to make his new breed with the males of a decided
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 succeed. 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[201] in
which the males alone are marked with black striæ. In the case of the
fowl, variations of colour limited in their transmission to the male sex
habitually occur. Even when this form of inheritance prevails, it might
well happen that some of the successive steps in the process of
variation might be transferred to the female, who would then come to
resemble in a slight degree the male, as occurs in some breeds of the
fowl. 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
would be 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 process,
though perhaps not impossible, to change through selection one form of
transmission into the other. Therefore, without distinct evidence in
each case, I am unwilling to admit that this has often been effected
with 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 undistinguishable 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 continually crossing with the duller females. It would be tedious
to follow out all the other possible results; but I may remind the
reader, as shewn in the eighth chapter, 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 less brightly-coloured than
the males.

In the chapter just referred to, instances were given, and any number
might have been added, of variations occurring at different ages, and
inherited at the same age. It was also shewn that variations which occur
late in life are commonly transmitted to the same sex in which they
first appeared; 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. If we suppose that
three-fourths of the young males of any species are on an average
destroyed by various enemies; then the chances would be as three to one
against any one individual more brightly-coloured than usual surviving
to propagate its kind. But in the case of birds which live on the ground
and which commonly need 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. The brightly-coloured young males being
destroyed and the mature ones being successful in their courtship, may
account, on the principle of a relation existing between the period of
variation and the form of transmission, for the males alone of many
birds, having acquired and transmitted brilliant colours to their male
offspring alone. But I by no means wish to maintain that the influence
of age on the form of transmission is indirectly the sole cause of the
great difference in brilliancy between the sexes of many birds.

As with all birds in which the sexes differ in colour, it is an
interesting question whether the males alone have been modified through
sexual selection, the females being left, as far as this agency is
concerned, unchanged or only partially changed; or whether the females
have been specially modified through natural selection for the sake of
protection, I will discuss this question at considerable length, even
at greater length 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 under a
similar point of view some other differences between the sexes. A breed
of fowls formerly existed in Germany[202] 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 Gallinaceæ 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 the wing-spurs, which
could not be injurious during nidification, 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 with the species of Gallus. Hence it
might be argued that the females had aboriginally been furnished with
well-developed spurs, but that these had subsequently been lost either
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 spurs. Are we to infer from this fact that they construct
a different sort of nest, not liable to be injured by their spurs, from
that made by their nearest allies, so that there has been no need for
the removal of their spurs? Or are we to suppose that these females
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 as a consequence 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
the inherited habit of not disturbing their nests.

The vocal organs and the variously-modified feathers 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.[203]
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 continued use in this sex
alone—the successive variations and the effects of use having been from
the first limited in their transmission in a greater or less degree to
the male offspring.

Many analogous cases could be advanced; for instance the plumes on the
head, which are 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 sometimes occurring in the same group of
birds. It would be difficult to account for a difference of this kind
between the sexes on the principle of 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 _à 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[204] 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 as the female makes her nest in a
hole, these feathers become, as I am informed by Mr. R. B. Sharpe, much
crumpled during nidification.

In these two 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. Judging from these cases, if with the peahen,
the development of the tail had been checked only when it became
inconveniently or dangerously long, she would have acquired 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
Sœmmerring’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, owing to the length of
tail having been injurious in a greater or less degree to the females of
the several 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 bearing on 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,[205] that when both sexes are
coloured in a strikingly-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 supports the belief that
the females which sit on open nests have been specially modified for the
sake of protection. 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[206] 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
males sit on the eggs and aid in feeding the young as well as the
females: this is the case, for instance, with _Pyranga æstiva_,[207] 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 would more than
compensate for some additional danger.

Mr. Wallace admits that with the King-crows (Dicrurus), Orioles, and
Pittidæ, the females are conspicuously coloured, yet they 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;[208] and that with the birds of the third group
the females are brightly coloured chiefly on the under surface. Besides
these cases the whole great family of pigeons, which are sometimes
brightly, and almost always conspicuously coloured, and which are
notoriously liable to the attacks of birds of prey, offers a serious
exception to the rule, for pigeons 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 very 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.[209]

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 rays of the sun;[210] so that it is no valid
objection to his view that many birds having both sexes obscurely
coloured build concealed nests.[211] The female Hornbills (_Buceros_),
for instance, of India and Africa are protected, during nidification,
with extraordinary care, for the male plaisters up the hole in which the
female sits on her eggs, and leaves only a small orifice through which
he feeds her; she is thus kept a close prisoner during the whole period
of incubation;[212] yet female hornbills 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 Grallinæ of Australia, the Superb Warblers
(Maluridæ) of the same country, the Sun-birds (Nectariniæ), and with
several of the Australian Honey-suckers or Meliphagidæ.[213]

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 constructed by her. 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.[214] Nor is there any close relation
between a well-pronounced difference in colour between the two 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_) differs 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 build
in holes. 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 case of 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[215] 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 (Capitonidæ),
plaintain-eaters (Musophagæ), 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,[216] 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 analogous 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 Dromolæa are of a
lustrous black; so that these three birds are far from receiving
protection from their colours, yet they are able to survive, for they
have acquired the habit, when in danger, of taking refuge in holes or
crevices in the rocks.

With respect to the above-specified groups of birds, 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. This conclusion, as far as it
can be trusted, is interesting, namely, 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.

Even in the groups in which, according to Mr. Wallace, the females from
being protected during nidification, 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 on the principle of some of the variations in the males
having been from the first limited in their 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[217] 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 more
beautiful than the females, though the latter are likewise beautiful.
All the species of kingfisher 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.[218] 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 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
undistinguishable, 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.[219] In the family of the tits (_Parinæ_), which build concealed
nests, the female of our common blue tomtit (_Parus cæruleus_) is “much
less brightly coloured” than the male; and in the magnificent Sultan
yellow tit of India the difference is greater.[220]

Again in the great group of the woodpeckers,[221] 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,[222] and
would be thus far 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.[223] 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 in most
cases been 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.[224]

As far as I can discover there are very few groups of birds containing a
considerable number of species, in which all have both sexes brilliantly
coloured and alike; but this appears to be the case, as I hear from Mr.
Sclater, with the Musophagæ or plaintain-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 (_Cotingidæ_) 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 a remarkable 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 the
same general rules of sexual similarity and dissimilarity, depending on
the form of transmission, would, in both cases, hold good. In a similar
manner the same form of transmission has generally prevailed throughout
the same natural groups, although marked exceptions to this rule occur.
Within the same family or even genus, the sexes may be identically alike
or very different in colour. Instances have already been given relating
to the same genus, as with sparrows, fly-catchers, thrushes and grouse.
In the family of pheasants the males and females of almost all the
species are wonderfully dissimilar, but are quite similar in the eared
pheasant or _Crossoptilon auritum_. In two species of Chloephaga, a genus
of geese, the males 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.[225]

The laws of inheritance can alone account for the following cases, in
which the female by acquiring at a late period of life certain
characters proper to the male, ultimately comes to resemble him in a
more or less complete manner. 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 striæ
and spots on the axillary feathers; and does not completely assume the
uniform black colour of the male for the first three years. The same
excellent observer remarks that in the spring of the second year the
female spoonbill (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, are not developed in her so early in life as
in the male. The upper mandible in the male of an Indian parrakeet
(_Palæornis Javanicus_) 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.[226]

In these cases, the females follow a normal course of development in
ultimately becoming like the males; and such cases must not be
confounded with those in which diseased or old females assume masculine
characters, or with those in which perfectly fertile females, whilst
young, acquire through variation or some unknown cause the characters of
the male.[227] 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, &c., of
egrets, herons, and many other birds, which are developed and retained
only during the summer, serve exclusively for ornamental or 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, in which the summer and
winter plumages differ very little in colour. With defenceless species,
in which either 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 Birds of Paradise, the Argus pheasant and peacock, do not
cast their plumes during the winter; and it can hardly be maintained
that there is something in the constitution of these birds, at least of
the Gallinaceæ, rendering a double moult impossible, for the ptarmigan
moults thrice in the year.[228] 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. Such
variations being inherited either by both sexes or by the males alone,
according to the form of inheritance which prevailed. This appears more
probable than that these species in all cases originally tended to
retain their ornamental plumage during the winter, but were saved from
this through natural selection, owing to 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 means of natural selection, of a tendency to 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, on 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 all 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 young differ in colour from the
adults, and the colours of the former are not, as far as we can see, of
any special service, they may generally be attributed, like various
embryological structures, to the retention by the young of the character
of an early progenitor. But this view can be maintained with confidence,
only when the young of several species closely resemble each other, 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 naturalist, who believes in the gradual evolution
of species, will doubt that the progenitor of the lion and puma was a
striped animal, the young having retained vestiges of the stripes, like
the kittens of black cats, which when grown up are not in the least
striped. Many species of deer, which when mature are not spotted, are
whilst young covered with white spots, as are likewise some few species
in their adult state. So again the young in the whole family of pigs
(Suidæ), 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 Gallinaceæ,
and of some distantly-allied birds such as ostriches, are whilst covered
with down longitudinally striped; but this character points back to a
state of things so remote that it hardly concerns us. Young crossbills
(Loxia) have at first straight beaks like those of other finches, and in
their immature striated plumage they resemble the mature redpole 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 each other, 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 by many species throughout life, 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
genera when adult are similarly marked. In some closely-allied and
resplendent Indian cuckoos (Chrysococcyx), the species when mature
differ considerably from each other 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.[229] 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 orders 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. With such species the young of the
different species cannot resemble each other more closely than do the
parents; nor can they present striking resemblances to allied forms in
their adult state. 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 or rules under which the
differences and resemblances, between the plumage of the young and the
old, of both sexes or of 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, firstly, 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 rather 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 resemble, more or less
closely, the adult female, whilst the adult male differs, often in the
most conspicuous manner, from the adult female. 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 both 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 in number, 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 the
male in these groups does differ from the female, as with certain
parrots, kingfishers, pigeons, &c., the young of both sexes resemble the
adult female.[230] 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 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.[231] Again, the
plumage of the male goosander (_Mergus merganser_) is more conspicuously
coloured, with the scapular and secondary wing-feathers much longer than
in the female, 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 resemble in all respects the adult female, so
that their crests are actually of greater length though narrower than in
the adult male.[232]

When the young and the females closely resemble each other and both
differ from the male, the most obvious conclusion is that the male alone
has 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,[233] 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 being undistinguishable, and
therefore absolutely unchanged. This is the case with certain Indian
chats (Thamnobia), with certain honey-suckers (Nectarinia), shrikes
(Tephrodornis), certain kingfishers (Tanysiptera), Kallij pheasants
(Gallophasis), and tree-partridges (Arboricola).

In some analogous cases, namely with birds having a distinct 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 undistinguishable in their winter as well as in
their immature plumage. This is the case with some of the closely-allied
Indian wagtails or Motacillæ. Mr. Swinhoe[234] informs me that three
species of Ardeola, a genus of herons, which represent each other 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 progenitor of the genus was 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 the modification of the plumage
in the males alone to this action, seeing that the females and the
young, though similarly exposed, have not been affected. Hardly any fact
in nature 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 sexes
must 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; we see
only that this is subordinate in importance to the accumulated results
of selection. When, however, 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, judging from a widely-spread analogy, a certain
amount of fluctuating variability. In this case sexual selection, which
depends on an element eminently liable to change—namely 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 (judging from what we know of the results on domestic
animals of man’s unintentional selection), be a surprising fact 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 species, together with
their young, differ hardly at all from each other, so that the males
alone can be distinguished, yet in most cases the females of the 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 Gallinaceæ: 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 each other
very closely in colour, whilst the males differ to an extraordinary
degree. So it is with the females of most of the Cotingidæ, Fringillidæ,
and many other families. There can indeed be no doubt that, as a general
rule, the females have been modified to a less extent 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;[235] 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,[236] 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 which
occur, independently of selection by man, and which we cannot explain,
in certain sub-breeds of the game-fowl, in which the females are very
different, whilst the males can hardly be distinguished.[237]

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 transference, in a greater or
less degree, 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, &c., we shall see that they differ from each other 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
undistinguishable. There is no improbability in the plain, though
peculiar 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 plainly 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,[238] we may conclude that his plumage has been, at least to a
certain extent, influenced by sexual selection. If so, we may further
infer that the 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, both during
former and recent times, by the males through sexual selection. 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 bluebreast (_Cyanecula suecica_) has a rich blue breast,
including a sub-triangular red mark; now marks of approximately 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 Gallinaceæ offer many analogous cases; for none of the
species, such as partridges, quails, guinea-fowls, &c., 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 two 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, this 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 nidification, 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.[239] 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 thus modified. Although it would be
a difficult, perhaps an impossible process, as shewn in the last
chapter, to convert through selection one form of transmission into
another, 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 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 golden 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 the principle of
protection, as accounting for the less bright colours of female birds,
it occurred to me that possibly both sexes and the young might
aboriginally have been brightly coloured in an equal degree; 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. It is also a somewhat
strange fact, 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, 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-coloured 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.[240]

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 which occurred in the females or in the young would have
been of no service to them, and would not have been selected; moreover,
if dangerous, would have been eliminated. Thus the females and the young
will either have been left unmodified, or, and this has much more
commonly occurred, will have been partially modified by receiving
through transference from the males some of the 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 more brightly 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 occurs 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,[241] 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
Gallinaceæ. In most of the species the female is more distinctly
coloured and brighter than the male,[242] 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 more
vociferous, 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.[243] Mr. Blyth believes, that the young of both sexes resemble
the adult male.

[Illustration: Fig. 60. Rhynchæa capensis (from Brehm).]

The females of the three species of Painted Snipes (Rhynchæa) “are not
only larger, but much more richly coloured than the males.”[244] 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 _Rhynchæa Australis_ it is simple in the male, whilst in the
female it makes four distinct convolutions before entering the
lungs.[245] 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 so closely resembles _R. Australis_ 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.[246] There is also reason to believe that
the male undertakes the duty of incubation, for Mr. Swinhoe[247] 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. The male
alone of _P. fulicarius_ undertakes, according to Professor Steenstrup,
the duty of incubation, as 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.[248] 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.[249] The female is
said by Mr. T. W. Wood[250] 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
(_Dromœus irroratus_) is considerably larger than the male, and she
possesses a slight top-knot, but is otherwise undistinguishable 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.”[251] 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.[252]

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 their 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 nightjar “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.”[253]

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
acted on the females in the present class 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 of less size, and have
less strength. 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”[254]—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 and
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 brighter colours, other
ornaments, or vocal powers. Sexual selection would then soon 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
both 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 with birds under confinement, in
the same manner as often occurs in the case of brilliantly coloured male
birds. With many species of herons the young differ greatly from the
adults, and their summer plumage, 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 two last classes, on the young having
retained a former or ancient state of plumage, which has been exchanged
for a new plumage by the old of both sexes. When the adults are brightly
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 two first classes, the transmission, though limited to the
same age, has not been limited to the same sex. Consequently both 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 absolutely 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,[255]—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 parrokeets (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.[256] 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.[257]

Before proceeding, I may remark that under the present and two next
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 some
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 exceeded to a slight degree 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.[258] 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.[259] 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 albinoes, as shewn by the colour of their beaks and legs, which
nearly resembled the same parts in the adults.[260]

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.[261] In the
house-sparrow (_P. domesticus_) the male differs much from the female
and from the young. These resemble each other, and likewise 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, 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. The belief that the
males varied whilst young, and transmitted their variations to their
offspring of both sexes is perhaps the most probable. I may here add
that I have endeavoured, with little success, by consulting various
works, to decide how far with birds the period of variation 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,[262] second, and fourth classes of
cases; but they fail in an equal number, namely, in the third, often in
the fifth,[263] and in the sixth small class. They hold good, however,
as far as I can judge, with a considerable majority of the species of
birds. Whether or not this be so, we may conclude from the facts given
in the eighth chapter that the period of variation has been 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 were
first developed would falsely appear to us to have been earlier than it
really was. 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.[264] 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 powers of reproduction are gained,
it is a remarkable fact that various birds occasionally breed whilst
retaining their immature plumage.[265]

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, &c., 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.[266] 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
which retained their immature dress for the longest period would
prevail, and thus the character of the species would ultimately be
modified.[267] If, on the other hand, the young never succeeded in
obtaining a female, the habit of early reproduction would perhaps be
sooner or later quite 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, and with the crest and plumes of certain herons; for
instance, the _Ardea Ludovicana_;[268] but it is very doubtful whether
the continued development of such feathers is the result of the
selection of successive beneficial variations, 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,[269] the young generally resemble the females,—as
with the so-called goldfinch of North America, and apparently with the
splendid Maluri of Australia.[270] With the 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, which occurs much more
rarely, 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.[271] 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.[272] With respect to the third case, namely, that of
the young having an intermediate character between the summer and winter
adult plumages, Yarrell[273] 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 female in her 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 through
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, if experience had not taught us to the
contrary, it seems the most natural thing that the young should at first
always resemble to a certain extent, and gradually become more and more
like, the adults of the same sex. 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; the male
blackbird (_Turdus merula_) can be distinguished in the nest from the
female, as the main wing-feathers, which are not moulted so soon as the
body-feathers, retain a brownish tint until the second general
moult.[274] 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 shewing more pure
white.[275] The males of a forest-thrush and of a rock-thrush (viz.
_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.[276] So that the
very same feathers which in the young blackbird assume their mature
character and become black after the others, in these two species assume
this character and become blue before the others. The most probable view
with reference to these cases 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 themselves first
acquired them; for if they had varied whilst quite young, they would
probably have transmitted all their characters to their offspring of
both sexes.[277]

In _Aïthurus polytmus_ (one of the humming-birds) 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 chesnut-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 resemble to a certain extent 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
independently rendered beautiful; and not that the 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 Rhynchæa 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 in number the
females, 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 greatly exceeded the males, we could
understand how the males at one time, and the females at another time,
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 numerous instances under all six classes, that an
intimate relation exists between the plumage of the young and that of
the adults, either of one sex or both sexes. 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 the species of the same group, we do not know; but with respect to
the form of transmission, one important determining cause seems to have
been the age at which the variations first appeared.

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 both are brightly 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
brightly-coloured species being more brilliantly coloured 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)
brightly-coloured, and as these form whole groups, we may infer that
their early progenitors were likewise brightly-coloured. With this
exception, if we look to the birds of the world, it appears that their
beauty has been greatly increased since that period, of which we have a
partial record in their immature plumage.


_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 for this purpose, so as to escape the notice of their enemies;
or, in some instances, so as to approach their prey unobserved, in the
same manner as owls have had their plumage rendered soft, that their
flight may not be overheard. Mr. Wallace remarks[278] 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
strongly-pronounced colours have been acquired by tree-haunting birds
through sexual selection, but that green tints have had an advantage
through natural selection over other colours for the sake of protection.

In regard to birds which live on the ground, everyone 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
nightjars when crouched on the ground. Animals inhabiting deserts offer
the most striking instances, for the bare surface affords no
concealment, and all the smaller quadrupeds, reptiles, and birds depend
for safety on their colours. As Mr. Tristram has remarked,[279] in
regard to the inhabitants of the Sahara, all are protected by their
“isabelline or sand-colour.” Calling to my recollection the desert-birds
which I had seen in South America, as well as most of the ground-birds
in 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 had their plumage coloured in a
protective manner; and this colouring is all the more striking, as with
most of these birds it is different 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
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
both 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 through natural selection from
inheriting the colours of their male parents: we must look to the law of
sexually limited transmission, as before explained.

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 nightjar, 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.

There are many birds both sexes of which 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, black-cock, 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 greatly
to their beauty; we see this in the bright yellow beak of the male
blackbird, in the crimson skin over the eyes of the black-cock and
capercailzie, in the variously and brightly-coloured beak of the
Scoter-drake (Oidemia), in the red beak of the chough (_Corvus
graculus_, Linn.), of the black swan, and black stork. This leads me to
remark that it is not at all 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.[280] The naked skin at the base of the beak and
round the eyes is likewise often brilliantly coloured; and Mr. Gould, in
speaking of one species,[281] 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 in toucans being encumbered
with immense beaks, though rendered as light as possible by their
cancellated structure, for an object falsely appearing to us
unimportant, namely, the display of fine colours, 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, &c., 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, &c.,
have acquired their more or less completely white plumage through sexual
selection. The species which inhabit snowy regions of course come under
a different head. The white plumage of some of the above-named birds
appears in both sexes only when they are mature. This is likewise the
case with certain gannets, tropic-birds, &c., 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 case of the _Anastomus oscitans_
previously alluded to, 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.[282]

The cause of aquatic birds having acquired a white plumage so much more
frequently 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. 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 of distinct 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 have procured more food than the
less strongly coloured individuals. Hence conspicuous colours cannot
have been gradually acquired for this purpose through natural
selection.[283]

As sexual selection depends on so fluctuating an element as taste, we
can understand how it is that within the same group of birds, with
habits of life nearly the same, there should exist white or nearly
white, as well as black, or nearly black species,—for instance, white
and black cockatoos, storks, ibises, swans, terns, and petrels. Piebald
birds likewise sometimes occur in the same groups, 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 of specimens or series of coloured plates,
for the sexes frequently 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 in the female.

It would even appear that mere novelty, or change for the sake of
change, has sometimes acted like a charm on female birds, in the same
manner as changes of fashion with us. The Duke of Argyll says,[284]—and
I am glad to have the unusual satisfaction of following for even a short
distance in his footsteps—“I am more and more convinced that variety,
mere variety, must be admitted to be an object and an aim in Nature.” I
wish the Duke had explained what he here means by Nature. Is it meant
that the Creator of the universe ordained diversified results for His
own satisfaction, or for that of man? The former notion seems to me as
much wanting in due reverence as the latter in probability.
Capriciousness of taste in the birds themselves appears a more fitting
explanation. For example; the males of some parrots can hardly be said
to be more beautiful, at least according to our taste, than the females,
but they differ from them in such points, as the male having a
rose-coloured collar instead of, as in the female, “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.[285] As so many male birds have for their chief ornament elongated
tail-feathers or elongated crests, the shortened tail, formerly
described in the male of a humming-bird, and the shortened crest of the
male goosander almost seem like one of the many opposite 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 apparently 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 of the allied
_Buphus coromandus_ in their winter plumage 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,[286] should have been specially 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 reason to believe that whiteness has been
gained by many birds as a sexual ornament. We may therefore conclude
that an 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; the whiteness having afterwards been retained by the young
whilst exchanged by the adults for more strongly pronounced tints. But
if we could look still further backwards in time 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 the progenitors in their
adult condition of the _Ardea asha_, the _Buphus_, and of some allies,
have undergone, during a long line of descent, the following changes of
colour: firstly 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 the sake of novelty.


_Summary of the Four Chapters on Birds._—Most male birds are highly
pugnacious during the breeding-season, and some possess weapons
especially 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 emitting strange cries, or of producing 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
very 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 in which the sexes differ, the males differ much
more from each other 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 will have determined the nature of the initial
changes, and largely influenced the final result. The gradations, which
may be observed between the males of allied species, indicate the nature
of the steps which have been passed through, and explain in the most
interesting manner certain characters, such as the indented ocelli of
the tail-feathers of the peacock, and the wonderfully-shaded ocelli of
the wing-feathers of the Argus pheasant. It is evident that the
brilliant colours, top-knots, fine plumes, &c., 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 produced some definite effect on
both sexes, the more important result will have been an increased
tendency to fluctuating variability or to augmented individual
differences; and such differences will have afforded an excellent
groundwork 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 sometimes have been transmitted in one way and
sometimes in another is, in most cases, not 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 in a greater or lesser degree 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 case of 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 the species, in which the sexes differ in colour, it is possible
that at first there existed a tendency to transmit the successive
variations equally to both sexes; and that the females were prevented
from acquiring the bright colours of the males, on account of the danger
to which they would have been exposed during incubation. But it would
be, as far as I can see, an extremely difficult process to convert, by
means of natural selection, one form of transmission into another. On
the other hand 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 have been rendered as conspicuously coloured as the males,
their instincts have often been modified, and they have been 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 brightly-coloured than their males. They
have, also, become so quarrelsome that they often fight together like
the males of the most pugnacious species. If, as seems probable, they
habitually drive away rival females, 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 means of
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 left 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 they will be liable to be lost by the accidental deaths of
the young, and if dangerous will be eliminated through natural
selection. Thus we can understand how it is that variations arising late
in life have chiefly been preserved for the ornamentation and arming 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.[287]




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.


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.”[288] 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 it is believed by some naturalists
that the frequently deformed state of their lower jaws is caused by
these struggles.[289]

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.[290] 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 singly approached the wood;
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 resided in the Falkland Islands he
imported a young English stallion, which, with eight mares, frequented
the hills near Port William. 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 already provided with efficient cutting or tearing teeth
for the ordinary purposes of life, as in 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 of these several cases. In the females of the walrus
the tusks are sometimes quite absent.[291] In the male elephant of India
and in the male dugong[292] the upper incisors form offensive weapons.
In the male narwhal one alone of the upper teeth 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.”[293] 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. It is not, however, very uncommon to find
double-horned male narwhals in which both teeth are well developed. In
the females both teeth are rudimentary. The male cachalot has a larger
head than that of the female, and it no doubt aids these animals in
their aquatic battles. Lastly, the adult male ornithorhynchus is
provided with a remarkable apparatus, namely a spur on the fore-leg,
closely resembling the poison-fang of a venomous snake; its use is not
known, but we may suspect that it serves as a weapon of offence.[294] It
is represented by a mere rudiment in the female.

When the males are provided with weapons which the females do not
possess, there can hardly be a doubt that they are used for fighting
with other males, and that they have been acquired through sexual
selection.

It is not probable, at least in most cases, that the females have
actually been saved from acquiring such weapons, owing to their being
useless and superfluous, or in some way injurious. On the contrary, as
they are often used by the males of many animals 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.
No doubt with female deer the development during each recurrent season
of great branching horns, and with female elephants the development of
immense tusks, would have been a great waste of vital power, on the
admission that they were of no use to the females. Consequently
variations in the size of these organs, leading to their suppression,
would have come under the control of natural selection, and if limited
in their transmission to the female offspring would not have interfered
with their development through sexual selection in the males. But how on
this view can we explain the presence of horns in the females of certain
antelopes, and of tusks in the females of many animals, which are only
of slightly less size than in the males? The explanation in almost all
cases must, I believe, be sought in the laws of transmission.

As the reindeer is the single species in the whole family of Deer in
which the female is furnished with horns, though somewhat smaller,
thinner, and less branched than in the male, it might naturally be
thought that they must be of some special use to her. There is, however,
some evidence opposed to this view. The female retains her horns from
the time when they are fully developed, namely in September, throughout
the winter, until May, when she brings forth her young; whilst the male
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 sheds his horns during the winter, it is very improbable that
they can be of any special service to the female at this season, which
includes the larger proportion of the time during which she bears horns.
Nor is it probable that she can have inherited horns from some ancient
progenitor of the whole family of deer, for, from the fact of the males
alone of so many species in all quarters of the globe possessing horns,
we may conclude that this was the primordial character of the group.
Hence it appears that horns must have been transferred from the male to
the female at a period subsequent to the divergence of the various
species from a common stock; but that this was not effected for the sake
of giving her any special advantage.[295]

We know that the horns are developed at a most unusually early age in
the reindeer; but what the cause of this may have been is not known. The
effect, however, has apparently been the transference of the horns to
both sexes. It is intelligible on the hypothesis of pangenesis, that a
very slight change in the constitution of the male, either in the
tissues of the forehead or in the gemmules of the horns, might lead to
their early development; and as the young of both sexes have nearly the
same constitution before the period of reproduction, the horns, if
developed at an early age in the male, would tend to be developed
equally in both sexes. In support of this view, we should bear in mind
that the 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.[296] Moreover the females of some other species of
deer either normally or occasionally exhibit 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.”[297] 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
transmission to both sexes.

Turning to the sheath-horned ruminants: with antelopes a graduated
series can be formed, beginning with the species, the females of which
are completely destitute of horns—passing to those which have horns so
small as to be almost rudimentary, as in _Antilocapra Americana_—to
those which have fairly well-developed horns, but manifestly smaller and
thinner than in the male, and sometimes of a different shape,[298] and
ending with those in which both sexes have horns of equal size. As with
the reindeer, so with antelopes there exists 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, depend, not on their being of some special
use, but simply on the form of inheritance which has prevailed. It
accords with this view that even in the same restricted genus both sexes
of some species, and the males alone of other species, are thus
provided. It is 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. The males of this species
have long straight spirated horns, nearly parallel to each other, and
directed backwards. Those of the female, when present, are very
different in shape, for they are not spirated, and spreading widely bend
round, so that their points are directed forwards. It is a still more
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. In all cases the differences between the horns of the males and
females, and of castrated and entire males, probably depend on various
causes,—on the more or less complete transference of male characters to
the females,—on the former state of the progenitors of the
species,—and partly perhaps on the horns being differently nourished,
in nearly the same manner as the spurs of the domestic cock, when
inserted into the comb or other parts of the body, assume various
abnormal forms from being differently nourished.

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.[299] In several domestic breeds of the sheep and goat, the
males alone are furnished with horns; and it is a significant fact, that
in one such breed of sheep on the Guinea coast, the horns are not
developed, as Mr. Winwood Reade informs me, in the castrated male; so
that they are affected in this respect like the horns of stags. In some
breeds, as in that of N. Wales, in which both sexes are properly horned,
the ewes are very liable to be hornless. In these same sheep, as I have
been informed by a trustworthy witness who purposely inspected a flock
during the lambing-season, the horns at birth are generally more fully
developed in the male than in the female. 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.[300] 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.”[301] Hence with most
sheath-horned ruminants the horns of the male are either longer or
stronger than those of the female. With the _Rhinoceros simus_, as I may
here 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.[302] From these various facts we may
conclude that horns of all kinds, even when they are equally developed
in both sexes, were primarily acquired by the males in order to conquer
other males, and have been transferred more or less completely to the
female, in relation to the force of the equal form of inheritance.

The tusks of the elephant, in the different species or races, differ
according to sex, in nearly the same manner as 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.”[303] 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_—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 extreme 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 for other purposes. The
elephant uses his tusks in attacking the tiger; according to Bruce, he
scores the trunks of trees until they can be easily thrown down, and he
likewise thus extracts the farinaceous cores of palms; in Africa he
often uses one tusk, this being always the same, to probe the ground and
thus to 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 any animal are occasionally put, is
that observed by Captain Hutton[304] with the wild goat (_Capra
ægagrus_) of the Himalayas, and as it is 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 so much need this strange kind of shield.

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 as easily as a
child. Goats and certain species of sheep, for instance the _Ovis
cycloceros_ of Afghanistan,[305] 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 his 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 other males in single combat; this goat possessed
enormous horns, measuring 39 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.[306] Hence a dog who pins a buffalo by the nose is immediately
crushed. We must, however, remember that the Italian buffalo has long
been domesticated, and it is by no means certain that the wild
parent-form had similarly shaped 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.

[Illustration: Fig. 61. 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 spring-boc (_Ant.
euchore_) has rather short upright horns, with the sharp points bent
inwards almost at a right angle, 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. 61) are directed
backwards, and are of such length that their points reach beyond the
middle of the back, over which they stand in an almost parallel line.
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 front 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 endeavour to get the upturned points under each
other’s bodies; 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 manœuvre. It has been recorded
that one of these antelopes has used his horns 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 branching of the horns offers a curious
case of difficulty; for certainly a single straight point would inflict
a much more serious wound than several diverging points. 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., each of which bears the
astonishing number of thirty-three branches. Richardson figures a pair
of antlers of the wild reindeer with twenty-nine points.[307] 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,[308] M. Bailly actually came to the conclusion that their
horns were 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
Colinsay, 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 action, 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 in regard both to red-deer
and fallow-deer, that when they fight 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 with 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 terminal points 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.[309]

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 partly as ornaments. That the branched antlers of stags,
as well as the elegant lyrated horns of certain antelopes, with their
graceful double curvature, (fig. 62), 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 partly modified for this purpose, though mainly for
actual service in battle; but I have no evidence in favour of this
belief.

[Illustration: Fig. 62. Strepsiceros Kudu (from Andrew Smith’s ‘Zoology
of South Africa’).]

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[310] 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 subsequently 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.”

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 with serious effect downwards.[311] The walrus, though having
so short a neck and so unwieldy a body, “can strike either upwards, or
downwards, or sideways, with equal dexterity.”[312] The Indian elephant
fights, as I was informed by the late Dr. Falconer, 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 hoodah.[313]

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 one form of weapon, has often been
replaced in the course of ages by another form, as we may infer from
what follows. With ruminants the development of horns generally stands
in an inverse relation with that of even moderately well-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 Camelidæ have in
their upper jaws, in addition to their true canines, a pair of
canine-shaped incisors.[314] 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. With _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 deer have been known occasionally to exhibit rudiments of
these teeth.[315] 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 widely like camels and guanacoes. Whenever the adult
male possesses canines now in an inefficient state, 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 had
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 caused (but not in the case of the horse) 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 assigned by some
authors.[316] 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 and a quarter pounds. With sheep,
although the horns are not periodically renewed, 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 dead 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.”[317] 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 the red-deer for about twelve weeks, they are extremely
sensitive to a blow; so that in Germany the stags at this time change
their habits to a certain extent, and avoid dense forests, frequenting
young woods and low thickets.[318] 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 quadrupeds, when, as is often the case, the sexes differ in size,
the males are, I believe, always larger and stronger. This holds good in
a marked manner, as I am informed by Mr. Gould, 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.[319] The greater strength of the
male is invariably displayed, as Hunter long ago remarked,[320] 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 so-called spontaneous
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.

Under this point of view I was anxious to obtain information in regard
to the Scotch deerhound, 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, a well-known breeder of these
dogs, who has weighed and measured many of his own dogs, and who, with
great kindness, has collected for me the following facts from various
sources. Superior male dogs, measured at the shoulder, range from
twenty-eight inches, which is low, to thirty-three, or even thirty-four
inches in height; and in weight from eighty pounds, which is low, to
120, or even more pounds. The females range in height from twenty-three
to twenty-seven, or even to twenty-eight inches; and in weight from
fifty to seventy, or even eighty pounds.[321] Mr. Cupples concludes that
from ninety-five to one hundred pounds for the male, and seventy 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
Colinsay, 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 deerhound is not acquired until rather late in life.
The males are almost exclusively 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 a rather late period 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 deerhound may probably be
accounted for.

[Illustration: Fig. 63. 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.
Rhinoceroses, as the same observer remarks, in fighting parry each
other’s sidelong blows with their horns, which loudly clatter together,
as do the tusks of boars. Although wild boars fight desperately
together, they seldom, according to Brehm, receive fatal blows, as these
fall on each other’s tusks, or on the layer of gristly skin covering the
shoulder, which the German hunters call the shield; and here we have a
part specially modified for defence. With boars in the prime of life
(see fig. 63) 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 thus used. They may, however,
still continue to serve, and even in a still more effective manner, 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 so much in length during old age, and curve
so much upwards, that they can be used as a means of attack.
Nevertheless an old boar is not so dangerous to man as one at the age
of six or seven years.[322]

[Illustration: Fig 64. Skull of the Babirusa Pig (from Wallace’s ‘Malay
Archipelago’)]

In the full-grown male Babirusa pig of Celebes (fig. 64), 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 would, however, if the head were held a little
laterally, serve as an excellent guard; and hence, perhaps it is that in
old animals they “are generally broken off, as if by fighting.”[323]
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 and opposite tusks assume in a less degree and only
during old age nearly the same form, and then serve in like manner
solely for defence.

[Illustration: Fig. 65. Head of Æthiopian Wart-hog, from ‘Proc. Zool.
Soc.’ 1869. (I now find that this drawing represents the head of a
female, but it serves to shew, on a reduced scale, the characters of the
male.)]

In the wart-hog (_Phacochœrus æthiopicus_, fig. 65) 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 thus used to a certain extent. But the
wart-hog is not destitute of other special means of protection, for
there exists, on each side of the face, beneath the eyes, a rather
stiff, yet flexible, cartilaginous, oblong pad (fig. 65), 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 protect in an admirable manner the somewhat prominent eyes.
These boars, as I may add on the authority of Mr. Bartlett, when
fighting together, stand directly face to face.

Lastly, the African river-hog (_Potamochoerus 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 purpose of the above-described projections and excrescences,
that these were covered with blood, and were scored and abraded in an
extraordinary manner.

The mane of the lion forms a good defence against the one danger to
which he is liable, namely the attacks of rival lions: 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.”[324] 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_)[325] 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, excepting
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 elephas_) 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, as we may feel assured, have
been equally protected.


_On Preference or Choice in Pairing, as shewn by either sex of
Quadrupeds._—Before describing, in the next chapter, the differences
between the sexes in voice, odour emitted, and ornamentation, 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 of organisation
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, as so
incessantly occurs, by several males, she would often have the
opportunity, whilst they were fighting together, of escaping with, or at
least of temporarily pairing with, some one male. This latter
contingency has often been observed in Scotland with female red-deer, as
I have been informed by Sir Philip Egerton.[326]

It is scarcely possible that much should be known about female
quadrupeds exerting in a state of nature any choice in their marriage
unions. The following very curious details on the courtship of one of
the eared seals, _Callorhinus ursinus_, are given[327] 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 large size.[328] The well-known veterinary Blaine
states[329] that his own female pug 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 a female deerhound now (1868) in his kennel has 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 other cases, and I will only
add that Mr. Barr, who has carefully bred many blood-hounds, states that
in almost every instance particular individuals of the opposite sex shew
a decided preference for each other. Finally Mr. Cupples, after
attending to this subject for another year, has recently 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 character, 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,
should be so particular in their choice. Mr. Blenkiron has never known a
mare to reject a horse; but this has occurred in Mr. Wright’s stable, so
that the mare had to be cheated. Prosper Lucas[330] quotes various
statements from French authorities, and remarks, “On voit des étalons
qui s’éprennent d’une jument, et négligent toutes les autres.” He gives,
on the authority of Baëlen, similar facts in regard to bulls. Hoffberg,
in describing the domesticated reindeer of Lapland, says, “Fœmina
majores et fortiores mares præ cæteris admittunt, ad eos confugiunt, a
junioribus agitatæ, qui hos in fugam conjiciunt.”[331] A clergyman, who
has bred many pigs, assures me 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 two 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,[332] are said to be
completely mute excepting at this season. As the throats (i.e. the
larynx and thyroid bodies[333]) of stags become periodically enlarged at
the commencement of the breeding-season, it might be thought that their
powerful voices must be then in some way 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 their 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 hands in rage or agony. No doubt
stags challenge each other to mortal combat by bellowing; but it is not
likely that this habit could have led through sexual selection, that is
by the loudest-voiced males having been the most successful in their
conflicts, to the periodical enlargement of the vocal organs; for the
stags with the most powerful voices, unless at the same time the
strongest, best-armed, and most courageous, would not have gained any
advantage over their rivals with weaker voices. The stags, moreover,
which had weaker voices, though not so well able to challenge other
stags, would have been drawn to the place of combat as certainly as
those with stronger voices.

It is possible that the roaring of the lion may be of some actual
service to him in 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 any 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,[334] 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 of the year; 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, with our present state of knowledge, the most probable view.

The male gorilla has a tremendous voice, and when adult is furnished
with a laryngeal sack, as is likewise the adult male orang.[335] The
gibbons rank amongst the noisiest of monkeys, and the Sumatra species
(_Hylobates syndactylus_) is also furnished with a laryngeal sack; but
Mr. Blyth, who has had opportunities for observation, does not believe
that the male is more noisy 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 with the beaver.[336] Another
gibbon, the _H. agilis_, is highly remarkable, from having the power of
emitting a complete and correct octave of musical notes,[337] 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, when the weather is
warm, make the forests resound during the morning and evening with their
overwhelming voices. The males begin the dreadful concert, in which the
females, with their less powerful voices, sometimes join, and which is
often continued during many hours. An excellent observer, Rengger,[338]
could not perceive that they were excited to begin their concert 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 to 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 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_),
when about three years old, is greatly elongated during the
breeding-season, and can then be erected. In this state it is sometimes
a foot in length. The female at no period of life is thus provided, and
her voice is different. That of the male consists of a wild, hoarse,
gurgling noise, which is audible at a great distance, and is believed to
be strengthened by the proboscis. Lesson compares the erection of the
proboscis, to the swelling of the wattles of male gallinaceous birds,
whilst they court the females. In another allied kind of seal, namely,
the bladder-nose (_Cystophora cristata_), the head is covered by a great
hood or bladder. This is internally supported by the septum of the nose,
which is produced far backwards and rises into a crest seven inches in
height. The hood is clothed with short hair, and is muscular; it 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 by
man they likewise roar or bellow; and whenever irritated the bladder is
inflated. 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. This latter view is not probable, if what the
sealers have long maintained is correct, namely, that the hood or
bladder is very poorly developed in the females and in the males whilst
young.[339]


_Odour._—With some animals, as with the notorious skunk of America, the
overwhelming odour which they emit appears to serve exclusively as a
means of defence. With shrew-mice (Sorex) both sexes possess abdominal
scent-glands, and there can be little doubt, from the manner in which
their bodies are rejected by birds and beasts of prey, that their odour
is protective; nevertheless the glands become enlarged in the males
during the breeding-season. In many quadrupeds the glands are of the
same size in both sexes;[340] but their use is not known. In other
species the glands are confined to the males, or are more developed in
them 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 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 have perceived the whole air tainted with the odour of the male
_Cervus campestris_, at the distance of half a mile to leeward of a
herd; and a silk handkerchief, in which I carried home a skin, though
repeatedly 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.[341] Besides the general odour, with which the whole
body of certain ruminants seems to be permeated during 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 seen in the case of an
antelope. They are “usually larger in the male than in the female, and
their development is checked by castration.”[342] According to Desmarest
they are altogether absent in the female of _Antilope subgutturosa_.
Hence, there can be no doubt that they stand in some 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, from its position, is 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.[343]

In most cases, when during the breeding-season the male alone emits a
strong odour, this 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 which are far from agreeable to us; and that dogs, though
they will not eat carrion, sniff and roll in 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 more 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 in 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 a
thin and narrow crest runs along the whole length of the back; for a
crest of this kind would afford scarcely any protection, and the ridge
of the back is not a likely place 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_[344] (see fig. 68, p. 300) and _Portax picta_, may be given as
instances. The crests of certain stags and of the male wild goat stand
erect, when these animals are enraged or terrified;[345] but it can
hardly be supposed that they have been acquired 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
front-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.

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.
The bull alone has curled hair on the forehead.[346] In three
closely-allied sub-genera of the goat family, the males alone possess
beards, sometimes of large size; in two other sub-genera both sexes have
a beard, but this 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
seasons that it may be called rudimentary.[347] 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. 66). So it is with the whiskers of some species of
Macacus,[348] 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.

[Illustration: Fig. 66. Pithecia Satanas, male (from Brehm).]

The males of various members of the Ox family (Bovidæ), 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
dewlap of the bull, or the crests of hair along the backs of certain
male antelopes, are of any direct or ordinary use to them. 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 which the whiskers,
moustache, and other tufts of hair on the face serve; and no one will
suppose that these are useful as a protection. Must we attribute to mere
purposeless variability in the male all these appendages of hair or
skin? It cannot be denied that this is possible; for with many
domesticated quadrupeds, certain characters, apparently not derived
through reversion from any wild parent-form, have appeared in, and are
confined to, the males, or are more largely developed in them than in
the females,—for instance the hump in the male zebu-cattle of India,
the tail in fat-tailed rams, the arched outline of the forehead in the
males of several breeds of sheep, the mane in the ram of an African
breed, and, lastly, the mane, long hairs on the hinder legs, and the
dewlap in the male alone of the Berbura goat.[349] The mane which occurs
in the rams alone of the above-mentioned African breed of sheep, is a
true secondary sexual character, for it is not developed, as I hear from
Mr. Winwood Reade, 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 African ram with a mane was descended from the same
primitive stock with the other breeds of sheep, or the Berbura male-goat
with his mane, dewlap, &c., from the same stock with other goats; and if
selection has not been applied to these characters, then they must be
due to simple variability, together with sexually-limited inheritance.

In this case it would appear reasonable to extend the same view to the
many analogous characters occurring in animals under a state of nature.
Nevertheless I cannot persuade myself that this view is applicable in
many cases, as in that of the extraordinary development of hair on the
throat and forelegs of the male Ammotragus, or of the immense beard of
the male Pithecia. With those antelopes in which the male when adult is
more strongly-coloured than the female, and with those monkeys in which
this is likewise the case, and in which the hair on the face is of a
different colour from that on the rest of the head, being arranged in
the most diversified and elegant manner, it seems probable that the
crests and tufts of hair have been acquired as ornaments; and this I
know is the opinion of some naturalists. If this view be correct, there
can be little doubt that they have been acquired, or at least modified,
through sexual selection.


_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.”[350] In the _Didelphis
opossum_ of Cayenne the female is said to be a little more red than the
male. With 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.”[351] 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 some few bats the fur of the male is lighter and brighter than
in the female.[352]

The terrestrial Carnivora and Insectivora rarely exhibit sexual
differences of any kind, and their colours are almost always exactly the
same in both sexes. The ocelot (_Felis pardalis_), however, offers an
exception, 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.”[353] The sexes of the allied _Felis mitis_ also differ, but
even 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 very 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.”[354]

With Ruminants sexual differences of colour occur more commonly than in
any other order. A difference of this kind is general with 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. The male, as I am informed by Mr. Blyth, without
shedding his hair, periodically becomes darker during the
breeding-season. Young males cannot be distinguished from young females
until above 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 distinctive of sexual colouring,
becomes obvious, when we hear[355] 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.[356]

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 have in this species, as Mr. Blyth
informs me, an exactly parallel series of facts, as with 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 undistinguishable from each other. In the
_Antilope niger_ the male is black, the female as well as the young
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 as in the female brown; 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.”[357] 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 the female _Capra ægagrus_ is said
to be more uniformly tinted than their respective males. Deer rarely
present any sexual differences in colour. Judge Caton, however, informs
me that with the males of the Wapiti deer (_Cervus Canadensis_) the
neck, belly, and legs are much darker than the same parts 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 nuptial plumage.[358] 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 characterise the adult
males.[359] Lastly, the mature male of the beautifully coloured and
spotted Axis deer is considerably darker, as I am informed by Mr. Blyth,
than the female; and this hue the castrated male never acquires.

The last Order which we have to consider—for I am not aware that sexual
differences in colour occur in the other mammalian groups—is that of
the Primates. The male of the _Lemur macaco_ is coal-black, whilst the
female is reddish-yellow, but highly variable in colour.[360] Of the
Quadrumana of the New World, the females and young of _Mycetes caraya_
are greyish-yellow and alike; in the second year the young male becomes
reddish-brown, in the third year 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 in _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.[361] 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 equally beautiful and curious moustache monkey (_Cercopithecus
cephus_) the only difference between the sexes is that the tail of the
male is chesnut and that of the female grey; but Mr. Bartlett informs me
that all the hues become more strongly 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 Müller, 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.

[Illustration: Fig. 67. 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
(_Cynocephalus leucophus_) the females and young are much
paler-coloured, with less green, than the adult males. No other member
of the whole class of mammals is coloured in so extraordinary a manner
as the adult male mandrill (_Cynocephalus 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 réellement pas
d’élégance.”[362] 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 most 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. 67.) In the adult females
and in the young of both sexes these protuberances are scarcely
perceptible; and the naked parts are much less brightly 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 brightly
coloured than the female, and differs in a greater degree from the young
of both sexes. But as a reversed style of colouring is characteristic of
the two sexes with some few birds, 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 periodically becomes, as I was assured by
the keepers in the Zoological Gardens, even more vivid, and her face is
also pale red. On the other hand with the adult male and with 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. The colours of the female either do not
differ in a sufficient degree from those of the male, or are not of a
suitable nature, to afford her protection, and therefore cannot be
explained on this principle. In some, perhaps in many cases, the
differences may be the result of variations confined to one sex and
transmitted to the same sex, without any good having been thus gained,
and therefore without the aid of selection. We have instances of this
kind with our domesticated animals, as in the males of certain cats
being rusty-red, whilst the females are tortoise-shell coloured.
Analogous cases occur under 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, were males. On the other hand, both
sexes of wolves, foxes, and apparently of American squirrels, are
occasionally born black. Hence it is quite possible that with some
mammals the blackness of the males, especially when this colour is
congenital, may simply be the result, without the aid of selection, of
one or more variations having occurred, which from the first were
sexually limited in their transmission. Nevertheless it can hardly be
admitted that the diversified, vivid, and contrasted colours of certain
quadrupeds, for instance of the above-mentioned monkeys and antelopes,
can thus be accounted for. We should bear in mind that these colours do
not appear in the male at birth, as in the case of most ordinary
variations, but only at or near maturity; and that unlike ordinary
variations, if the male be emasculated, they never appear or
subsequently disappear. It is on the whole a much more probable
conclusion 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. The probability of this view is strengthened by the
differences in colour between the sexes occurring almost exclusively, as
may be observed by going through the previous details, in those groups
and subgroups of mammals, which present other and distinct secondary
sexual characters; these being likewise due to the action of sexual
selection.

Quadrupeds manifestly take notice of colour. Sir S. Baker repeatedly
observed that the African elephant and rhinoceros attacked with special
fury white or grey horses. I have elsewhere shewn[363] that half-wild
horses apparently prefer pairing with those of the same colour, and that
herds of fallow-deer of a different colour, 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.”[364]

In an early chapter we have seen that the mental powers of the higher
animals do not differ in kind, though so 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;”[365]—as negroes, as well as 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 have been coloured for the
sake of ornament even more brilliantly than the face; but this is really
not more strange than that the tails of many birds should have been
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, 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 for reproduction; if
emasculated he either never acquires such characters or subsequently
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 either of hair or feathers, or other 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 safely 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 may be extended
to mammals. With a considerable number of species, especially 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 nearly so striking a manner as in most of the
lower classes. Audubon remarks that he often mistook the musk-rat,[366]
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, namely the rabbit, for as this animal runs
to its burrow, it is made conspicuous to the sportsman and no doubt to
all beasts of prey, by its upturned pure-white tail. No one has ever
doubted that the quadrupeds which inhabit 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 long on the
ground a white coat would be injurious; consequently species thus
coloured 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[367] 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, the 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 by degrees, until they became as white as snow.

[Illustration: Fig. 68. Tragelaphus scriptus, male (from the Knowsley
Menagerie).]

[Illustration: Fig. 69. Damalis pygarga, male (from the Knowsley
Menagerie).]

Although we must admit that many quadrupeds have received their present
tints as a protection, 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 this purpose. We may take as an illustration certain
antelopes: when we see that the square white patch on the throat, the
white marks on the fetlocks, and the round black spots on the ears, are
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. 68),—we may conclude that these colours
and various marks have been at least intensified through sexual
selection. It is inconceivable that such colours and marks can be of any
direct or ordinary service to these animals; and as they have almost
certainly been intensified through sexual selection, it is probable that
they were originally gained through this same process, 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. 62) have narrow white vertical lines on their
hinder 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 abruptly separated from the white belly and 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. 69); 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.[368] 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[369] 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 analogous marks and
colours are rather brighter in the male than in the female. The zebra is
conspicuously striped, and stripes on the open plains of South Africa
cannot afford any protection. Burchell[370] 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.” Here we have no evidence of sexual selection, as throughout
the whole group of the Equidæ the sexes are identical in colour.
Nevertheless he who attributes the white and dark vertical stripes on
the flanks of various antelopes to sexual selection, 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 with 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 genus Tapir, the young are marked with
longitudinal stripes, and thus differ from every 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 the spots are much plainer, as I
have seen in the Zoological Gardens, 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.[371] 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 at all seasons in the adults; and
lastly, to their absence at all ages, 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 resembled to a certain extent
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. It offers, also, one of those interesting cases
of a form linking together two groups, as it is intermediate in certain
osteological characters between the pachyderms and ruminants, which were
formerly thought to be quite distinct.[372]

A curious difficulty here arises. If we admit that coloured spots and
stripes have been 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 nearly sure that
the spots and stripes disappeared in the progenitors of our existing
species at or near maturity, so that they were retained by the young
and, owing to the law of inheritance at corresponding ages, by the young
of all succeeding generations. It may have been a great advantage to
the lion and puma from the open nature of the localities which they
commonly haunt, 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 we know to be the case.
In regard to deer, pigs, and tapirs, Fritz Müller has suggested to me
that these animals by the removal through natural selection of their
spots or stripes would have been less easily seen by their enemies; and
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 equally well protected, and still more strange that
with some species the adults should have retained their spots, either
partially or completely, during part of the year. We know, though we
cannot explain the cause, 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. Very few horses, except dun-coloured
kinds, exhibit 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.[373] 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 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. tæniopus_,
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.[374]

[Illustration: Fig. 70. 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.]

[Illustration: Fig. 71. Head of Semnopithecus comatus.]

[Illustration: Fig. 72. Head of Cebus capucinus.]

[Illustration: Fig. 73. Head of Ateles marginatus.]

[Illustration: Fig. 74. Head of Cebus vellerosus.]


_Quadrumana._—Before we conclude, it will be advisable to add a few
remarks to those already given on the ornamental characters 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 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. 70 to 74) 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 any ordinary use 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.

With respect to the strange manner in which both sexes of some species
are coloured, and of the beauty of others, a few instances will suffice.
The face of the _Cercopithecus petaurista_ (fig. 75) 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 æthiops_ is grotesque, with its black face, white whiskers
and collar, chesnut 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,[375] 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.[376] 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 every 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.

[Illustration: Fig 75. Cercopithecus petaurista (from Brehm).]

Although, according to our taste, many kinds of monkeys are far from
beautiful, other species are universally admired for their elegant
appearance and bright colours. The _Semnopithecus nemæus_, though
peculiarly coloured, is described as extremely pretty; the orange-tinted
face is surrounded by long whiskers of glossy whiteness, with a line of
chesnut-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 all
of a pure white; a gorget of chesnut surmounts the chest; the hind
thighs are black, with the legs chesnut-red. I will mention only two
other monkeys on account of their beauty; and I have selected these as
they present 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 chesnut; 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. 76); 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 chesnut; 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,
finely contrasted with a white transverse crest over the eyebrows and
with a long white peaked beard, of which the basal portion is
black.[377]

[Illustration: Fig. 76. Cercopithecus Diana (from Brehm).]

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.


_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 all been acquired or modified through that form of
selection which I have called sexual selection. This does not depend on
any superiority in the general struggle for life, but on certain
individuals of one sex, generally the male sex, having been successful
in conquering other males, and on their having left a larger number of
offspring to inherit their superiority, than 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 may be
effected 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 may have been strengthened
by use during maturity, under the powerful excitements of love,
jealousy, or rage, and 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 females, 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 of defence, have been partly
modified for the sake of 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 colours, 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
coloured in some species in the most brilliant manner. 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 subgroups 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 in regard to weapons, such
as horns and tusks, these have often been transmitted either
exclusively, or in a much higher degree to the males than to the
females. This is a surprising circumstance, for as the males generally
use their weapons as a defence against enemies of all kinds, these
weapons would have been of service to the female. Their absence in this
sex can be accounted for, as far as we can see, 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 these
have been modified through sexual selection, either for fighting with
each other or for alluring the opposite sex, far more commonly than the
females.




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
species of 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,[378] the superciliary ridge is
generally more strongly 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 tribes the women are said, whether truly
I know not, to differ slightly in tint from the men; and with Europeans,
the women are perhaps the more brightly coloured of the two, as may be
seen when both sexes have been equally exposed to the weather.

Man is more courageous, pugnacious, and energetic than woman, and has a
more inventive genius. His brain is absolutely larger, but whether
relatively to the larger size of his body, in comparison with that of
woman, 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 her
body rounder, in parts more prominent; and her pelvis is broader than in
man;[379] 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 their heads. It is probably due
to the rather late appearance in life of the successive variations, by
which man 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; 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.[380] 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.[381] In
regard to colour, the newborn negro child is reddish nut-brown, which
soon becomes slaty-grey; the black colour being fully developed within a
year in the Sudan, but not until three years in Egypt. The eyes of the
negro are at first blue, and the hair chesnut-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.[382]

I have specified the foregoing familiar differences between the male and
female sex in mankind, because they are curiously the same as in the
Quadrumana. With these animals the female is mature at an earlier age
than the male; at least this is certainly the case with the _Cebus
azaræ_.[383] With most of the species the males are larger and much
stronger than the females, of which fact the gorilla offers 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,[384] 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.[385] 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 a female than in the male monkey.
Even in the colour of the beard there is a curious parallelism between
man and the Quadrumana, for when in man the beard differs in colour from
the hair of the head, as is often the case, it is, I believe, invariably
of a lighter tint, being often reddish. I have observed this fact in
England, and Dr. Hooker, who attended to this little point for me in
Russia, found no exception to the rule. In Calcutta, Mr. J. Scott, of
the Botanic Gardens, was so kind as to observe with care the many races
of men to be seen there, as well as in some other parts of India,
namely, two races in Sikhim, the Bhoteas, Hindoos, Burmese, and Chinese.
Although most of these races have very little hair on the face, yet he
always found that when there was any difference in colour between the
hair of the head and the beard, the latter was invariably of a lighter
tint. Now with monkeys, as has already been stated, the beard frequently
differs in a striking manner in colour from the hair of the head, and in
such cases it is invariably of a lighter hue, being often pure white,
sometimes yellow or reddish.[386]

In regard to the general hairyness 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.[387]
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 gorilla and orang, there is a considerably greater
difference between the sexes, 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 the case of mankind.

The secondary sexual characters of man are all highly variable, even
within the limits of the same race or sub-species; and they differ much
in the several races. These two rules generally hold good throughout the
animal kingdom. In the excellent observations made on board the
_Novara_,[388] the male Australians were found to exceed the females by
only 65 millim. in height, whilst with the Javanese 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.
The numerous measurements of various other races, with respect to
stature, the circumference of the neck and chest, and the length of the
back-bone and arms, which were carefully made, nearly all shewed that
the males differed much more from each other than did the females. This
fact indicates that, as far as these characters are concerned, it is the
male which has been chiefly modified, since the races diverged from
their common and primeval source.

The development of the beard and the hairiness of the body differ
remarkably in the men belonging to distinct races, and even to different
families in the same race. We Europeans see this amongst ourselves. In
the island of St. Kilda, according to Martin,[389] the men do not
acquire beards, which are very thin, until the age of thirty or upwards.
On the Europæo-Asiatic continent, beards prevail until we pass beyond
India, though with the natives of Ceylon they are frequently absent, as
was noticed in ancient times by Diodorus.[390] Beyond India beards
disappear, as with the Siamese, Malays, Kalmucks, Chinese, and Japanese;
nevertheless the Ainos,[391] who inhabit the northernmost islands of the
Japan archipelago, are the most hairy men in the world. With negroes the
beard is scanty or absent, and they have no whiskers; in both sexes the
body is almost destitute of fine down.[392] On the other hand, the
Papuans of the Malay archipelago, who are nearly as black as negroes,
possess well-developed beards.[393] 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.”[394]

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 during 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.[395] I am informed by Mr. D. Forbes, who
particularly attended to this subject, that the Aymaras and Quechuas 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 from each other so much as with most other races of
mankind.[396] This fact is analogous with what occurs with some allied
monkeys; thus the sexes of the chimpanzee are not as different as those
of the gorilla or orang.[397]

In the previous chapters we have seen that with mammals, birds, fishes,
insects, &c., many characters, which there is every reason to believe
were primarily gained through sexual selection by one sex alone, have
been transferred to both sexes. As this same form of transmission has
apparently prevailed to a large extent with mankind, it will save much
useless repetition if we consider the characters peculiar to the male
sex together with certain other characters common to both sexes.


_Law of Battle._—With barbarous nations, for instance with the
Australians, the women are the constant cause of war both between the
individuals 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 the North American Indians, the contest is reduced to a
system. That excellent observer, Hearne,[398] 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 or more years old, 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,[399] 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 become reduced through
disuse, as would the teeth through the not well understood principles of
correlation and the 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 quite 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 Gorilla and Orang, 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 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 some early male
progenitor, who, like the existing anthropoid apes, was thus
characterised. These characters will, however, have been preserved or
even augmented during the long ages whilst man was still in a barbarous
condition, by the strongest and boldest men having succeeded best in the
general struggle for life, as well as in securing wives, and thus having
left a large number of offspring. 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 mutual 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 very important part. I am aware that some
writers doubt whether there is any inherent difference; but this is at
least probable from the analogy of the lower animals which present other
secondary sexual characters. No one will dispute 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 should 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 attaining to a higher eminence, in whatever he takes up,
than woman can attain—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,—comprising 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 of averages, so well illustrated by Mr. Galton, in his
work on ‘Hereditary Genius,’ that if men are capable of decided eminence
over women in many subjects, the average standard of mental power in man
must be above that of woman.

The half-human male progenitors of man, and men in a savage state, have
struggled together 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 man, 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 invent and
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, who
possess every mental quality in the same perfection, with the exception
that the one has higher energy, perseverance, and courage, this one will
generally become more eminent, whatever the object may be, and will gain
the victory.[400] 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 in many subjects can be
gained. But these latter as well as the former faculties 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 thus gained will
have been transmitted more fully to the male than to the female
offspring. Thus man has ultimately become superior to woman. It is,
indeed, fortunate that the law of the equal transmission of characters
to both sexes has commonly prevailed throughout the whole class of
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 at a
late period of life by either sex, to be transmitted to the same sex at
the same age, and of characters acquired at an early age to be
transmitted to both sexes, are rules which, though general, do not
always hold good. If they always held good, we might conclude (but I am
here wandering beyond 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 between the sexes in mental
power could 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. The
whole body of women, however, could not be thus raised, unless during
many generations the women who excelled in the above robust virtues were
married, and produced offspring in larger numbers than other women. As
before remarked with respect to bodily strength, although men do not now
fight for the sake of obtaining wives, and this form of selection has
passed away, yet they generally have to undergo, during manhood, 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.[401]


_Voice and Musical Powers._—In some species of Quadrumana there is a
great difference between the adult sexes, in the power of the voice 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, &c., which
accompanies the elongation of the cords.”[402] With respect to the cause
of this difference between the sexes, I have nothing to add to the
remarks made 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,[403] the
voice differs in the different races of mankind; and with the natives of
Tartary, China, &c., 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 alone. The sounds thus
produced consist, I believe in all cases, of the same note, repeated
rhythmically;[404] and this is sometimes pleasing even to the ears of
man. Their chief, and in some cases exclusive use appears to be either
to call or to 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 Amphibians are the lowest Vertebrates
which breathe air; and many of these animals, namely, 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 largely 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. Both sexes of other species,
or the females alone, 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 more probably one of those apes which come
nearer to man, namely, the _Hylobates agilis_. This gibbon has an
extremely loud but musical voice. Mr. Waterhouse states,[405] “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
likewise a musician, confirms the foregoing statement, and remarks 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 almost all other animals, it is highly probable that it utters its
musical notes especially during the season of courtship.

The perception, if not the enjoyment, of musical cadences and of rhythm
is probably common to all animals, and no doubt depends on the common
physiological nature of their nervous systems. Even Crustaceans, which
are not capable of producing any voluntary sound, possess certain
auditory hairs, which have been seen to vibrate when the proper musical
notes are struck.[406] It is well known that some dogs howl when hearing
particular tones. 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.”[407] With all those animals, namely
insects, amphibians, and birds, the males of which during the season of
courtship incessantly produce musical notes or mere rhythmical sounds,
we must believe that the females are able to appreciate them, and are
thus excited or charmed; otherwise the incessant efforts of the males
and the complex structures often possessed exclusively by them would be
useless.

With man 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 direct use to man in
reference to his ordinary habits of life, they must be ranked amongst
the most mysterious with which he is endowed. They are present, though
in a very rude and as it appears almost latent condition, in men of all
races, even the most savage; but so different is the taste of the
different races, that our music gives not the least pleasure to savages,
and their music is to us hideous and unmeaning. Dr. Seemann, in some
interesting remarks on this subject,[408] “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 before-mentioned gibbon, the capacity of producing,
and no doubt of appreciating, musical notes, we have every reason to
believe that man possessed these faculties at a very remote period, for
singing and music are extremely ancient arts. Poetry, which may be
considered as the offspring of song, is likewise so ancient that many
persons have felt astonishment that it should have arisen during the
earliest ages of which we have any record.

The musical faculties, which are not wholly deficient in any race, are
capable of prompt and high development, as we see with Hottentots and
Negroes, who have readily become excellent musicians, although they do
not practise in their native countries anything that we should esteem as
music. But there is nothing anomalous in this circumstance: some species
of birds which never naturally sing, can without much difficulty be
taught to perform; thus the 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 quite possible or probable that a progenitor of the sparrow may
have been a songster. It is a much more remarkable fact that parrots,
which belong to a group distinct from the Insessores, and have
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 extremely rash to assume
that parrots are descended from some ancient progenitor which was a
songster. Many analogous cases could be advanced of organs and instincts
originally adapted for one purpose, having been utilised for some quite
distinct purpose.[409] Hence the capacity for high musical development,
which the savage races of man possess, may be due either to our
semi-human progenitors having practised some rude form of music, or
simply to their having acquired for some distinct purposes the proper
vocal organs. But in this latter case we must assume that they already
possessed, as in the above instance of the parrots, and as seems to
occur with many animals, some sense of melody.

Music affects every emotion, but does not by itself excite in us the
more terrible emotions of horror, rage, &c. It awakens the gentler
feelings of tenderness and love, which readily pass into devotion. It
likewise stirs up in us the sensation 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.
Nearly the same emotions, but much weaker and less complex, are probably
felt by birds when the male pours forth his full volume of song, in
rivalry with other males, for the sake of captivating the female. Love
is still the commonest theme of our own 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.”[410] Conversely, when
vivid emotions are felt and expressed by the orator or even in common
speech, musical cadences and rhythm are instinctively used. Monkeys also
express strong feelings in different tones—anger and impatience by
low,—fear and pain by high notes.[411] The sensations and ideas excited
in us by music, or by the cadences of impassioned 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 become to a certain extent
intelligible if we may assume that musical tones and rhythm were used by
the half-human progenitors of man, during the season of courtship, when
animals of all kinds are excited by the strongest passions. In this
case, from the deeply-laid principle of inherited associations, musical
tones would be likely to excite in us, in a vague and indefinite manner,
the strong emotions of a long-past age. Bearing in mind that the males
of some quadrumanous animals have their vocal organs much more developed
than in the females, and that one anthropomorphous species pours forth a
whole octave of musical notes and may be said to sing, the suspicion
does not appear improbable that the progenitors of man, either the males
or females, or both sexes, before they had acquired 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 hardly any means of judging whether the habit of singing was
first acquired by the male or female progenitors of mankind. 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.[412] But if so, this must have
occurred long ago, before the progenitors of man 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, at an extremely remote
period, his half-human ancestors aroused each other’s ardent passions,
during their mutual courtship and rivalry.


_On 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 certain characteristics,
or conversely that the women prefer certain men, 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 sexes; this
latter circumstance depending on the form of inheritance which prevails.

It will be well first to shew in some detail that savages pay the
greatest attention to their personal appearance.[413] 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.”[414] 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, earrings, &c. 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, &c., 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 much more common 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.”[415] 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 World 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[416] 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.”[417] 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 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 the two upper incisors, which, as Livingstone[418]
remarks, gives the face a hideous appearance, owing to the growth 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 great chief Sebituani tried in vain to alter this
fashion. In various parts of Africa and in the Malay Archipelago the
natives file the incisor teeth 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, with rings,
sticks, feathers, and other ornaments 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[419]
that his “wife 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 _pelelé_,
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 pelelé? She would not be
a woman at all with a mouth like a man, but no beard.’” [420]

Hardly any part of the body, which can be unnaturally modified, has
escaped. The amount of suffering thus caused must have been wonderfully
great, 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. As with savages the same
fashions prevail for long periods,[421] 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[422] 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.[423] In
most, but not all parts of the world, the men are more highly 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 to 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, perforating the nose, lips, or ears, in removing or filing
the teeth, &c., now prevail and have long prevailed in the most distant
quarters of the world. It is extremely improbable that these practices
which are followed by so many distinct nations are due to tradition from
any common source. They rather indicate the close similarity of the mind
of man, to whatever race he may belong, in the same manner as 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. As I have heard it maintained
that savages are quite indifferent about the beauty of their women,
valuing them solely as slaves, it may 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[424] gives an
amusing account of a Bushwoman, who used so 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.[425] In several
regions the women wear charms and 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.[426]

Hearne,[427] who lived many years with the American Indians, and who was
an excellent observer, 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 Mandschú form; that is to say, a broad face, high
cheek-bones, very broad noses, and enormous ears;”[428] 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
Mogul 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.”[429]

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.[430] 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 are similarly characterised;
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.”[431]

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 “honey-mouth,” 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 partly attributed,
according to this same traveller, to the belief held by most negroes
that demons and spirits are white.

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
Kafirs, 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 Kafir. 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.”[432] 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
Yura-caras, 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.[433]

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 Quechuas of S. America, likewise have very
long hair; and this, as Mr. D. Forbes informs me, is so much valued for
the sake of beauty, that cutting it off was the severest punishment
which he could inflict on them. In both 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 hairs from his face and body, yet he was
far from a hairy man. This fashion is carried to such an extreme that
the Indians of Paraguay eradicate their eyebrows and eyelashes, saying
that they do not wish to be like horses.[434]

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 are beardless; they carefully pluck
out the hairs on the face, and have a saying that “There is no woman for
a hairy man.”[435]

On the other hand, bearded races admire and greatly value their beards;
among the Anglo-Saxons every part of the body, according to their laws,
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.”[436]
In the East men swear solemnly by their beards. We have seen that
Chinsurdi, the chief of the Makalolo in Africa, evidently thought that
beards were a great ornament. With the Fijians in the Pacific the 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.”[437]

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.[438] 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 the above 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. He has
repeatedly found that he agreed with 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 an object of admiration. We should, however, bear in
mind that the depressed and very 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 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.”[439]

The truth of the principle, long ago insisted on by Humboldt,[440] 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 generally all the hairs on the
body, offers 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 flattened to such an extreme degree
as to appear to us like that of an idiot. 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 newborn children.” On the
other hand, “a broad, well-rounded occiput is considered a great
beauty” by the natives of the Fiji islands.[441]

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. So it is with the Malays of Sumatra, the Hottentots, certain
Negroes, and the natives of Brazil.[442] The Chinese have by nature
unusually small feet;[443] 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 I doubt whether many barbarous nations have 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.”[444] The same principle comes
largely into play in the art of selection; and we can thus understand,
as I have elsewhere explained,[445] the wonderful development of all the
races of animals and plants which are 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 behold, but they ardently desire to see each
characteristic feature a little more developed.

No doubt the perceptive powers of man and the lower animals are 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 no more than why certain
bodily sensations are agreeable and others disagreeable. 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 I know
of 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[446]
that ugliness consists in an approach to the structure of the lower
animals, and this no doubt is true with the more civilised nations, in
which intellect is highly appreciated; but a nose twice as prominent, or
eyes twice as large as usual, would not be an approach in structure to
any of the lower animals, and yet would be utterly hideous. The men of
each race prefer what they are accustomed to behold; they cannot endure
any great change; but they like variety, and admire each characteristic
point carried to a moderate extreme.[447] 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 points strongly
developed. No doubt characters of all kinds may easily be too much
developed for beauty. Hence a perfect beauty, which implies many
characters modified in a particular manner, will in every race be 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 in
our women 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 through sexual selection by the females
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 will have been 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 of life. 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, with the
exception of 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
largely depends on their intellectual powers and energy, or on the
fruits of these same powers in their forefathers.

There is, however, reason to believe that sexual selection has effected
something in certain civilised and semi-civilised nations. Many persons
are convinced, as it appears to me with justice, that the members of 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 of beauty,
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.”[448] 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,[449] who makes this statement, says that the women of
San-Giuliano are famous at the present day as the most beautiful in the
island, and are sought by artists as models. But it is obvious that the
evidence in the above cases is doubtful.

The following case, though relating to savages, is well worth giving
from 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 worse-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[450] 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.

_On the Causes which prevent or check the Action of Sexual Selection
with Savages._—The chief causes are, firstly, so-called communal
marriages or promiscuous intercourse; secondly, infanticide, especially
of female infants; 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 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 each other. The licentiousness of many savages is no doubt
astonishingly great, but it seems to me that more evidence is requisite
before we fully admit that their existing intercourse is absolutely
promiscuous. Nevertheless all those who have most closely studied the
subject,[451] and whose judgment is worth much more than mine, believe
that communal marriage was the original and universal form throughout
the world, including the intermarriage of brothers and sisters. The
indirect evidence in favour of this belief is extremely 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
alone, 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 communal 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 have been 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 many 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 of the
case 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. 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 ingeniously accounts[452] for the strange and
widely-extended habit of exogamy,—that is, the men of one tribe always
taking wives from a distinct tribe,—by communism having been the
original form of marriage; 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 might ultimately have become the universal habit. We
can also, according to Sir J. Lubbock,[452] 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 most 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.[453]

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 certain that the habit of
marriage has been gradually developed, and that almost promiscuous
intercourse was once extremely common throughout the world. Nevertheless
from the analogy of the lower animals, more particularly of those which
come nearest to man in the series, I cannot believe that this habit
prevailed at an extremely remote period, when man had hardly 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, as seems to be the case with the Orang. Several kinds, as some
of the Indian and American monkeys, are strictly monogamous, and
associate all the year round with their wives. Others are polygamous, as
the Gorilla and several American species, and each family lives
separate. Even when this occurs, the families inhabiting the same
district are probably to a certain extent social: the Chimpanzee, for
instance, is occasionally met with in large bands. Again, other species
are polygamous, but several males, each with their own females, live
associated in a body, as with several species of Baboons.[454] 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 offspring,
were to select the more attractive females, this would suffice for the
work of sexual selection.

Therefore, if we look far enough back in the stream of time, it is
extremely improbable that primeval men and women lived promiscuously
together. Judging from the social habits of man as he now exists, and
from most savages being polygamists, the most probable view is that
primeval man aboriginally lived in small communities, each with as many
wives as he could support and obtain, whom he would have jealously
guarded against all other men. Or he may have lived with several wives
by himself, 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.”[455] 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 with 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,[456] “that death alone can separate husband and wife.”
An intelligent Kandyan chief, of course a polygamist, “was perfectly
scandalized 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.[457] 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, as Azara states, 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. Wherever infanticide
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 most 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 and their happier fate, when few in
number, are assigned by the women themselves, and by various observers,
as additional motives for infanticide. In Australia, where female
infanticide is still common, Sir G. Grey estimated the proportion of
native women to men as one to three; but others say as two to three. In
a village on the eastern frontier of India, Colonel Macculloch found not
a single female child.[458]

When, owing to female infanticide, the women of a tribe are few in
number, 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 of capture
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 a
most 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, it is not probable that they would have selected the
more attractive women; they would have been too glad to have seized on
any woman. 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 have tended to
keep all the people inhabiting the same country nearly uniform in
character; and this would have greatly interfered with the power of
sexual selection in differentiating the tribes.

The scarcity of women, consequent on female infanticide, leads, also, to
another practice, namely polyandry, which is 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.[459] 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.[460] The very ugly men would perhaps altogether fail in
getting a wife, or get one later in life, but the handsomer men,
although the most 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
other parts of the world. The same consequences with reference to sexual
selection would to a certain extent follow when women are valued almost
exclusively as slaves or beasts of burden, as is the case with most
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 would
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 always comes into play together 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,[461] and generally marry young. Consequently they must be
subjected to occasional hard struggles for existence, and the favoured
individuals will alone survive.

Turning to primeval times when men had only doubtfully attained the rank
of manhood, they would probably have lived, as already stated, either as
polygamists or temporarily as monogamists. Their intercourse, judging
from analogy, would not then have been promiscuous. They would, no
doubt, have defended their females to the best of their power from
enemies of all kinds, and would probably have hunted for their
subsistence, as well as for that of their offspring. The most powerful
and able males would have succeeded best in the struggle for life and in
obtaining attractive females. At this early period the progenitors of
man, from having only feeble powers of reason, would not have looked
forward to distant contingencies. They would have been governed more by
their instincts and even 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 infanticide. There would have been no artificial scarcity of
women, and polyandry would not have been followed; there would have been
no early betrothals; women would not have been valued as mere slaves;
both sexes, if the females as well as the males were permitted to exert
any choice, would have chosen their partners, not for mental charms, or
property, or social position, but almost solely from external
appearance. All the adults would have married or paired, and all the
offspring, as far as that was possible, would have been reared; so that
the struggle for existence would have been periodically severe to an
extreme degree. Thus during these primordial times all the conditions
for sexual selection would have been much 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 much more powerful at a very remote period than at the present
day.


_On the Manner of Action of Sexual Selection with mankind._—With
primeval men under the favourable conditions just stated, and with those
savages who at the present time enter into any marriage tie (but subject
to greater or less interference according as the habits of female
infanticide, early betrothals, &c., are more or less practised), sexual
selection will probably have acted in the following manner. The
strongest and most vigorous men,—those who could best defend and hunt
for their families, and during later times the chiefs or
head-men,—those who were provided with the best weapons and who
possessed the most property, such as a larger number of dogs or other
animals, would have succeeded in rearing a greater average number of
offspring, than would the weaker, poorer and lower members of the same
tribes. There can, also, be no doubt that such men would generally have
been 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. Until recently, as I hear from Mr. Mantell, 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,[462] “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 common standard. 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 modify to a certain extent the character of the tribe.

With our domestic animals, when a foreign breed 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, whenever the means of comparison exist, a greater or
less amount of change. 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 two careful breeders rear
during many years animals of the same family, and do not compare them
together or with a common standard, the animals are found after a time
to have become to the surprise of their owners slightly different.[463]
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 to maturity the greater 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, in which some form of marriage
was practised, to spread over an unoccupied continent; they would soon
split up into distinct hordes, which would be 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;[464] and then unconscious selection would come into action
through the more powerful and leading savages preferring certain women
to others. Thus the differences between the tribes, at first very
slight, would gradually and inevitably be increased to a greater and
greater degree.


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,
instead of having been the selected, have been the selectors. We
recognise such cases by the females having been rendered 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, namely, with
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 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 decked this
sex in order to charm the females. As women have long been selected for
beauty, it is not surprising that some of the successive variations
should have been transmitted in a limited manner; and consequently that
women should have transmitted their beauty in a somewhat higher degree
to their female than to their male offspring. Hence women have become
more beautiful, as most persons will admit, than men. Women, however,
certainly transmit most of their characters, including beauty, to their
offspring of both sexes; so that the continued preference by the men of
each race of the more attractive women, according to their standard of
taste, would tend 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 most 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 the progenitors of
man. Man in all probability owes his beard, and perhaps some other
characters, to inheritance from an ancient progenitor who gained in this
manner 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 a beloved man; and with
the Charruas of S. America, as Azara states, the power of divorce is
perfectly free. With the Abipones, when a man chooses a wife he 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. 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.” 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.” 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.” So with the wild tribes of
the Malay archipelago there is a similar 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.”

Turning to Africa: the Kafirs buy their wives, and girls are severely
beaten by their fathers if they will not accept a chosen husband; yet 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. With the
degraded bushwomen 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.”[465] 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.”

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 handsomer 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 well endowed. 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 these two forms of
selection seem actually to have occurred, whether or not simultaneously,
with mankind, especially during the earlier periods of our long history.

We will now consider in a little more detail, relatively to sexual
selection, some of the characters which distinguish the several races of
man from each other and from the lower animals, namely, the more or less
complete absence of hair from 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, as far as I can see,
whether they have been acted on chiefly through 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
fœtus, 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 under a hot climate,
for he is thus exposed 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,
so that his body cannot have been divested of hair through natural
selection.[466] Nor have we any grounds for believing, as shewn in a
former chapter, that this can be due to the direct action of the
conditions to which man has long been exposed, 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 is a character
which 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 in 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. As these
animals gradually reach maturity the naked surfaces, as I am informed by
Mr. Bartlett, grow larger, relatively to the size of their bodies. The
hair, however, appears to have been removed in these cases, not for the
sake of nudity, but that the colour of the skin should be more fully
displayed. So again with many birds the head and neck have been divested
of feathers through sexual selection, for the sake of exhibiting the
brightly-coloured skin.

As woman has a less hairy body than man, and as this character is common
to all races, we may conclude that our female semi-human progenitors
were probably first partially divested of hair; and that this occurred
at an extremely remote period before the several races had diverged from
a common stock. As our female progenitors gradually acquired this new
character of nudity, they must have transmitted it in an almost equal
degree to their young offspring of both sexes; so that its transmission,
as in the case of many ornaments with mammals and birds, has not been
limited either by age or sex. There is nothing surprising in a partial
loss of hair having been esteemed as ornamental by the ape-like
progenitors of man, for we have seen that with animals of all kinds
innumerable strange characters have been thus esteemed, and have
consequently been modified through sexual selection. Nor is it
surprising that a character in a slight degree injurious should have
been thus acquired; for we know that this is the case with the plumes of
some birds, and with the horns of some stags.

The females of certain anthropoid apes, as stated in a former chapter,
are somewhat less hairy on the under surface than are 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. Hence the king of Siam had to bribe a man to
marry the first hairy woman in the family, who transmitted this
character to her young offspring of both sexes.[467]

Some races are much more hairy than others, especially on the male side;
but it must not be assumed that the more hairy races, for instance
Europeans, have retained a primordial condition more completely than
have the naked races, such as the Kalmucks or Americans. It is a more
probable view that the hairiness of the former is due to partial
reversion, for characters which have long been inherited are always apt
to return. 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,[468] and possibly with the Ainos, who inhabit the northern
islands of the Japan archipelago. But the laws of inheritance are so
complex than we can seldom understand their action. If the greater
hairiness of certain races be the result of reversion, unchecked by any
form of selection, the extreme variability of this character, even
within the limits of the same race, ceases to be remarkable.

With respect to the beard, if we turn to our best guide, namely the
Quadrumana, we find beards equally well developed in both sexes of many
species, but in others, 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 as an ornament through sexual
selection, transmitting them in most cases, in an equal or nearly equal
degree, to their offspring of both sexes. We know from Eschricht[469]
that with mankind, the female as well as the male fœtus is furnished
with much hair on the face, especially round the mouth; and this
indicates that we are descended from a progenitor, of which 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 when her body became almost completely divested of
hair. Even the colour of the beard with mankind 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. There is less improbability
in the men of the bearded races having retained their beards from
primordial times, than in the case of the hair on the body; for with
those Quadrumana, in which the male has a larger beard than that of the
female, it is fully developed only at maturity, and the later stages of
development may have been exclusively transmitted to mankind. We should
then see what is actually the case, namely, our male children, before
they arrive at maturity, as destitute of beards as are our female
children. On the other hand the great variability of the beard within
the limits of the same race and in different races indicates that
reversion has come into action. However this may be, we must not
overlook the part which sexual selection may have played even during
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.[470]

It is rather difficult to form a judgment how the long hair on our
heads became developed. Eschricht[471] states that in the human fœtus
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 consequently must 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 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 the colour of the
skin has been modified through sexual selection is wanting in the case
of mankind; for the sexes do not differ in this respect, or only
slightly and doubtfully. On the other hand we know from 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 be 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
has been gained through sexual selection; but this view is supported by
various analogies, and we know that negroes admire their own blackness.
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 shall be transmitted to both
sexes or to one alone. The resemblance of _Pithecia satanas_ with his
jet black skin, white rolling eyeballs, and hair parted on the top of
the head, to a negro in miniature, 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 good reason to
believe that the red, blue, orange, almost white and black tints of
their skin, even when common to both sexes, and the bright colours of
their fur, as well as the ornamental tufts of hair about the head, have
all been acquired through sexual selection. As the newly-born infants of
the most distinct races do not differ nearly as much in colour as do the
adults, although their bodies are completely destitute of hair, we have
some slight indication that the tints of the different races were
acquired subsequently to the removal of the hair, which, as before
stated, must have occurred at a very early period.


_Summary._—We may conclude that the greater size, strength, courage,
pugnacity, and even energy of man, in comparison with the same qualities
in 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, 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 to man as he now exists. The females apparently were
first denuded of hair in like manner 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 through the same means; so that women have acquired sweeter
voices and become more beautiful than men.

It deserves particular attention that with mankind all the conditions
for sexual selection were much more favourable, 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 not then have been so utterly licentious as many
savages now are; and each male would have jealously guarded his wife or
wives. He would not then 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 during a very
remote epoch; and this conclusion throws light on the remarkable fact
that at the most ancient period, of which we have as yet obtained 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 properly 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 amongst the lower animals, in
certain characters which are of no service to them in their ordinary
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 have been 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 as 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 by far the
most efficient.




CHAPTER XXI.

GENERAL 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 here 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 long endure; but false views,
if supported by some evidence, do little harm, as 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 arrived at in this work, 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 unmistakeable. The great principle of evolution
stands up clear and firm, when these groups of 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, independently of the uses to which the parts may be put, on the
same plan with that of other mammals—the occasional reappearance of
various structures, for instance of several distinct 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 are by no means requisite; slight
fluctuating differences in the individual suffice for the work of
natural selection. 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, will be long inherited. When one
part is modified, other parts will 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
as far as we can judge with our little knowledge, are not now of any
service to him, nor have been so during any former period of his
existence, either in relation to his general conditions of life, or 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 the unknown causes which produce them 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 the
greater number of cases we can only say that the cause of each slight
variation and of each monstrosity lies much more in the nature or
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 all 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 appropriately called sub-species. Some of these, for
instance 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 through inheritance from a common progenitor; and a
progenitor thus characterised would probably have deserved to rank as
man.

It must not be supposed that the divergence of each race from the other
races, and of all the races 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 best
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 and neglects all the inferior individuals. 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 in a much greater degree than the other
pairs which inhabit 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 position in the zoological
series. We thus learn that man is descended from a hairy quadruped,
furnished with a tail and pointed ears, 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 would the common and 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, either from
some reptile-like or 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 branchiæ, 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 developed. This animal seems to have been
more like the larvæ of our existing marine Ascidians than any other
known form.


The greatest difficulty which presents itself, when we are driven to the
above conclusion on the origin of man, is the high standard of
intellectual power and of moral disposition which he has attained. But
every one who admits the general principle of evolution, must see that
the mental powers of the higher animals, which are the same in kind with
those of mankind, 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. The development of these powers in animals 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 these faculties 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, enabling him to use language, to invent and
make weapons, tools, traps, &c.; by which means, in combination with 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, through a previous considerable advance, 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. The large size of the brain in man, in comparison with that of
the lower animals, relatively to the size of their bodies, may be
attributed in chief part, as Mr. Chauncey Wright has well remarked,[472]
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, and if they did arise could not be followed out. The higher
intellectual powers of man, such as those of ratiocination, abstraction,
self-consciousness, &c., will have followed from the continued
improvement of other mental faculties; but without considerable culture
of the mind, both in the race and in the individual, it is doubtful
whether these high powers would be exercised, and thus fully attained.

The development of the moral qualities is a more interesting and
difficult problem. Their foundation lies in the social instincts,
including in this term the family ties. These instincts are of a highly
complex nature, and in the case of the lower animals give special
tendencies towards certain definite actions; but the more important
elements for us are love, and the distinct emotion of sympathy. Animals
endowed with the social instincts take pleasure in each other’s company,
warn each other of danger, defend and aid each other in many ways. These
instincts are not extended 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 comparing his past and future
actions and motives,—of approving of some and disapproving of others;
and the fact that man is the one being who with certainty can be thus
designated makes the greatest of all distinctions between him and the
lower animals. But in our third chapter I have endeavoured to shew that
the moral sense follows, firstly, from the enduring and always present
nature of the social instincts, in which respect man agrees with the
lower animals; and secondly, from his mental faculties being highly
active and his impressions of past events extremely vivid, in which
respects he differs from the lower animals. Owing to this condition of
mind, man cannot avoid looking backwards and comparing the impressions
of past events and actions. He also continually looks forward. Hence
after some temporary desire or passion has mastered his social
instincts, he will reflect and compare the now weakened impression of
such past impulses, with the ever present social instinct; and he will
then feel that sense of dissatisfaction which all unsatisfied instincts
leave behind them. Consequently he resolves to act differently for the
future—and this is conscience. Any instinct which is 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 partly impelled by a wish to aid the members of the
same 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 being able to express his desires by words, which thus
become the guide to the aid required and bestowed. The motive to give
aid is likewise somewhat modified in man: it no longer consists solely
of a blind instinctive impulse, but is largely influenced by the praise
or blame of his fellow men. Both the appreciation and the bestowal of
praise and blame 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 more remote 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, from coming within the scope of public
opinion, receive praise, and their opposites receive blame. But with the
less civilised nations reason often errs, and many bad customs and base
superstitions come within the same scope, and consequently are esteemed
as high virtues, and their breach as heavy crimes.

The moral faculties are generally esteemed, and with justice, as of
higher value than the intellectual powers. But we should always 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
fact 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 of men more
vivid and strengthens the habit of recalling and comparing past
impressions, will make the conscience more sensitive, and may even
compensate to a certain extent for weak social affections and
sympathies.

The moral nature of man has reached the highest standard as yet
attained, partly through the advancement of the reasoning powers and
consequently of a just public opinion, but especially through the
sympathies being rendered more tender and widely diffused through the
effects of habit, example, instruction, and reflection. It is not
improbable that virtuous tendencies may through long practice be
inherited. With the more civilised races, the conviction of the
existence of an all-seeing Deity has had a potent influence on the
advancement of morality. Ultimately man no longer accepts the praise or
blame of his fellows as his chief guide, though few escape this
influence, but his habitual convictions controlled by reason afford him
the safest rule. His conscience then becomes his 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 the reasoning powers
of man, 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, possessing only a little more power than man; for the belief in
them is far more general than of a beneficent Deity. The idea of a
universal and beneficent Creator of the universe 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 lowly-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 the minute germinal vesicle to the
child either before or after birth, man becomes an immortal being; and
there is no greater cause for anxiety because the period in the
gradually ascending organic scale cannot possibly be determined.[473]

I am aware that the conclusions arrived at in this work will be
denounced by some as highly irreligious; but he who thus 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 these volumes; for,
as I have attempted to shew, it has played an important part in the
history of the organic world. As summaries have been given to each
chapter, it would be superfluous here to add a detailed summary. 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 two 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; and it deserves notice that we here find the intellectual
faculties developed, but in two very distinct lines, to the highest
standard, namely in the Hymenoptera (ants, bees, &c.) amongst the
Arthropoda, and in the Mammalia, including man, amongst the Vertebrata.

In the most distinct classes of the animal kingdom, with mammals,
birds, reptiles, fishes, insects, and even crustaceans, the differences
between the sexes follow almost exactly 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 producing 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 left 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 securing or charming the female are often developed in the male
during only part of the year, namely the breeding season. They have in
many cases been transferred in a greater or less degree to the females;
and in the latter case they appear in her as mere rudiments. They are
lost 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 resembles her young offspring throughout
life. In almost every great class a few anomalous cases occur in which
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 throughout all the
higher divisions of the animal kingdom 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 the individuals of the same
sex, generally the male sex, 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 continues for a long time choosing 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 sexes; as well as the age at which they shall be developed. It
appears that variations which arise 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, and 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. The characters which we have the best reason
for supposing to have been thus acquired are confined to one sex; and
this alone renders it probable that they are in some way connected with
the act of reproduction. These characters in innumerable instances 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 most active in courtship; they are the best
armed, and are rendered the most 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 display should be purposeless. Lastly we have distinct
evidence with some quadrupeds and birds that the individuals of the one
sex are capable of feeling a strong antipathy or preference for certain
individuals of the opposite sex.

Bearing these facts in mind, and not forgetting the marked results of
man’s unconscious selection, 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 larger 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 females 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 an astonishing fact that the females of many birds and some mammals
should be endowed with sufficient taste for what has apparently been
effected through sexual selection; and this is even more astonishing in
the case of reptiles, fish, and insects. But we really know very little
about the minds of the lower animals. It cannot be supposed that male
Birds of Paradise or Peacocks, for instance, should take so much 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, namely 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 be able to appreciate the
exquisite shading of the ball-and-socket ornaments and the elegant
patterns on the wing-feathers 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, as well as the
primary feathers, are displayed in a manner quite peculiar to this one
species during the act of courtship, and at no other time, 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 females having preferred during many
generations the more highly ornamented males; the æsthetic capacity of
the females having been advanced through exercise or habit in the same
manner as our own taste is gradually improved. In the male, through the
fortunate chance of a few feathers not having been modified, we can
distinctly see how simple spots with a little fulvous shading on one
side might have been developed by small and graduated 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 standard of taste which is implied by the
beauty of the males, and which generally coincides with our own
standard, should reflect that in each member of the vertebrate series
the nerve-cells of the brain are the direct offshoots of those possessed
by the common progenitor of the whole group. It thus becomes
intelligible that the brain and mental faculties should be capable under
similar conditions of nearly the same course of development, and
consequently of performing nearly the same functions.

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 has
apparently acted on both the male and female side, causing the two sexes
of man 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 cerebral 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, stripes and marks, and ornamental appendages, have all
been indirectly gained by the one sex or the other, through the
influence of love and jealousy, through the appreciation of the
beautiful in sound, colour or form, and through the exertion of a
choice; and these powers of the mind manifestly depend on the
development of the cerebral system.


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 are the lower animals when 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 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. All do good service who aid
towards this end. When the principles of breeding and of inheritance are
better understood, we shall not hear ignorant members of our legislature
rejecting with scorn a plan for ascertaining by an easy method 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 will 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 he must remain subject to a severe struggle. Otherwise he would
soon sink into indolence, and the more highly-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, &c., than through
natural selection; though to this latter agency the social instincts,
which afforded the basis for the development of the moral sense, may be
safely attributed.


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 persons. 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, practises
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 hopes 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 allows us to discover it. I have
given the evidence to the best of my ability; and we must 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.


  [1] Yarrell’s ‘Hist. of British Fishes,’ vol. ii. 1836, p. 417,
  425, 436. Dr. Günther informs me that the spines in _R.
  clavata_ are peculiar to the female.

  [2] See Mr. R. Warington’s interesting articles in ‘Annals and
  Mag. of Nat. Hist.’ Oct. 1852 and Nov. 1855.

  [3] Noel Humphreys, ‘River Gardens,’ 1857.

  [4] Loudon’s ‘Mag. of Natural History,’ vol. iii. 1830, p. 331.

  [5] ‘The Field,’ June 29th, 1867. For Mr. Shaw’s statement, see
  ‘Edinburgh Review,’ 1843. Another experienced observer
  (Scrope’s ‘Days of Salmon Fishing,’ p. 60) remarks that the
  male would, if he could, keep, like the stag, all other males
  away.

  [6] Yarrell, ‘History of British Fishes,’ vol. ii. 1836, p. 10.

  [7] ‘The Naturalist in Vancouver’s Island,’ vol. i. 1866, p.
  54.

  [8] ‘Scandinavian Adventures,’ vol. i. 1854, p. 100, 104.

  [9] See Yarrell’s account of the Rays in his ‘Hist. of British
  Fishes,’ vol. ii. 1836, p. 416, with an excellent figure, and
  p. 422, 432.

  [10] As quoted in ‘The Farmer,’ 1868, p. 369.

  [11] I have drawn up this description from Yarrell’s ‘British
  Fishes,’ vol. i. 1836, p. 261 and 266.

  [12] ‘Catalogue of Acanth. Fishes in the British Museum,’ by
  Dr. Günther, 1861, p. 138-151.

  [13] ‘Game Birds of Sweden,’ &c., 1867, p. 466.

  [14] With respect to this and the following species I am
  indebted to Dr. Günther for information: see also his paper on
  the Fishes of Central America, in ‘Transact. Zoolog. Soc.’ vol.
  vi. 1868, p. 485.

  [15] Dr. Günther makes this remark; ‘Catalogue of Fishes in the
  British Museum,’ vol. iii. 1861, p. 141.

  [16] See Dr. Günther on this genus, in ‘Proc. Zoolog. Soc.’
  1868, p. 232.

  [17] F. Buckland, in ‘Land and Water,’ July, 1868, p. 377, with
  a figure.

  [18] Dr. Günther, ‘Catalogue of Fishes,’ vol. iii. p. 221 and
  240.

  [19] See also ‘A Journey in Brazil,’ by Prof. and Mrs. Agassiz,
  1868, p. 220.

  [20] Yarrell, ‘British Fishes,’ vol. ii. 1836, p. 10, 12, 35.

  [21] W. Thompson, in ‘Annals and Mag. of Nat. History,’ vol.
  vi. 1841, p. 440.

  [22] ‘The American Agriculturist,’ 1868, p. 100.

  [23] ‘Annals and Mag. of Nat. Hist.’ Oct. 1852.

  [24] Loudon’s ‘Mag. of Nat. Hist.’ vol. v. 1832, p. 681.

  [25] Bory de Saint Vincent, in ‘Dict. Class. d’Hist. Nat.’ tom.
  ix. 1826, p. 151.

  [26] 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 goldfish 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 Hang-chow 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.”

  [27] ‘Westminster Review,’ July, 1867, p. 7.

  [28] “Indian Cyprinidæ,” by Mr. J. M’Clelland, ‘Asiatic
  Researches,’ vol. xix. part ii. 1839, p. 230.

  [29] ‘Proc. Zoolog. Soc.’ 1865, p. 327, pl. xiv. and xv.

  [30] Yarrell, ‘British Fishes,’ vol. ii. p. 11.

  [31] According to the observations of M. Gerbe; see Günther’s
  ‘Record of Zoolog. Literature,’ 1865, p. 194.

  [32] Cuvier, ‘Règne Animal,’ vol. ii. 1829, p. 242.

  [33] See Mr. Warington’s most interesting description of the
  habits of the _Gasterosteus leiurus_, in ‘Annals and Mag. of
  Nat. Hist.’ November, 1855.

  [34] Prof. Wyman, in ‘Proc. Boston Soc. of Nat. Hist.’ Sept.
  15, 1857. Also W. Turner, in ‘Journal of Anatomy and Phys.’
  Nov. 1, 1866, p. 78. Dr. Günther has likewise described other
  cases.

  [35] Yarrell, ‘Hist. of British Fishes,’ vol. ii. 1836, p. 329,
  338.

  [36] Dr. Günther, 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.

  [37] The Rev. C. Kingsley, in ‘Nature,’ May, 1870, p. 40.

  [38] Bell, ‘History of British Reptiles,’ 2nd edit. 1849, p.
  156-159.

  [39] Bell, ibid. p. 146, 151.

  [40] ‘Zoology of the Voyage of the “Beagle,”’ 1843. “Reptiles,”
  by Mr. Bell, p. 49.

  [41] ‘The Reptiles of India,’ by Dr. A. Günther, Ray Soc. 1864,
  p. 413.

  [42] Bell, ‘History of British Reptiles,’ 1849, p. 93.

  [43] J. Bishop, in ‘Todd’s Cyclop. of Anat. and Phys.’ vol. iv.
  p. 1503.

  [44] Bell, ibid. p. 112-114.

  [45] Mr. C. J. Maynard, ‘The American Naturalist,’ Dec. 1869,
  p. 555.

  [46] See my ‘Journal of Researches during the Voyage of the
  “Beagle,”’ 1845, p. 384.

  [47] ‘Travels through Carolina,’ &c., 1791, p. 128.

  [48] Owen, ‘Anatomy of Vertebrates,’ vol. i. 1866, p. 615.

  [49] Sir Andrew Smith, ‘Zoolog. of S. Africa: Reptilia,’ 1849,
  pl. x.

  [50] Dr. A. Günther, ‘Reptiles of British India,’ Ray Soc.
  1864, p. 304, 308.

  [51] Owen, ‘Anatomy of Vertebrates,’ vol. i. 1866, p. 615.

  [52] The celebrated botanist Schleiden incidently remarks
  (‘Ueber den Darwinismus: Unsere Zeit,’ 1869, s. 269), that
  Rattle-snakes use their rattles as a sexual call, by which the
  two sexes find each other. I do not know whether this
  suggestion rests on any direct observations. These snakes pair
  in the Zoological Gardens, but the keepers have never observed
  that they use their rattles at this season more than at any
  other.

  [53] “Rambles in Ceylon,” ‘Annals and Mag. of Nat. Hist.’ 2nd
  series, vol. ix. 1852, p. 333.

  [54] ‘Westminster Review,’ July 1st, 1867, p. 32.

  [55] Mr. N. L. Austen kept these animals alive for a
  considerable time, see ‘Land and Water,’ July, 1867, p. 9.

  [56] All these statements and quotations, in regard to
  Cophotis, Sitana and Draco, as well as the following facts in
  regard to Ceratophora, are Footnote: taken from Dr. Günther’s
  magnificent work on the ‘Reptiles of British India,’ Ray Soc.
  1864, p. 122, 130, 135.

  [57] Bell, ‘History of British Reptiles,’ 2nd edit. 1849, p.
  40.

  [58] 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. Günther, p. 143.

  [59] ‘Ibis,’ vol. iii. (new series) 1867, p. 414.

  [60] Gould, ‘Handbook to the Birds of Australia,’ 1865, vol.
  ii. p. 383.

  [61] Quoted by Mr. Gould, ‘Introduction to the Trochilidæ,’
  1861, p. 29.

  [62] Gould, ibid. p. 52.

  [63] W. Thompson, ‘Nat. Hist. of Ireland: Birds,’ vol. ii.
  1850, p. 327.

  [64] Jerdon, ‘Birds of India,’ 1863, vol. ii. p. 96.

  [65] Macgillivray, ‘Hist. Brit. Birds,’ vol. iv. 1852, p.
  177-181.

  [66] Sir R. Schomburgk, in ‘Journal of R. Geograph. Soc.’ vol.
  xiii. 1843, p. 31.

  [67] ‘Ornithological Biography,’ vol. i. p. 191. For pelicans
  and snipes, see vol. iii. p. 381, 477.

  [68] Gould, ‘Handbook of Birds of Australia,’ vol. i. p. 395;
  vol. ii. p. 383.

  [69] Mr. Hewitt in the ‘Poultry Book by Tegetmeier,’ 1866, p.
  137.

  [70] Layard, ‘Annals and Mag. of Nat. Hist.’ vol. xiv. 1854, p.
  63.

  [71] Jerdon, ‘Birds of India,’ vol. iii. p. 574.

  [72] Brehm, ‘Illust. Thierleben,’ 1867, B. iv. s. 351. Some of
  the foregoing statements are taken from L. Lloyd, ‘The Game
  Birds of Sweden,’ &c., 1867, p. 79.

  [73] Jerdon, ‘Birds of India:’ on Ithaginis, vol. iii. p. 523;
  on Galloperdix, p. 541.

  [74] 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’Amérique mérid.’ tom.
  iv. 1809, p. 179, 253.

  [75] 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.

  [76] Audubon, ‘Ornith. Biography,’ vol. ii. p. 492; vol. i. p.
  4-13.

  [77] Mr. Blyth, ‘Land and Water,’ 1867, p. 212.

  [78] Richardson, on Tetrao umbellus, ‘Fauna Bor. Amer.: Birds,’
  1831, p. 343. L. Lloyd, ‘Game Birds of Sweden,’ 1867, p. 22,
  79, on the capercailzie and black-cock. Brehm, however, asserts
  (‘Thierleben,’ &c., 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 grey-hens in Scandinavia, and
  with other species in N. America.

  [79] ‘Ornithological Biography,’ vol. ii. p. 275.

  [80] Brehm, ‘Thierleben,’ &c., B. iv. 1867, p. 990. Audubon,
  ‘Ornith. Biography,’ vol. ii. p. 492.

  [81] ‘Land and Water,’ July 25th, 1868, p. 14.

  [82] Audubon’s ‘Ornitholog. Biography;’ on Tetrao cupido, vol.
  ii. p. 492; on the Sturnus, vol. ii. p. 219.

  [83] ‘Ornithological Biograph.’ vol. v. p. 601.

  [84] The Hon. Daines Barrington, ‘Philosoph. Transact.’ 1773,
  p. 252.

  [85] ‘Ornithological Dictionary,’ 1833, p. 475.

  [86] ‘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.”

  [87] ‘Philosophical Transactions,’ 1773, p. 263. White’s
  ‘Natural History of Selborne,’ vol. i. 1825, p. 246.

  [88] ‘Naturges. der Stubenvögel,’ 1840, s. 252.

  [89] Mr. Bold, ‘Zoologist,’ 1843-44, p. 659.

  [90] D. Barrington, ‘Phil. Transact.’ 1773, p. 262. Bechstein,
  ‘Stubenvögel,’ 1840, s. 4.

  [91] This is likewise the case with the water-ouzel, see Mr.
  Hepburn in the ‘Zoologist,’ 1845-1846, p. 1068.

  [92] L. Lloyd, ‘Game Birds of Sweden,’ 1867, p. 25.

  [93] Barrington, ibid. p. 264. Bechstein, ibid. s. 5.

  [94] 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 from a
  caged bird a republican air.

  [95] Bishop, in ‘Todd’s Cyclop. of Anat. and Phys.’ vol. iv. p.
  1496.

  [96] As stated by Barrington in ‘Philosoph. Transact.’ 1773, p.
  262.

  [97] Gould, ‘Handbook to the Birds of Australia,’ vol. i. 1865,
  p. 308-310. See also Mr. T. W. Wood in the ‘Student,’ April,
  1870, p. 125.

  [98] See remarks to this effect in Gould’s ‘Introduction to the
  Trochilidæ,’ 1861, p. 22.

  [99] ‘The Sportsman and Naturalist in Canada,’ by Major W. Ross
  King, 1866, p. 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.

  [100] Richardson, ‘Fauna Bor. Americana: Birds,’ 1831, p. 359.
  Audubon, ibid. vol. iv. p. 507.

  [101] 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.

  [102] Bates, ‘The Naturalist on the Amazons,’ 1863, vol. ii. p.
  284; Wallace, in ‘Proc. Zool. Soc.’ 1850, p. 206. A new
  species, with a still larger neck-appendage (_C. penduliger_),
  has lately been discovered, see ‘Ibis,’ vol. i. p. 457.

  [103] Bishop, in Todd’s ‘Cyclop. of Anat. and Phys.’ vol. iv.
  p. 1499.

  [104] 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.

  [105] ‘Elements of Comp. Anat.’ by R. Wagner, Eng. translat.
  1845, p. 111. With respect to the swan, as given above,
  Yarrell’s ‘Hist. of British Birds,’ 2nd edit. 1845, vol. iii.
  p. 193.

  [106] C. L. Bonaparte, quoted in the ‘Naturalist Library:
  Birds,’ vol. xiv. p. 126.

  [107] L. Lloyd, ‘The Game Birds of Sweden,’ &c., 1867, p. 22,
  81.

  [108] Jenner, ‘Philosoph. Transactions,’ 1824, p. 20.

  [109] For the foregoing several facts see, on Birds of
  Paradise, Brehm, ‘Thierleben,’ Band iii. s. 325. On Grouse,
  Richardson, ‘Fauna Bor. Americ.: Birds,’ p. 343 and 359; Major
  W. Ross King, ‘The Sportsman in Canada,’ 1866, p. 156; 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, p. 84, 88, 89, and 95. On the Hoopoe, Mr.
  Swinhoe, in ‘Proc. Zoolog. Soc.’ June 23, 1863. On the
  Night-Jar, Audubon, ibid. vol. ii. p. 255. The English
  Night-Jar likewise makes in the spring a curious noise during
  its rapid flight.

  [110] See M. Meves’ interesting paper in ‘Proc. Zool. Soc.’
  1858, p. 199. For the habits of the snipe, Macgillivray, ‘Hist.
  British Birds,’ vol. iv. p. 371. For the American snipe, Capt.
  Blakiston, ‘Ibis,’ vol. v. 1863, p. 131.

  [111] Mr. Salvin, in ‘Proc. Zool. Soc.’ 1867, p. 160. I am much
  indebted to this distinguished ornithologist for sketches of
  the feathers of the Chamæpetes, and for other information.

  [112] Jerdon, ‘Birds of India,’ vol. iii. p. 618, 621.

  [113] Gould, ‘Introduction to the Trochilidæ,’ 1861, p. 49.
  Salvin, ‘Proc. Zoolog. Soc.’ 1867, p. 160.

  [114] Sclater, in ‘Proc. Zool. Soc.’ 1860, p. 90, and in
  ‘Ibis,’ vol. iv. 1862, p. 175. Also Salvin, in ‘Ibis,’ 1860, p.
  37.

  [115] ‘The Nile Tributaries of Abyssinia,’ 1867, p. 203.

  [116] 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,
  ‘Ornith. Biography,’ vol. ii. p. 51, and vol. iii. p. 89. On
  the White-throat, Macgillivray, ‘Hist. British Birds,’ vol. ii.
  p. 354. On the Indian Bustard, Jerdon, ‘Birds of India,’ vol.
  iii. p. 618.

  [117] Gould, ‘Handbook to the Birds of Australia,’ vol. i. p.
  444, 449, 455. The bower of the Satin Bower-bird may always be
  seen in the Zoological Society’s Gardens, Regent’s Park.

  [118] See remarks to this effect, on the “Feeling of Beauty
  among Animals,” by Mr. J. Shaw, in the ‘Athenæum,’ Nov. 24th,
  1866, p. 681.

  [119] Mr. Monteiro, ‘Ibis,’ vol. iv. 1862, p. 339.

  [120] ‘Land and Water,’ 1868, p. 217.

  [121] Jardine’s ‘Naturalist Library: Birds,’ vol. xiv. p. 166.

  [122] Sclater, in the ‘Ibis,’ vol. vi. 1864, p. 114.
  Livingstone, ‘Expedition to the Zambesi,’ 1865, p. 66.

  [123] Jerdon, ‘Birds of India,’ vol. iii. p. 620.

  [124] Wallace, in ‘Annals and Mag. of Nat. Hist.’ vol. xx.
  1857, p. 416; and in his ‘Malay Archipelago,’ vol. ii. 1869, p.
  390.

  [125] See my work on ‘The Variation of Animals and Plants under
  Domestication,’ vol. i. p. 289, 293.

  [126] Quoted from M. de Lafresnaye, in ‘Annals and Mag. of Nat.
  Hist.’ vol. xiii. 1854, p. 157: see also Mr. Wallace’s much
  fuller account in vol. xx. 1857, p. 412, and in his Malay
  Archipelago.

  [127] Wallace, ‘The Malay Archipelago,’ vol. ii. 1869, p. 405.

  [128] 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.

  [129] ‘Land and Water,’ 1867, p. 394.

  [130] Mr. D. G. Elliot, in ‘Proc. Zool. Soc.’ 1869, p. 589.

  [131] ‘Nitzsch’s Pterylography,’ edited by P. L. Sclater. Ray
  Soc. 1867, p. 14.

  [132] 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.

  [133] In regard to the previous statements on moulting, see, on
  snipes, &c., Macgillivray, ‘Hist. Brit. Birds,’ vol. iv. p.
  371; on Glareolæ, curlews, and bustards, Jerdon, ‘Birds of
  India,’ vol. iii. p. 615, 630, 683; on Totanus, ibid, p. 700;
  on the plumes of herons, ibid, p. 738, and Macgillivray, vol.
  iv. p. 435 and 444, and Mr. Stafford Allen, in the ‘Ibis,’ vol.
  v. 1863, p. 33.

  [134] On the moulting of the ptarmigan, see Gould’s ‘Birds of
  Great Britain.’ On the honey-suckers, Jerdon, ‘Birds of India,’
  vol. i. p. 359, 365, 369. On the moulting of Anthus, see Blyth,
  in ‘Ibis,’ 1867, p. 32.

  [135] 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. p. 617,
  637, 709, 711. Also Blyth in ‘Land and Water,’ 1867, p. 84. 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 Nat.
  Hist.’ vol. i. 1848, p. 455; see, also, on this subject, my
  ‘Variation of Animals under Domestication,’ vol. i. p. 236.

  [136] See Macgillivray, ‘Hist. British Birds’ (vol. v. p. 34,
  70, and 223), on the moulting of the Anatidæ, with quotations
  from Waterton and Montagu. Also Yarrell, ‘Hist. of British
  Birds,’ vol. iii. p. 243.

  [137] On the pelican, see Sclater, in ‘Proc. Zool. Soc.’ 1868,
  p. 265. On the American finches, see Audubon, ‘Ornith.
  Biography,’ vol. i. p. 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.

  [138] See also ‘Ornamental Poultry,’ by Rev. E. S. Dixon, 1848,
  p. 8.

  [139] ‘Birds of India,’ introduct. vol. i. p. xxiv.; on the
  peacock, vol. iii. p. 507. See Gould’s ‘Introduction to the
  Trochilidæ,’ 1861, p. 15 and 111.

  [140] ‘Journal of R. Geograph. Soc.’ vol. x. 1840, p. 236.

  [141] ‘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.

  [142] Mr. T. W. Wood has given (‘The Student,’ April, 1870, p.
  115) a full account of this manner of display, which he calls
  the lateral or one-sided, by the gold pheasant and by the
  Japanese pheasant, _Ph. versicolor_.

  [143] The Reign of Law,’ 1867, p. 263.

  [144] For the description of these birds, see Gould’s ‘Handbook
  to the Birds of Australia,’ vol. i. 1865, p. 417.

  [145] ‘Birds of India,’ vol. ii. p. 96.

  [146] 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, p.
  210, 457.

  [147] Tegetmeier, ‘The Poultry Book,’ 1866, p. 139.

  [148] Nordmann describes (‘Bull. Soc. Imp. des Nat. Moscow,’
  1861, tom. xxxiv. p. 264) the balzen of _Tetrao urogalloides_
  in Amur Land. He estimated the number of assembled males at
  above a hundred, the females, which lie hid in the surrounding
  bushes, not being counted. The noises uttered differ from those
  of the _T. urogallus_ or the capercailzie.

  [149] 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, p. 19, 78. Richardson, ‘Fauna Bor.
  Americana,’ Birds, p. 362. References in regard to the
  assemblages of other birds have previously 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.

  [150] Quoted by Mr. T. W. Wood in the ‘Student,’ April, 1870,
  p. 125.

  [151] Gould, ‘Handbook of Birds of Australia,’ vol. i. p. 300,
  308, 448, 451. On the ptarmigan, above alluded to, see Lloyd,
  ibid. p. 129.

  [152] On magpies, Jenner, in ‘Phil. Transact.’ 1824, p. 21.
  Macgillivray, ‘Hist. British Birds,’ vol. i. p. 570. Thompson,
  in ‘Annals and Mag. of Nat. Hist.’ vol. viii. 1842, p. 494.

  [153] 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 Phœnicura, 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 same
  day.

  [154] 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
  starling 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.

  [155] The following case has been given (‘The Times,’ Aug. 6th,
  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 in 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.”

  [156] For instance, Mr. Yarrell states (‘Hist. British Birds,’
  vol. iii. 1845, p. 585) that a gull was not able to swallow a
  small bird which had been given to it. The gull “paused for a
  moment, and then, as if suddenly recollecting himself, ran off
  at full speed to a pan of water, shook the bird about in it
  until well soaked, and immediately gulped it down. Since that
  time he invariably has had recourse to the same expedient in
  similar cases.”

  [157] ‘A Tour in Sutherlandshire,’ vol. i. 1849, p. 185.

  [158] ‘Acclimatization of Parrots,’ by C. Buxton, M.P. ‘Annals
  and Mag. of Nat. Hist.’ Nov. 1868, p. 381.

  [159] ‘The Zoologist,’ 1847-1848, p. 1602.

  [160] Hewitt on wild ducks, ‘Journal of Horticulture,’ Jan. 13,
  1863, p. 39. Audubon on the wild turkey, ‘Ornith. Biography,’
  vol. i. p. 14. On the mocking thrush, ibid. vol. i. p. 110.

  [161] The ‘Ibis,’ vol. ii. 1860, p. 344.

  [162] On the ornamented nests of humming-birds, Gould,
  ‘Introduction to the Trochilidæ,’ 1861, p. 19. On the
  bower-birds, Gould, ‘Handbook to the Birds of Australia,’ 1865,
  vol. i. p. 444-461. Mr. Ramsay in the ‘Ibis,’ 1867, p. 456.

  [163] ‘Hist. of British Birds,’ vol. ii. p. 92.

  [164] ‘Zoologist,’ 1853-1854, p. 3946.

  [165] Waterton, ‘Essays on Nat. Hist.’ 2nd series, p. 42, 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.

  [166] Audubon, ‘Ornitholog. Biography,’ vol. i. p. 191, 349;
  vol. ii. p. 42, 275; vol. iii. p. 2.

  [167] ‘Rare and Prize Poultry,’ 1854, p. 27.

  [168] ‘The Variation of Animals and Plants under
  Domestication,’ vol. ii. p. 103.

  [169] Boitard and Corbié, ‘Les Pigeons,’ 1824, p. 12. Prosper
  Lucas (‘Traité de l’Héréd. Nat.’ tom. ii. 1850, p. 296) has
  himself observed nearly similar facts with pigeons.

  [170] ‘Die Taubenzucht,’ 1824, s. 86.

  [171] ‘Ornithological Biography,’ vol. i. p. 13.

  [172] ‘Proc. Zool. Soc.’ 1835, p. 54. The japanned peacock is
  considered by Mr. Sclater as a distinct species, and has been
  named _Pavo nigripennis_.

  [173] Rudolphi, ‘Beyträge zur Anthropologie,’ 1812, s. 184.

  [174] ‘Die Darwin’sche Theorie, und ihre Stellung zu Moral und
  Religion,’ 1869, s. 59.

  [175] 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.

  [176] Mr. Hewitt, quoted in ‘Tegetmeier’s Poultry Book,’ 1866,
  p. 165.

  [177] Quoted in Lloyd’s ‘Game Birds of Sweden,’ p. 345.

  [178] According to Dr. Blasius (‘Ibis,’ vol. ii. 1860, p. 297),
  there are 425 indubitable species of birds which breed in
  Europe, besides 60 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.

  [179] ‘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.

  [180] ‘Introduct. to the Trochilidæ,’ p. 102.

  [181] Gould, ‘Handbook of Birds of Australia,’ vol. ii. p. 32
  and 68.

  [182] Audubon, ‘Ornitholog. Biography,’ 1838, vol. iv. p. 389.

  [183] Jerdon, ‘Birds of India,’ vol. i. p. 108; and Mr. Blyth,
  in ‘Land and Water,’ 1868, p. 381.

  [184] Graba, ‘Tagebuch, Reise nach Färo,’ 1830, s. 51-54.
  Macgillivray, ‘Hist. British Birds,’ vol. iii. p. 745. ‘Ibis,’
  vol. v. 1863, p. 469.

  [185] Graba, ibid. s. 54. Macgillivray, ibid. vol. v. p. 327.

  [186] ‘Variation of Animals and Plants under Domestication.’
  vol. ii. p. 92.

  [187] On these points see also ‘Variation of Animals and Plants
  under Domestication,’ vol. i. p. 253; vol. ii. p. 73, 75.

  [188] See, for instance, on the irides of a Podica and
  Gallicrex in ‘Ibis,’ vol. ii. 1860, p. 206; and vol. v. 1863,
  p. 426.

  [189] See also Jerdon, ‘Birds of India,’ vol. i. p. 243-245.

  [190] ‘Zoology of the Voyage of H.M.S. Beagle,’ 1841, p. 6.

  [191] Bechstein, ‘Naturgeschichte Deutschlands,’ B. iv. 1795,
  s. 31, on a sub-variety of the Monck pigeon.

  [192] 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
  Africæ Australis,’ p. 186. See also an interesting paper by the
  Rev. H. H. Higgins, on the origin of the ocelli in the
  Lepidoptera in the ‘Quarterly Journal of Science,’ July, 1868,
  p. 325.

  [193] Jerdon, ‘Birds of India,’ vol. iii. p. 517.

  [194] ‘Variation of Animals and Plants under Domestication,’
  vol. i. p. 254.

  [195] When the Argus pheasant displays his wing-feathers like a
  great fan, those nearest to the body stand more upright than
  the outer ones, so that the shading of the ball-and-socket
  ocelli ought to be slightly different on the different
  feathers, in order to bring out their full effect, relatively
  to the incidence of the light. Mr. T. W. Wood, who has the
  experienced eye of an artist, asserts (‘Field,’ Newspaper, May
  28, 1870, p. 457) that this is the case; but after carefully
  examining two mounted specimens (the proper feathers from one
  having been given to me by Mr. Gould for more accurate
  comparison) I cannot perceive that this acme of perfection in
  the shading has been attained; nor can others to whom I have
  shewn these feathers recognise the fact.

  [196] ‘The Reign of Law,’ 1867, p. 247.

  [197] ‘Introduction to the Trochilidæ,’ 1861, p. 110.

  [198] Fourth edition, 1866, p. 241.

  [199] ‘Westminster Review,’ July, 1867. ‘Journal of Travel,’
  vol. i. 1868, p. 73.

  [200] Temminck says that the tail of the female _Phasianus
  Sœmmerringii_ is only six inches long, ‘Planches
  coloriées,’ vol. v. 1838, p. 487 and 488: the measurements
  above given were made for me by Mr. Sclater. For the common
  pheasant, see Macgillivray, ‘Hist. Brit. Birds,’ vol. i. p.
  118-121.

  [201] Dr. Chapuis, ‘Le Pigeon Voyageur Belge,’ 1865, p. 87.

  [202] Bechstein, ‘Naturgesch. Deutschlands,’ 1793, B. iii. s.
  339.

  [203] Daines Barrington, however, thought it probable (‘Phil.
  Transact.’ 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.

  [204] Mr. Ramsay, in ‘Proc. Zoolog. Soc.’ 1868, p. 50.

  [205] ‘Journal of Travel,’ edited by A. Murray, vol. i. 1868,
  p. 78.

  [206] ‘Journal of Travel,’ edited by A. Murray, vol. i. 1868,
  p. 281.

  [207] Audubon, ‘Ornithological Biography,’ vol. i. p. 233.

  [208] Jerdon, ‘Birds of India,’ vol. ii. p. 108. Gould’s
  ‘Handbook of the Birds of Australia,’ vol. i. p. 463.

  [209] 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.

  [210] 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, than during cool, cloudy, or rainy weather.

  [211] I may specify, as instances of obscurely-coloured birds
  building concealed nests, the species belonging to eight
  Australian genera, described in Gould’s ‘Handbook of the Birds
  of Australia,’ vol. i. p. 340, 362, 365, 383, 387, 389, 391,
  414.

  [212] Jerdon, ‘Birds of India,’ vol. i. p. 244.

  [213] On the nidification and colours of these latter species,
  see Gould’s ‘Handbook,’ &c., vol. i. p. 504, 527.

  [214] 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
  of 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, according to the above
  standard, as conspicuous: Passer, 2 species; Sturnus, of which
  the female is considerably less brilliant than the male;
  Cinclus; Motacilla 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.
  cæruleus, Upupa, Picus, 4 sp., Coracias, Alcedo, and Merops.

  [215] ‘Journal of Travel,’ edited by A. Murray, vol. i. p. 78.

  [216] 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.

  [217] See his ‘Monograph of the Trogonidæ,’ first edition.

  [218] Namely Cyanalcyon. Gould’s ‘Handbook of the Birds of
  Australia,’ vol. i. p. 133; see, also, p. 130, 136.

  [219] Every gradation of difference between the sexes may be
  followed in the parrots of Australia. See Gould’s ‘Handbook,’
  &c., vol. ii. p. 14-102.

  [220] Macgillivray’s ‘British Birds,’ vol. ii. p. 433. Jerdon,
  ‘Birds of India,’ vol. ii. p. 282.

  [221] All the following facts are taken from M. Malherbe’s
  magnificent ‘Monographie des Picidées,’ 1861.

  [222] Audubon’s ‘Ornithological Biography,’ vol. ii. p. 75; see
  also the ‘Ibis,’ vol. i. p. 268.

  [223] Gould’s ‘Handbook of the Birds of Australia,’ vol. ii. p.
  109-149.

  [224] See remarks to this effect in my work on ‘Variation under
  Domestication,’ vol. ii. chap, xii.

  [225] The ‘Ibis,’ vol. vi. 1864, p. 122.

  [226] On Ardetta, Translation of Cuvier’s ‘Règne 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 Palæornis, see,
  also, Jerdon, ‘Birds of India,’ vol. i. p. 263. On the wild
  turkey, Audubon, ibid. vol. i. p. 15: I hear from Judge Caton
  that in Illinois the female very rarely acquires a tuft.

  [227] Mr. Blyth has recorded (Translation of Cuvier’s ‘Règne
  Animal,’ p. 158) various instances with Lanius, Ruticilla,
  Linaria, and Anas. Audubon has also recorded a similar case
  (‘Ornith. Biog.’ vol. v. p. 519) with _Tyranga æstiva_.

  [228] See Gould’s ‘Birds of Great Britain.’

  [229] 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 ‘Règne
  Animal,’ p. 159. I give the case of Loxia from Mr. Blyth’s
  information. On thrushes, see also Audubon, ‘Ornith.
  Biography,’ 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.

  [230] See, for instance, Mr. Gould’s account (‘Handbook of 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. p. 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 _Palæornis rosa_, in which the
  young are more like the female than the male. See Audubon
  (‘Ornith. Biograph.’ vol. ii. p. 475) on the two sexes and the
  young of _Columba passerina_.

  [231] I owe this information to Mr. Gould who shewed me the
  specimens; see also his ‘Introduction to the Trochilidæ,’ 1861,
  p. 120.

  [232] Macgillivray, ‘Hist. Brit. Birds,’ vol. v. p. 207-214.

  [233] 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.

  [234] 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,’ Jan. 1861, p. 52.

  [235] Wallace, ‘The Malay Archipelago,’ vol. ii. 1869, p. 394.

  [236] These species are described, with coloured figures, by M.
  F. Pollen, in ‘Ibis,’ 1866, p. 275.

  [237] ‘Variation of Animals, &c., under Domestication,’ vol. i.
  p. 251.

  [238] Macgillivray, ‘Hist. British Birds,’ vol. i. p. 172-174.

  [239] See, on this subject, chap. xxiii. in the ‘Variation of
  Animals and Plants under Domestication.’

  [240] Audubon, ‘Ornith. Biography,’ vol. i. p. 193.
  Macgillivray, ‘Hist. Brit. Birds,’ vol. iii. p. 85. See also
  the case before given of _Indopicus carlotta_.

  [241] ‘Westminster Review,’ July, 1867, and A. Murray, ‘Journal
  of Travel,’ 1868, p. 83.

  [242] For the Australian species, see Gould’s ‘Handbook,’ &c.,
  vol. ii. p. 178, 180, 186, and 188. In the British Museum
  specimens of the Australian Plain-wanderer (_Pedionomus
  torquatus_) may be seen, shewing similar sexual differences.

  [243] Jerdon, ‘Birds of India,’ vol. iii. p. 596. Mr. Swinhoe,
  in ‘Ibis,’ 1865, p. 542; 1866, p. 131, 405.

  [244] Jerdon, ‘Birds of India,’ vol. iii. p. 677.

  [245] Gould’s ‘Handbook of the Birds of Australia,’ vol. ii. p.
  275.

  [246] ‘The Indian Field,’ Sept. 1858, p. 3.

  [247] ‘Ibis,’ 1866, p. 298.

  [248] 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.

  [249] 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.

  [250] ‘The Student,’ April, 1870, p. 124.

  [251] 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.

  [252] Mr. Sclater, on the incubation of the Struthiones, ‘Proc.
  Zoo. Soc.,’ June 9, 1863.

  [253] For the Milvago, see ‘Zoology of the Voyage of the
  “Beagle,”’ Birds, 1841, p. 16. For the Climacteris and
  nightjar (Eurostopodus), see Gould’s ‘Handbook of the Birds of
  Australia,’ vol. i. p. 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 he may altogether 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 (‘Proc. Zool. Soc.’ 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.

  [254] Jerdon, ‘Birds of India,’ vol. iii. p. 598.

  [255] Jerdon, ‘Birds of India,’ vol. i. p. 222, 228. Gould’s
  ‘Handbook of the Birds of Australia,’ vol. i. 124, 130.

  [256] Gould, Ibid. vol. ii. p. 37, 46, 56.

  [257] Audubon, ‘Ornith. Biography,’ vol. ii. p. 55.

  [258] ‘Variation of Animals and Plants under Domestication,’
  vol. ii. p. 79.

  [259] Charlesworth, ‘Mag. of Nat. Hist.’ vol. i. 1837, p. 305,
  306.

  [260] ‘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_).

  [261] I am indebted to Mr. Blyth for information in regard to
  this genus. The sparrow of Palestine belongs to the sub-genus
  Petronia.

  [262] For instance, the males of _Tanagra æstiva_ and
  _Fringilla cyanea_ require three years, the male of _Fringilla
  ciris_ four years, to complete their beautiful plumage. (See
  Audubon, ‘Ornith. Biography,’ vol. i. p. 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. J. 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.

  [263] 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. p. 133, 139, 211.

  [264] Mr. Blyth, in Charlesworth’s ‘Mag. of Nat. Hist.’ vol. i.
  1837, p. 300. Mr. Bartlett has informed me in regard to
  gold-pheasants.

  [265] I have noticed the following cases in Audubon’s ‘Ornith.
  Biography. The Redstart of America’ (_Muscicapa 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 cærulea_ 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.

  [266] See the last footnote.

  [267] 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, in
  accordance with Mr. Cope’s views, expressed under the terms of
  the “retardation and acceleration of generic characters;” but I
  cannot follow the views of this eminent naturalist to their
  full extent. See Mr. Cope, “On the Origin of Genera,” from the
  ‘Proc. of Acad. Nat. Sc. of Philadelphia,’ Oct. 1868.

  [268] Jerdon, ‘Birds of India,’ vol. iii. p. 507, on the
  peacock. Audubon, ibid. vol. iii. p. 139, on the Ardea.

  [269] For illustrative cases see vol. iv. of Macgillivray’s
  ‘Hist. Brit. Birds;’ on Tringa, &c., p. 229, 271; on the
  Machetes, p. 172; on the _Charadrius hiaticula_, p. 118; on the
  _Charadrius pluvialis_, p. 94.

  [270] For the goldfinch of N. America, _Fringilla tristis_,
  Linn., see Audubon, ‘Ornith. Biography,’ vol. i. p. 172. For
  the Maluri, Gould’s ‘Handbook of the Birds of Australia,’ vol.
  i. p. 318.

  [271] I am indebted to Mr. Blyth for information in regard to
  the Buphus; see also Jerdon, ‘Birds of India,’ vol. iii. p.
  749. On the Anastomus, see Blyth, in ‘Ibis,’ 1867, p. 173.

  [272] 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.

  [273] ‘History of British Birds,’ vol. i. 1839, p. 159.

  [274] Blyth, in Charlesworth’s ‘Mag. of Nat. Hist.’ vol. i.
  1837, p. 362; and from information given to me by him.

  [275] Audubon, ‘Ornith. Biography,’ vol. i. p. 113.

  [276] Mr. C. A. Wright, in ‘Ibis,’ vol. vi. 1864, p. 65.
  Jerdon, ‘Birds of India,’ vol. i. p. 515.

  [277] 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 with 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.

  [278] ‘Westminster Review,’ July, 1867, p. 5.

  [279] ‘Ibis,’ 1859, vol. i. p. 429, _et seq._

  [280] 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 beak 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.

  [281] Ramphastos carinatus, Gould’s ‘Monograph of Ramphastidæ.’

  [282] On Larus, Gavia, and Sterna, see Macgillivray, ‘Hist.
  Brit. Birds,’ vol. v. p. 515, 584, 626. On the Anser
  hyperboreus, Audubon, ‘Ornith. Biography,’ vol. iv. p. 562. On
  the Anastomus, Mr. Blyth, in ‘Ibis,’ 1867, p. 173.

  [283] It may be noticed that with vultures, which roam far and
  wide through the higher regions of the atmosphere, like marine
  birds over the ocean, three or four species are almost wholly
  or largely white, and many other species are black. This fact
  supports the conjecture that these conspicuous colours may aid
  the sexes in finding each other during the breeding-season.

  [284] ‘The Journal of Travel,’ edited by A. Murray, vol. i.
  1868, p. 286.

  [285] See Jerdon on the genus Palæornis, ‘Birds of India,’ vol.
  i. p. 258-260.

  [286] The young of _Ardea rufescens_ and _A. cærulea_ of the
  U. States are likewise white, the adults being coloured in
  accordance with their specific names. Audubon (‘Ornith.
  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.”

  [287] 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. By this means I have been saved from
  making mistakes about the names of the species, and from giving
  any facts which are actually 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.

  [288] See Waterton’s account of two hares fighting,
  ‘Zoologist,’ vol. i. 1843, p. 211. On moles, Bell, ‘Hist. of
  British Quadrupeds,’ 1st edit. p. 100. On squirrels, Audubon
  and Bachman, ‘Viviparous Quadrupeds of N. America,’ 1846, p.
  269. On beavers, Mr. A. H. Green, in ‘Journal of Lin. Soc.
  Zoolog.’ vol. x. 1869, p. 362.

  [289] On the battles of seals, see Capt. C. Abbott in ‘Proc.
  Zool. Soc.’ 1868, p. 191; also Mr. R. Brown, ibid. 1869, 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.

  [290] See Scrope (‘Art of Deer-stalking,’ p. 17) on the locking
  of the horns with the Cervus elephas. 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.

  [291] 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, ‘Proc. Zool. Soc.’ 1868, p. 429.

  [292] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 283.

  [293] Mr. R. Brown, in ‘Proc. Zool. Soc.’ 1869, p. 553.

  [294] Owen on the Cachalot and Ornithorhynchus, ibid. vol. iii.
  p. 638, 641.

  [295] On the structure and shedding of the horns of the
  reindeer, Hoffberg, ‘Amœnitates 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.

  [296] 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 edit. 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.”

  [297] On the Cervulus, Dr. Gray, ‘Catalogue of the Mammalia in
  British Museum,’ part iii. p. 220. On the _Cervus Canadensis_
  or Wapiti see Hon. J. D. Caton, ‘Ottawa Acad. of Nat.
  Sciences,’ May, 1868, p. 9.

  [298] 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.

  [299] Gray, ‘Catalogue Mamm. Brit. Mus.’ part iii. 1852, p.
  160.

  [300] Richardson, ‘Fauna Bor. Americana,’ p. 278.

  [301] ‘Land and Water,’ 1867, p. 346.

  [302] Sir Andrew Smith, ‘Zoology of S. Africa,’ pl. xix. Owen,
  ‘Anatomy of Vertebrates,’ vol. iii. p. 624.

  [303] Sir J. Emerson Tennent, ‘Ceylon,’ 1859, vol. ii. p. 274.
  For Malacca, ‘Journal of Indian Archipelago,’ vol. iv. p. 357.

  [304] ‘Calcutta Journal of Nat. Hist.’ vol. ii. 1843, p. 526.

  [305] 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.

  [306] M. E. M. Bailly, “sur l’usage des Cornes,” &c., ‘Annal.
  des Sc. Nat.’ tom. ii. 1824, p. 369.

  [307] Owen, on the Horns of Red-deer, ‘British Fossil Mammals,’
  1846, p. 478; ‘Forest Creatures,’ by Charles Boner, 1861, p.
  76, 62. Richardson on the Horns of the Reindeer, ‘Fauna Bor.
  Americana,’ 1829, p. 210.

  [308] 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 Sc. Nat.’ tom. ii. 1824, p. 371.

  [309] See a most interesting account in the Appendix to Hon. J.
  D. Caton’s paper, as above quoted.

  [310] ‘The American Naturalist,’ Dec. 1869, p. 552.

  [311] Pallas, ‘Spicilegia Zoologica,’ fasc. xiii. 1779, p. 18.

  [312] Lamont, ‘Seasons with the Sea-Horses,’ 1861, p. 141.

  [313] See also Corse (‘Philosoph. Transact.’ 1799, p. 212) on
  the manner in which the short-tusked Mooknah variety of the
  elephant attacks other elephants.

  [314] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 349.

  [315] See Rüppell (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 (‘Palæont. 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.

  [316] Emerson Tennent, ‘Ceylon,’ 1859, vol. ii. p. 275; Owen,
  ‘British Fossil Mammals,’ 1846, p. 245.

  [317] Richardson, ‘Fauna Bor. Americana,’ on the moose, _Alces
  palmata_, p. 236, 237; also on the expanse of the horns ‘Land
  and Water,’ 1869, p. 143. See also Owen, ‘British Fossil
  Mammals,’ on the Irish elk, p. 447, 455.

  [318] ‘Forest Creatures,’ by C. Boner, 1861, p. 60.

  [319] See the very interesting paper by Mr. J. A. Allen in
  ‘Bull. Mus. Comp. Zoolog. of Cambridge; United States,’ vol.
  ii. No. 1, p. 82. The weights were ascertained by a careful
  observer, Capt. Bryant.

  [320] ‘Animal Economy,’ p. 45.

  [321] See also Richardson’s ‘Manual on the Dog,’ p. 59. Much
  valuable information on the Scottish deerhound 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.

  [322] Brehm, ‘Thierleben,’ B. ii. s. 729-732.

  [323] See Mr. Wallace’s interesting account of this animal,
  ‘The Malay Archipelago,’ 1869, vol. i. p. 435.

  [324] ‘The Times,’ Nov. 10th, 1857. In regard to the Canada
  lynx, see Audubon and Bachman, ‘Quadrupeds of N. America,’
  1846, p. 139.

  [325] 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.

  [326] 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.

  [327] Mr. J. A. Allen in ‘Bull. Mus. Comp. Zoolog. of
  Cambridge, United States,’ vol. ii. No. 1, p. 99.

  [328] ‘Dogs: their Management,’ by E. Mayhew, M.R.C.V.S., 2nd
  edit. 1864, p. 187-192.

  [329] Quoted by Alex. Walker ‘On Intermarriage,’ 1838, p. 276;
  see also p. 244.

  [330] ‘Traité de l’Héréd. Nat.’ tom. ii. 1850, p. 296.

  [331] ‘Amœnitates Acad.’ vol. iv. 1788, p. 160.

  [332] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 585.

  [333] Ibid. p. 595.

  [334] See, for instance, Major W. Ross King (‘The Sportsman in
  Canada,’ 1866, p. 53, 131) on the habits of the moose and wild
  reindeer.

  [335] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 600.

  [336] Mr. Green, in ‘Journal of Linn. Soc.’ vol. x. Zoology,
  1869, p. 362.

  [337] C. L. Martin, ‘General Introduction to the Nat. Hist. of
  Mamm. Animals,’ 1841, p. 431.

  [338] ‘Naturgeschichte der Säugethiere von Paraguay,’ 1830, s.
  15, 21.

  [339] 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, who doubts about the rudimentary
  condition of the bladder in the female, in ‘Proc. Zoolog. Soc.’
  1868, p. 435.

  [340] 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.

  [341] Rengger, ‘Naturgeschichte der Säugethiere von Paraguay,’
  1830, s. 355. This observer also gives some curious particulars
  in regard to the odour emitted.

  [342] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 632. See,
  also, Dr. Murie’s observations on their glands in ‘Proc.
  Zoolog. Soc.’ 1870, p. 340. Desmarest, On the _Antilope
  subgutturosa_, ‘Mammalogie,’ 1820, p. 455.

  [343] Pallas, ‘Spicilegia Zoolog.’ fasc. xiii. 1799, p. 24;
  Desmoulins, ‘Dict. Class. d’Hist. Nat.’ tom. iii. p. 586.

  [344] Dr. Gray, ‘Gleanings from the Menagerie at Knowsley,’ pl.
  28.

  [345] Judge Caton on the wapiti, ‘Transact. Ottawa Acad. Nat.
  Sciences,’ 1868, p. 36, 40; Blyth, ‘Land and Water,’ on _Capra
  ægagrus_, 1867, p. 37.

  [346] ‘Hunter’s Essays and Observations,’ edited by Owen, 1861,
  vol. i. p. 236.

  [347] See Dr. Gray’s ‘Cat. of Mammalia in British Museum,’ part
  iii. 1852, p. 144.

  [348] Rengger, ‘Säugethiere,’ &c., s. 14; Desmarest,
  ‘Mammalogie,’ p. 66.

  [349] 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.

  [350] _Osphranter rufus_, Gould, ‘Mammals of Australia,’ vol.
  ii. 1863. On the Didelphis, Desmarest, ‘Mammalogie,’ p. 256.

  [351] ‘Annals and Mag. of Nat. Hist.’ Nov. 1867, p. 325. On the
  _Mus minutus_, Desmarest, ‘Mammalogie,’ p. 304.

  [352] J. A. Allen, in ‘Bulletin of Mus. Comp. Zoolog. of
  Cambridge, United States,’ 1869, p. 207.

  [353] Desmarest, ‘Mammalogie,’ 1820, p. 223. On _Felis mitis_,
  Rengger, ibid. s. 194.

  [354] Dr. Murie on the Otaria, ‘Proc. Zool. Soc.’ 1869, p. 108.
  Mr. R. Brown, on the _P. groenlandica_, ibid. 1868, p. 417. See
  also on the colours of seals, Desmarest, ibid. p. 243, 249.

  [355] Judge Caton, in ‘Trans. Ottawa Acad. of Nat. Sciences,’
  1868, p. 4.

  [356] Dr. Gray, ‘Cat. of Mamm. in Brit. Mus.’ part iii. 1852,
  p. 134-142; also Dr. Gray, ‘Gleanings from the Menagerie of
  Knowsley,’ in which there is a splendid drawing of the Oreas
  derbyanus: 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 Society’s Gardens.

  [357] 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. 327. 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.

  [358] ‘Ottawa Academy of Sciences,’ May 21, 1868, p. 3, 5.

  [359] S. Müller, 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, ‘Cat.
  Brit. Mus.’ p. 146; Desmarest, ‘Mammalogie,’ p. 482. On the
  _Cervus paludosus_, Rengger, ibid. s. 345.

  [360] Sclater, ‘Proc. Zool. Soc.’ 1866, p. 1. The same fact has
  also been fully ascertained by MM. Pollen and van Dam.

  [361] On Mycetes, Rengger, ibid. s. 14; and Brehm,
  ‘Illustrirtes 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. Müller, ‘Zoog.
  Indischen Archipel.’ tab. x.

  [362] Gervais, ‘Hist. Nat. des Mammifères,’ 1854, p, 103.
  Figures are given of the skull of the male. Desmarest,
  ‘Mammalogie,’ p. 70. Geoffroy St.-Hilaire and F. Cuvier, ‘Hist.
  Nat. des Mamm.’ 1824, tom. i.

  [363] ‘The Variation of Animals and Plants under
  Domestication,’ 1868, vol. ii. p. 102, 103.

  [364] ‘Essays and Observations by J. Hunter,’ edited by Owen,
  1861, vol. i. p. 194.

  [365] Sir S. Baker, ‘The Nile Tributaries of Abyssinia,’ 1867.

  [366] _Fiber zibethicus_, Audubon and Bachman, ‘The Quadrupeds
  of N. America,’ 1846, p. 109.

  [367] ‘Novæ species Quadrupedum e Glirium ordine,’ 1778, p. 7.
  What I have called the roe is the _Capreolus Sibiricus
  subecaudatus_ of Pallas.

  [368] See the fine plates in A. Smith’s ‘Zoology of S. Africa,’
  and Dr. Gray’s ‘Gleanings from the Menagerie of Knowsley.’

  [369] ‘Westminster Review,’ July 1, 1867, p. 5.

  [370] ‘Travels in South Africa,’ 1824, vol. ii. p. 315.

  [371] 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.

  [372] Falconer and Cautley, ‘Proc. Geolog. Soc.’ 1843; and
  Falconer’s ‘Pal. Memoirs,’ vol. i. p. 196.

  [373] ‘The Variation of Animals and Plants under
  Domestication,’ 1868, vol. i. p. 61-64.

  [374] ‘Proc. Zool. Soc.’ 1862, p. 164. See, also, Dr. Hartmann,
  ‘Ann. d. Landw.’ Bd. xliii. s. 222.

  [375] I observed this fact in the Zoological Gardens; and
  numerous cases may be seen in the coloured plates in Geoffroy
  St.-Hilaire and F. Cuvier, ‘Hist. Nat. des Mammifères,’ tom. i.
  1824.

  [376] Bates, ‘The Naturalist on the Amazons,’ 1863, vol. ii. p.
  310.

  [377] I have seen most of the above-named monkeys in the
  Zoological Society’s Gardens. The description of the
  _Semnopithecus nemæus_ is taken from Mr. W. C. Martin’s ‘Nat.
  Hist. of Mammalia,’ 1841, p. 460; see also p. 475, 523.

  [378] Schaaffhausen, translation in ‘Anthropological Review,’
  Oct. 1868, p. 419, 420, 427.

  [379] Ecker, translation in ‘Anthropological Review,’ Oct.
  1868, p. 351-356. The comparison of the form of the skull in
  men and women has been followed out with much care by Welcker.

  [380] Ecker and Welcker, ibid. p. 352, 355; Vogt, ‘Lectures on
  Man,’ Eng. translat. p. 81.

  [381] Schaaffhausen, ‘Anthropolog. Review,’ ibid. p. 429.

  [382] 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,’ &c. 1822, p. 451. For
  the infants of the Guaranys, see Rengger, ‘Säugethiere,’ &c. s.
  3. See also Godron, ‘De l’Espèce,’ tom. ii. 1859, p. 253. For
  the Australians, Waitz, ‘Introduct. to Anthropology,’ Eng.
  translat. 1863, p. 99.

  [383] Rengger, ‘Säugethiere,’ &c. 1830, s. 49.

  [384] As in _Macacus cynomolgus_ (Desmarest, ‘Mammalogie,’ p.
  65) and in _Hylobates agilis_ (Geoffroy St.-Hilaire and F.
  Cuvier, ‘Hist. Nat. des Mamm.’ 1824, tom. i. p. 2).

  [385] ‘Anthropological Review,’ Oct. 1868, p. 353.

  [386] Mr. Blyth informs me that he has never seen more than one
  instance of the beard, whiskers, &c., in a monkey becoming
  white with old age, as is so commonly the case with us. This,
  however, occurred in an aged and confined _Macacus cynomolgus_,
  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
  seen, as he informs me, an instance with the Aymaras and
  Quechuas of S. America.

  [387] 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
  Encyclopedia,’ vol. ii. p. 149, 150.

  [388] The results were deduced by Dr. Weisbach from the
  measurements made by Drs. K. Scherzer and Schwarz, see ‘Reise
  der _Novara_: Anthropolog. Theil,’ 1867, s. 216, 231, 234, 236,
  239, 269.

  [389] ‘Voyage to St. Kilda’ (3rd edit. 1753) p. 37.

  [390] Sir J. E. Tennent, ‘Ceylon,’ vol. ii. 1859, p. 107.

  [391] Quatrefages, ‘Revue des Cours Scientifiques,’ Aug. 29,
  1868, p. 630; Vogt, ‘Lectures on Man,’ Eng. translat. p. 127.

  [392] On the beards of negroes, Vogt, ‘Lectures,’ &c. ibid. 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 those
  of Europeans.

  [393] Wallace, ‘The Malay Arch.’ vol. ii. 1869, p. 178.

  [394] Dr. J. Barnard Davis on Oceanic Races, in ‘Anthropolog.
  Review,’ April, 1870, p. 185, 191.

  [395] Catlin, ‘North American Indians,’ 3rd edit. 1842, vol.
  ii. p. 227. On the Guaranys, see Azara, ‘Voyages dans
  l’Amérique Mérid.’ tom. ii. 1809, p. 58; also Rengger,
  ‘Säugethiere von Paraguay,’ s. 3.

  [396] 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.

  [397] Rütimeyer, ‘Die Grenzen der Thierwelt; eine Betrachtung
  zu Darwin’s Lehre,’ 1868, s. 54.

  [398] ‘A Journey from Prince of Wales Fort,’ 8vo. edit. 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 S. America see Azara, ‘Voyages,’ &c. tom. ii. p. 94.

  [399] On the fighting of the male gorillas, see Dr. Savage, in
  ‘Boston Journal of Nat. Hist.’ vol. v. 1847, p. 423. On
  _Presbytis entellus_, see the ‘Indian Field,’ 1859, p. 146.

  [400] 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?

  [401] 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.

  [402] Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 603.

  [403] ‘Journal of the Anthropolog. Soc.’ April, 1869, p. lvii.
  and lxvi.

  [404] Dr. Scudder, “Notes on Stridulation,” in ‘Proc. Boston
  Soc. of Nat. Hist.’ vol. xi. April, 1868.

  [405] Given in W. C. L. Martin’s ‘General Introduct. to Nat.
  Hist. of Mamm. Animals,’ 1841, p. 432; Owen, ‘Anatomy of
  Vertebrates,’ vol. iii. p. 600.

  [406] Helmholtz, ‘Théorie Phys. de la Musique,’ 1868, p. 187.

  [407] Mr. R. Brown, in ‘Proc. Zoo. Soc.’ 1868, p. 410.

  [408] ‘Journal of Anthropolog. Soc.’ Oct. 1870, p. clv. See
  also the several later chapters in Sir John Lubbock’s
  ‘Prehistoric Times,’ second edition, 1869, which contain an
  admirable account of the habits of savages.

  [409] Since this chapter has been printed I have seen a
  valuable article by Mr. Chauncey Wright (‘North Amer. 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.”
  This principle has an important bearing, as I have attempted to
  shew in the second chapter of this work, on the acquisition by
  man of some of his mental characteristics.

  [410] 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 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.

  [411] Rengger, ‘Säugethiere von Paraguay,’ s. 49.

  [412] See an interesting discussion on this subject by Häckel,
  ‘Generelle Morph.’ B. ii. 1866, s. 246.

  [413] 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, Prof. Mantegazza, ‘Rio de la Plata,
  Viaggi e Studi,’ 1867, p. 525-545; all the following
  statements, when other references are not given, are taken from
  this work. See, also, Waitz, ‘Introduct. to Anthropolog.’ Eng.
  transl. 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 (p.
  42, 48) I have taken some facts about savages dyeing their
  teeth and hair, and piercing their teeth.

  [414] 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.

  [415] ‘The Nile Tributaries,’ 1867; ‘The Albert N’yanza,’ 1866,
  vol. i. p. 218.

  [416] Quoted by Prichard, ‘Phys. Hist. of Mankind,’ 4th. edit.
  vol. i. 1851, p. 321.

  [417] 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.

  [418] ‘Travels’, p. 533.

  [419] ‘The Albert N’yanza,’ 1866, vol. i. p. 217.

  [420] Livingstone, ‘British Association,’ 1860; report given in
  the ‘Athenæum,’ July 7, 1860, p. 29.

  [421] 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 the invariability of the
  tattooing of the Amazonian Indians.

  [422] Rev. R. Taylor, ‘New Zealand and its Inhabitants,’ 1855,
  p. 152.

  [423] Mantegazza, ‘Viaggi e Studi,’ p. 542.

  [424] ‘Travels in S. Africa,’ 1824; vol. i. p. 414.

  [425] See, for references, ‘Gerland über das Aussterben der
  Naturvölker,’ 1868, s. 51, 53, 55; also Azara, ‘Voyages,’ &c.
  tom. ii. p. 116.

  [426] On the vegetable productions used by the North-Western
  American Indians, ‘Pharmaceutical Journal,’ vol. x.

  [427] ‘A Journey from Prince of Wales Fort,’ 8vo. edit. 1796,
  p. 89.

  [428] Quoted by Prichard, ‘Phys. Hist. of Mankind,’ 3rd edit.
  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,’ vol. ii. 1859, p. 107.

  [429] Prichard, as taken from Crawfurd and Finlayson, ‘Phys.
  Hist. of Mankind,’ vol. iv. p. 534, 535.

  [430] “Idem illustrissimus viator dixit mihi præcinctorium vel
  tabula fæminæ, quod nobis teterrimum est, quondam permagno
  æstimari ab hominibus in hac gente. Nunc res mutata est, et
  censet talem conformationem minime optandam est.”

  [431] ‘The Anthropological Review,’ November, 1864, p. 237. For
  additional references, see Waitz, ‘Introduct. to Anthropology,’
  Eng. translat. 1863, vol. i. p. 105.

  [432] ‘Mungo Park’s Travels in Africa,’ 4to. 1816, p. 53, 131.
  Burton’s statement is quoted by Schaaffhausen, ‘Archiv für
  Anthropolog.’ 1866, s. 163. On the Banyai, Livingstone,
  ‘Travels,’ p. 64. On the Kafirs, the Rev. J. Shooter, ‘The
  Kafirs of Natal and the Zulu Country,’ 1857 p. 1.

  [433] For the Javanese and Cochin-Chinese, see Waitz,
  ‘Introduct. to Anthropology,’ Eng. translat. vol. i. p. 305. On
  the Yura-caras, A. d’Orligny, as quoted in Prichard, ‘Phys.
  Hist. of Mankind,’ vol. v. 3rd edit. p. 476.

  [434] ‘North American Indians,’ by G. Catlin, 3rd edit. 1842,
  vol. i. p. 49; vol. ii. p. 227. On the natives of Vancouver
  Island, see Sproat, ‘Scenes and Studies of Savage Life,’ 1868,
  p. 25. On the Indians of Paraguay, Azara, ‘Voyages,’ tom. ii.
  p. 105.

  [435] 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,’ &c. 1822, p. 272.

  [436] Lubbock, ‘Origin of Civilisation,’ 1870, p. 321.

  [437] Dr. Barnard Davis quotes Mr. Pritchard and others for
  these facts in regard to the Polynesians, in ‘Anthropological
  Review,’ April, 1870, p. 185, 191.

  [438] Ch. Comte has remarks to this effect in his ‘Traité de
  Législation,’ 3rd edit. 1837, p. 136.

  [439] 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.

  [440] ‘Personal Narrative,’ Eng. translat. vol. iv. p. 518, and
  elsewhere. Mantegazza, in his ‘Viaggi e Studi,’ 1867, strongly
  insists on this same principle.

  [441] On the skulls of the American tribes, see Nott and
  Gliddon, ‘Types of Mankind,’ 1854, p. 440; Prichard, ‘Phys.
  Hist. of Mankind,’ vol. i. 3rd edit. 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 edit. 1869, p. 506)
  gives an excellent résumé on this subject.

  [442] On the Huns, Godron, ‘De l’Espèce,’ tom. ii. 1859, p.
  300. On the Tahitians, Waitz, ‘Anthropolog.’ 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.

  [443] This fact was ascertained in the ‘Reise der _Novara_:
  Anthropolog. Theil,’ Dr. Weisbach, 1867, s. 265.

  [444] ‘Smithsonian Institution, 1863, p. 289. On the fashions
  of Arab women, Sir S. Baker, ‘The Nile Tributaries,’ 1867, p.
  121.

  [445] ‘The Variation of Animals and Plants under
  Domestication,’ vol. i. p. 214; vol. ii. p. 240.

  [446] Schaaffhausen, ‘Archiv für Anthropologie,’ 1866, s. 164.

  [447] Mr. Bain has collected (‘Mental and Moral Science,’ 1868,
  p. 304-314) about a dozen more or less different theories of
  the idea of beauty; but none are quite the same with that here
  given.

  [448] These quotations are taken from Lawrence (‘Lectures on
  Physiology,’ &c. 1822, p. 393), who attributes the beauty of
  the upper classes in England to the men having long selected
  the more beautiful women.

  [449] “Anthropologie,” ‘Revue des Cours Scientifiques,’ Oct.
  1868, p. 721.

  [450] ‘The Variation of Animals and Plants under
  Domestication,’ vol. i. p. 207.

  [451] Sir J. Lubbock, ‘The Origin of Civilisation,’ 1870, chap.
  iii. especially p. 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 on the classificatory system
  of relationship (‘Proc. American Acad. 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.

  [452] Address to British Association ‘On the Social and
  Religious Condition of the Lower Races of Man,’ 1870, p. 20.

  [453] ‘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.

  [454] Brehm (‘Illust. 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 (‘Anat. of Vertebrates,’ vol. iii.
  p. 746) on American monogamous species. Other references might
  be added.

  [455] Dr. Savage, in ‘Boston Journal of Nat. Hist.’ vol. v.
  1845-47, p. 423.

  [456] ‘Prehistoric Times,’ 1869, p. 424.

  [457] Mr. M’Lennan, ‘Primitive Marriage,’ 1865. See especially
  on exogamy and infanticide, p. 130, 138, 165.

  [458] Dr. Gerland (‘Ueber das Aussterben der Naturvölker,’
  1868) has collected much information on infanticide, see
  especially s. 27, 51, 54. Azara (‘Voyages,’ &c. tom. ii. p. 94,
  116) enters in detail on the motives. See also M’Lennan (ibid.
  p. 139) for cases in India.

  [459] ‘Primitive Marriage,’ p. 208; Sir J. Lubbock, ‘Origin of
  Civilisation,’ p. 100. See also Mr. Morgan, loc. cit., on
  former prevalence of polyandry.

  [460] ‘Voyages,’ &c. tom. ii. p. 92-95.

  [461] 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 Mérid.’ tom. ii. 1809, p. 21)
  makes precisely the same remark in regard to the wild Indians
  of South America.

  [462] ‘Anthropological Review,’ Jan. 1870, p. xvi.

  [463] ‘The Variation of Animals and Plants under
  Domestication,’ vol. ii. p. 210-217.

  [464] 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 M. Bombet,
  English translat. p. 278.

  [465] Azara, ‘Voyages,’ &c. tom. ii. p. 23. Dobrizhoffer, ‘An
  Account of the Abipones,’ vol. ii. 1822, p. 207. 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, p. 52-60. On the
  Bushwomen, Burchell, ‘Travels in S. Africa,’ vol. ii. 1824, p.
  59.

  [466] ‘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 Assoc. 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. At any rate it is
  surprising that he should picture to himself a superior
  intelligence plucking the hair from the backs of savage men (to
  whom, according to his own account it would have been useful
  and beneficial), in order that the descendants of the poor
  shorn wretches might after many deaths from cold and damp in
  the course of many generations,” have been forced to raise
  themselves in the scale of civilisation through the practice of
  various arts, in the manner indicated by Mr. Wallace.

  [467] ‘The Variation of Animals and Plants under
  Domestication,’ vol. ii. 1868, p. 327.

  [468] ‘Investigations into Military and Anthropological
  Statistics of American Soldiers,’ by B. A. Gould, 1869; p.
  568:—Observations were carefully made on the pilosity 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 pure blacks and mulattoes were included in the
  above enumeration; and this is an unfortunate circumstance, as
  in accordance with the principle, the truth of which I have
  elsewhere proved, crossed races would be eminently liable to
  revert to the primordial hairy character of their early
  ape-like progenitors.

  [469] “Ueber die Richtung der Haare am Menschlichen Körper,” in
  Müller’s ‘Archiv für Anat. und Phys.’ 1837, s. 40.

  [470] Mr. Sproat (‘Scenes and Studies of Savage Life,’ 1868, p.
  25) suggests, with reference to the beardless natives of
  Vancouver’s Island, that the custom of plucking out the hairs
  on the face, “continued from one generation to another, would
  perhaps at last produce a race distinguishable by a thin and
  straggling growth of beard.” But the custom would not have
  arisen until the beard had already become, from some
  independent cause, greatly reduced. Nor have we any direct
  evidence that the continued eradication of the hair would lead
  to any inherited effect. Owing to this cause of doubt, I have
  not hitherto alluded to the belief held by some distinguished
  ethnologists, for instance M. Gosse of Geneva, that artificial
  modifications of the skull tend to be inherited. I have no wish
  to dispute this conclusion; and we now know from Dr.
  Brown-Séquard’s remarkable observations, especially those
  recently communicated (1870) to the British Association, that
  with guinea-pigs the effects of operations are inherited.

  [471] ‘Ueber die Richtung,’ ibid. s. 40.

  [472] On the “Limits of Natural Selection,” in the ‘North
  American Review,’ Oct. 1870, p. 295.

  [473] The Rev. J. A. Picton gives a discussion to this effect
  in his ‘New Theories and the Old Faith,’ 1870.




  INDEX.


  A.

  ABBOTT, C., on the battles of seals, ii. 240.

  ABDUCTOR of the fifth metatarsal, presence of, in man, i. 128.

  ABERCROMBIE, Dr., on disease of the brain affecting speech, i. 58.

  ABIPONES, marriage-customs of the, ii. 373.

  ABOU-SIMBEL, caves of, i. 217.

  ABORTION, prevalence of the practice of, i. 134.

  ABSTRACTION, i. 62.

  _Acalles_, stridulation of, i. 384.

  _Acanthodactylus capensis_, sexual differences of colour in, ii. 36.

  _Accentor modularis_, ii. 198.

  ACCLIMATISATION, difference of, in different races of men, i. 216.

  _Achetidæ_, stridulation of the, i. 352, 353, 355;
    rudimentary stridulating organs in female, i. 359.

  _Acilius sulcatus_, elytra of the female, i. 343.

  _Acomus_, development of spurs in the female of, ii. 162.

  _Acridiidæ_, stridulation of the, i. 352, 356;
    rudimentary stridulating organs in female, i. 359.

  ACTING, i. 232.

  _Actiniæ_, bright colours of, i. 322.

  ADMIRAL butterfly, i. 392.

  ADOPTION of the young of other animals by female monkeys, i. 41.

  ADVANCEMENT in the organic scale, Von Baer’s definition of, i. 211.

  AEBY, on the difference between the skulls of man and the quadrumana,
    i. 190.

  ÆSTHETIC faculty, not highly developed in savages, i. 64.

  AFFECTION, maternal, i. 40;
    manifestation of, by animals, i. 40;
    parental and filial, partly the result of natural selection, i. 81;
    shown by birds in confinement, for certain persons, ii. 110;
    mutual, of birds, ii. 108.

  AFRICA, probably the birthplace of man, i. 199;
    South, crossed population of, i. 225;
    South, retention of colour by the Dutch in, i. 242;
    South, proportion of the sexes in the butterflies of, i. 310;
    tattooing practised in, ii. 339;
    Northern, coiffure of natives of, ii. 340.

  AGASSIZ, L., on conscience in dogs, i. 78;
    on the coincidence of the races of man with zoological provinces,
      i. 218;
    on the number of species of man, i. 226;
    on the courtship of the land-snails, i. 324;
    on the brightness of the colours of male fishes during the breeding
      season, ii. 13;
    on the frontal protuberance of the males of _Geophagus_ and
      _Cichla_, ii. 13, 20;
    on the slight sexual differences of the South Americans, ii. 323;
    on the tattooing of the Amazonian Indians, ii. 342.

  AGE, in relation to the transmission of characters in birds, ii. 183;
    variation in accordance with, in birds, ii. 213.

  _Agelæus phœniceus_, ii. 116.

  _Ageronia feronia_, noise produced by, i. 387.

  _Agrion_, dimorphism in, i. 363.

  _Agrion Ramburii_, sexes of, i. 362.

  AGRIONIDÆ, difference in the sexes of, i. 362.

  _Agrotis exclamationis_, i. 369.

  AGUE, tertian, dog suffering from, i. 13.

  _Aïthurus polytmus_, young of, ii. 220.

  AINOS, hairiness of the, ii. 321.

  _Alca torda_, young of, ii. 217.

  _Alces palmata_, ii. 259.

  ALDER and Hancock, MM., on the nudibranch mollusca, i. 326.

  ALGEN, Mr., on the stridulation of _Scolytus_, i. 379.

  ALLEN, J. A., on the relative size of the sexes of _Callorhinus
      ursinus_, ii. 260;
    on the mane of _Otaria jubata_, ii. 267;
    on the pairing of seals, ii. 279;
    on sexual differences in the colour of bats, ii. 286.

  ALLEN, S., on the habits of _Hoplopterus_, ii. 48;
    on the plumes of herons, ii. 82;
    on the vernal moult of _Herodias bubulcus_, ii. 84.

  ALLIGATOR, courtship of the male, i. 272, ii. 29;
    roaring of the male, i. 331.

  AMADAVAT, pugnacity of male, ii. 49.

  _Amadina Lathami_, display of plumage by the male, ii. 95.

  _Amadina castanotis_, display of plumage by the male, ii. 95.

  AMAZONS, butterflies of the, i. 309;
    fishes of the, ii. 17.

  AMERICA, variation in the skulls of aborigines of, i. 108;
    wide range of aborigines of, i. 218;
    lice of the natives of, i. 220;
    general beardlessness of the natives of, ii. 322.

  AMERICA, North, butterflies of, i. 309;
    Indians of, women a cause of strife among the, ii. 324;
    Indians of, their notions of female beauty, ii. 344, 347.

  AMERICA, South, character of the natives of, i. 216;
    population of parts of, i. 225;
    piles of stones in, i. 233;
    extinction of the fossil horse of, i. 239;
    desert-birds of, ii. 224;
    slight sexual difference of the aborigines of, ii. 323;
    prevalence of infanticide in, ii. 361.

  AMERICAN languages, often highly artificial, i. 112.

  AMERICANS, wide geographical range of, i. 112;
    and negroes, difference of, i. 247;
    aversion of, to hair on the face, ii. 348;
    native, variability of, i. 226.

  _Ammophila_, on the jaws of, i. 342.

  _Ammotragus tragelaphus_, hairy forelegs of, ii. 282, 285.

  AMPHIBIA, affinity of, to the ganoid fishes, i. 204;
    vocal organs of the, ii. 331.

  AMPHIBIANS, i. 213, ii. 24;
    breeding whilst immature, ii. 215.

  _Amphioxus_, i. 204.

  AMPHIPODA, males sexually mature while young, ii. 215.

  AMUNOPH III., negro character of features of, i. 217.

  ANAL appendages of insects, i. 342.

  ANALOGOUS variation in the plumage of birds, ii. 74.

  _Anas_, ii. 180.

  _Anas acuta_, male plumage of, ii. 84.

  _Anas boschas_, male plumage of, ii. 84.

  _Anas histrionica_, ii. 214.

  _Anastomus oscitans_, sexes and young of, ii. 217;
    white nuptial plumage of, ii. 228.

  ANATIDÆ, voices of, ii. 60.

  _Anax junius_, difference in the sexes of, i. 362.

  ANGLO-SAXONS, estimation of the beard among the, ii. 349.

  ANIMALS, cruelty of savages to, i. 94;
    domesticated, more fertile than wild, i. 132;
    characters common to man and, i. 185;
    domestic, change of breeds of, ii. 369.

  ANNELIDA, i. 327.

  ANNULOSA, i. 327.

  _Anolis cristatellus_, male, crest of, ii. 32;
    pugnacity of the male, ii. 32;
    throat-pouch of, ii. 33.

  _Anobium tessellatum_, sounds produced by, i. 384.

  _Anser canadensis_, ii. 116.

  _Anser cygnoides_, ii. 114;
    knob at the base of the beak of, ii. 129.

  _Anser hyperboreus_, whiteness of, ii. 228.

  ANTELOPE, prong-horned, horns of, i. 289.

  ANTELOPES, generally polygamous, i. 267;
    horns of, i. 289, ii. 245;
    canine teeth of some male, ii. 241;
    use of horns of, ii. 251;
    dorsal crests in, ii. 282;
    dewlaps of, ii. 284;
    winter change of two species of, ii. 299;
    peculiar markings of, ii. 299.

  ANTENNÆ, furnished with cushions in the male of _Penthe_, i. 343.

  _Anthidium manicatum_, large male of, i. 347.

  _Anthocharis cardamines_, i. 388, 393, 394;
    sexual difference of colour in, i. 409.

  _Anthocharis genutia_, i. 393.

  _Anthocharis sara_, i. 393.

  _Anthophora acervorum_, large male of, i. 347.

  _Anthophora retusa_, difference of the sexes in, i. 366.

  _Anthus_, moulting of, ii. 83.

  ANTHROPIDÆ, i. 195.

  ANTIGUA, Dr. Nicholson’s observations on yellow fever in, i. 245.

  ANTICS of birds, ii. 68.

  _Antilocapra americana_, horns of, i. 289, ii. 245.

  _Antilope bezoartica_, horned females of, ii. 246, 248;
    sexual difference in the colour of, ii. 288.

  _Antilope Dorcas_ and _euchore_, ii. 245.

  _Antilope euchore_, horns of, ii. 251.

  _Antilope montana_, rudimentary canines in the young male of, ii. 258.

  _Antilope niger, sing-sing, caama_, and _gorgon_, sexual differences
    in the colours of, ii. 289.

  _Antilope oreas_, horns of, i. 289.

  _Antilope saiga_, polygamous habits of, i. 267.

  _Antilope strepsiceros_, horns of, i. 289.

  _Antilope subgutturosa_, absence of suborbital pits in, ii. 280.

  ANTIPATHY, shown by birds in confinement, to certain persons, ii. 110.

  ANTS, i. 186;
    playing together, i. 39;
    memory in, i. 45;
    intercommunication of, by means of the antennæ, i. 58;
    large size of the cerebral ganglia in, i. 145;
    soldier-, large jaws of, i. 155;
    difference of the sexes in, i. 365;
    recognition of each other by, after separation, i. 365.

  ANTS, White, habits of, i. 364.

  ANURA, ii. 25.

  _Apatania muliebris_, male unknown, i. 314.

  _Apathus_, difference of the sexes in, i. 366.

  _Apatura Iris_, i. 386, 388.

  APES, anthropomorphous, i. 196;
    difference of the young, from the adult, i. 13;
    building platforms, i. 53;
    probable speedy extermination of the, i. 201;
    Gratiolet on the evolution of, i. 230;
    semi-erect attitude of some, i. 142;
    mastoid processes of, i. 143;
    influence of the jaw-muscles on the physiognomy of, i. 144;
    female, destitute of large canines, i. 156;
    imitative faculties of, i. 161;
    canine teeth of male, ii. 241;
    females of some, less hairy beneath than the males, ii. 377.

  APES, long-armed, their mode of progression, i. 143.

  _Apis mellifica_, large male of, i. 347.

  APOLLO, Greek statues of, ii. 350.

  APOPLEXY in _Cebus Azaræ_, i. 12.

  APPROBATION, influence of the love of, i. 86, 92, 164, 165.

  APPENDAGES, anal, of insects, i. 342.

  _Aprosmictus scapulatus_, ii. 174.

  AQUATIC birds, frequency of white plumage in, ii. 229.

  _Aquila chrysaëtos_, ii. 105.

  ARAB women, elaborate and peculiar coiffure of, ii. 353.

  ARABS, gashing of cheeks and temples among the, ii. 339.

  ARACHNIDA, i. 337.

  ARAKHAN, artificial widening of the forehead by the natives of,
    ii. 351.

  _Arboricola_, young of, ii. 190.

  _Archeopteryx_, i. 204.

  ARCTIIDÆ, coloration of the, i. 396.

  _Ardea asha_, _rufescens_, and _cærulea_, change of colour in,
    ii. 231, 232.

  _Ardea cærulea_, breeding in immature plumage, ii. 214.

  _Ardea gularis_, change of plumage in, ii. 232.

  _Ardea herodias_, love-gestures of the male, ii. 68.

  _Ardea ludoviciana_, age of mature plumage in, ii. 213;
    continued growth of crest and plumes in the male of, ii. 216.

  _Ardea nycticorax_, cries of, ii. 51.

  _Ardeola_, young of, ii. 190.

  _Ardetta_, changes of plumage in, ii. 179.

  ARGENTEUIL, i. 29.

  ARGUS pheasant, ii. 72, 97, 181;
    display of plumage by the male, ii. 91;
    ocellated spots of the, ii. 134, 141;
    gradation of characters in the, ii. 141.

  ARGYLL, Duke of, the fashioning of implements peculiar to man,
      i. 52;
    on the contest in man between right and wrong, i. 104;
    on the physical weakness of man, i. 156;
    on the primitive civilisation of man, i. 181;
    on the plumage of the male Argus pheasant, ii. 91;
    on _Urosticte Benjamini_, ii. 151;
    on the nests of birds, ii. 167;
    on variety as an object in nature, ii. 230.

  _Argynnis aglaia_, colouring of the lower surface of, i. 396.

  _Aricoris epitus_, sexual differences in the wings of, i. 345.

  ARISTOCRACY, increased beauty of the, ii. 356.

  ARMS, proportions of, in soldiers and sailors, i. 116;
    direction of the hair on the, i. 192.

  ARMS and hands, free use of, indirectly correlated with diminution
    of canines, i. 144.

  ARREST of development, i. 121, 122.

  ARROW-HEADS, stone, general resemblance of, i. 233.

  ARROWS, use of, i. 232.

  ARTERIES, variations in the course of the, i. 108.

  ARTERY, effect of tying, upon the lateral channels, i. 116.

  ARTHROPODA, i. 328.

  ARTS practised by savages, i. 234.

  ASCENSION, coloured incrustation on the rocks of, i. 326.

  ASCIDIA, affinity of the lancelet to, i. 205;
    tadpole-like larvæ of, i. 205.

  ASCIDIANS, i. 324;
    bright colours of some, i. 322.

  _Asinus_, Asiatic and African species of, ii. 306.

  _Asinus tæniopus_, ii. 306.

  ASS, colour-variations of the, ii. 305.

  _Ateles_, effects of brandy on an, i. 12;
    absence of the thumb in, i. 140.

  _Ateles beelzebuth_, ears of, i. 23.

  _Ateles marginatus_, colour of the ruff of, ii. 291;
    hair on the head of, ii. 109;
    on the recognition of a dog by a turkey, ii. 110;
    on the selection of a mate by female birds, ii. 307.

  _Ateuchus_, stridulation of, i. 384.

  _Ateuchus cicatricosus_, habits of, i. 376.

  _Athalia_, proportions of the sexes in, i. 314.

  ATTENTION, manifestations of, in animals, i. 44.

  AUDOUIN, V., on a hymenopterous parasite with a sedentary male,
    i. 273.

  AUDUBON, J. J., on the pugnacity of male birds, ii. 43, 48;
    on _Tetrao cupido_, ii. 50;
    on _Ardea nycticorax_, ii. 51;
    on _Sturnella ludoviciana_, ii. 51;
    on the vocal organs of _Tetrao cupido_, ii. 56;
    on the drumming of the male _Tetrao umbellus_, ii. 61;
    on sounds produced by the nightjar, ii. 63;
    on _Ardea herodias_ and _Cathartes jota_, ii. 68;
    on the spring change of colour in some finches, ii. 86;
    on _Mimus polyglottus_, ii. 116;
    on the turkey, ii. 119, 121;
    on variation in the male scarlet tanager, ii. 126;
    on the habits of _Pyranga æstiva_, ii. 167;
    on local differences in the nests of the same species of birds,
      ii. 171;
    on the habits of woodpeckers, ii. 175;
    on _Bombycilla carolinensis_, ii. 180;
    on young females of _Tanagra æstiva_ acquiring male characters,
      ii. 180;
    on the immature plumage of thrushes, ii. 185;
    on the immature plumage of birds, ii. 186 _et seq._;
    on birds breeding in immature plumage, ii. 214;
    on the growth of the crest and plumes in the male _Ardea
      ludoviciana_, ii. 216;
    on the change of colour in some species of _Ardea_, ii. 231;
    on the speculum of _Mergus cucullatus_, ii. 291;
    on the musk-rat, ii. 298.

  AUDUBON and Bachman, MM., on squirrels fighting, ii. 239;
    on the Canadian lynx, ii. 267.

  AUSTEN, N. L., on _Anolis cristatellus_, ii. 32, 33.

  AUSTRALIA, half-castes killed by the natives of, i. 220;
    lice of the natives of, i. 220;
    not the birthplace of man, i. 199;
    prevalence of female infanticide in, ii. 364.

  AUSTRALIA, South, variation in the skulls of aborigines of, i. 108.

  AUSTRALIANS, colour of newborn children of, ii. 318;
    relative height of the sexes of, ii. 320;
    women a cause of war among the, ii. 323.

  AXIS deer, sexual difference in the colour of the, ii. 290.

  AYMARAS, measurements of the, i. 119;
    no grey hair among the, ii. 320;
    hairlessness of the face in the, ii. 322;
    long hair of the, ii. 348.

  AZARA, on the proportion of men and women among the Guaranys,
      i. 302;
    on _Palamedea cornuta_, ii. 48;
    on the beards of the Guaranys, ii. 322;
    on strife for women among the Guanas, ii. 324;
    on infanticide, ii. 344, 364;
    on the eradication of the eyebrows and eyelashes by the Indians
      of Paraguay, ii. 348;
    on polyandry among the Guanas, ii. 366;
    celibacy unknown among the savages of South America, ii. 367;
    on the freedom of divorce among the Charruas, ii. 372.


  B.

  BABBAGE, C., on the greater proportion of illegitimate female births,
    i. 302.

  BABIRUSA, tusks of the, ii. 264.

  BABOON, employing a mat for shelter against the sun, i. 53;
    manifestation of memory by a, i. 45;
    protected from punishment by its companions, i. 78;
    rage excited in, by reading, i. 42.

  BABOON, Cape, mane of the male, ii. 267;
    Hamadryas, mane of the male, ii. 267.

  BABOONS, effects of intoxicating liquors on, i. 12;
    ears of, i. 23;
    manifestation of maternal affection by, i. 41;
    using stones and sticks as weapons, i. 51;
    co-operation of, i. 75;
    silence of, on plundering expeditions, i. 79;
    diversity of the mental faculties in, i. 110;
    hands of, i. 139;
    habits of, i. 141;
    variability of the tail in, i. 150;
    apparent polygamy of, i. 266;
    polygamous and social habits of, ii. 362.

  BACHMAN, Dr., on the fertility of mulattoes, i. 221.

  BAER, K. E. von, on embryonic development, i. 14.

  BAGEHOT, W., on the social virtues among primitive men, i. 93;
    on the value of obedience, i. 162;
    on human progress, i. 166;
    on the persistence of savage tribes in classical times, i. 239.

  BAILLY, E. M., on the fighting of stags, ii. 252;
    on the mode of fighting of the Italian buffalo, ii. 250.

  BAIN, A., on the sense of duty, i. 71;
    aid springing from sympathy, i. 77;
    on the basis of sympathy, i. 82;
    on love of approbation, &c., i. 86;
    on the idea of beauty, ii. 354.

  BAIRD, W., on a difference in colour between the males and females
    of some Entozoa, i. 321.

  BAKER, Mr., observation on the proportion of the sexes
    in pheasant-chicks, i. 306.

  BAKER, Sir S., on the fondness of the Arabs for discordant music,
      ii. 67;
    on sexual difference in the colours of an antelope, ii. 289;
    on the elephant and rhinoceros attacking white or grey horses,
      ii. 295;
    on the disfigurements practised by the negroes, ii. 296;
    on the gashing of the cheeks and temples practised in Arab
      countries, ii. 339;
    on the coiffure of the North Africans, ii. 340;
    on the perforation of the lower lip by the women of Latooka,
      ii. 341;
    on the distinctive characters of the coiffure of central African
      tribes, ii. 342;
    on the coiffure of Arab women, ii. 353.

  “BALZ” of the Black-cock, ii. 45, 100.

  BANTAM, Sebright, i. 259, 294.

  BANTENG, horns of, ii. 247;
    sexual differences in the colours of the, ii. 289.

  BANYAI, colour of the, ii. 346.

  BARBARISM, primitive, of civilised nations, i. 181.

  BARBS, filamentous, of the feathers, in certain birds, ii. 74.

  BARR, Mr., on sexual preference in dogs, ii. 272.

  BARRINGTON, Daines, on the language of birds, i. 55;
    on the clucking of the hen, ii. 51;
    on the object of the song of birds, ii. 52;
    on the singing of female birds, ii. 54;
    on birds acquiring the songs of other birds, ii. 55;
    on the muscles of the larynx in song-birds, ii. 55;
    on the want of the power of song by female birds, ii. 163.

  BARROW, on the widow-bird, ii. 98.

  BARTLETT, A. D., on the tragopan, i. 270;
    on the development of the spurs in _Crossoptilon auritum_, i. 290;
    on the fighting of the males of _Plectropterus gambensis_, ii. 46;
    on the knot, ii. 82;
    on display in male birds, ii. 87;
    on the display of plumage by the male _Polyplectron_, ii. 89;
    on _Crossoptilon auritum_ and _Phasianus Wallichii_, ii. 93;
    on the habits of _Lophophorus_, ii. 121;
    on the colour of the mouth in _Buceros bicornis_, ii. 129;
    on the incubation of the cassowary, ii. 204;
    on the Cape Buffalo, ii. 250;
    on the use of the horns of antelopes, ii. 251;
    on the fighting of male wart-hogs, ii. 266;
    on _Ammotragus tragelaphus_, ii. 282;
    on the colours of _Cercopithecus cephus_, ii. 291;
    on the colours of the faces of monkeys, ii. 310;
    on the naked surfaces of monkeys, ii. 377.

  BARTRAM, on the courtship of the male alligator, ii. 29.

  BASQUE language, highly artificial, i. 61.

  BATE, C. S., on the superior activity of male crustacea, i. 272;
    on the proportions of the sexes in crabs, i. 315;
    on the chelæ of crustacea, i. 330;
    on the relative size of the sexes in crustacea, i. 332;
    on the colours of crustacea, i. 335.

  BATES, H. W., on variation in the form of the head of Amazonian
      Indians, i. 111;
    on the proportion of the sexes among Amazonian butterflies, i. 309;
    on sexual differences in the wings of butterflies, i. 345;
    on the field-cricket, i. 353;
    on _Pyrodes pulcherrimus_, i. 367;
    on the horns of Lamellicorn beetles, i. 370, 371;
    on the colours of _Epicaliæ_, &c., i. 388;
    on the coloration of tropical butterflies, i. 391;
    on the variability of _Papilio Sesostris_ and _Childrenæ_, i. 402;
    on male and female butterflies inhabiting different stations,
      i. 403;
    on mimickry, i. 411;
    on the caterpillar of a _Sphinx_, i. 416;
    on the vocal organs of the umbrella-bird, ii. 58;
    on the toucans, ii. 227;
    on _Brachyurus calvus_, ii. 309.

  BATOKAS, knocking out two upper incisors, ii. 340.

  BATRACHIA, ii. 25;
    eagerness of male, i. 272.

  BATS, sexual differences in the colour of, ii. 286.

  BATTLE, law of, i. 182;
    among beetles, i. 375;
    among birds, ii. 40;
    among mammals, ii. 239 _et seq._;
    in man, ii. 323.

  BEAK, sexual difference in the forms of the, ii. 39;
    in the colour of the, ii. 72.

  BEAKS, of birds, bright colours of, ii. 227.

  BEARD, development of, in man, ii. 317;
    analogy of the, in man and the quadrumana, ii. 319;
    variation of the development of the, in different races of men,
      ii. 321;
    estimation of, among bearded nations, ii. 349;
    probable origin of the, ii. 379.

  BEARDS, in monkeys, i. 192;
    of mammals, ii. 282.

  BEAUTIFUL, taste for the, in birds, ii. 108;
    in the quadrumana, ii. 296.

  BEAUTY, sense of, in animals, i. 63;
    appreciation of, by birds, ii. 111;
    influence of, ii. 338, 343;
    variability of the standard of, ii. 370.

  BEAVAN, Lieut., on the development of the horns in _Cervus Eldi_,
    i. 288.

  BEAVER, instinct and intelligence of the, i. 37, 38;
    voice of the, ii. 277;
    castoreum of the, ii. 279.

  BEAVERS, battles of male, ii. 239.

  BECHSTEIN, on female birds choosing the best singers among the males,
      ii. 52;
    on rivalry in song-birds, ii. 53;
    on the singing of female birds, ii. 54;
    on birds acquiring the songs of other birds, ii. 55;
    on pairing the canary and siskin, ii. 115;
    on a sub-variety of the monk pigeon, ii. 132;
    on spurred hens, ii. 162.

  BEDDOE, Dr., on causes of difference in stature, i. 115.

  BEE-EATER, ii. 56.

  BEES, i. 73;
    destruction of drones and queens by, i. 82;
    pollen-baskets and stings of, i. 155;
    female, secondary sexual characters of, i. 254;
    difference of the sexes in, i. 365.

  BEETLE, luminous larva of a, i. 345.

  BEETLES, i. 366;
    size of the cerebral ganglia in, i. 145;
    dilatation of the fore tarsi in male, i. 343;
    blind, i. 367;
    stridulation of, i. 378.

  BELGIUM, ancient inhabitants of, i. 237.

  BELL, Sir C, on emotional muscles in man, i. 5;
    “snarling muscles,” i. 127;
    on the hand, i. 141.

  BELL, T., on the numerical proportion of the sexes in moles, i. 305;
    on the newts, ii. 24;
    on the croaking of the frog, ii. 27;
    on the difference in the coloration of the sexes in _Zootoca
      vivipara_, ii. 36;
    on moles fighting, ii. 239.

  BELL-BIRD, sexual difference in the colour of the, ii. 79.

  BELL-BIRDS, colours of, ii. 228.

  BENEVOLENCE, manifested by birds, ii. 109.

  BENNETT, A. W., on the habits of _Dromœus irroratus_, ii. 205.

  BENNETT, Dr., on birds of paradise, ii. 89.

  _Bernicla antarctica_, colours of, ii. 228.

  BERNICLE gander pairing with a Canada goose, ii. 114.

  BETTONI, E., on local differences in the nests of Italian birds,
    ii, 171.

  BHOTEAS, colour of the beard in, ii. 319.

  _Bhringa_, disciform tail-feathers of, ii. 83.

  _Bibio_, sexual differences in the genus, i. 349.

  BICHAT, on beauty, ii. 354.

  BILE, coloured, in many animals, i. 323.

  BIMANA, i. 190.

  BIRDS, imitations of the songs of other birds by, i. 44;
    dreaming, i. 46;
    language of, i. 55;
    sense of beauty in, i. 63;
    pleasure of, in incubation, i. 79;
    male, incubation by, i. 210;
    and reptiles, alliance of, i. 213;
    sexual differences in the beak of some, i. 255;
    migratory, arrival of the male before the female, i. 259;
    apparent relation between polygamy and marked sexual differences in,
      i. 270;
    monogamous, becoming polygamous under domestication, i. 270;
    eagerness of male in pursuit of the female, i. 272;
    wild, numerical proportion of the sexes in, i. 306;
    secondary sexual characters of, ii. 38;
    difference of size in the sexes of, ii. 43;
    fights of male, witnessed by females, ii. 49;
    display of male, to captivate the females, ii. 50;
    close attention of, to the songs of others, ii. 52;
    acquiring the song of their foster-parents, ii. 55;
    brilliant, rarely good songsters, ii. 56;
    love-antics and dances of, ii. 68;
    coloration of, ii. 74 _et seqq._;
    moulting of, ii. 80 _et seqq._;
    unpaired, ii. 103;
    male, singing out of season, ii. 106;
    mutual affection of, ii. 108;
    in confinement, distinguish persons, ii. 110;
    hybrid, production of, ii. 113;
    European, number of species of, ii. 124;
    variability of, ii. 124;
    gradation of secondary sexual characters in, ii. 135;
    obscurely coloured, building concealed nests, ii. 169;
    young female, acquiring male characters, ii. 180;
    breeding in immature plumage, ii. 214;
    moulting of, ii. 214;
    aquatic, frequency of white plumage in, ii. 229;
    vocal courtship of, ii. 331;
    naked skin of the head and neck in, ii. 377.

  _Birgus latro_, habits of, i. 334.

  BIRKBECK, Mr. on the finding of new mates by Golden Eagles, ii. 105.

  BIRTHPLACE of man, i. 199.

  BIRTHS, numerical proportions of the sexes in, in animals and man,
      i. 263, 265;
    male and female, numerical proportion of, in England, i. 300.

  BISCHOFF, Prof., on the agreement between the brains of man and
      of the Orang, i. 11;
    figure of the embryo of the dog, i. 15;
    on the convolutions of the brain in the human fœtus, i. 16;
    on the difference between the skulls of man and the quadrumana,
      i. 190.

  BISHOP, J., on the vocal organs of frogs, ii. 28;
    on the vocal organs of corvine birds, ii. 55;
    on the trachea of the _Merganser_, ii. 60.

  BISON, American, mane of the male, ii. 267.

  BITTERNS, dwarf, coloration of the sexes of, ii. 179.

  _Biziura lobata_, musky odour of the male, ii. 38;
     large size of male, ii. 43.

  BLACKBIRD, sexual differences in the, i. 268;
    proportion of the sexes in the, i. 307;
    acquisition of a song by a, ii. 55;
    colour of the beak in the sexes of the, ii. 72, 227;
    pairing with a thrush, ii. 113;
    colours and nidification of the, ii. 170;
    young of the, ii. 219;
    sexual difference in coloration of the, ii. 226.

  BLACK-BUCK, Indian, sexual difference in the colour of the, ii. 288.

  BLACKCAP, arrival of the male, before the female, i. 259;
    young of the, ii. 219.

  BLACK-COCK, polygamous, i. 269;
    proportion of the sexes in the, i. 306;
    pugnacity and love-dance of the, ii. 45;
    call of the, ii. 60;
    moulting of the, ii. 83;
    duration of the courtship of the, ii. 100;
    sexual difference in coloration of the, ii. 226;
    crimson eye-cere of the, ii. 227;
    and pheasant, hybrids of, ii. 113.

  BLACK-GROUSE, characters of young, ii. 185, 194.

  BLACKWALL, J., on the speaking of the magpie, i. 59;
    on the desertion of their young by swallows, i. 84;
    on the superior activity of male spiders, i. 272;
    on the proportion of the sexes in spiders, i. 314;
    on sexual variation of colour in spiders, i. 337;
    on male spiders, i. 338.

  BLADDER-NOSE Seal, hood of the, ii. 278.

  BLAINE, on the affections of dogs, ii. 270.

  BLAIR, Dr., on the relative liability of Europeans to yellow fever,
    i. 243.

  BLAKE, C. C., on the jaw from La Naulette, i. 126.

  BLAKISTON, Capt., on the American snipe, ii. 64;
    on the dances of _Tetrao phasianellus_, ii. 69.

  BLASIUS, Dr., on the species of European birds, ii. 124.

  _Bledius taurus_, hornlike processes of male, i. 374.

  BLEEDING, tendency to profuse, i. 292.

  BLENKIRON, Mr., on sexual preference in horses, ii. 272.

  BLENNIES, crest developed on the head of male, during the breeding
    season, ii. 12.

  _Blethisa multipunctata_, stridulation of, i. 379.

  BLOCH, on the proportions of the sexes in Fishes, i. 308.

  BLOOD, arterial, red colour of, i. 323.

  BLOOD-PHEASANT, number of spurs in, ii. 46.

  BLUEBREAST, red-throated, sexual differences of the, ii. 195.

  BLUMENBACH, on Man, i. 111;
    on the large size of the nasal cavities in American aborigines,
      i. 119;
    on the position of man, i. 190;
    on the number of species of man, i. 226.

  BLYTH, E., observations on Indian crows, i. 77;
    on the structure of the hand in species of _Hylobates_, i. 140;
    on the ascertainment of the sex of nestling bullfinches by pulling
      out breast-feathers, ii. 24;
    on the pugnacity of the males of _Gallinula cristata_, ii. 41;
    on the presence of spurs in the female _Euplocamus erythropthalmus_,
      ii. 46;
    on the pugnacity of the amadavat, ii. 49;
    on the spoonbill, ii. 60;
    on the moulting of _Anthus_, ii. 83;
    on the moulting of bustards, plovers, and _Gallus bankiva_, ii. 84;
    on the Indian honey-buzzard, ii. 126;
    on sexual differences in the colour or the eyes of hornbills,
      ii. 129;
    on _Oriolus melanocephalus_, ii. 178;
    on _Palæornis javanicus_, ii. 179;
    on the genus _Ardetta_, ii. 179;
    on the peregrine falcon, ii. 180;
    on young female birds acquiring male characters, ii. 180;
    on the immature plumage of birds, ii. 185;
    on representative species of birds, ii. 190;
    on the young of _Turnix_, ii. 202;
    on anomalous young of _Lanius rufus_ and _Colymbus glacialis_,
      ii. 211;
    on the sexes and young of the sparrows, ii. 212;
    on dimorphism in some herons, ii. 214;
    on orioles breeding in immature plumage, ii. 214;
    on the sexes and young of _Buphus_ and _Anastomus_, ii. 217;
    on the young of the blackcap and blackbird, ii. 219;
    on the young of the stonechat, ii. 220;
    on the white plumage of _Anastomus_, ii. 229;
    on the horns of _Antilope bezoartica_, ii. 246;
    on the horns of Bovine animals, ii. 247;
    on the mode of fighting of _Ovis cycloceros_, ii. 249;
    on the voice of the Gibbons, ii. 276;
    on the crest of the male wild goat, ii. 282;
    on the colours of _Portax picta_, ii. 287;
    on the colours of _Antilope bezoartica_, ii. 288;
    on the development of the horns in the Koodoo and Eland antelopes,
      i. 289;
    on the colour of the Axis deer, ii. 290;
    on sexual difference of colour in _Hylobates hoolock_, ii. 291;
    on the hog-deer, ii. 303;
    on the beard and whiskers in a monkey becoming white with age,
      ii. 319.

  BOAR, wild, polygamous in India, i. 267;
    use of the tusks by the, ii. 256;
    fighting of, ii. 263.

  BOITARD and Corbié, MM., on the transmission of sexual peculiarities
      in pigeons, i. 283;
    on the antipathy shown by some female pigeons to certain males,
      ii. 118.

  BOLD, Mr., on the singing of a sterile hybrid canary, ii. 53.

  BOMBET, on the variability of the standard of beauty in Europe,
    ii. 370.

  _Bombus_, difference of the sexes in, i. 366.

  BOMBYCIDÆ, coloration of, i. 394;
    pairing of the, i. 401.

  _Bombycilla carolinensis_, red appendages of, ii. 179.

  _Bombyx cynthia_, i. 346;
    proportion of the sexes in, i. 309, 313;
    pairing of, i. 401.

  _Bombyx mori_, difference of size of the male and female cocoons of,
      i. 346;
    pairing of, i. 401.

  _Bombyx Pernyi_, proportion of sexes of, i. 313.

  _Bombyx Yamamai_, i. 346;
    M. Personnat on, i. 310;
    proportion of sexes of, i. 313.

  BONAPARTE, C. L., on the call-notes of the wild turkey, ii. 60.

  BOND, F., on the finding of new mates by crows, ii. 104.

  BONE, implements of, skill displayed in making, i. 138.

  BONER, C., on the transfer of male characters to an old female chamois,
      ii. 245;
    on the antlers of the red deer, ii. 252;
    on the habits of stags, ii. 259;
    on the pairing of red deer, ii. 269.

  BONES, increase of, in length and thickness, when carrying a greater
    weight, i. 116.

  BONNET monkey, i. 192.

  BOOMERANG, i. 183.

  _Boreus hyemalis_, scarcity of the male, i. 314.

  BORY St. Vincent, on the number of species of man, i. 226;
    on the colours of _Labrus pavo_, ii. 16.

  _Bos gaurus_, horns of, ii. 247.

  _Bos primigenius_, ii. 240.

  _Bos sondaicus_, horns of, ii. 247;
    colours of, ii. 289.

  BOTOCUDOS, i. 181;
    mode of life of, i. 247;
    disfigurement of the ears and lower lip of the, ii. 341.

  BOUCHER de Perthes, J. C. de, on the antiquity of man, i. 3.

  BOURBON, proportion of the sexes in a species of _Papilio_ from,
    i. 310.

  BOURIEN, on the marriage-customs of the savages of the Malay
    Archipelago, ii. 373.

  BOVIDÆ, dewlaps of, ii. 284.

  BOWER-BIRDS, ii. 102;
    habits of the, ii. 69;
    ornamented playing-places of, i. 63, ii. 112.

  BOWS, use of, i. 232.

  BRACHIOPODA, i. 329.

  BRACHYCEPHALIC structure, possible explanation of, i. 148.

  _Brachyscelus_, second pair of antennæ in the male, i. 337.

  BRACHYURA, i. 332.

  _Brachyurus calvus_, scarlet face of, ii. 309.

  BRAIN, of man, agreement of the, with that of lower animals, i. 10;
    convolutions of, in the human fœtus, i. 16;
    larger in some existing mammals than in their tertiary prototypes,
      i. 51;
    relation of the development of the, to the progress of language,
      i. 57;
    disease of the, affecting speech, i. 58;
    influence of development of mental faculties upon the size of the,
      i. 145;
    influence of the development of, on the spinal column and skull,
      i. 146;
    difference in the convolutions of, in different races of men,
      i. 216.

  BRAKENRIDGE, Dr., on the influence of climate, i. 115.

  BRAUBACH, Prof., on the quasi-religious feeling of a dog towards
      his master, i. 68;
    on the self-restraint of dogs, i. 78.

  BRAUER, F., on dimorphism in _Neurothemis_, i. 363.

  BRAZIL, skulls found in caves of, i. 218;
    population of, i. 225;
    compression of the nose by the natives of, ii. 352.

  BREAK between man and the apes, i. 200.

  BREAM, proportion of the sexes in the, i. 308.

  BREEDING, age of, in birds, ii. 214.

  BREEDING season, sexual characters making their appearance in the,
    in birds, ii. 80.

  BREHM, on the effects of intoxicating liquors on monkeys, i. 12;
    on the recognition of women by male _Cynocephali_, i. 13;
    on revenge taken by monkeys, i. 40;
    on manifestations of maternal affection by monkeys and baboons,
      i. 41;
    on the instinctive dread of monkeys for serpents, i. 42;
    on a baboon using a mat for shelter from the sun, i. 53;
    on the use of stones as missiles by baboons, i. 51;
    on the signal-cries of monkeys, i. 57;
    on sentinels posted by monkeys, i. 74;
    on co-operation of animals, i. 75;
    on an eagle attacking a young _Cercopithecus_, i. 76;
    on baboons in confinement protecting one of their number from
      punishment, i. 78;
    on the habits of baboons when plundering, i. 79;
    on the diversity of the mental faculties of monkeys, i. 110;
    on the habits of baboons, i. 141;
    on polygamy in _Cynocephalus_ and _Cebus_, i. 266;
    on the numerical proportion of the sexes in birds, i. 306;
    on the love-dance of the Black-cock, ii. 45;
    on _Palamedea cornuta_, ii. 48;
    on the habits of the Black-grouse, ii. 49;
    on sound produced by Birds of Paradise, ii. 63;
    on assemblages of grouse, ii. 101;
    on the finding of new mates by birds, ii. 106;
    on the fighting of wild boars, ii. 263;
    on the habits of _Cynocephalus hamadryas_, ii. 362.

  BRENT, Mr., on the courtship of fowls, ii. 117.

  BRESLAU, numerical proportion of male and female births in, i. 301.

  BRIDGMAN, Laura, i. 57.

  BRIMSTONE butterfly, i. 393;
    sexual difference of colour in the, i. 409.

  BRITISH, ancient, tattooing practised by, ii. 339.

  BROCA, Prof., on the occurrence of the supra-condyloid foramen in
      the human humerus, i. 28;
    on the capacity of Parisian skulls at different periods, i. 146;
    on the influence of natural selection, i. 152;
    on hybridity in man, i. 220;
    on human remains from Les Eyzies, i. 237;
    on the cause of the difference between Europeans and Hindoos,
      i. 240.

  BRODIE, Sir B., on the origin of the moral sense in man, i. 71.

  BRONN, H. G., on the copulation of insects of distinct species,
   i. 342.

  BRONZE period, men of, in Europe, i. 160.

  BROWN, R., sentinels of seals generally females, i. 74;
    on the battles of seals, ii. 240;
    on the narwhal, ii. 242;
    on the occasional absence of the tusks in the female walrus,
      ii. 242;
    on the bladder-nose seal, ii. 278;
    on the colours of the sexes in _Phoca groenlandica_, ii. 287;
    on the appreciation of music by seals, ii. 333;
    on plants used as love-philters, by North American women, ii. 344.

  BROWN-SÉQUARD, Dr., on the inheritance of the effects of operations
    by guinea pigs, ii. 380.

  BRUCE, on the use of the elephant’s tusks, ii. 249.

  BRULERIE, P. de la, on the habits of _Ateuchus cicatricosus_, i. 376;
    on the stridulation of _Ateuchus_, i. 384.

  BRÜNNICH, on the pied ravens of the Feroe islands, ii. 126.

  BRYANT, Capt., on the courtship of _Callorhinus ursinus_, ii. 269.

  _Bubas bison_, thoracic projection of, i. 372.

  _Bucephalus capensis_, difference of the sexes of, in colour, ii. 29.

  _Buceros_, nidification and incubation of, ii. 169.

  _Buceros bicornis_, sexual differences in the colouring of the casque,
     beak, and mouth in, ii. 129.

  _Buceros corrugatus_, sexual difference in the beak of, ii. 72.

  BÜCHNER, L., on the origin of man, i. 4;
    on the want of self-consciousness, &c., in low savages, i. 62;
    on the use of the human foot as a prehensile organ, i. 142;
    on the mode of progression of the apes, i. 142.

  BUCKLAND, F., on the numerical proportion of the sexes in rats,
      i. 305;
    on the proportion of the sexes in the trout, i. 308;
    on _Chimæra monstrosa_, ii. 12.

  BUCKLAND, W., on the complexity of crinoids, i. 61.

  BUCKLER, W., proportion of sexes of Lepidoptera reared by, i. 313.

  BUCKINGHAMSHIRE, numerical proportion of male and female births in,
    i. 300.

  _Bucorax abyssinicus_, inflation of the neck-wattle of the male,
    during courtship, ii. 72.

  _Budytes Raii_, i. 260.

  BUFFALO, Cape, ii. 250.

  BUFFALO, Indian, horns of the, ii. 247.

  BUFFALO, Italian, mode of fighting of the, ii. 250.

  BUFFON, on the number of species of man, i. 226.

  BUGS, i. 349.

  BUIST, R., on the proportion of the sexes in salmon, i. 308;
    on the pugnacity of the male salmon, ii. 3.

  BULBUL, pugnacity of the male, ii. 41;
    display of under tail-coverts by the male, ii. 96.

  BULL, mode of fighting of the, ii. 250;
    curled frontal hair of the, ii. 282.

  BULLFINCH, sexual differences in the, i. 269;
    piping, ii. 52;
    female, singing of the, ii. 54;
    courtship of the, ii. 94;
    widowed, finding a new mate, ii. 105;
    attacking a reed-bunting, ii. 111;
    nestling, sex ascertained by pulling out breast-feathers, ii. 214.

  BULLFINCHES distinguishing persons, ii. 110;
    rivalry of female, ii. 121.

  BULLS, two young, attacking an old one, i. 75;
    wild, battles of, ii. 240.

  BULL-TROUT, male, colouring of, during the breeding season, ii. 14.

  BUNTING, reed, head feathers of the male, ii. 95;
   attacked by a bullfinch, ii. 111.

  BUNTINGS, characters of young, ii. 184.

  _Buphus coromandus_, sexes and young of, ii. 217;
   change of colour in, ii. 231, 232.

  BURCHELL, Dr., on the zebra, ii. 302;
    on the extravagance of a Bushwoman in adorning herself, ii. 344;
    celibacy unknown among the savages of South Africa, ii. 367;
    on the marriage-customs of the Bushwomen, ii. 374.

  BURKE, on the number of species of man, i. 226.

  BURMESE, colour of the beard in, ii. 319.

  BURTON, Capt., on negro ideas of female beauty, ii. 346;
    on a universal ideal of beauty, ii. 351.

  BUSHMEN, i. 157.

  BUSHWOMAN, extravagant ornamentation of a, ii. 344.

  BUSHWOMEN, hair of, i. 216;
    marriage-customs of, ii. 374.

  BUSK, Prof. G., on the occurrence of the supra-condyloid foramen
    in the human humerus, i. 28.

  BUSTARD, throat-pouch of the male, ii. 58;
    humming noise produced by a male, ii. 65;
    Indian, ear-tufts of a, ii. 73.

  BUSTARDS, occurrence of sexual differences and of polygamy among the,
      i. 269;
    love-gestures of the male, ii. 68;
    double moult in, ii. 81, 83.

  BUTLER, A. G., on sexual differences in the wings of _Aricoris epitus_,
      i. 345;
    on the colouring of the sexes in species of _Thecla_, i. 389;
    on the resemblance of _Iphias glaucippe_ to a leaf, i. 394;
    on the rejection of certain moths and caterpillars by lizards and
      frogs, i. 417.

  BUTTERFLY, noise produced by a, i. 387;
    Emperor, i. 386, 388;
    meadow brown, instability of the ocellated spots of, ii. 132.

  BUTTERFLIES, proportion of the sexes in, i. 309;
    forelegs atrophied in some male, i. 344;
    sexual difference in the neuration of the wings of, i. 345;
    pugnacity of male, i. 386;
    protective resemblances of the lower surface of, i. 392;
    display of the wings by, i. 396;
    white, alighting upon bits of paper, i. 400;
    attracted by a dead specimen of the same species, i. 400;
    courtship of, i. 400;
    male and female, inhabiting different stations, i. 403.

  BUXTON, C., observations on macaws, i. 76;
    on an instance of benevolence in a parrot, ii. 109.

  BUZZARD, Indian honey-, variation in the crest of, ii. 126.


  C.

  CABBAGE butterflies, i. 393.

  CACHALOT, large head of the male, ii. 242.

  CADENCES, musical, perception of, by animals, ii. 333.

  CÆCUM, i. 27;
    large, in the early progenitors of man, i. 206.

  _Cairina moschata_, pugnacity of the male, ii. 43.

  _Callianassa_, chelæ of, figured, i. 330.

  _Callionymus lyra_, characters of the male, ii. 7.

  _Callorhinus ursinus_, relative size of the sexes of, ii. 260;
    courtship of, ii. 269.

  _Calotes nigrilabris_, sexual difference in the colour of, ii. 36.

  CAMBRIDGE, O. Pickard, on the sexes of spiders, i. 315.

  CAMEL, canine teeth of male, ii. 241, 257.

  CAMPBELL, J., on the Indian elephant, i. 267, 268;
    on the proportion of male and female births in the harems of Siam,
      i. 303.

  _Campylopterus hemileucurus_, i. 307.

  CANARIES distinguishing persons, ii. 110.

  CANARY, polygamy of the, i. 270;
    change of plumage in, after moulting, i. 294;
    female, selecting the best singing male, ii. 52;
    sterile hybrid, singing of a, ii. 53;
    female, singing of the, ii. 54;
    selecting a greenfinch, ii. 115;
    and siskin, pairing of, ii. 115.

  CANESTRINI, G., on rudimentary characters and the origin of man, i. 4;
    on rudimentary characters, i. 17;
    on the movement of the ear in man, i. 20;
    on the variability of the vermiform appendage in man, i. 27;
    on the abnormal division of the malar bone in man, i. 124;
    on abnormal conditions of the human uterus, i. 124;
    on the persistence of the frontal suture in man, i. 125;
    on the proportion of the sexes in silk-moths, i. 309, 311.

  CANINE teeth in man, i. 126;
    diminution of, in man, i. 144;
    diminution of, in horses, i. 144;
    disappearance of, in male ruminants, i. 144;
    large, in the early progenitors of man, i. 206.

  CANINES, and horns, inverse development of, ii. 257.

  CANOES, use of, i. 137, 234.

  _Cantharis_, difference of colour in the sexes of a species of,
    i. 367.

  CAPERCAILZIE, proportion of the sexes in the, i. 306;
    pugnacity of the male, ii. 45;
    pairing of the, ii. 49;
    autumn meetings of the, ii. 54;
    call of the, ii. 61;
    duration of the courtship of, ii. 100;
    behaviour of the female, ii. 121;
    inconvenience of black colour to the female, ii. 154;
    sexual difference in coloration of the, ii. 226;
    crimson eye-cere of the male, ii. 227;
    polygamous, i. 269.

  CAPITAL, i. 169.

  CAPITONIDÆ, colours and nidification of the, ii. 171.

  _Capra ægagrus_, ii. 249;
    crest of the male, ii. 282;
    sexual difference in the colour of, ii. 289.

  _Capreolus Sibiricus subecaudatus_, ii. 298.

  CAPRICE, common to man and animals, i. 65.

  _Caprimulgus_, noise made by the males of some species of, with their
    wings, ii. 62.

  _Caprimulgus virginianus_, pairing of, ii. 49.

  CARABIDÆ, bright colours of, i. 367.

  CARBONNIER, on the natural history of the pike, i. 308;
    on the relative size of the sexes in fishes, ii. 7.

  _Carcineutes_, sexual difference of colour in, ii. 173.

  _Carcinus mænas_, i. 331, 333.

  _Carduelis elegans_, sexual differences of the beak in, ii. 39.

  CARNIVORA, marine, polygamous habits of, i. 268;
    sexual differences in the colours of, ii. 286.

  CARP, numerical proportion of the sexes in the, i. 308.

  CARR, R., on the peewit, ii. 48.

  CARRIER pigeon, late development of the wattle in the, i. 293.

  CARRION beetles, stridulation of, i. 378.

  CARUS, Prof. V., on the development of the horns in merino sheep,
    i. 289.

  CASSOWARY, sexes and incubation of the, ii. 204.

  CASTOREUM, ii. 279.

  _Casuarius galeatus_, ii. 204.

  CAT, convoluted body in the extremity of the tail of a, i. 30;
    sick, sympathy of a dog with a, i. 77.

  CATARACT in _Cebus Azaræ_, i. 12.

  CATARRH, liability of _Cebus Azaræ_ to, i. 11.

  CATARRHINE monkeys, i. 196.

  CATERPILLARS, bright colours of, i. 415.

  _Cathartes aura_, ii. 116.

  _Cathartes jota_, love-gestures of the male, ii. 68.

  CATLIN, G., on the development of the beard among North American
      Indians, ii. 322;
    on the great length of the hair in some North American tribes,
      ii. 348.

  CATON, J. D., on the development of the horns in _Cervus virginianus_
      and _strongyloceros_, i. 288;
    on the presence of traces of horns in the female wapiti, ii. 245;
    on the fighting of deer, ii. 252;
    on the crest of the male wapiti, ii. 282;
    on the colours of the Virginian deer, ii. 288;
    on sexual differences of colour in the wapiti, ii. 289;
    on the spots of the Virginian deer, ii. 303.

  CATS, dreaming, i. 46;
    tortoise-shell, i. 283, 285, 293;
    enticed by valerian, ii. 281;
    colours of, ii. 299.

  CATTLE, domestic, sexual differences of, late developed, i. 293;
    rapid increase of, in South America, i. 135;
    domestic, lighter in winter in Siberia, i. 282;
    horns of, i. 289, ii. 247;
    numerical proportion of the sexes in, i. 305.

  CAUDAL vertebræ, number of, in macaques and baboons, i. 150;
    basal, of monkeys, imbedded in the body, i. 151.

  _Cebus_, maternal affection in a, i. 40;
    gradation of species of, i. 227.

  _Cebus Azaræ_, liability of, to the same diseases as man, i. 11;
    distinct sounds produced by, i. 53;
    early maturity of the female, ii. 318.

  _Cebus capucinus_, polygamous, i. 266;
    sexual differences of colour in, ii. 290;
    hair on the head of, ii. 307.

  _Cebus vellerosus_, hair on the head of, ii. 307.

  CECIDOMYIDÆ, proportions of the sexes in, i. 314.

  CELIBACY, unknown among the savages of South Africa and South America,
    ii. 367.

  CENTIPEDES, i. 339.

  CEPHALOPODA, absence of secondary sexual characters in, i. 325.

  _Cephalopterus ornatus_, ii. 58, 59.

  _Cephalopterus penduliger_, ii. 59.

  _Cerambyx heros_, stridulant organ of, i. 380.

  _Ceratophora aspera_, nasal appendages of, ii. 34.

  _Ceratophora Stoddartii_, nasal horn of, ii. 34.

  _Cerceris_, habits of, i. 364.

  _Cercocebus æthiops_, whiskers, &c., of, ii. 308.

  _Cercopithecus_, young, seized by an eagle and rescued by the troop,
      i. 76;
    definition of species of, i. 227.

  _Cercopithecus cephus_, sexual difference of colour in, ii. 291, 311.

  _Cercopithecus cynosurus_ and _griseo-viridis_, colour of the scrotum
    in, ii. 291.

  _Cercopithecus Diana_, sexual differences of colour in, ii. 291, 311,
    312.

  _Cercopithecus griseo-viridis_, i. 75.

  _Cercopithecus petaurista_, whiskers, &c., of, ii. 308.

  CERES, of birds, bright colours of, ii. 227.

  _Ceriornis Temminckii_, swelling of the wattles of the male during
    courtship, ii. 72.

  _Cervulus_, weapons of, ii. 257.

  _Cervulus moschatus_, rudimentary horns of the female, ii. 245.

  _Cervus alces_, i. 288.

  _Cervus campestris_, odour of, ii. 279.

  _Cervus canadensis_, traces of horns in the female, ii. 245;
    attacking a man, ii. 253;
    sexual difference in the colour of, ii. 289.

  _Cervus elaphus_, battles of male, ii. 240;
    horns of, with numerous points, ii. 252.

  _Cervus Eldi_, i. 288.

  _Cervus mantchuricus_, ii. 303.

  _Cervus paludosus_, colours of, ii. 290.

  _Cervus strongyloceros_, i. 288.

  _Cervus virginianus_, i. 288;
    horns of, in course of modification, ii. 255.

  _Ceryle_, male black-belted in some species of, ii. 173.

  CETACEA, nakedness of, i. 148.

  CEYLON, frequent absence of beard in the natives of, ii. 321.

  CHAFFINCH, proportion of the sexes in the, i. 306, 307;
    courtship of the, ii. 94.

  CHAFFINCHES, ii. 53;
    new mates found by, ii. 105.

  _Chalcophaps indicus_, characters of young, ii. 185.

  _Chalcosoma atlas_, sexual differences of, i. 368.

  _Chamæleon_, sexual differences in the genus, ii. 34.

  _Chamæleon bifurcus_, ii. 34, 35.

  _Chamæleon Owenii_, ii. 34, 36.

  CHAMELEONS, ii. 32.

  CHAMOIS, danger-signals of, i. 74;
    transfer of male characters to an old female, ii. 245.

  _Chamæpetes unicolor_, modified wing-feather in the male, ii. 64.

  CHAPUIS, Dr., on the transmission of sexual peculiarities in pigeons,
      i. 283;
    on streaked Belgian pigeons, i. 294, ii. 157.

  CHAR, male, colouring of, during the breeding season, ii. 14.

  CHARACTERS, male, developed in females, i. 280;
    natural, artificial exaggeration of, by man, ii. 351;
    secondary sexual, transmitted through both sexes, i. 279.

  _Charadrius hiaticula_ and _pluvialis_, sexes and young of, ii. 216.

  CHARDIN on the Persians, ii. 356.

  CHARMS, worn by women, ii. 344.

  CHARRUAS, freedom of divorce among the, ii. 372.

  _Chasmorhynchus_, difference of colour in the sexes of, ii. 79;
    colours of, ii. 228.

  CHASTITY, early estimation of, i. 96.

  CHATTERERS, sexual differences in, i. 269.

  CHEIROPTERA, absence of secondary sexual characters in, i. 268.

  CHELÆ of crustacea, i. 330, 336.

  CHELONIA, sexual differences in, ii. 28.

  _Chenalopex ægyptiacus_, wing-knobs of, ii. 46.

  _Chera progne_, ii. 84, 120.

  CHEST, proportions of, in soldiers and sailors, i. 117;
    large, of the Quechua and Aymara Indians, i. 119.

  CHEVROTAINS, canine teeth of, ii. 257.

  _Chiasognathus_, stridulation of, i. 384.

  _Chiasognathus Grantii_, mandibles of, i. 377.

  CHILDREN, legitimate and illegitimate, proportion of the sexes in,
    i. 302.

  CHILOE, lice of the natives of, i. 220;
    population of, i. 225.

  _Chimæra monstrosa_, bony process on the head of the male, ii. 12.

  CHIMÆROID fishes, prehensile organs of male, ii. 1.

  CHIMPANZEE, ii. 323;
    ears of the, i. 21;
    representatives of the eyebrows in the, i. 25;
    platforms built by the, i. 36;
    cracking nuts with a stone, i. 51;
    hands of the, i. 139;
    absence of mastoid processes in the, i. 143;
    direction of the hair on the arms of the, i. 192;
    supposed evolution of the, i. 230;
    polygamous and social habits of the, ii. 362.

  CHINA, North, idea of female beauty in, ii. 344.

  CHINA, Southern, inhabitants of, i. 246.

  CHINESE, use of flint tools by the, i. 183;
    difficulty of distinguishing the races of the, i. 215;
    colour of the beard in, ii. 319;
    general beardlessness of the, ii. 321;
    opinions of the, on the appearance of Europeans and Cingalese,
      ii. 345, 347;
    compression of the feet of, ii. 352.

  CHINSURDI, his opinion of beards, ii. 341, 349.

  _Chlamydera maculata_, ii. 70.

  _Chloëon_, pedunculated eyes of the male of, i. 341.

  _Chloephaga_, coloration of the sexes in, ii. 178.

  _Chlorocœlus Tanana_ (figured), i. 355.

  CHORDA DORSALIS, i. 207.

  CHOUGH, red beak of the, ii. 227.

  CHROMIDÆ, frontal protuberance in male, ii. 13;
    sexual differences in colour of, ii. 20.

  _Chrysemys picta_, long claws of the male, ii. 28.

  _Chrysococcyx_, characters of young of, ii. 185.

  _Chrysomela cerealis_, bright colours of, i. 367.

  CHRYSOMELIDÆ, stridulation of, i. 379.

  _Cicada pruinosa_, i. 351.

  _Cicada septendecim_, i. 351.

  CICADÆ, songs of the, i. 350;
    rudimentary sound-organs in females of, i. 359.

  CICATRIX of a burn, causing modification of the facial bones, i. 147.

  _Cichla_, frontal protuberance of male, ii. 13.

  CIMETIÈRE du Sud, Paris, i. 28.

  _Cincloramphus cruralis_, large size of male, ii. 43.

  _Cinclus aquaticus_, ii. 170.

  CINGALESE, Chinese opinion of the appearance of the, ii. 345.

  CIRRIPEDES, complemental males of, i. 255.

  CIVILISATION, effects of, upon natural selection, i. 170;
    influence of, in the competition of nations, i. 239.

  CLANGING of Geese, &c., ii. 51.

  CLAPARÈDE, E., on natural selection applied to man, i. 137.

  CLARKE, on the marriage-customs of the Kalmucks, ii. 373.

  CLASSIFICATION, i. 188.

  CLAUS, C., on the sexes of _Saphirina_, i. 336.

  CLEFT-PALATE, inherited, i. 121.

  _Climacteris erythrops_, sexes of, ii. 206.

  CLIMATE, i. 115;
    cool, favourable to human progress, i. 167;
    power of supporting extremes of, by man, i. 237;
    want of connexion of, with colour, i. 241.

  CLOACA, existence of a, in the early progenitors of man, i. 207.

  CLOACAL passage existing in the human embryo, i. 16.

  CLUB, origin of the, i. 234.

  CLUCKING of fowls, ii. 51.

  _Clythra 4-punctata_, stridulation of, i. 379.

  COBRA, ingenuity of a, ii. 31.

  _Coccus_, i. 186.

  COCCYX, i. 29, 30;
    in the human embryo, i. 16;
    convoluted body at the extremity of the, i. 30;
    imbedded in the body, i. 151.

  COCHIN-CHINA, notions of beauty of the inhabitants of, ii. 345, 347.

  COCK, game, killing a kite, ii. 44;
    blind, fed by its companions, i. 77;
    comb and wattles of the, ii. 98;
    preference shown by the, for young hens, ii. 121;
    game, transparent zone in the hackles of a, ii. 136.

  COCK of the rock, ii. 100.

  COCKATOOS, ii. 226, 228, 230;
    nestling, ii. 109;
    black, immature plumage of, ii. 188.

  CŒLENTERATA, absence of secondary sexual characters in, i. 321.

  COFFEE, fondness of monkeys for, i. 12.

  COLD, supposed effects of, i. 116;
    power of supporting, by man, i. 237.

  COLEOPTERA, i. 366;
    stridulant organs of, discussed, i. 381.

  COLLINGWOOD, C., on the pugnacity of the butterflies of Borneo,
      i. 386;
    on butterflies being attracted by a dead specimen of the same
      species, i. 400.

  COLOMBIA, flattened heads of savages of, ii. 340.

  COLONISTS, success of the English as, i. 179.

  COLORATION, protective, in birds, ii. 223.

  COLOUR, supposed to be dependent on light and heat, i. 115;
    correlation of, with immunity from certain poisons and parasites,
      i. 242;
    purpose of, in lepidoptera, i. 399;
    relation of, to sexual functions, in fishes, ii. 14;
    difference of, in the sexes of snakes, ii. 29;
    sexual differences of, in lizards, ii. 36;
    influence of, in the pairing of birds of different species, ii. 115;
    relation of, to nidification, ii. 167, 172;
    sexual differences of, in mammals, ii. 286, 294;
    recognition of, by quadrupeds, ii. 295;
    of children, in different races of man, ii. 318;
    of the skin in man, ii. 381.

  COLOURS, admired alike by man and animals, i. 64;
    bright, due to sexual selection, i. 322;
    bright, among the lower animals, i. 322, 323;
    bright, protective to butterflies and moths, i. 395;
    bright, in male fishes, ii. 7, 13;
    transmission of, in birds, ii. 159.

  COLQUHOUN, example of reasoning in a retriever, i. 48.

  _Columba passerina_, young of, ii. 188.

  _Colymbus glacialis_, anomalous young of, ii. 211.

  COMB, development of, in fowls, i. 295.

  COMBS and wattles in male birds, ii. 98.

  COMMUNITY, preservation of variations useful to the, by natural
    selection, i. 155.

  COMPOSITÆ, gradation of species among the, i. 227.

  COMTE, C., on the expression of the ideal of beauty by sculpture,
    ii. 380.

  CONDITIONS of life, action of changed, upon man, i. 113;
    influence of, on plumage of birds, ii. 196.

  CONDOR, eyes and comb of the, ii. 129.

  CONJUGATIONS, origin of, i. 61.

  CONSCIENCE, i. 91, 104;
    absence of, in some criminals, i. 92.

  CONSTITUTION, difference of, in different races of men, i. 216.

  CONSUMPTION, liability of _Cebus Azaræ_ to, i. 12;
    connexion between complexion and, i. 244.

  CONVERGENCE, i. 230.

  COOING of pigeons and doves, ii. 60.

  COOK, Capt., on the nobles of the Sandwich Islands, ii. 356.

  COPE, E. D., on the dinosauria, i. 204;
    on the origin of genera, ii. 215.

  _Cophotis ceylanica_, sexual differences of, ii. 32, 36.

  _Copris_, i. 370.

  _Copris Isidis_, sexual differences of, i. 369.

  _Copris lunaris_, stridulation of, i. 380.

  CORALS, bright colours of, i. 322.

  CORAL-SNAKES, ii. 31.

  _Cordylus_, sexual difference of colour in a species of, ii. 36.

  CORFU, habits of the chaffinch in, i. 307.

  CORNELIUS, on the proportions of the sexes in _Lucanus Cervus_,
    i. 313.

  CORPORA WOLFFIANA, i. 207;
    agreement of, with the kidneys of fishes, i. 16.

  CORRELATED variation, i. 130.

  CORRELATION, influence of, in the production of races, i. 247.

  CORSE, on the mode of fighting of the elephant, ii. 257.

  _Corvus corone_, ii. 104.

  _Corvus graculus_, red beak of, ii. 227.

  _Corvus pica_, nuptial assembly of, ii. 102.

  _Corydalis cornutus_, large jaws of the male, i. 342.

  _Cosmetornis_, ii. 181.

  _Cosmetornis vexillarius_, elongation of wing-feathers in, ii. 73, 97.

  COTINGIDÆ, sexual differences in, i. 269;
    coloration of the sexes of, ii. 177;
    resemblance of the females of distinct species of, ii. 192.

  _Cottus scorpius_, sexual differences in, ii. 9.

  COUNTING, origin of, i. 181;
    limited power of, in primeval man, i. 234.

  COURAGE, variability of, in the same species, i. 40;
    universal high appreciation of, i. 95;
    importance of, i. 162;
    a characteristic of men, ii. 328.

  COURTSHIP, greater eagerness of males in, i. 272;
    of fishes, ii. 2;
    of birds, ii. 50, 100.

  COW, winter change of the, ii. 299.

  CRAB, devil, i. 332.

  CRAB, shore, habits of, i. 331.

  _Crabro cribrarius_, dilated tibiæ of the male, i. 343.

  CRABS, proportions of the sexes in, i. 315.

  CRANZ, on the inheritance of dexterity in seal-catching, i. 117.

  CRAWFURD, on the number of species of man, i. 226.

  _Crenilabrus massa_ and _C. melops_, nests built by, ii. 19.

  CREST, origin of, in Polish fowls, i. 284.

  CRESTS, of birds, difference of, in the sexes, ii. 189;
    dorsal hairy, of mammals, ii. 282.

  CRICKET, field-, stridulation of the, i. 353;
    pugnacity of male, i. 360.

  CRICKET, house-, stridulation of the, i. 352, 354.

  CRICKETS, sexual differences in, i. 361.

  CRIOCERIDÆ, stridulation of the, i. 379.

  CRINOIDS, complexity of, i. 61.

  CROAKING of frogs, ii. 27.

  CROCODILES, musky odour of, during the breeding season, ii. 29.

  CROCODILIA, ii. 28.

  CROSSBILLS, characters of young, ii. 184.

  CROSSES in man, i. 225.

  CROSSING of races, effects of the, i. 241.

  _Crossoptilon auritum_, ii. 93, 166, 196;
    adornment of both sexes of, i. 290;
    sexes alike in, ii. 178.

  CROTCH, G. R., on the stridulation of beetles, i. 379, 382;
    on the stridulation of _Heliopathes_, i. 383;
    on the stridulation of _Acalles_, i. 384.

  CROW Indians, long hair of the, ii. 348.

  CROW, young of the, ii. 209.

  CROWS, ii. 226;
    vocal organs of the, ii. 55;
    living in triplets, ii. 106.

  CROWS, carrion, new mates found by, ii. 104.

  CROWS, Indian, feeding their blind companions, i. 77.

  CRUELTY of savages to animals, i. 94.

  CRUSTACEA, amphipod, males sexually mature while young, ii. 215;
    parasitic, loss of limbs by female, i. 255;
    prehensile feet and antennæ of, i. 256;
    male, more active than female, i. 272;
    parthenogenesis in, i. 315;
    secondary sexual characters of, i. 328;
    auditory hairs of, ii. 333.

  CRYSTAL worn in the lower lip by some Central African women, ii. 341.

  CUCKOO fowls, i. 294.

  CULICIDÆ, i. 254, 349.

  CULLEN, Dr., on the throat-pouch of the male bustard, ii. 58.

  CULTIVATION of plants, probable origin of, i. 167.

  CUPPLES, Mr., on the numerical proportion of the sexes in dogs, sheep,
      and cattle, i. 304, 305;
    on the Scotch deerhound, ii. 261;
    on sexual preference in dogs, ii. 271, 272.

  CURCULIONIDÆ, sexual difference in length of snout in some, i. 255;
    hornlike processes in male, i. 374;
    musical, i. 378, 379.

  CURIOSITY, manifestations of, by animals, i. 42.

  CURLEWS, double moult in, ii. 80.

  CURSORES, comparative absence of sexual differences among the, i. 269.

  CURTIS, J., on the proportion of the sexes in _Athalia_, i. 314.

  CUVIER, F., on the recognition of women by male quadrumana, i. 13.

  CUVIER, G., views of, as to the position of man, i. 190;
    on instinct and intelligence, i. 37;
    on the number of caudal vertebræ in the mandrill, i. 150;
    on the position of the seals, i. 190;
    on _Hectocotyle_, i. 325.

  _Cyanecula suecica_, sexual differences of, ii. 195.

  _Cyanalcyon_, sexual difference in colours of, ii. 173;
    immature plumage of, ii. 188.

  _Cychrus_, sounds produced by, i. 382.

  _Cycnia mendica_, sexual difference of colour in, i. 398.

  _Cygnus ferus_, trachea of, ii. 59.

  _Cygnus olor_, white young of, ii. 211.

  _Cyllo Leda_, instability of the ocellated spots of, ii. 133.

  _Cynanthus_, variation in the genus, ii. 125.

  CYNIPIDÆ, proportions of the sexes in, i. 314.

  _Cynocephalus_, difference of the young, from the adult, i. 13;
    male, recognition of women by, i. 13;
    polygamous habits of species of, i. 266.

  _Cynocephalus chacma_, i. 41.

  _Cynocephalus gelada_, i. 51.

  _Cynocephalus hamadryas_, i. 51;
    sexual difference of colour in, ii. 291.

  _Cynocephalus leucophus_, colours of the sexes of, ii. 292.

  _Cynocephalus mormon_, colours of the male, ii. 292, 296, 310.

  _Cynocephalus porcarius_, mane of the male, ii. 267.

  _Cypridina_, proportions of the sexes in, i. 315.

  CYPRINIDÆ, proportion of the sexes in the, i. 308.

  CYPRINIDÆ, Indian, ii. 17.

  CYPRINODONTIDÆ, sexual differences in the, ii. 7, 9.

  _Cyprinus auratus_, ii. 16.

  _Cyprinus phoxinus_, spawning of, ii. 15.

  _Cypris_, relations of the sexes in, i. 315.

  _Cystophora cristata_, hood of, ii. 278.


  D.

  _Dacelo_, sexual difference of colour in, ii. 174.

  _Dacelo Gaudichaudi_, young male of, ii. 188.

  DAL-RIPA, a kind of ptarmigan, i. 306.

  _Damalis albifrons_, peculiar markings of, ii. 301.

  _Damalis pygarga_, peculiar markings of, ii. 300.

  DAMPNESS of climate, supposed influence of, on the colour of the skin,
    i. 116, 242.

  _Danaidæ_, i. 387.

  DANCES of birds, ii. 68.

  DANCING, i. 232.

  DANIELL, Dr., his experience of residence in West Africa, i. 245.

  DARFUR, protuberances artificially produced in, ii. 339.

  DARWIN, F., on the stridulation of _Dermestes murinus_, i. 379.

  _Dasychira pudibunda_, sexual difference of colour in, i. 398.

  DAVIS, A. H., on the pugnacity of the male stag-beetle, i. 375.

  DAVIS, J. B., on the capacity of the skull in various races of men,
      i. 146;
    on the beards of the Polynesians, ii. 322.

  DEATH-RATE higher in towns than in rural districts, i. 175.

  DEATH-TICK, i. 384.

  DE CANDOLLE, Alph., on a case of inherited power of moving the scalp,
    i. 20.

  DECLENSIONS, origin of, i. 61.

  DECORATION in birds, ii. 71.

  _Decticus_, i. 355.

  DEER, spots of young, ii. 184, 303;
    horns of, ii. 243, 248;
    use of horns of, ii. 252, 263;
    size of the horns of, ii. 259;
    female, pairing with one male, whilst others are fighting for her,
      ii. 269;
    male, attracted by the voice of the female, ii. 276;
    male, odour emitted by, ii. 279;
    development of the horns in, i. 288;
    horns of a, in course of modification, ii. 255.

  DEER, Axis, sexual, difference in the colour of the, ii. 290.

  DEER, fallow, different coloured herds of, ii. 295.

  DEER, Mantchurian, ii. 303.

  DEER, Virginian, ii. 303;
    colour of the, not affected by castration, ii. 288;
    colours of, ii. 289.

  DEERHOUND, Scotch, greater size of the male, i. 293, ii. 260.

  DEFENSIVE organs of mammals, ii. 263.

  DE GEER, C., on a female spider destroying a male, i. 339.

  DEKAY, Dr., on the bladder-nose seal, ii. 278.

  DEMERARA, yellow fever in, i. 243.

  _Dendrocygna_, ii. 185.

  _Dendrophila frontalis_, young of, ii. 220.

  DENNY, H., on the lice of domestic animals, i. 219.

  _Dermestes murinus_, stridulation of, i. 379.

  DESCENT traced through the mother alone, ii. 359.

  DESERTS, protective colouring of animals inhabiting, ii. 224.

  DESMAREST, on the absence of suborbital pits in _Antilope
      subgutturosa_, ii. 280;
    on the whiskers of _Macacus_, ii. 283;
    on the colour of the opossum, ii. 286;
    on the colours of the sexes of _Mus minutus_, ii. 286;
    on the colouring of the ocelot, ii. 287;
    on the colours of seals, ii. 287;
    on _Antilope caama_, ii. 289;
    on the colours of goats, ii. 290;
    on sexual difference of colour in _Ateles marginatus_, ii. 291;
    on the mandrill, ii. 293;
    on _Macacus cynomolgus_, ii. 318.

  DESMOULINS, on the number of species of man, i. 226;
    on the musk-deer, ii. 281.

  DESOR, on the imitation of man by monkeys, i. 44.

  DESPINE, P., on criminals destitute of conscience, i. 92.

  DEVELOPMENT, embryonic, of man, i. 14, 16;
    correlated, ii. 130.

  DEVIL, not believed in by the Fuegians, i. 67.

  DEVIL-CRAB, i. 332.

  DEVONIAN, fossil insect from the, i. 360.

  DEWLAPS, of cattle and antelopes, ii. 284.

  _Diadema_, sexual differences of colouring in the species of, i. 388.

  _Diadema anomala_, mimickry by the female of, i. 413.

  _Diadema bolina_, i. 413.

  DIAMOND-BEETLES, bright colours of, i. 367.

  DIASTEMA, occurrence of, in man, i. 126.

  DIASTYLIDÆ, proportion of the sexes in, i. 315.

  DIODORUS, on the absence of beard in the natives of Ceylon, ii. 321.

  _Dicrurus_, racket-shaped feathers in, ii. 73;
    nidification of, ii. 167.

  _Dicrurus macrocercus_, change of plumage in, ii. 179.

  _Didelphis opossum_, sexual difference in the colour of, ii. 286.

  DIFFERENCES, comparative, between different species of birds of
    the same sex, ii. 192.

  DIGITS, supernumerary, more frequent in men than in women, i. 276;
    supernumerary, inheritance of, i. 285;
    supernumerary, early development of, i. 292.

  DIMORPHISM in females of water-beetles, i. 343;
    in _Neurothemis_ and _Agrion_, i. 363.

  _Dipelicus Cantori_, sexual differences of, i. 369.

  DIPLOPODA, prehensile limbs of the male, i. 340.

  _Dipsas cynodon_, sexual difference in the colour of, ii. 29.

  DIPTERA, i. 348.

  DISEASE, generated by the contact of distinct peoples, i. 239.

  DISEASES common to man and the lower animals, i. 11;
    difference of liability to, in different races of men, i. 216;
    new, effects of, upon savages, i. 238;
    sexually limited, i. 292.

  DISPLAY, coloration of Lepidoptera for, i. 395;
    of plumage by male birds, ii. 86, 96.

  DISTRIBUTION, wide, of man, i. 137;
    geographical, as evidence of specific distinctness in man, i. 218.

  DISUSE, effects of, in producing rudimentary organs, i. 18;
    and use of parts, effects of, i. 116;
    of parts, influence of, on the races of men, i. 247.

  DIVORCE, freedom of, among the Charruas, ii. 372.

  DIXON, E. S., on the habits of the guinea-fowl, i. 270;
    on the pairing of different species of geese, ii. 114;
    on the courtship of peafowl, ii. 121.

  DOBRIZHOFFER, on the marriage-customs of the Abipones, ii. 374.

  DOGS, suffering from Tertian ague, i. 13;
    memory of, i. 45;
    domestic, progress of, in moral qualities, i. 50;
    distinct tones uttered by, i. 54;
    parallelism between his affection for his master and religious
      feeling, i. 68;
    sociability of the, i. 74;
    sympathy of, with a sick cat, i. 77;
    sympathy of, with his master, i. 77;
    possible use of the hair on the forelegs of the, i. 193;
    races of the, i. 229;
    diverging when drawing sledges over thin ice, i. 40;
    dreaming, i. 46, 158;
    exercise of reasoning faculties by, i. 48;
    their possession of conscience, i. 78;
    numerical proportion of male and female births in, i. 304;
    sexual affection between individuals of, ii. 270;
    howling at certain notes, ii. 333;
    rolling in carrion, ii. 281.

  DOLICHOCEPHALIC structure, possible cause of, i. 148.

  DOLPHINS, nakedness of, i. 148.

  DOMESTIC animals, races of, i. 229;
    change of breeds of, ii. 369.

  DOMESTICATION, influence of, in removing the sterility of hybrids,
    i. 222.

  D’ORBIGNY, A., on the influence of dampness and dryness on the colour
      of the skin, i. 242;
    on the Yura-caras ii. 347.

  DOTTEREL, ii. 203.

  DOUBLEDAY, E., on sexual differences in the wings of butterflies,
    i. 345.

  DOUBLEDAY, H., on the proportion of the sexes in the smaller moths,
      i. 311;
    on the attraction of the males of _Lasiocampa quercus_
      and _Saturnia carpini_ by the female, i. 312;
    on the proportion of the sexes in the Lepidoptera, i. 312;
    on the ticking of _Anobium tessellatum_, i. 385;
    on the structure of _Ageronia feronia_, i. 387;
    on white butterflies alighting upon paper, i. 400.

  DOUGLAS, J. W., on the sexual differences of the _Hemiptera_, i. 349;
    on the colours of British _Homoptera_, i. 352.

  DOWN, of birds, ii. 80.

  _Draco_, gular appendages of, ii. 33.

  DRAGONET, Gemmeous, ii. 7.

  DRAGON-FLIES, caudal appendages of male, i. 344;
    relative size of the sexes of, i. 347;
    difference in the sexes of, i. 361;
    want of pugnacity by the male, i. 364.

  DRAKE, breeding plumage of the, ii. 84.

  DREAMS, i. 46;
    a possible source of the belief in spiritual agencies, i. 66.

  DRILL, sexual difference of colour in the, ii. 291.

  _Dromœus irroratus_, ii. 204.

  _Dromolæa_, Saharan species of, ii. 172.

  DRONGO shrike, ii. 179.

  DRONGOS, racket-shaped feathers in the tails of, ii. 73, 83.

  DRYNESS, of climate, supposed influence of, on the colour of the skin,
    i. 242.

  _Dryopithecus_, i. 199.

  DUCK, harlequin, age of mature plumage in the, ii. 213;
    breeding in immature plumage, ii. 214.

  DUCK, long-tailed, preference of male, for certain females, ii. 122.

  DUCK, pintail, pairing with a wigeon, ii. 114.

  DUCK, voice of the, ii. 60;
    pairing with a shield-drake, ii. 114;
    immature plumage of the, ii. 188.

  DUCK, wild, sexual differences in the, i. 268;
    speculum and male characters of, i. 291;
    pairing with a pintail drake, ii. 115.

  DUCKS, dogs and cats recognised by, ii. 110;
    wild, becoming polygamous under partial domestication, i. 270.

  DUGONG, tusks of, ii. 242;
    nakedness of, i. 148.

  DUJARDIN, on the relative size of the cerebral ganglia in insects,
    i. 145.

  DUNCAN, Dr., on the fertility of early marriages, i. 174.

  DUPONT, M., on the occurrence of the supra-condyloid foramen in
    the humerus of man, i. 29.

  DURAND, J. P., on causes of variation, i. 113.

  DUREAU de la Malle, on the songs of birds, i. 55;
    on the acquisition of an air by blackbirds, ii. 55.

  DUTCH, retention of their colour by the, in South Africa, i. 242.

  DUTY, sense of, i. 70.

  DUVAUCEL, female _Hylobates_ washing her young, i. 40.

  DYAKS, pride of, in mere homicide, i. 94.

  _Dynastes_, large size of males of, i. 347.

  DYNASTINI, stridulation of, i. 381.

  _Dytiscus_, dimorphism of females of, i. 343;
    grooved elytra of the female, i. 343.


  E.

  EAGLE, young _Cercopithecus_ rescued from, by the troop, i. 75.

  EAGLE, white-headed, breeding in immature plumage, ii. 214.

  EAGLES, golden, new mates found by, ii. 105.

  EAR, motion of the, i. 20;
    external shell of the, useless in man, i. 21;
    rudimentary point of the, in man, i. 22.

  EARS, piercing and ornamentation of the, ii. 341.

  _Echidna_, i. 201.

  _Echini_, bright colours of some, i. 322.

  ECHINODERMATA, absence of secondary sexual characters in, i. 321.

  ECKER, figure of the human embryo, i. 15;
    on sexual differences in the pelvis in man, ii. 317;
    on the presence of a sagittal crest in Australians, ii. 319.

  EDENTATA, former wide range of, in America, i. 219;
    absence of secondary sexual characters in, i. 268.

  _Edolius_, racket-shaped feathers in, ii. 73.

  EDWARDS, Mr., on the proportion of the sexes in North American species
    of _Papilio_, i. 309.

  EGERTON, Sir P., on the use of the antlers of deer, ii. 252;
    on the pairing of red deer, ii. 269;
    on the bellowing of stags, ii. 275.

  EGGS, hatched by male fishes, ii. 20.

  EGRET, Indian, sexes and young of, ii. 217.

  EGRETS, breeding plumage of, ii. 82;
    white, ii. 228.

  EHRENBERG, on the mane of the male Hamadryas baboon, ii. 267.

  EKSTRÖM, M., on _Harelda glacialis_, ii. 122.

  _Elachista rufocinerea_, habits of male, i. 311.

  ELAND, development of the horns of the, i. 289.

  ELANDS, sexual differences of colour in, ii. 288.

  _Elaphomyia_, sexual differences in, i. 349.

  _Elaphrus uliginosus_, stridulation of, i. 379.

  _Elaps_, ii. 31.

  ELATERIDÆ, proportions of the sexes in, i. 313.

  ELATERS, luminous, i. 345.

  ELEPHANT, i. 200;
    nakedness of the, i. 148;
    rate of increase of the, i. 135;
    Indian, polygamous habits of the, i. 267;
    pugnacity of the male, ii. 240;
    tusks of, ii. 242, 243, 248, 249, 258;
    Indian, mode of fighting, of the, ii. 257;
    male, odour emitted by the, ii. 279;
    attacking white or grey horses, ii. 295.

  ELEVATION of abode, modifying influence of, i. 120.

  ELIMINATION of inferior individuals, i. 172.

  ELK, ii, 249;
    winter change of the, ii. 299.

  ELK, Irish, horns of the, ii. 259.

  ELLICE Islands, beards of the natives, ii. 322, 349.

  ELLIOT, R., on the numerical proportion of the sexes in young rats,
      i. 305;
    on the proportion of the sexes in sheep, i. 305.

  ELLIOTT, D. G., on _Pelecanus erythrorhynchus_, ii. 80.

  ELLIOTT, Sir W., on the polygamous habits of the Indian wild boar,
    i. 267.

  ELLIS, on the prevalence of infanticide in Polynesia, ii. 364.

  ELPHINSTONE, Mr., on local differences of stature among the Hindoos,
      i. 115;
    on the difficulty of distinguishing the native races of India,
      i. 215.

  ELYTRA, of the females of _Dytiscus_, _Acilius_, _Hydroporus_, i. 343.

  _Emberiza_, characters of young, ii. 184.

  _Emberiza miliaria_, ii. 185.

  _Emberiza schœniculus_, ii. 111;
    head-feathers of the male, ii. 95.

  EMBRYO of man, i. 14, 15;
    of the dog, i. 15.

  EMBRYOS of mammals, resemblance of the, i. 32.

  EMIGRATION, i. 172.

  EMOTIONS experienced by the lower animals in common with man, i. 39;
    manifested by animals, i. 42.

  EMPEROR moth, i. 398.

  EMULATION of singing-birds, ii. 53.

  EMU, sexes and incubation of, ii. 204.

  ENDURANCE, estimation of, i. 95.

  ENERGY, a characteristic of men, ii. 328.

  ENGLAND, numerical proportion of male and female births in, i. 300.

  ENGLEHEART, Mr., on the finding of new mates by starlings, ii. 106.

  ENGLISH, success of, as colonists, i. 179.

  ENGRAVERS, short-sighted, i. 118.

  ENTOMOSTRACA, i. 332.

  ENTOZOA, difference of colour between the males and females of some,
    i. 321.

  EOCENE, possible divergence of man during the, i. 200.

  EOLIDÆ, colours of, produced by the biliary glands, i. 323.

  _Epeira_, i. 337.

  _Epeira nigra_, small size of the male of, i. 338.

  EPHEMERÆ, i. 341.

  EPHEMERIDÆ, i. 361.

  EPHEMERINA, proportions of the sexes in, i. 314.

  _Ephippiger vitium_, stridulating organs of, i. 354, 358.

  _Epicalia_, sexual differences of colouring in the species of, i. 388.

  _Equus hemionus_, winter change of, ii. 298.

  _Erateina_, coloration of, i. 397.

  ERECT attitude of man, i. 141, 142.

  ESCHRICHT, on the development of hair in man, i. 24;
    on a lanuginous moustache in a female fœtus, i. 25;
    on the want of definition between the scalp and the forehead
      in some children, i. 192;
    on the arrangement of the hair in the human fœtus, i. 193;
    on the hairiness of the face in the human fœtus of both sexes,
      ii. 379, 380.

  _Esmeralda_, difference of colour in the sexes of, i. 368.

  _Esox lucius_, i. 308.

  _Esox reticulatus_, ii. 14.

  ESQUIMAUX, i. 157, 167;
    their belief in the inheritance of dexterity in seal-catching,
      i. 117;
    mode of life of, i. 246.

  _Estrelda amandava_, pugnacity of the male, ii. 49.

  _Eubagis_, sexual differences of colouring in the species of, i. 389.

  _Euchirus longimanus_, sound produced by, i. 381.

  _Eudromias morinellus_, ii. 203.

  _Eulampis jugularis_, colours of the female, ii. 168.

  EULER, on the rate of increase in the United States, i. 131.

  _Eumomota superciliaris_, racket-shaped feathers in the tail of,
    ii. 73.

  _Eupetomena macroura_, colours of the female, ii. 168.

  _Euphema splendida_, ii. 174.

  _Euplocamus erythropthalmus_, possession of spurs by the female,
    ii. 46.

  _Euplœa midamas_, mimickry of, by the female of _Diadema anomala_,
    i. 413.

  EUROPE, ancient inhabitants of, i. 237.

  EUROPEANS, difference of, from Hindoos, i. 240;
    hairiness of, probably due to reversion, ii. 378.

  _Eurostopodus_, sexes of, ii. 206.

  _Eurygnathus_, different proportions of the head in the sexes of,
    i. 344.

  _Eustephanus_, sexual differences of species of, ii. 39;
    young of, ii. 220.

  EXAGGERATION of natural characters by man, ii. 351.

  EXOGAMY, ii. 360, 364.

  EXPRESSION, resemblances in, between man and the apes, i. 191.

  EXTINCTION of races, causes of, i. 238.

  EYE, destruction of the, i. 116;
    change of position in, i. 147;
    obliquity of, regarded as a beauty by the Chinese and Japanese,
      ii. 345.

  EYEBROWS, elevation of, i. 19;
    development of long hairs in, i. 25;
    in monkeys, i. 192;
    eradicated in parts of South America and Africa, ii. 340;
    eradication of, by the Indians of Paraguay, ii. 348.

  EYELIDS, coloured black, in part of Africa, ii. 339.

  EYELASHES, eradication of, by the Indians of Paraguay, ii. 348.

  EYES, difference in the colour of, in the sexes of birds, ii. 128;
    pillared, of the male of _Chloëon_, i. 341.

  EYTON, T. C., observations on the development of the horns
    in the fallow-deer, i. 288.

  EYZIES, Les, human remains from, i. 237.


  F.

  FABRE, M., on the habits of _Cerceris_, i. 364.

  FACIAL bones, causes of modification of the, i. 147.

  FACULTIES, mental, variation of, in the same species, i. 36;
    diversity of, in the same race of men, i. 109;
    inheritance of, i. 110;
    diversity of, in animals of the same species, i. 110;
    of birds, ii. 108.

  FAKIRS, Indian, tortures undergone by, i. 96.

  _Falco leucocephalus_, ii. 214.

  _Falco peregrinus_, ii. 104, 179.

  _Falco tinnunculus_, ii. 109.

  FALCON, peregrine, new mate found by, ii. 104.

  FALCONER, H., on the mode of fighting of the Indian elephant, ii. 257;
    on canines in a female deer, ii. 258;
    on _Hyomoschus aquaticus_, ii. 304.

  FALKLAND islands, horses of, i. 236.

  FALLOW-DEER, different coloured herds of, ii. 295.

  FAMINES, frequency of, among savages, i. 333.

  FARR, Dr., on the structure of the uterus, i. 123;
    on the effects of profligacy, i. 173;
    on the influence of marriage on mortality, i. 175.

  FARRAR, F. W., on the origin of language, i. 56;
    on the crossing or blending of languages, i. 60;
    on the absence of the idea of God in certain races of men, i. 65;
    on early marriages of the poor, i. 173;
    on the middle ages, i. 178.

  FASHIONS, long prevalence of, among savages, ii. 343, 352.

  FAYE, Prof., on the numerical proportion of male and female births
      in Norway and Russia, i. 301;
    on the greater mortality of male children at and before birth,
      i. 302.

  FEATHERS, modified, producing sounds, ii. 63 _et seqq._, 163;
    elongated, in male birds, ii. 72, 97;
    racket-shaped, ii. 73;
    barbless and with filamentous barbs in certain birds, ii. 74;
    shedding of margins of, ii. 85.

  FEEDING, high, probable influence of, in the pairing of birds
    of different species, ii. 115.

  FEET, modification of, in man, i. 141;
    thickening of the skin on the soles of the, i. 118.

  _Felis canadensis_, throat-ruff of, ii. 267.

  _Felis pardalis_ and _F. mitis_, sexual differences in the colouring
    of, ii. 287.

  FEMALE, behaviour of the, during courtship, i. 273.

  FEMALE birds, differences of, ii. 193.

  FEMALES, presence of rudimentary male organs in, i. 208;
    preference of, for certain males, i. 262;
    pursuit of, by males, i. 272;
    occurrence of secondary sexual characters in, i. 276;
    development of male characters by, i. 280.

  FEMALES and males, comparative mortality of, while young, i. 264, 276;
    comparative numbers of, i. 261, 263.

  FEMUR and tibia, proportions of, in the Aymara Indians, i. 119.

  FERGUSON, Mr., on the courtship of fowls, ii. 118.

  FERTILIZATION, phenomena of, in plants, i. 273;
    in the lower animals, i. 274.

  FEVERS, immunity of Negroes and Mulattoes from, i. 243.

  _Fiber zibethicus_, protective colouring of, ii. 298.

  FIDELITY of savages to one another, i. 95;
    importance of, i. 162.

  FIELD-SLAVES, difference of, from house-slaves, i. 246.

  FIJIANS, burying their old and sick parents alive, i. 77;
    estimation of the beard among the, ii. 349;
    admiration of, for a broad occiput, ii. 352.

  FIJI Islands, beards of the natives, ii. 322, 349;
    marriage-customs of the, ii. 373.

  FILIAL affection, partly the result of natural selection, i. 81.

  FILUM terminale, i. 30.

  FINCH, racket-shaped feathers in the tail of a, ii. 73.

  FINCHES, spring change of colour in, ii. 85;
    British, females of the, ii. 193.

  FINGERS, partially coherent, in species of _Hylobates_, i. 140.

  FINLAYSON, on the Cochin Chinese, ii. 345.

  FIRE, use of, i. 137, 183, 234.

  FISCHER, on the pugnacity of the male of _Lethrus cephalotes_, i. 376.

  FISH, proportion of the sexes in, i. 307;
    eagerness of male, i. 272.

  FISHES, kidneys of, represented by Corpora Wolffiana in the human
      embryo, i. 16;
    male, hatching ova in their mouths, i. 210;
    receptacles for ova possessed by, i. 254;
    relative size of the sexes in, ii. 7;
    freshwater, of the tropics, ii. 17;
    protective resemblances in, ii. 18;
    nest-building, ii. 19;
    spawning of, ii. 19;
    sounds produced by, ii. 23, 331;
    continued growth of, ii. 216.

  _Flexor pollicis longus_, similar variation of, in man, i. 129.

  FLINT tools, i. 183.

  FLINTS, difficulty of chipping into form, i. 138.

  FLORIDA, _Quiscalus major_ in, i. 307.

  FLOUNDER, coloration of the, ii. 18.

  FLOWER, W. H., on the abductor of the fifth metatarsal in apes,
      i. 128;
    on the position of the Seals, i. 190;
    on the throat-pouch of the male Bustard, ii. 58.

  FLY-CATCHERS, colours and nidification of, ii. 170.

  FŒTUS, human, woolly covering of the, i. 25;
    arrangement of the hair on, i. 193.

  FOOD, influence of, upon stature, i. 115.

  FOOT, prehensile, in the early progenitors of man, i. 206;
    prehensile power of the, retained in some savages, i. 142.

  FORAMEN, supra-condyloid, exceptional occurrence of in the humerus
      of man, i. 28, 130;
    in the early progenitors of man, i. 206.

  FORBES, D., on the Aymara Indians, i. 119;
    on local variation of colour in the Quechuas, i. 246;
    on the hairlessness of the Aymaras and Quechuas, ii. 322;
    on the long hair of the Aymaras and Quechuas, ii. 320, 348.

  FOREL, F., on white young swans, ii. 211.

  _Formica rufo_, size of the cerebral ganglia in, i. 145.

  FOSSILS, absence of, connecting man with the apes, i. 201.

  FOWL, occurrence of spurs in the female, i. 280;
    game, early pugnacity of, i. 295;
    Polish, early development of cranial peculiarities of, i. 295;
    variations in plumage of, ii. 74;
    examples of correlated development in the, ii. 130;
    domestic, breeds and sub-breeds of, ii. 178.

  FOWLS, spangled Hamburgh, i. 281, 294;
    sexual peculiarities in, transmitted only to the same sex, i. 283;
    loss of secondary sexual characters by male, i. 284;
    inheritance of changes of plumage by, i. 281;
    Polish, origin of the crest in, i. 284;
    period of inheritance of characters by, i. 294;
    cuckoo-, i. 294;
    development of the comb in, i. 295;
    numerical proportion of the sexes in, i. 306;
    courtship of, ii. 117;
    mongrel, between a black Spanish cock and different hens, ii. 131;
    pencilled Hamburgh, difference of the sexes in, ii. 158;
    Spanish, sexual differences of the comb in, ii. 158;
    spurred, in both sexes, ii. 162.

  FOX, W. D., on some half-tamed wild ducks becoming polygamous,
      and on polygamy in the guinea-fowl and canary-bird, i. 270;
    on the proportion of the sexes in cattle, i. 305;
    on the pugnacity of the peacock, ii. 46;
    on a nuptial assembly of magpies, ii. 102;
    on the finding of new mates by crows, ii. 104;
    on partridges living in triplets, ii. 107;
    on the pairing of a goose with a Chinese gander, ii. 114.

  FOXES, wariness of young, in hunting districts, i. 50;
    black, ii. 294.

  FRANCE, numerical proportion of male and female births in, i. 301.

  FRANCESCO, B., on the Simian resemblances of man, i. 4.

  FRASER, C., on the different colours of the sexes in a species
    of _Squilla_, i. 335.

  _Fringilla cannabina_, ii. 86.

  _Fringilla ciris_, age of mature plumage in, ii. 213.

  _Fringilla cyanea_, age of mature plumage in, ii. 213.

  _Fringilla leucophrys_, young of, ii. 217.

  _Fringilla spinus_, ii. 115.

  _Fringilla tristis_, change of colour in, in spring, ii. 85;
    young of, ii. 216.

  FRINGILLIDÆ, resemblance of the females of distinct species of,
    ii. 192.

  FROGS, ii. 25;
    male, temporary receptacles for ova possessed by, i. 254;
    ready to breed before the females, i. 260;
    vocal organs of, ii. 28.

  FRONTAL bone, persistence of the suture in, i. 124.

  FRUITS, poisonous, avoided by animals, i. 36.

  FUEGIANS, i. 167, 181;
    mental capacity of the, i. 34;
    quasi-religious sentiments of the, i. 67;
    power of sight in the, i. 118;
    skill of, in stone-throwing, i. 138;
    resistance of the, to their severe climate, i. 156, 237;
    difference of stature among the, i. 115;
    mode of life of the, i. 246;
    resemblance of, in mental characters, to Europeans, i. 232;
    aversion of, to hair on the face, ii. 348;
    said to admire European women, ii. 351.

  FULGORIDÆ, songs of the, i. 351.

  FUR, whiteness of, in arctic animals, in winter, i. 282.

  FUR-BEARING animals, acquired sagacity of, i. 50.


  G.

  _Gallicrex_, sexual difference in the colour of the irides in,
    ii. 128.

  _Gallicrex cristatus_, red caruncle occurring in the male during
    the breeding-season, ii. 80.

  GALLINACEÆ, frequency of polygamous habits and of sexual differences
      in the, i. 269;
    love-gestures of, ii. 68;
    decomposed feathers in, ii. 74;
    stripes of young, ii. 184;
    comparative sexual differences between the species of, ii. 192, 194;
    plumage of, ii. 195.

  GALLINACEOUS birds, weapons of the male, ii. 44;
    racket-shaped feathers on the heads of, ii. 73.

  _Gallinula chloropus_, pugnacity of male, ii. 40.

  _Gallinula cristata_, pugnacity of the male, ii. 41.

  _Galloperdix_, spurs of, ii. 46;
    development of spurs in the female, ii. 162.

  _Gallophasis_, young of, ii. 190.

  _Gallus bankiva_, ii. 158;
    neck-hackles of, ii. 84.

  _Gallus Stanleyi_, pugnacity of the male, ii. 44.

  GALLS, i. 152.

  GALTON, Mr., on the struggle between the social and personal impulses,
      i. 104;
    on hereditary genius, i. 111;
    on the effects of natural selection on civilised nations, i. 168;
    on the sterility of sole daughters, i. 170;
    on the degree of fertility of people of genius, i. 171;
    on the early marriages of the poor, i. 173;
    on the ancient Greeks, i. 177;
    on the Middle Ages, i. 178;
    on the progress of the United States, i. 179;
    on South African notions of beauty, ii. 347.

  _Gammarus_, use of the chelæ of, i. 331.

  _Gammarus marinus_, i. 334.

  GANNETS, white only when mature, ii. 228.

  GANOIDEI, i. 204.

  GANOID fishes, i. 212.

  GAOUR, horns of the, ii. 247.

  GAP between man and the apes, i. 200.

  GAPER, sexes and young of, ii. 217.

  GARDNER, on an example of rationality in a _Gelasimus_, i. 334.

  _Garrulus glandarius_, ii. 104.

  GÄRTNER, on sterility of hybrid plants, i. 223.

  GASTEROPODA, i. 324;
    pulmoniferous, courtship of, i. 324.

  _Gasterosteus_, i. 271;
    nidification of, ii. 20.

  _Gasterosteus leiurus_, ii. 2, 14, 20.

  _Gasterosteus trachurus_, ii. 2.

  _Gastrophora_, wings of, brightly coloured beneath, i. 397.

  GAUCHOS, want of humanity among the, i. 101.

  GAUDRY, M., on a fossil monkey, i. 197.

  _Gavia_, seasonal change of plumage in, ii. 228.

  GEESE, clanging noise made by, ii. 51;
    pairing of different species of, ii. 114;
    Canada, selection of mates by, ii. 116.

  GEGENBAUR, C., on the number of digits in the Ichthyopterygia,
      i. 125;
    on the hermaphroditism of the remote progenitors of the vertebrata,
      i. 207.

  _Gelasimus_, use of the enlarged chela of the male, i. 331;
    pugnacity of males of, i. 333;
    proportions of the sexes in a species of, i. 315;
    rational actions of a, i. 334;
    difference of colour in the sexes of a species of, i. 336.

  GEMMULES, sexual selection of, i. 285.

  GENESIS, i. 318.

  GENIUS, ii. 328;
    hereditary, i. 111.

  GENIUS, fertility of men and women of, i. 171.

  GEOFFROY-SAINT-HILAIRE, Isid., on the recognition of women by male
      quadrumana, i. 13;
    on the occurrence of a rudimentary tail in man, i. 29;
    on monstrosities, i. 113;
    on animal-like anomalies in the human structure, i. 125;
    on the correlation of monstrosities, i. 130;
    on the distribution of hair in man and monkeys, i. 149;
    on the caudal vertebræ of monkeys, i. 150;
    on correlated variability, i. 151;
    on the classification of man, i. 186;
    on the long hair on the heads of species of _Semnopithecus_, i. 192;
    on the hair in monkeys, i. 194;
    on the development of horns in female deer, ii. 244;
    and F. Cuvier, on the mandrill, ii. 293;
    on Hylobates, ii. 318, 320.

  GEOGRAPHICAL distribution, as evidence of specific distinctions
    in man, i. 218.

  GEOMETRÆ, brightly coloured beneath, i. 397.

  _Geophagus_, frontal protuberance of male, ii. 13, 20;
    eggs hatched by the male, in the mouth or branchial cavity, ii. 200.

  GEORGIA, change of colour in Germans settled in, i. 246.

  _Geotrupes_, stridulation of, i. 380, 382.

  GERBE, M., on the nest-building of _Crenilabrus massa_
    and _C. melops_, ii. 19.

  GERLAND, Dr., on the prevalence of infanticide, i. 94; ii. 344, 364;
    on the extinction of races, i. 237, 238.

  GERVAIS, P., on the hairiness of the gorilla, i. 149;
    on the mandrill, ii. 293.

  GESTURE-LANGUAGE, i. 232.

  GHOST-MOTH, sexual difference of colour in the, i. 399, 402.

  GIBB, Sir D., on differences of the voice in different races of men,
    ii. 330.

  GIBBON, Hoolock, nose of, i. 192.

  GIBBONS, voice of, ii. 276.

  GIRAFFE, mute, except in the rutting season, ii. 274;
    its mode of using the horns, ii. 250.

  GIRAUD-TEULON, on the cause of short sight, i. 118.

  GLANDERS, communicable between man and the lower animals, i. 11.

  GLANDS, odoriferous, in mammals, ii. 279, 281.

  _Glareola_, double moult in, ii. 80.

  _Glomeris limbata_, difference of colour in the sexes of, i. 340.

  GLOWWORM, female, apterous, i. 255;
    luminosity of the, i. 345.

  GNATS, dances of, i. 349.

  GNU, sexual differences in the colour of the, ii. 289.

  GOAT, male, wild, falling on his horns, ii. 249;
    male, odour emitted by, ii. 279;
    male, wild, crest of the, ii. 282;
    Berbura, mane, dewlap, &c., of the male, ii. 284;
    Kemas, sexual difference in the colour of the, ii. 289.

  GOATS, sexual differences in the horns of, i. 283;
    horns of, i. 289, ii. 246;
    domestic, sexual differences of, late developed, i. 293;
    beards of, ii. 282;
    mode of fighting of, ii. 249, 250.

  GOAT-SUCKER, Virginian, pairing of the, ii. 49.

  GOBIES, nidification of, ii. 20.

  GOD, want of the idea of, in some races of men, i. 65.

  GODRON, M., on variability, i. 112;
    on difference of stature, i. 115;
    on the want of connexion between climate and the colour of the skin,
      i. 241;
    on the odour of the skin, i. 248;
    on the colour of infants, ii. 318.

  GOLDFINCH, ii. 56, 85;
    proportion of the sexes in the, i. 307;
    sexual differences of the beak in the, ii. 39;
    courtship of the, ii. 95.

  GOLDFINCH, North American, young of, ii. 216.

  GOLDFISH, ii. 16.

  _Gomphus_, proportions of the sexes in, i. 314;
    difference in the sexes of, i. 362.

  _Gonepteryx Rhamni_, i. 393;
    sexual difference of colour in, i. 409.

  GOODSIR, Prof., on the affinity of the lancelet to the ascidians,
    i. 205.

  GOOSANDER, young of, ii. 189.

  GOOSE, Antarctic, colours of the, ii. 228.

  GOOSE, Canada, pairing with a Bernicle gander, ii. 114.

  GOOSE, Chinese, knob on the beak of the, ii. 129.

  GOOSE, Egyptian, ii. 46.

  GOOSE, Sebastopol, plumage of, ii. 74.

  GOOSE, Snow-, whiteness of the, ii. 228.

  GOOSE, Spur-winged, ii. 46.

  GORILLA, ii. 323;
    semi-erect attitude of the, i. 142;
    mastoid processes of the, i. 143;
    direction of the hair on the arms of the, i. 192;
    supposed evolution of the, i. 230;
    polygamy of the, i. 266, ii. 361, 362;
    voice of the, ii. 276;
    cranium of, ii. 318;
    fighting of male, ii. 324.

  GOSSE, P. H., on the pugnacity of the male Humming-birds, ii. 40.

  GOSSE, M., on the inheritance of artificial modifications of
    the skull, ii. 380.

  GOULD, B. A., on variation in the length of the legs in man, i. 108;
    measurements of American soldiers, i. 114, 116;
    on the proportions of the body and capacity of the lungs
      in different races of men, i. 216;
    on the inferior vitality of mulattoes, i. 221.

  GOULD, J., on the arrival of male snipes before the females, i. 260;
    on the numerical proportion of the sexes in birds, i. 306;
    on _Neomorpha_, ii. 39;
    on the species of _Eustephanus_, ii. 39;
    on the Australian Musk-duck, ii. 39;
    on the relative size of the sexes in _Biziura lobata_
      and _Cincloramphus cruralis_, ii. 43;
    on _Lobivanellus lobatus_, ii. 48;
    on the habits of _Menura Alberti_, ii. 56;
    on the rarity of song in brilliant birds, ii. 58;
    on _Selasphorus platycercus_, ii. 65;
    on the Bower-birds, ii. 69, 102;
    on the ornamental plumage of the Humming-birds, ii. 78;
    on the moulting of the ptarmigan, ii. 83;
    on the display of plumage by the male Humming-birds, ii. 86;
    on the shyness of adorned male birds, ii. 97;
    on the decoration of the bowers of Bower-birds, ii. 112;
    on the decoration of their nests by Humming-birds, ii. 112;
    on variation in the genus _Cynanthus_, ii. 125;
    on the colour of the thighs in a male parakeet, ii. 126;
    on _Urosticte Benjamini_, ii. 151, 152;
    on the nidification of the Orioles, ii. 168;
    on obscurely-coloured birds building concealed nests, ii. 169;
    on Trogons and Kingfishers, ii. 173;
    on Australian parrots, ii. 174;
    on Australian pigeons, ii. 175;
    on the moulting of the ptarmigan, ii. 181;
    on the immature plumage of birds, ii. 186 _et seq._;
    on the Australian species of _Turnix_, ii. 201;
    on the young of _Aïthurus polytmus_, ii. 220;
    on the colours of the bills of Toucans, ii. 227;
    on the relative size of the sexes in the Marsupials of Australia,
      ii. 260;
    on the colours of the Marsupials, ii. 286.

  GOUREAU, on the stridulation of _Mutilla europæa_, i. 366.

  GOUT, sexually transmitted, i. 292.

  GRABA, on the Pied Ravens of the Feroe Islands, ii. 126;
    on the Bridled Guillemot, ii. 127.

  GRADATION of secondary sexual characters in birds, ii. 135.

  GRALLATORES, absence of secondary sexual characters in, i. 270;
    double moult in some, ii. 81.

  _Grallina_, nidification of, ii. 169.

  GRASSHOPPERS, stridulation of the, i. 356.

  GRATIOLET, Prof., on the anthropomorphous apes, i. 196;
    on the evolution of the anthropomorphous apes, i. 230.

  GRAY, Asa, on the gradation of species among the Compositæ, i. 227.

  GRAY, J. E., on the caudal vertebræ of monkeys, i. 150;
    on the presence of rudiments of horns in the female
      of _Cervulus moschatus_, ii. 245;
    on the horns of goats and sheep, ii. 246;
    on the beard of the Ibex, ii. 283;
    on the Berbura goat, ii. 285;
    on sexual differences in the coloration of Rodents, ii. 286;
    on the colours of the Elands, ii. 288;
    on the Sing-sing antelope, ii. 289;
    on the colours of goats, ii. 290;
    on the Hog-deer, ii. 303.

  “GREATEST happiness principle,” i. 97, 98.

  GREEKS, ancient, i. 177.

  GREEN, A. H., on beavers fighting, ii. 239;
    on the voice of the beaver, ii. 277.

  GREENFINCH, selected by a female canary, ii. 115.

  GREG, W. R., on the early marriages of the poor, i. 173;
    on the Ancient Greeks, i. 178;
    on the effects of natural selection on civilised nations, i. 167.

  GRENADIERS, Prussian, i. 112.

  GREY, Sir G., on female infanticide in Australia, ii. 364.

  GREYHOUNDS, numerical proportion of the sexes in, i. 263, 265;
    numerical proportion of male and female births in, i. 304.

  GROUSE, red, monogamous, i. 269;
    pugnacity of young male, ii. 48;
    producing a sound by scraping their wings upon the ground, ii. 61;
    duration of courtship of, ii. 100;
    colours and nidification of, ii. 170.

  GRUBE, Dr., on the occurrence of the supra-condyloid foramen
    in the humerus of man, i. 28.

  _Grus americanus_, age of mature plumage in, ii. 213;
    breeding in immature plumage, ii. 214.

  _Grus virgo_, trachea of, ii. 60.

  _Gryllus campestris_, i. 353;
    pugnacity of male, i. 360.

  _Gryllus domesticus_, i. 354.

  _Grypus_, sexual differences in the beak in, ii. 39.

  GUANACOES, battles of, ii. 239;
    canine teeth of, ii. 257.

  GUANAS, strife for women among the, ii. 324;
    polyandry among the, ii. 366.

  GUANCHE skeletons, occurrence of the supra-condyloid foramen
    in the humerus of, i. 29.

  GUARANYS, proportion of men and women among, i. 302;
    colour of newborn children of the, ii. 318;
    beards of the, ii. 322.

  GUENÉE, A., on the sexes of _Hyperythra_, i. 310.

  GUILDING, L., on the stridulation of the _Locustidæ_, i. 352.

  GUILLEMOT, variety of the, ii. 127.

  GUINEA, sheep of, with males only horned, i. 289.

  GUINEA-FOWL, monogamous, i. 269;
    occasional polygamy of the, i. 270;
    markings of the, ii. 134.

  GUINEA-PIGS, inheritance of the effects of operations by, ii. 380.

  GULL, instance of reasoning in a, ii. 108.

  GULLS, seasonal change of plumage in, ii. 228;
    white, ii. 228.

  GÜNTHER, Dr., on hermaphroditism in _Serranus_, i. 208;
    on male fishes hatching ova in their mouths, i. 210, ii. 20;
    on mistaking infertile female fishes for males, i. 308;
    on the prehensile organs of male Plagiostomous fishes, ii. 2;
    on the pugnacity of the male salmon and trout, ii. 3;
    on the relative size of the sexes in fishes, ii. 7;
    on sexual differences in fishes, ii. 8 _et seqq._;
    on the genus _Callionymus_, ii. 9;
    on a protective resemblance in a Pipe-fish, ii. 18;
    on the genus _Solenostoma_, ii. 22;
    on _Megalophrys montana_, ii. 26;
    on the coloration of frogs and toads, ii. 26;
    on sexual differences in the Ophidia, ii. 29;
    on differences of the sexes of lizards, ii. 32 _et seqq._

  _Gynanisa Isis_, ocellated spots of, ii. 132.

  GYPSIES, uniformity of, in various parts of the world, i. 242.


  H.

  HABITS, bad, facilitated by familiarity, i. 101;
    variability of the force of, i. 183.

  HÄCKEL, E., on the origin of man, i. 4;
    on rudimentary characters, i. 17;
    on the canine teeth in man, i. 126;
    on death caused by inflammation of the vermiform appendage, i. 28;
    on the steps by which man became a biped, i. 142;
    on man as a member of the Catarrhine group, i. 199;
    on the position of the Lemuridæ, i. 202;
    on the genealogy of the Mammalia, i. 203;
    on the lancelet, i. 204;
    on the transparency of pelagic animals, i. 323;
    on the musical powers of women, ii. 337.

  HAGEN, H., and Walsh, B. D., on American neuroptera, i. 314.

  HAIR, development of, in man, i. 24;
    character of, supposed to be determined by light and heat, i. 116;
    distribution of, in man, i. 149, ii. 375;
    possibly removed for ornamental purposes, i. 149;
    arrangement and direction of, i. 192;
    of the early progenitors of man, i. 206;
    different texture of, in distinct races, i. 216;
    and skin, correlation of colour of, i. 248;
    development of, in mammals, ii. 281;
    management of, among different peoples, ii. 340;
    great length of, in some North American tribes, ii. 348;
    elongation of the, on the human head, ii. 380.

  HAIRINESS, difference of, in the sexes, in man, ii. 320;
    variation of, in races of men, ii. 321.

  HAIRS and excretory pores, numerical relation of, in sheep, i. 248.

  HAIRY family, Siamese, ii. 378.

  HAMADRYAS baboon, turning over stones, i. 75;
    mane of the male, ii. 267.

  HAMILTON, C., on the cruelty of the Kafirs to animals, i. 94;
    on the engrossment of the women by the Kafir chiefs, ii. 369.

  HAMMERING, difficulty of, i. 138.

  HANCOCK, A., on the colours of the nudibranch mollusca, i. 326.

  HANDS, larger at birth, in the children of labourers, i. 117;
    structure of, in the quadrumana, i. 139;
    and arms, freedom of, indirectly correlated with diminution
      of canines, i. 144.

  HANDWRITING, inherited, i. 58.

  HARCOURT, E. Vernon, on _Fringilla cannabina_, ii. 86.

  _Harelda glacialis_, ii. 122.

  HARE, protective colouring of the, ii. 298.

  HARES, battles of male, ii. 239.

  HARLAN, Dr., on the difference between field- and house-slaves, i. 246.

  HARRIS, J. M., on the relation of complexion to climate, i. 245.

  HARRIS, T. W., on the Katy-did locust, i. 353;
    on the stridulation of the grasshoppers, i. 357;
    on _Œcanthus nivalis_, i. 361;
    on the colouring of Lepidoptera, i. 396;
    on the colouring of _Saturnia Io_, i. 398.

  HARRY-LONG-LEGS, pugnacity of male, i. 349.

  HARTMAN, Dr., on the singing of _Cicada septendecim_, i. 351.

  HAUGHTON, S., on a variation of the _flexor pollicis longus_ in man,
    i. 129.

  HAWKS, feeding orphan nestling, ii. 107.

  HAYES, Dr., on the diverging of sledge-dogs on thin ice, i. 46.

  HEAD, altered position of, to suit the erect attitude of man, i. 143;
    hairiness of, in man, i. 149;
    processes of, in male beetles, i. 370;
    artificial alterations of the form of the, ii. 351.

  HEARNE, on strife for women among the North American Indians, ii. 324;
    on the North American Indians’ notion of female beauty, ii. 344;
    repeated elopements of a North American woman, ii. 372.

  HEART, in the human embryo, i. 16.

  HEAT, supposed effects of, i. 116.

  _Hectocotyle_, i. 325.

  HEDGE-WARBLER, ii. 198;
    young of the, ii. 209.

  HEEL, small projection of, in the Aymara Indians, i. 120.

  HEGT, M., on the development of the spurs in peacocks, i. 290.

  HELICONIDÆ, i. 387;
    mimickry of, by other butterflies, i. 411.

  _Heliopathes_, stridulation peculiar to the male, i. 383.

  _Heliothrix auriculata_, young of, ii. 188, 189.

  _Helix pomatia_, example of individual attachment in, i. 325.

  HELLINS, J., proportions of sexes of Lepidoptera reared by, i. 313.

  HELMHOLTZ, on the vibration of the auditory hairs of crustacea,
    ii. 333.

  HEMIPTERA, i. 349.

  _Hemitragus_, beardless in both sexes, ii. 283.

  HEPBURN, Mr., on the autumn song of the water-ouzel, ii. 54.

  _Hepialus humuli_, sexual difference of colour in the, i. 399, 402.

  HERBS, poisonous, avoided by animals, i. 36.

  HERMAPHRODITISM of embryos, i. 207.

  _Herodias bubulcus_, vernal moult of, ii. 84.

  HERON, love-gestures of a, ii. 68.

  HERON, Sir R., on the habits of peafowl, ii. 119, 120, 152.

  HERONS, decomposed feathers in, ii. 74;
    breeding plumage of, ii. 82, 83;
    young of the, ii. 208;
    sometimes dimorphic, ii. 214;
    continued growth of crest and plumes in the males of some, ii. 216;
    change of colour in some, ii. 231.

  _Hetærina_, difference in the sexes of, i. 362;
    proportion of the sexes in, i. 314.

  _Heterocerus_, stridulation of, i. 379.

  HEWITT, Mr. on a game-cock killing a kite, ii. 44;
    on the recognition of dogs and cats by ducks, ii. 110;
    on the pairing of a wild duck with a pintail drake, ii. 115;
    on the courtship of fowls, ii. 117;
    on the coupling of pheasants with common hens, ii. 122.

  HINDOO, his horror of breaking his caste, i. 99, 103.

  HINDOOS, local difference of stature among, i. 115;
    difference of, from Europeans, i. 240;
    colour of the beard in, ii. 319.

  _Hipparchia Janira_, instability of the ocellated spots of, ii. 132.

  _Hipparchiæ_, i. 387.

  _Hippocampus_, development of, i. 210;
    marsupial receptacles of the male, ii. 21.

  HIPPOPOTAMUS, nakedness of, i. 148.

  HIPS, proportions of, in soldiers and sailors, i. 117.

  HODGSON, S., on the sense of duty, i. 71.

  HOFFBERG, on the horns of the reindeer, ii. 244;
    on sexual preferences shown by reindeer, ii. 273.

  HOG, wart-, ii. 265;
    river-, ii. 266.

  HOG-DEER, ii. 303.

  HOLLAND, Sir H., on the effects of new diseases, i. 238.

  HOMOLOGOUS structures, correlated variation of, i. 130.

  HOMOPTERA, i. 350;
    stridulation of the, and orthoptera, discussed, i. 360.

  HONDURAS, _Quiscalus major_ in, i. 307.

  HONEY-BUZZARD of India, variation in the crest of, ii. 126.

  HONEY-SUCKERS, moulting of the, ii. 83;
    Australian, nidification of, ii. 169.

  HONOUR, law of, i. 99.

  HOOKER, Jos., on the colour of the beard in man, ii. 319.

  HOOLOCK GIBBON, nose of, i. 192.

  HOOPOE, ii. 56;
    sounds produced by the male, ii. 62.

  _Hoplopterus armatus_, wing-spurs of, ii. 48.

  HORNBILL, African, inflation of the neck-wattle of the male during
    courtship, ii. 72.

  HORNBILLS, sexual difference in the colour of the eyes in, ii. 129;
    nidification and incubation of, ii. 169.

  HORNE, C., on the rejection of a brightly-coloured locust by lizards
    and birds, i. 361.

  HORNS, of deer, ii. 243, 248, 259;
    and canine teeth, inverse development of, ii. 257;
    sexual differences of, in sheep and goats, i. 283;
    loss of, in female merino sheep, i. 284;
    development of, in deer, i. 288;
    development of, in antelopes, i. 289;
    from the head and thorax, in male beetles, i. 370.

  HORSE, polygamous, i. 267;
    canine teeth of male, ii. 241;
    winter change of the, ii. 298;
    fossil, extinction of the, in South America, i. 239.

  HORSES, dreaming, i. 46;
    rapid increase of, in South America, i. 135;
    diminution of canine teeth in, i. 144;
    of the Falkland Islands and Pampas, i. 236;
    numerical proportion of the sexes in, i. 263, 265;
    lighter in winter in Siberia, i. 282;
    sexual preferences in, ii. 272;
    pairing preferentially with those of the same colour, ii. 295;
    numerical proportion of male and female births in, i. 303;
    formerly striped, ii. 305.

  HOTTENTOT women, peculiarities of, i. 225.

  HOTTENTOTS, lice of, i. 220;
    readily become musicians, ii. 334;
    notions of female beauty of the, ii. 345;
    compression of nose by, ii. 352.

  HOUSE-SLAVES, difference of, from field-slaves, i. 246.

  HUBER, P., on ants playing together, i. 39;
    on memory in ants, i. 45;
    on the intercommunication of ants, i. 58;
    on the recognition of each other by ants after separation, i. 365.

  HUC, on Chinese opinions of the appearance of Europeans, ii. 345.

  HUMAN kingdom, i. 186.

  HUMAN sacrifices, i. 68.

  HUMANITY, unknown among some savages, i. 94;
    deficiency of, among savages, i. 101.

  HUMBOLDT, A. von, on the rationality of mules, i. 48;
    on a parrot preserving the language of a lost tribe, i. 236;
    on the cosmetic arts of savages, ii. 339, 340;
    on the exaggeration of natural characters by man, ii. 351;
    on the red painting of American Indians, ii. 352.

  HUME, D., on sympathetic feelings, i. 85.

  HUMMING-BIRD, racket-shaped feathers in the tail of a, ii. 73;
    display of plumage by the male, ii. 86.

  HUMMING-BIRDS, ornament their nests, i. 63, ii. 112;
    polygamous, i. 269;
    proportion of the sexes in, i. 307, ii. 221;
    sexual differences in, ii. 39, 40, 151;
    pugnacity of male, ii. 40;
    modified primaries of male, ii. 65;
    coloration of the sexes of, ii. 78;
    young of, ii. 220;
    nidification of the, ii. 168;
    colours of female, ii. 168.

  HUMPHREYS, H. N., on the habits of the Stickleback, i. 271, ii. 2.

  HUNGER, instinct of, i. 89.

  HUNS, ancient, flattening of the nose by the, ii. 352.

  HUNTER, J., on the number of species of man, i. 226;
    on secondary sexual characters, i. 253;
    on the general behaviour of female animals during courtship, i. 273;
    on the muscles of the larynx in song-birds, ii. 55;
    on the curled frontal hair of the Bull, ii. 282;
    on the rejection of an ass by a female zebra, ii. 295.

  HUNTER, W. W., on the recent rapid increase of the Santali, i. 133;
    on the Santali, i. 241.

  HUSSEY, Mr., on a partridge distinguishing persons, ii. 110.

  HUTCHINSON, Col., example of reasoning in a retriever, i. 48.

  HUTTON, Capt., on the male wild goat falling on his horns, ii. 249.

  HUXLEY, T. H., on the structural agreement of man with the apes, i. 3;
    on the agreement of the brain in man with that of lower animals,
      i. 10;
    on the adult age of the Orang, i. 13;
    on the embryonic development of man, i. 14;
    on the origin of man, i. 4, 17;
    on variation in the skulls of the natives of Australia, i. 108;
    on the abductor of the fifth metatarsal in apes, i. 128;
    on the position of man, i. 191;
    on the sub-orders of primates, i. 195;
    on the Lemuridæ, i. 202;
    on the Dinosauria, i. 204;
    on the amphibian affinities of the Ichthyosaurians, i. 204;
    on variability of the skull in certain races of man, i. 226;
    on the races of man, i. 229.

  HYBRID birds, production of, ii. 113.

  HYDROPHOBIA communicable between man and the lower animals, i. 11.

  _Hydroporus_, dimorphism of females of, i. 343.

  _Hyelaphus porcinus_, ii. 303.

  _Hygrogonus_, ii. 21.

  _Hyla_, singing species of, ii. 27.

  _Hylobates_, maternal affection in a, i. 40;
    absence of the thumb in, i. 140;
    upright progression of some species of, i. 143;
    direction of the hair on the arms of species of, i. 192;
    females of, less hairy below than males, ii. 320.

  _Hylobates agilis_, i. 140;
    hair on the arms of, i. 193;
    musical voice of the, ii. 277;
    superciliary ridge of, ii. 318;
    voice of, ii. 332.

  _Hylobates hoolock_, sexual difference of colour in, ii. 291.

  _Hylobates lar_, i. 140;
     hair on the arms of, i. 193.

  _Hylobates leuciscus_, i. 140.

  _Hylobates syndactylus_, i. 140;
    laryngeal sac of, ii. 276.

  HYMENOPTERA, i. 364;
    large size of the cerebral ganglia in, i. 145;
    classification of, i. 188;
    sexual differences in the wings of, i. 345;
    aculeate, relative size of the sexes of, i. 347.

  HYMENOPTERON, parasitic, with a sedentary male, i. 272.

  _Hyomoschus aquaticus_, ii. 304.

  _Hyperythra_, proportion of the sexes in, i. 310.

  _Hypogymna dispar_, sexual difference of colour in, i. 398.

  _Hypopyra_, coloration of, i. 397.


  I.

  IBEX, male, falling on his horns, ii. 249;
    beard of the, ii. 283.

  IBIS, scarlet, young of the, ii. 208;
    white, change of colour of naked skin in, during the breeding
      season, ii. 80.

  _Ibis tantalus_, age of mature plumage in, ii. 213;
    breeding in immature plumage, ii. 214, 215.

  IBISES, decomposed feathers in, ii. 74;
    white, ii. 228, and black, ii. 230.

  ICHNEUMONIDÆ, difference of the sexes in, i. 365.

  ICHTHYOPTERYGIA, i. 125.

  ICHTHYOSAURIANS, i. 204.

  IDEAS, general, i. 62.

  IDIOTS, microcephalous, imitative faculties of, i. 57;
    microcephalous, their characters and habits, i. 121.

  _Iguana tuberculata_, ii. 32.

  IGUANAS, ii. 32.

  ILLEGITIMATE and legitimate children, proportion of the sexes in,
    i. 302.

  IMAGINATION, existence of, in animals, i. 45.

  IMITATION, i. 39;
    of man by monkeys, i. 44;
    tendency to, in monkeys, microcephalous idiots and savages, i. 56;
    influence of, i. 161.

  IMMATURE plumage of birds, ii. 183, 187.

  IMPLACENTATA, i. 202.

  IMPLEMENTS, employed by monkeys, i. 51;
    fashioning of, peculiar to man, i. 52.

  IMPREGNATION, period of, influence of, upon sex, i. 303.

  IMPROVEMENT, progressive, man alone supposed to be capable of, i. 49.

  INCISOR teeth, knocked out or filed by some savages, ii. 340.

  INCREASE, rate of, i. 131;
    necessity of checks in, i. 135.

  INDECENCY, hatred of, a modern virtue, i. 96.

  INDIA, difficulty of distinguishing the native races of, i. 215;
    Cyprinidæ of, ii. 17;
    colour of the beard in races of men of, ii. 319.

  INDIAN, North American, honoured for scalping a man of another tribe,
    i. 93.

  INDIVIDUALITY, i. 62.

  INDIVIDUATION, i. 318.

  _Indopicus carlotta_, colours of the sexes of, ii. 175.

  INFANTICIDE, prevalence of, i. 94, 134;
    supposed cause of, ii. 344;
    prevalence and causes of, ii. 363 _et seq._

  INFERIORITY, supposed physical, of man, i. 156.

  INFLAMMATION of the bowels, occurrence of, in _Cebus Azaræ_, i. 12.

  INHERITANCE, i. 110;
    of effects of use of vocal and mental organs, i. 58;
    of moral tendencies, i. 102, 104;
    of long and short sight, i. 118;
    laws of, i. 279;
    sexual, i. 285;
    sexually limited, ii. 154.

  INQUISITION, influence of the, i. 179.

  INSANITY, hereditary, i. 111.

  INSECT, fossil, from the Devonian, i. 360.

  INSECTIVORA, ii. 286;
    absence of secondary sexual characters in, i. 268.

  INSECTS, relative size of the cerebral ganglia in, i. 145;
    male, appearance of, before the females, i. 260;
    pursuit of female, by the males, i. 272;
    period of development of sexual characters in, i. 291;
    secondary sexual characters of, i. 341;
    stridulation of, ii. 331.

  INSESSORES, vocal organs of, ii. 55.

  INSTEP, depth of, in soldiers and sailors, i. 117.

  INSTINCT and intelligence, i. 37.

  INSTINCT, migratory, vanquishing the maternal, i. 83, 90.

  INSTINCTIVE actions, the result of inheritance, i. 80.

  INSTINCTIVE impulses, difference of the force of, i. 87, 89;
    and moral impulses, alliance of, i. 88.

  INSTINCTS, i. 36;
    complex origin of, through natural selection, i. 38;
    possible origin of some, i. 38;
    acquired, of domestic animals, i. 79;
    variability of the force of, i. 83;
    difference of force between the social and other, i. 89, 104;
    utilised for new purposes, ii. 335.

  INSTRUMENTAL music of birds, ii. 61, 66.

  INTELLECT, influence of, in natural selection in civilised society,
    i. 171.

  INTELLECTUAL faculties, their influence on natural selection in man,
      i. 158;
    probably perfected through natural selection, i. 160.

  INTELLIGENCE, Mr. H. Spencer on the dawn of, i. 37.

  INTEMPERANCE, no reproach among savages, i. 96;
    its destructiveness, i. 172.

  INTOXICATION in monkeys, i. 12.

  _Iphias glaucippe_, i. 394.

  IRIS, sexual difference in the colour of the, in birds, ii. 72, 128.

  ISCHIO-PUBIC muscle, i. 127.

  _Ithaginis cruentus_, number of spurs in, ii. 46.

  _Iulus_, tarsal suckers of the males of, i. 340.


  J.

  JACKALS learning to bark from dogs, i. 44.

  JACK-SNIPE, coloration of the, ii. 226.

  JACQUINOT, on the number of species of man, i. 226.

  JAEGER, Dr., on the difficulty of approaching herds of wild animals,
      i. 74;
    on the increase of length in bones, i. 116;
    on the deposition of a male Silver pheasant on account of spoiled
      plumage, ii. 120.

  JAGUARS, black, ii. 294.

  JANSON, E. W., on the proportions of the sexes in _Tomicus villosus_,
      i. 314;
    on stridulant beetles, i. 379.

  JAPAN, encouragement of licentiousness in, i. 134.

  JAPANESE, general beardlessness of the, ii. 321;
    aversion of the, to whiskers, ii. 349.

  JARDINE, Sir W., on the Argus pheasant, ii. 72, 97.

  JARROLD, Dr., on modifications of the skull induced by unnatural
    position, i. 147.

  JAVANESE, relative height of the sexes of, ii. 320;
    notions of female beauty, ii. 347.

  JAW, influence of the muscles of the, upon the physiognomy
    of the apes, i. 144.

  JAWS, smaller in the same ratio with the extremities, i. 117;
    influence of food upon the size of, i. 118;
    diminution of, in man, i. 144;
    in man, reduced by correlation, ii. 325.

  JAY, young of the, ii. 209;
    Canada, young of the, ii. 209.

  JAYS, new mates found by, ii. 104;
    distinguishing persons, ii. 110.

  JEFFREYS, J. Gwyn, on the form of the shell in the sexes
      of the Gasteropoda, i. 324;
    on the influence of light upon the colours of shells, i. 326.

  JELLY-FISH, bright colours of some, i. 322.

  JENNER, Dr., on the voice of the rook, ii. 61;
    on the finding of new mates by magpies, ii. 103;
    on retardation of the generative organs in birds, ii. 107.

  JENYNS, L., on the desertion of their young by swallows, i. 84;
    on male birds singing after the proper season, ii. 107.

  JERDON, Dr., on birds dreaming, 46;
    on the pugnacity of the male bulbul, ii. 41;
    on the pugnacity of the male _Ortygornis gularis_, ii. 44;
    on the spurs of _Galloperdix_, ii. 46;
    on the habits of _Lobivanellus_, ii. 48;
    on the spoonbill, ii. 60;
    on the drumming of the Kalij pheasant, ii. 63;
    on Indian bustards, ii. 65;
    on _Otis bengalensis_, ii. 69;
    on the ear-tufts of _Sypheotides auritus_, ii. 73;
    on the double moults of certain birds, ii. 82;
    on the moulting of the honey-suckers, ii. 83;
    on the moulting of bustards, plovers, and drongos, ii. 84;
    on display in male birds, ii. 86;
    on the spring change of colour in some finches, ii. 86;
    on the display of the under tail-coverts by the male bulbul, ii. 96;
    on the Indian honey-buzzard, ii. 126;
    on sexual differences in the colour of the eyes of hornbills,
      ii. 129;
    on the markings of the Tragopan pheasant, ii. 134;
    on the nidification of the Orioles, ii. 168;
    on the nidification of the hornbills, ii. 169;
    on the Sultan yellow-tit, ii. 174;
    on _Palæornis javanicus_, ii. 180;
    on the immature plumage of birds, ii. 186 _et seq._;
    on representative species of birds, ii. 190;
    on the habits of _Turnix_, ii. 202;
    on the continued increase of beauty of the peacock, ii. 216;
    on coloration in the genus _Palæornis_, ii. 231.

  JEVONS, W. S., on the migrations of man, i. 135.

  JEWS, ancient, use of flint tools by the, i. 183;
    uniformity of, in various parts of the world, i. 242;
    numerical proportion of male and female births among the, i. 301;
    ancient, tattooing practised by, ii. 339.

  JOHNSTONE, Lieut., on the Indian elephant, i. 268.

  JOLLOFS, fine appearance of the, ii. 357.

  JONES, Albert, proportion of sexes of Lepidoptera, reared by, i. 313.

  JUAN FERNANDEZ, humming-birds of, ii. 221.

  _Junonia_, sexual differences of colouring in species of, i. 389.

  JUPITER, Greek statues of, ii. 350.


  K.

  KAFIR skull, occurrence of the diastema in a, i. 126.

  KAFIRS, their cruelty to animals, i. 94;
    lice of the, i. 220;
    colour of the, ii. 347;
    engrossment of the handsomest women by the chiefs of the, ii. 369;
    marriage-customs of the, ii. 373.

  KALIJ-PHEASANT, drumming of the male, ii. 62;
    young of, ii. 190.

  _Kallima_, resemblance of, to a withered leaf, i. 392.

  KALMUCKS, aversion of, to hairs on the face, ii. 349;
    marriage-customs of the, ii. 373.

  KANGAROO, great red, sexual difference in the colour of, ii. 286.

  KANT, Imm., on duty, i. 70;
    on self-restraint, i. 86;
    on the number of species of man, i. 226.

  KATY-DID, stridulation of the, i. 352.

  KELLER, Dr., on the difficulty of fashioning stone implements, i. 138.

  KESTRELS, new mates found by, ii. 104.

  KIDNEY, i. 116.

  KING, W. R., on the vocal organs of _Tetrao cupido_, ii. 56;
    on the drumming of grouse, ii. 63;
    on the reindeer, ii. 244;
    on the attraction of male deer by the voice of the female, ii. 276.

  KING and Fitzroy, on the marriage-customs of the Fuegians, ii. 374.

  KING-CROWS, nidification of, ii. 167.

  KINGFISHER, ii. 56;
    racket-shaped feathers in the tail of a, ii. 73.

  KINGFISHERS, colours and nidification of the, ii. 171, 173, 176;
    immature plumage of the, ii. 188, 190;
    young of the, ii. 209.

  KING LORY, ii. 174;
    immature plumage of the, ii. 188.

  KINGSLEY, C., on the sounds produced by _Umbrina_, ii. 23.

  KIRBY and Spence, on the courtship of insects, i. 272;
    on sexual differences in the length of the snout in curculionidæ,
      i. 255;
    on the elytra of _Dytiscus_, i. 343;
    on peculiarities in the legs of male insects, i. 344;
    on the relative size of the sexes in insects, i. 345;
    on the luminosity of insects, i. 345;
    on the Fulgoridæ, i. 351;
    on the habits of _Termites_, i. 364;
    on difference of colour in the sexes of beetles, i. 367;
    on the horns of the male lamellicorn beetles, i. 371;
    on hornlike processes in male curculionidæ, i. 374;
    on the pugnacity of the male stag-beetle, i. 375.

  KITE, killed by a game-cock, ii. 44.

  KNOT, retention of winter plumage by the, ii. 82.

  KNOX, R., on the semilunar fold, i. 23;
    on the occurrence of the supra-condyloid foramen in the humerus
      of man, i. 28;
    on the features of the young Memnon, i. 217.

  KOALA, length of the cæcum in, i. 27.

  KÖLREUTER, on the sterility of hybrid plants, i. 223.

  _Kobus ellipsiprymnus_, proportion of the sexes in, i. 305.

  KOODOO, development of the horns of the, i. 289;
    markings of the, ii. 300.

  KÖPPEN, F. T., on the migratory locust, i. 352.

  KORDOFAN, protuberances artificially produced in, ii. 339.

  KOWALEVSKY, A., on the affinity of the Ascidia to the Vertebrata,
    i. 205.

  KOWALEVSKY, W., on the pugnacity of the male Capercailzie, ii. 45;
    on the pairing of the Capercailzie, ii. 49.

  KRAUSE, on a convoluted body at the extremity of the tail in
    a _Macacus_ and a cat, i. 30.

  KUPPFER, Prof., on the affinity of the Ascidia to the Vertebrata,
    i. 205.


  L.

  _Labidocera Darwinii_, prehensile organs of the male, i. 329.

  _Labrus_, splendid colours of the species of, ii. 16.

  _Labrus mixtus_, sexual differences in, ii. 9.

  _Labrus pavo_, ii. 16.

  LACERTILIA, sexual differences of, ii. 32.

  LAFRESNAYE, M. de, on Birds of Paradise, ii. 78.

  LAMARCK, on the origin of man, i. 4.

  LAMELLIBRANCHIATA, i. 324.

  LAMELLICORN beetles, hornlike processes from the head and thorax of,
      i. 370, 373;
    analogy of, to Ruminants, i. 373;
    influence of sexual selection on, i. 377.

  LAMELLICORNIA, stridulation of, i. 380.

  LAMONT, Mr., on the tusks of the Walrus, ii. 242;
    on the use of its tusks by the Walrus, ii. 257.

  _Lampornis porphyrurus_, colours of the female, ii. 168.

  LANCELET, i. 204, 212.

  LANDOIS, H., on the production of sound by the Cicadæ, i. 351;
    on the stridulating organ of the Crickets, i. 354;
    on _Decticus_, i. 355;
    on the stridulating organs of the Acridiidæ, i. 356;
    on the presence of rudimentary stridulating organs in some female
      Orthoptera, i. 359;
    on the stridulation of _Necrophorus_, i. 378;
    on the stridulant organ of _Cerambyx heros_, i. 380;
    on the stridulating organs in the Coleoptera, i. 382;
    on the ticking of _Anobium_, i. 385;
    on the stridulant organ of _Geotrupes_, i. 380.

  LANGUAGE an art, i. 55;
    articulate, origin of, i. 56;
    relation of the progress of, to the development of the brain, i. 57;
    effects of inheritance in production of, i. 58;
    complex structure of, among barbarous nations, i. 61;
    natural selection in, i. 61;
    gesture, i. 232;
    primeval, i. 235;
    of a lost tribe preserved by a parrot, i. 236.

  LANGUAGES, presence of rudiments in, i. 60;
    classification of, i. 60;
    variability of, i. 60;
    crossing or blending of, i. 60;
    complexity of, no test of perfection or proof of special creation,
      i. 62;
    resemblance of, evidence of community of origin, i. 189.

  LANGUAGES and species, identity of evidence of their gradual
    development, i. 59.

  _Lanius_, ii. 180;
    characters of young, ii. 185.

  _Lanius rufus_, anomalous young of, ii. 211.

  LANKESTER, E. R., on comparative longevity, i. 168, 171;
    on the destructive effects of intemperance, i. 173.

  LANUGO, of the human fœtus, i. 25; ii. 375.

  LAPPONIAN language, highly artificial, i. 61.

  LARK, proportion of the sexes in the, i. 307;
    female, singing of the, ii. 54.

  LARKS, attracted by a mirror, ii. 112.

  LARTET, E., on the size of the brain in mammals, i. 51;
    comparison of cranial capacities of skulls of recent and tertiary
      mammals, i. 146;
    on _Dryopithecus_, i. 199.

  _Larus_, seasonal change of plumage in, ii. 228.

  LARVA, luminous, of a Brazilian beetle, i. 345.

  LARYNX, muscles of the, in song-birds, ii. 55.

  _Lasiocampa quercus_, attraction of males by the female, i. 311;
    sexual difference of colour in, i. 398.

  LATHAM, R. G., on the migrations of man, i. 136.

  LATOOKA, perforation of the lower lip by the women of, ii. 341.

  LAURILLARD, on the abnormal division of the malar bone in man, i. 124.

  LAWRENCE, W., on the superiority of savages to Europeans in power
      of sight, i. 118;
    on the colour of negro infants, ii. 318;
    on the fondness of savages for ornaments, ii. 338;
    on beardless races, ii. 349;
    on the beauty of the English aristocracy, ii. 357.

  LAYARD, E. L., on an instance of rationality in a Cobra, ii. 30;
    on the pugnacity of _Gallus Stanleyi_, ii. 44.

  LAYCOCK, Dr., on vital periodicity, i. 12.

  LEAVES, decaying, tints of, i. 323.

  LECKY, Mr., on the sense of duty, i. 71;
    on suicide, i. 94;
    on the practice of celibacy, i. 96;
    his view of the crimes of savages, i. 97;
    on the gradual rise of morality, i. 103.

  LECONTE, J. L., on the stridulant organ in the Coprini and Dynastini,
    i. 381.

  LEE, H., on the numerical proportion of the sexes in the trout,
    i. 308.

  LEG, calf of the, artificially modified, ii. 340.

  LEGITIMATE and illegitimate children, proportion of the sexes in,
    i. 302.

  LEGS, variation of the length of the, in man, i. 108;
    proportions of, in soldiers and sailors, i. 116;
    fore, atrophied in some male butterflies, i. 344;
    peculiarities of, in male insects, i. 344.

  “LEK” of the black-cock and capercailzie, ii. 100.

  LEMOINE, Albert, on the origin of language, i. 56.

  _Lemur macaco_, sexual difference of colour in, ii. 290.

  LEMURIDÆ, i. 195;
    their origin, i. 213;
    position and derivation of the, i. 202;
    ears of the, i. 23;
    variability of the muscles in the, i. 128.

  LEMURS, uterus in the, i. 123;
    tailless species of, i. 194.

  LEOPARDS, black, ii. 294.

  LEPIDOPTERA, i. 386;
    numerical proportions of the sexes in the, i. 309;
    colouring of, i. 387;
    ocellated spots of, ii. 132.

  _Lepidosiren_, i. 204, 212.

  LENGUAS, disfigurement of the ears of the, ii. 341.

  _Leptorhynchus angustatus_, pugnacity of male, i. 375.

  _Leptura testacea_, difference of colour in the sexes of, i. 367.

  LEQUAY, on the occurrence of the supra-condyloid foramen in
    the humerus of man, i. 29.

  LEROY, on the wariness of young foxes in hunting-districts, i. 50;
    on the desertion of their young by swallows, i. 84.

  LESSE, valley of the, i. 29.

  LESSON, on the Birds of Paradise, i. 269, ii. 98;
    on the sea-elephant, ii. 278.

  _Lestis bombylans_, difference of the sexes in, i. 366.

  _Lethrus cephalotes_, pugnacity of the males of, i. 371, 376.

  LEUCKART, R., on the _vesicula prostatica_, i. 31;
    on the influence of the age of parents on the sex of offspring,
      i. 302.

  _Levator claviculæ_ muscle, i. 128.

  _Libellula depressa_, colour of the male, i. 363.

  LIBELLULIDÆ, relative size of the sexes of, i. 347;
    difference in the sexes of, i. 361.

  LICE of domestic animals and man, i. 219.

  LICENTIOUSNESS, prevalence of, among savages, i. 96;
    a check upon population, i. 134.

  LICHTENSTEIN, on _Chera progne_, ii. 120.

  LIFE, inheritance at corresponding periods of, i. 280, 285.

  LIGHT, supposed effects of, i. 116;
    influence of, upon the colours of shells, i. 326.

  LILFORD, Lord, the ruff attracted by bright objects, ii. 111.

  _Limosa lapponica_, ii. 204.

  _Linaria_, ii. 180.

  _Linaria montana_, i. 307.

  LINNÆUS, views of, as to the position of man, i. 190.

  LINNET, numerical proportion of the sexes in the, i. 307;
    crimson forehead and breast of the, ii. 86;
    courtship of the, ii. 94.

  _Linyphia_, i. 337.

  LION, polygamous, i. 268;
    mane of the, defensive, ii. 266;
    roaring of the, ii. 275.

  LIONS, stripes of young, ii. 183.

  LIPS, piercing of the, by savages, ii. 341.

  _Lithobius_, prehensile appendages of the female, i. 340.

  _Lithosia_, coloration in, i. 396.

  _Littorina littorea_, i. 324.

  LIVINGSTONE, Dr., on the influence of dampness and dryness
      on the colour of the skin, i. 242;
    on the liability of negroes to tropical fevers after residence
      in a cold climate, i. 243;
    on the spur-winged goose, ii. 47;
    on weaver-birds, ii. 63;
    on an African nightjar, ii. 73, 97;
    on the battle-scars of South African male mammals, ii. 239;
    on the removal of the upper incisors by the Batokas, ii. 340;
    on the perforation of the upper lip by the Makalolo, ii. 342;
    on the Banyai, ii. 347.

  LIVONIA, numerical proportion of male and female births in, i. 301.

  LIZARDS, relative size of the sexes of, ii. 32;
    gular pouches of, ii. 33.

  LLOYD, L., on the polygamy of the capercailzie and bustard, i. 269;
    on the numerical proportion of the sexes in the capercailzie
      and black-cock, i. 306;
    on the salmon, ii. 5;
    on the colours of the sea-scorpion, ii. 9;
    on the pugnacity of male grouse, ii. 45;
    on the capercailzie and black-cock, ii. 49, 54;
    on the call of the capercailzie, ii. 61;
    on assemblages of grouse and snipes, ii. 101;
    on the pairing of a shield-drake with a common duck, ii. 114;
    on the battles of seals, ii. 240;
    on the elk, ii. 249.

  _Lobivanellus_, wing-spurs in, ii. 48.

  Local influences, effect of, upon stature, i. 114.

  LOCKWOOD, Mr., on the development of _Hippocampus_, i. 210.

  LOCUST, bright-coloured, rejected by lizards and birds, i. 361.

  LOCUST, migratory, i. 352.

  LOCUSTIDÆ, stridulation of the, i. 352, 354;
    descent of the, i. 356.

  LONGICORN beetles, difference of the sexes of, in colour, i. 367;
    stridulation of, i. 380.

  LONSDALE, Mr., on an example of personal attachment in
    _Helix pomatia_, i. 325.

  LOPHOBRANCHII, marsupial receptacles of the male, ii. 21.

  _Lophophorus_, habits of, ii. 121.

  _Lophorina atra_, sexual difference in coloration of, ii. 226.

  _Lophornis ornatus_, ii. 76.

  LORD, J. K., on _Salmo lycaodon_, ii. 5.

  LORY, King, ii. 174;
    immature plumage of the, ii. 188.

  LOVE-ANTICS and dances of birds, ii. 68.

  LOWNE, B. T., on _Musca vomitoria_, i. 145, 349.

  _Loxia_, characters of young of, ii. 184.

  LUBBOCK, Sir J., on the antiquity of man, i. 3;
    on the origin of man, i. 4;
    on the mental capacity of savages, i. 34;
    on the origin of implements, i. 52;
    on the simplification of languages, i. 62;
    on the absence of the idea of God among certain races of men, i. 65;
    on the origin of the belief in spiritual agencies, i. 66;
    on superstitions, i. 69;
    on the sense of duty, i. 71;
    on the practice of burying the old and sick among the Fijians,
      i. 77;
    non-prevalence of suicide among the lowest barbarians, i. 94;
    on the immorality of savages, i. 97;
    on Mr. Wallace’s claim to the origination of the idea of natural
      selection, i. 137;
    on the absence of remorse among savages, i. 164;
    on the former barbarism of civilised nations, i. 181;
    on improvements in the arts among savages, i. 182;
    on resemblances of the mental characters in different races
      of men, i. 232;
    on the power of counting in primeval man, i. 234;
    on the arts practised by savages, i. 234;
    on the prehensile organs of the male _Labidocera Darwinii_, i. 329;
    on _Chloëon_, i. 341;
    on _Smynthurus luteus_, i. 348;
    on strife for women among the North American Indians, ii. 324;
    on music, ii. 334;
    on the ornamental practices of savages, ii. 338;
    on the estimation of the beard among the Anglo-Saxons, ii. 349;
    on artificial deformation of the skull, ii. 352;
    on “communal marriages,” ii. 358, 360;
    on exogamy, ii. 360, 364;
    on the Veddahs, ii. 363;
    on polyandry, ii. 365.

  LUCANIDÆ, variability of the mandibles in the male, i. 376.

  _Lucanus_, large size of males of, i. 347.

  _Lucanus cervus_, numerical proportion of sexes of, i. 313;
    weapons of the male, i. 375.

  _Lucanus elaphus_, use of mandibles of, i. 377;
    large jaws of male, i. 342.

  LUCAS, Prosper, on sexual preference in horses and bulls, ii. 272.

  LUNAR periods, i. 212.

  LUND, Dr., on skulls found in Brazilian caves, i. 218.

  LUNGS, enlargement of, in the Quechua and Aymara Indians, i. 119;
    a modified swim-bladder, i. 207;
    different capacity of in races of man, i. 216.

  LUMINOSITY in insects, i. 345.

  LUSCHKA, Prof., on the termination of the coccyx, i. 30.

  LUST, instinct of, i. 89.

  LUXURY, comparatively innocuous, i. 171.

  _Lycæna_, sexual differences of colouring in species of, i. 390.

  LYELL, Sir C., on the antiquity of man, i. 3;
    on the origin of man, i. 4;
    on the parallelism of the development of species and languages,
      i. 59;
    on the extinction of languages, i. 60;
    on the Inquisition, i. 178;
    on the fossil remains of vertebrata, i. 201;
    on the fertility of mulattoes, i. 221.

  LYNX, Canadian, throat-ruff of the, ii. 267.

  LYRE-BIRD, assemblies of, ii. 101.


  M.

  _Macacus_, ears of, i. 23;
    convoluted body in the extremity of the tail of, i. 30;
    variability of the tail in species of, i. 150;
    whiskers of species of, ii. 283.

  _Macacus cynomolgus_, superciliary ridge of, ii. 318;
    beard and whiskers of, becoming white with age, ii. 319.

  _Macacus inornatus_, i. 151.

  _Macacus lasiotus_, facial spots of, ii. 308.

  _Macacus radiatus_, i. 192.

  _Macacus rhesus_, sexual difference in the colour of, ii. 293, 310.

  MACALISTER, Prof., on variations of the _palmaris accessorius_ muscle,
      i. 109;
    on muscular abnormalities in man, i. 128, 129;
    on the greater variability of the muscles in men than in women,
      i. 275.

  MACAWS, Mr. Buxton’s observations on, i. 76;
    screams of, ii. 61.

  MCCANN, J., on mental individuality, i. 63.

  MCCLELLAND, J., on the Indian cyprinidæ, ii. 17.

  MACCULLOCH, Col., on an Indian village without any female children,
    ii. 364.

  MACCULLOCH, Dr., on tertian ague in a dog, i. 13.

  MACGILLIVRAY, W., on the vocal organs of birds, i. 59;
    on the Egyptian goose, ii. 48;
    on the habits of woodpeckers, ii. 63;
    on the habits of the snipe, ii. 64;
    on the white-throat, ii. 69;
    on the moulting of the snipes, ii. 82;
    on the moulting of the anatidæ, ii. 85;
    on the finding of new mates by magpies, ii. 103;
    on the pairing of a blackbird and thrush, ii. 113;
    on pied ravens, ii. 126;
    on the guillemots, ii. 127;
    on the colours of the tits, ii. 174;
    on the immature plumage of birds, ii. 186 _et seqq._

  _Machetes_, sexes and young of, ii. 216.

  _Machetes pugnax_, numerical proportion of the sexes in, i. 306;
    supposed to be polygamous, i. 270;
    pugnacity of the male, ii. 41;
    double moult in, ii. 81.

  MACKINTOSH, on the moral sense, i. 70.

  MACLACHLAN, R., on _Apatania muliebris_ and _Boreus hyemalis_, i. 314;
    on the anal appendages of male insects, i. 342;
    on the pairing of dragon-flies, i. 347;
    on dragon-flies, i. 362, 363;
    on dimorphism in _Agrion_, i. 363;
    on the want of pugnacity in male dragon-flies, i. 364;
    on the ghost-moth in the Shetland Islands, i. 402.

  MCLENNAN, Mr., on the origin of the belief in spiritual agencies,
      i. 66;
    on the prevalence of licentiousness among savages, i. 96, ii. 358;
    on infanticide, i. 134, ii. 363;
    on the primitive barbarism of civilised nations, i. 181;
    on traces of the custom of the forcible capture of wives, i. 182,
      ii. 365;
    on polyandry, ii. 365.

  MCNEILL, Mr., on the use of the antlers of deer, ii. 252;
    on the Scotch deerhound, ii. 261;
    on the long hairs of the throat of the stag, ii. 268;
    on the bellowing of stags, ii. 274.

  _Macrorhinus proboscideus_, structure of the nose of, ii. 278.

  MAGPIE, power of speech of, i. 59;
    stealing bright objects, ii. 112;
    nuptial assemblies of, ii. 102;
    new mates found by, ii. 103;
    young of the, ii. 209;
    coloration of the, ii. 230.

  MAGPIES, vocal organs of the, ii. 55.

  MAILLARD, M., on the proportion of the sexes in a species
    of _Papilio_ from Bourbon, i. 310.

  MAINE, Mr., on the absorption of one tribe by another, i. 159;
    on the want of a desire for improvement, i. 166.

  MAKALOLO, perforation of the upper lip by the, ii. 341.

  MALAR bone, abnormal division of, in man, i. 124.

  MALAY, Archipelago, marriage-customs of the savages of the, ii. 373.

  MALAYS, line of separation between the Papuans and the, i. 218;
    general beardlessness of the, ii. 321;
    staining of the teeth among, ii. 339;
    aversion of some, to hairs on the face, ii. 349.

  MALAYS and Papuans, contrasted characters of, i. 216.

  MALE animals, struggles of, for the possession of the females,
      i. 259, 260;
    eagerness of, in courtship, i. 272, 273;
    generally more modified than female, i. 272, 275;
    differ in the same way from females and young, i. 285.

  MALE characters, developed in females, i. 280;
    transfer of, to female birds, ii. 193.

  MALE, sedentary, of a hymenopterous parasite, i. 272.

  MALEFACTORS, i. 172.

  MALES, presence of rudimentary female organs in, i. 208.

  MALES and females, comparative mortality of, while young, i. 264, 276;
    comparative numbers of, i. 261, 263.

  MALHERBE, on the woodpeckers, ii. 174.

  MALTHUS, T., on the rate of increase of population, i. 131, 132, 134.

  MALURIDÆ, nidification of the, ii. 169.

  _Malurus_, young of, ii. 216.

  MAMMÆ, i. 254;
    rudimentary, in male mammals, i. 17, 30, 208, 209, 210;
    supernumerary, in women, i. 125;
    of male human subject, i. 130.

  MAMMALIA, Prof. Owen’s classification of, i. 187;
    genealogy of the, i. 203.

  MAMMALS, secondary sexual characters of, ii. 239;
    weapons of, ii. 241;
    recent and tertiary, comparison of cranial capacity of, i. 146;
    relative size of the sexes of, ii. 260;
    pursuit of female, by the males, i. 272;
    parallelism of, with birds in secondary sexual characters, ii. 297;
    voices of, used especially during the breeding season, ii. 331.

  MAN, variability of, i. 108;
    erroneously regarded as more domesticated than other animals, i. 111;
    definitive origin of, i. 235;
    migrations of, i. 135;
    wide distribution of, i. 137;
    causes of the nakedness of, i. 149;
    supposed physical inferiority of, i. 156;
    numerical proportions of the sexes in, i. 264;
    a member of the Catarrhine group, i. 198;
    early progenitors of, i. 206;
    secondary sexual characters of, ii. 316;
    primeval condition of, ii. 367.

  MANDANS, correlation of colour and texture of hair in the, i. 248.

  MANDIBLE, left, enlarged in the male of _Taphroderes distortus_, i. 344.

  MANDIBLES, use of the, in _Ammophila_, i. 342;
    large, of _Corydalis cornutus_, i. 342;
    large, of male _Lucanus elaphus_, i. 342.

  MANDRILL, number of caudal vertebræ in the, i. 150;
    colours of the male, ii. 292, 296, 310.

  MANTEGAZZA, Prof., on the ornaments of savages, ii. 338 _et seqq._;
    on the beardlessness of the New Zealanders, ii. 349;
    on the exaggeration of natural characters by man, ii. 351.

  MANTELL, W., on the engrossment of pretty girls by the New Zealand
    chiefs, ii. 369.

  _Mantis_, pugnacity of species of, i. 360.

  MARCUS Aurelius, on the origin of the moral sense, i. 71;
    on the influence of habitual thoughts, i. 101.

  _Mareca penelope_, ii. 114.

  MARKS, retained throughout groups of birds, ii. 131.

  MARRIAGE, influence of, upon morals, i. 96;
    restraints upon, among savages, i. 133;
    influence of, on mortality, i. 175;
    development of, ii. 361.

  MARRIAGES, communal, ii. 358, 360;
    early, i. 174, 175.

  MARSHALL, Mr., on the brain of a Bushwoman, i. 216.

  MARSUPIALS, i. 202;
    possession of nipples by, i. 209;
    their origin from Monotremata, i. 213;
    uterus of, i. 122;
    development of the nictitating membrane in, i. 23;
    abdominal sacks of, i. 254;
    relative size of the sexes of, ii. 260;
    colours of, ii. 286.

  MARSUPIUM, rudimentary, in male marsupials, i. 208.

  MARTIN, W. C. L., on alarm manifested by an orang at the sight
      of a turtle, i. 43;
    on the hair in _Hylobates_, i. 194;
    on a female American deer, ii. 258;
    on the voice of _Hylobates agilis_, ii. 277;
    on _Semnopithecus nemæus_, ii. 312.

  MARTIN, on the beards of the inhabitants of St. Kilda, ii. 321.

  MARTINS deserting their young, i. 84.

  MARTINS, C., on death caused by inflammation of the vermiform
    appendage, i. 28.

  MASTOID processes in man and apes, i. 143.

  MAUDSLEY, Dr., on the influence of the sense of smell in man, i. 24;
    on Laura Bridgman, i. 58;
    on the development of the vocal organs, i. 59.

  MAYERS, W. F., on the domestication of the goldfish in China, ii. 17.

  MAYHEW, E., on the affection between individuals of different sexes
    in the dog, ii. 270.

  MAYNARD, C. J., on the sexes of _Chrysemys picta_, ii. 28.

  MECKEL, on correlated variation of the muscles of the arm and leg,
    i. 130.

  MEDICINES, effect produced by, the same in man and in monkeys, i. 12.

  _Medusæ_, bright colours of some, i. 322.

  MEGALITHIC structures, prevalence of, i. 233.

  _Megalophrys montana_, sexual differences in, ii. 26, 27.

  _Megapicus validus_, sexual difference of colour in, ii. 174.

  _Megasoma_, large size of males of, i. 347.

  MEIGS, Dr. A., on variation in the skulls of the natives of America,
    i. 108.

  MEINECKE, on the numerical proportion of the sexes in butterflies,
    i. 309.

  MELIPHAGIDÆ, Australian, nidification of, ii. 169.

  _Melita_, secondary sexual characters of, i. 331.

  _Meloë_, difference of colour in the sexes of a species of, i. 367.

  MEMORY, manifestations of, in animals, i. 45.

  MEMNON, young, i. 217.

  MENTAL characters, difference of, in different races of men, i. 216.

  MENTAL faculties, variation of, in the same species, i. 36, 110;
    diversity of, in the same race of men, i. 109;
    inheritance of, i. 110;
    similarity of the, in different races of man, i. 232;
    of birds, ii. 108.

  MENTAL powers, difference of, in the two sexes in man, ii. 326.

  _Menura Alberti_, ii. 102;
    song of, ii. 55.

  _Menura superba_, ii. 101, 102;
    long tails of both sexes of, ii. 164.

  MERGANSER, trachea of the male, ii. 60.

  _Mergus cucullatus_, speculum of, i. 291.

  _Mergus merganser_, young of, ii. 189.

  _Merganser serrator_, male plumage of, ii. 85.

  _Metallura_, splendid tail-feathers of, ii. 152.

  _Methoca ichneumonides_, large male of, i. 347.

  MEVES, M., on the drumming of the snipe, ii. 63.

  MEXICANS, civilisation of the, not foreign, i. 183.

  MEYER, on a convoluted body at the extremity of the tail in
    a _Macacus_ and a cat, i. 30.

  MEYER, Dr. A., on the copulation of phryganidæ of distinct species,
    i. 342.

  MIGRATIONS of man, effects of, i. 135.

  MIGRATORY instinct of birds, i. 79;
    vanquishing the maternal, i. 83, 90.

  MILL, J. S., on the origin of the moral sense, i. 71;
    on the “greatest happiness principle,” i. 97;
    on the difference of the mental powers in the sexes of man,
      ii. 328.

  MILLIPEDES, i. 339.

  MILNE-EDWARDS, H., on the use of the enlarged chela of the male
    _Gelasimus_, i. 331.

  _Milvago leucurus_, sexes and young of, ii. 205.

  MIMICKRY, i. 411.

  _Mimus polyglottus_, ii. 109.

  MIND, difference of, in man and the highest animals, i. 104;
    similarity of the, in different races, i. 232.

  MINNOW, proportion of the sexes in the, i. 308, 309.

  MINNOWS, spawning habits of, ii. 15.

  MIRROR, larks attracted by, ii. 112.

  MIVART, St. George, on the reduction of organs, i. 18;
    on the ears of the lemuroidea, i. 23;
    on variability of the muscles in lemuroidea, i. 128, 136;
    on the caudal vertebræ of monkeys, i. 150;
    on the classification of the primates, i. 196;
    on the orang and on man, i. 197;
    on differences in the lemuroidea, i. 198;
    on the crest of the male newt, ii. 24.

  MOCKING-THRUSH, partial migration of, ii. 109;
    young of the, ii. 219.

  MODIFICATIONS, unserviceable, i. 153.

  MOLES, numerical proportion of the sexes in, i. 305;
    battles of male, ii. 239.

  _Mollienesia petenensis_, sexual difference in, ii. 9.

  MOLLUSCA, beautiful colours and shapes of, i. 326;
    absence of secondary sexual characters in the, i. 324.

  MOLLUSCOIDA, i. 205, 324.

  _Monacanthus scopas_ and _M. Peronii_, sexual differences in, ii. 12.

  MONGOLIANS, perfection of the senses in, i. 119.

  MONKEY, protecting his keeper from a baboon, i. 78, 87;
    bonnet-, i. 192;
    rhesus, sexual difference in colour of the, ii. 293, 310;
    moustache-, colours of the, ii. 291.

  MONKEYS, liability of, to the same diseases as man, i. 11;
    male, recognition of women by, i. 13;
    revenge taken by, i. 40;
    maternal affection in, i. 40;
    variability of the faculty of attention in, i. 44;
    using stones and sticks, i. 51;
    imitative faculties of, i. 56;
    signal-cries of, i. 57;
    sentinels posted by, i. 74;
    diversity of the mental faculties in, i. 110;
    mutual kindnesses of, i. 75;
    hands of the, i. 139, 140;
    breaking hard fruits with stones, i. 140;
    basal caudal vertebræ of, imbedded in the body, i. 151;
    human characters of, i. 191;
    gradation of species of, i. 227;
    beards of, ii. 283;
    ornamental characters of, ii. 306;
    analogy of sexual differences of, with those of man, ii. 318;
    different degrees of difference in the sexes of, ii. 323;
    expression of emotions by, ii. 336;
    generally monogamous habits of, ii. 361;
    polygamous habits of some, ii. 362;
    naked surfaces of, ii. 376;
    American, manifestation of reason in, i. 47;
    American, direction of the hair on the arms of some, i. 192.

  MONOGAMY, not primitive, i. 182.

  MONOGENISTS, i. 228.

  _Mononychus pseudacori_, stridulation of, i. 382.

  MONOTREMATA, i. 202;
    development of the nictitating membrane in, i. 23;
    lactiferous glands of, i. 209;
    connecting mammals with reptiles, i. 213.

  MONSTROSITIES, analogous, in man and lower animals, i. 113;
    caused by arrest of development, i. 121;
    correlation of, i. 130;
    transmission of, i. 224.

  MONTAGU, G., on the habits of the black and red grouse, i. 269;
    on the pugnacity of the ruff, ii. 41;
    on the singing of birds, ii. 52;
    on the double moult of the male pintail, ii. 84.

  MONTEIRO, Mr., on _Bucorax abyssinicus_, ii. 72.

  MONTES DE OCA, M., on the pugnacity of male Humming-birds, ii. 40.

  _Monticola cyanea_, ii. 172.

  MONUMENTS, as traces of extinct tribes, i. 237.

  MOOSE, battles of, ii. 240;
    horns of the, an incumbrance, ii. 259.

  MORAL and instinctive impulses, alliance of, i. 88.

  MORAL faculties, their influence on natural selection in man, i. 158.

  MORAL rules, distinction between the higher and lower, i. 100.

  MORAL sense, origin of the, i. 102;
    so-called, derived from the social instincts, i. 97, 98.

  MORAL tendencies, inheritance of, i. 102.

  MORALITY, supposed to be founded in selfishness, i. 97;
    test of, the general welfare of the community, i. 98;
    gradual rise of, i. 103;
    influence of a high standard of, i. 166.

  MORGAN, L. H., on the Beaver, i. 37;
    on the reasoning powers of the Beaver, i. 46;
    on the forcible capture of wives, i. 182;
    on the castoreum of the beaver, ii. 279;
    marriage unknown in primeval times, ii. 359;
    on Polyandry, ii. 365.

  MORRIS, F. O., on hawks feeding an orphan nestling, ii. 107.

  MORTALITY, comparative, of females and males, i. 264, 276, 302.

  MORTON, on the number of species of man, i. 226.

  _Moschus moschiferus_, odoriferous organs of, ii. 280.

  _Motacillæ_, Indian, young of, ii. 190.

  MOTHS, i. 394;
    absence of mouth in some male, i. 254;
    apterous female, i. 255;
    male, prehensile use of the tarsi by, i. 256;
    male, attracted by females, i. 311;
    coloration of, i. 397;
    sexual differences of colour in, i. 398.

  MOTMOT, racket-shaped feathers in the tail of a, ii. 73.

  MOULT, double, ii. 181;
    double annual, in birds, ii. 80.

  MOULTING of birds, ii. 214.

  MOULTS, partial, ii. 83.

  MOUSTACHE-MONKEY, colours of the, ii. 291, 311.

  MOUSTACHES, in monkeys, i. 192.

  MUD-TURTLE, long claws of the male, ii. 28.

  MULATTOES, persistent fertility of, i. 221;
    immunity of, from yellow fever, i. 243.

  MULE, sterility and strong vitality of the, i. 221.

  MULES, rational, i. 48.

  MÜLLER, Ferd., on the Mexicans and Peruvians, i. 183.

  MÜLLER, Fritz, on astomatous males of _Tanais_, i. 255;
    on the disappearance of spots and stripes in adult mammals, ii. 305;
    on the proportions of the sexes in some Crustacea, i. 315;
    on secondary sexual characters in various Crustaceans, i. 328
      _et seqq._;
    on the luminous larva of a beetle, i. 345;
    musical contest between male _Cicadæ_, i. 351;
    on the sexual maturity of young amphipod Crustacea, ii. 215.

  MÜLLER, J., on the nictitating membrane and semilunar fold, i. 23.

  MÜLLER, Max, on the origin of language, i. 56;
    struggle for life among the words, &c., of languages, i. 60.

  MÜLLER, S., on the Banteng, ii. 290;
    on the colours of _Semnopithecus chrysomelas_, ii. 291.

  MUNTJAC-DEER, weapons of the, ii. 257.

  MURIE, J., on the reduction of organs, i. 18;
    on the ears of the Lemuroidea, i. 23;
    on variability of the muscles in the Lemuroidea, i. 128, 136;
    basal caudal vertebræ of _Macacus inornatus_ imbedded in the body,
      i. 151;
    on differences in the Lemuroidea, i. 198;
    on the throat-pouch of the male Bustard, ii. 58;
    on the mane of _Otaria jubata_, ii. 267;
    on the suborbital pits of Ruminants, ii. 280;
    on the colours of the sexes in _Otaria nigrescens_, ii. 287.

  MURRAY, A., on the _Pediculi_ of different races of men, i. 219.

  MURRAY, T. A., on the fertility of Australian women with white men,
    i. 220.

  _Mus coninga_, i. 50.

  _Mus minutus_, sexual difference in the colour of, ii. 286.

  _Musca vomitoria_, i. 145.

  _Muscicapa grisola_, ii. 170.

  _Muscicapa luctuosa_, ii. 170.

  _Muscicapa ruticilla_, breeding in immature plumage, ii. 214.

  MUSCLE, ischio-pubic, i. 127.

  MUSCLES, rudimentary, occurrence of, in man, i. 19;
    variability of the, i. 109;
    effects of use and disuse upon, i. 116;
    animal-like abnormalities of, in man, i. 127;
    correlated variation of, in the arm and leg, i. 130;
    variability of, in the hands and feet, i. 136;
    of the jaws, influence of, on the physiognomy of the Apes, i. 144;
    habitual spasms of, causing modifications of the facial bones,
      i. 147;
    of the early progenitors of man, i. 206;
    greater variability of the, in men than in women, i. 275.

  MUSCULUS STERNALIS, Prof. Turner on the, i. 19.

  MUSIC, i. 232;
    of birds, ii. 51;
    discordant, love of savages for, ii. 67;
    different appreciation of, by different peoples, ii. 333;
    origin of, ii. 333, 337;
    effects of, ii. 335.

  MUSICAL cadences, perception of, by animals, ii. 333;
    powers of man, ii. 330 _et seqq._

  MUSK-DEER, canine teeth of male, ii. 241, 256, 257;
    male, odoriferous organs of the, ii. 280;
    winter change of the, ii. 299.

  MUSK-DUCK, Australian, ii. 38;
    large size of male, ii. 43;
    of Guiana, pugnacity of the male, ii. 43.

  MUSK-OX, horns of, ii. 247.

  MUSK-RAT, protective resemblance of the, to a clod of earth, ii. 298.

  _Musophagæ_, colours and nidification of the, ii. 171;
    both sexes of, equally brilliant, ii. 177.

  MUSSELS opened by monkeys, i. 140.

  _Mustela_, winter change of two species of, ii. 298.

  MUTILATIONS, healing of, i. 13.

  _Mutilla europæa_, stridulation of, i. 366.

  MUTILLIDÆ, absence of ocelli in female, i. 341.

  _Mycetes caraya_, polygamous, i. 266;
    vocal organs of, ii. 277;
    beard of, ii. 283;
    sexual differences of colour in, ii. 290;
    voice of, ii. 332.

  _Mycetes seniculus_, sexual differences of colour in, ii. 290.

  MYRIAPODA, i. 339.


  N.

  NÄGELI, on the influence of natural selection on plants, i. 152;
    on the gradation of species of plants, i. 227.

  NAILS, coloured yellow or purple in part of Africa, ii. 339.

  NAPLES, greater proportion of female illegitimate children in, i. 301.

  NARWHAL, tusks of the, ii. 242, 248.

  NASAL cavities, large size of, in American aborigines, i. 119.

  NASCENT organs, i. 18.

  NATHUSIUS, H. von, on the improved breeds of pigs, i. 230;
    on the breeding of domestic animals, ii. 370.

  NATURAL selection, its effects on the early progenitors of man,
      i. 136;
    influence of, on man, i. 151, 154;
    limitation of the principle, i. 152;
    influence of, on social animals, i. 155;
    Mr. Wallace on the limitation of, by the influence of the mental
      faculties in man, i. 158;
    influence of, in the progress of the United States, i. 179.

  NATURAL and sexual selection contrasted, i. 278.

  NAULETTE, jaw from, large size of the canines in, i. 126.

  NEANDERTHAL skull, capacity of the, i. 146.

  NECK, proportion of, in soldiers and sailors, i. 117.

  _Necrophorus_, stridulation of, i. 378, 382.

  _Nectarinia_, young of, ii. 190.

  _Nectariniæ_, nidification of, ii. 169;
    moulting of the, ii. 83.

  NEGRO, resemblance of a, to Europeans, in mental characters, i. 232.

  NEGRO-WOMEN, their kindness to Mungo Park, i. 95.

  NEGROES, character of, i. 216;
    lice of, i. 220;
    blackness of, i. 224, ii. 381;
    variability of, i. 225, 226;
    immunity of, from yellow fever, i. 243;
    difference of, from Americans, i. 247;
    disfigurements of the, ii. 296;
    colour of newborn children of, ii. 318;
    comparative beardlessness of, ii. 321;
    readily become musicians, ii. 334;
    appreciation of beauty of their women by, ii. 344, 346;
    idea of beauty among, ii. 350;
    compression of the nose by some, ii. 352.

  NEOLITHIC period, 183.

  _Neomorpha_, sexual difference of the beak in, ii. 39.

  _Nephila_, i. 337.

  NESTS, made by fishes, ii. 19;
    decoration of, by Humming-birds, ii. 112.

  NEUMEISTER, on a change of colour in pigeons after several moultings,
    i. 294.

  NEURATION, difference of, in the two sexes of some butterflies
    and hymenoptera, i. 345.

  NEUROPTERA, i. 314, 361.

  _Neurothemis_, dimorphism in, i. 363.

  NEW ZEALAND, expectation by the natives of, of their extinction,
      i. 240;
    practice of tattooing in, ii. 342;
    aversion of natives of, to hairs on the face, ii. 349;
    pretty girls engrossed by the chiefs in, ii. 369.

  NEWTON, A., on the throat-pouch of the male bustard, ii. 58;
    on the difference between the females of two species of
      _Oxynotus_, ii. 193;
    on the habits of the phalarope, dotterel, and godwit, ii. 204.

  NEWTS, ii. 24.

  NICHOLSON, Dr., on the non-immunity of dark Europeans from yellow
    fever, i. 245.

  NICTITATING membrane, i. 23, 207.

  NIDIFICATION, of fishes, ii. 19;
    relation of, to colour, ii. 167, 172;
    of British birds, ii. 169.

  NIGHT-HERON, cries of the, ii. 51.

  NIGHTINGALE, arrival of the male before the female, i. 259;
    object of the song of the, ii. 52.

  NIGHTINGALES, new mates found by, ii. 105.

  NIGHTJAR, selection of a mate by the female, ii. 116;
    Australian, sexes of, ii. 206;
    coloration of the, ii. 226.

  NIGHTJARS, noise made by some male, with their wings, ii. 62;
    elongated feathers in, ii. 73, 97.

  NILGHAU, sexual differences of colour in the, ii. 287.

  NILSSON, Prof., on the resemblance of stone arrow-heads from various
      places, i. 233;
    on the development of the horns in the reindeer, i. 288.

  NIPPLES, absence of, in Monotremata, i. 209.

  NITZSCH, C. L., on the down of birds, ii. 80.

  NOCTUÆ, brightly-coloured beneath, i. 397.

  NOCTUIDÆ, coloration of, i. 394.

  NORDMANN, A., on _Tetrao urogalloides_, ii. 100.

  NOMADIC habits, unfavourable to human progress, i. 167.

  NORWAY, numerical proportion of male and female births in, i. 301.

  NOSE, resemblance of, in man and the apes, i. 192;
    piercing and ornamentation of the, ii. 341;
    flattening of the, ii. 352;
    very flat, not admired in negroes, ii. 350.

  NOTT and Gliddon, on the features of Rameses II., i. 217;
    on the features of Amunoph III., i. 218;
    on skulls from Brazilian caves, i. 218;
    on the immunity of negroes and mulattoes from yellow fever, i. 243;
    on the deformation of the skull among American tribes, ii. 352.

  NUDIBRANCH mollusca, bright colours of, i. 326.

  NUMERALS, Roman, i. 182.

  NUNEMAYA, natives of, bearded, ii. 322, 349.


  O.

  OBEDIENCE, value of, i. 162.

  OBSERVATION, powers of, possessed by birds, ii. 109.

  OCCUPATIONS, sometimes a cause of diminished stature, i. 115;
    effect of, upon the proportions of the body, i. 116.

  OCELLI, absence of, in female Mutillidæ, i. 341.

  OCELLI of birds, formation and variability of the, ii. 132.

  OCELOT, sexual differences in the colouring of the, ii. 287.

  _Ocyphaps lophotes_, ii. 96.

  ODONATA, i. 314.

  _Odonestis potatoria_, sexual difference of colour in, i. 398.

  ODOUR, correlation of, with colour of skin, i. 248;
    emitted by snakes in the breeding-season, ii. 30;
    of mammals, ii. 278.

  _Œcanthus nivalis_, difference of colour in the sexes of, i. 361.

  _Oidemia_, ii. 226, 227.

  OLIVIER, on sounds produced by _Pimelia striata_, i. 385.

  _Omaloplia brunnea_, stridulation of, i. 381.

  _Onitis furcifer_, processes of anterior femora of the male,
     and on the head and thorax of the female, i. 372.

  _Onthophagus_, i. 370.

  _Onthophagus rangifer_, sexual differences of, i. 369;
    variation in the horns of the male, i. 370.

  OPHIDIA, sexual differences of, ii. 29.

  OPOSSUM, wide range of, in America, i. 219.

  OPTIC nerve, atrophy of the, caused by destruction of the eye, i. 116.

  ORANG-OUTAN, ii. 323;
    Bischoff on the agreement of the brain of the, with that of man,
      i. 11;
    adult age of the, i. 13;
    ears of the, i. 21;
    vermiform appendage of, i. 27;
    platforms built by the, i. 36;
    alarmed at the sight of a turtle, i. 43;
    using a stick as a lever, i. 51;
    using missiles, i. 52;
    using the leaves of the _Pandanus_ as a night covering, i. 53;
    hands of the, i. 139;
    absence of mastoid processes in the, i. 143;
    direction of the hair on the arms of the, i. 192;
    its aberrant characters, i. 197;
    supposed evolution of the, i. 230;
    voice of the, ii. 276;
    monogamous habits of the, ii. 361;
    male, beard of the, ii. 284.

  ORANGES, treatment of, by monkeys, i. 139.

  ORANGE-TIP butterfly, i. 388, 393, 394.

  _Orchestia Darwinii_, dimorphism of males of, i. 332.

  _Orchestia Tucuratinga_, limbs of, i. 330, 331, 337.

  ORDEAL, i. 68.

  _Oreas canna_, colours of, ii. 288.

  _Oreas derbyanus_, colours of, ii. 288, 299.

  ORGANS, prehensile, i. 256;
    utilised for new purposes, ii. 335.

  ORGANIC scale, von Baer’s definition of progress in, i. 211.

  ORIOLES, nidification of, ii. 167.

  _Oriolus_, species of, breeding in immature plumage, ii. 214, 215.

  _Oriolus melanocephalus_, coloration of the sexes in, ii. 178.

  ORNAMENTS, prevalence of similar, i. 233;
    fondness of savages for, ii. 338;
    of male birds, ii. 50.

  ORNAMENTAL characters, equal transmission of, to both sexes,
      in mammals, ii. 297;
    of monkeys, ii. 306.

  _Ornithoptera croesus_, i. 310.

  _Ornithorhynchus_, i. 200;
    spur of the male, ii. 242;
    reptilian tendency of, i. 204.

  _Orocetes erythrogastra_, young of, ii. 219.

  ORRONY, Grotto of, i. 28.

  _Orsodacna atra_, difference of colour in the sexes of, i. 368.

  ORTHOPTERA, i. 352;
    metamorphosis of, i. 292;
    stridulating, auditory apparatus of, i. 353;
    colours of, i. 360;
    rudimentary stridulating organs in female, i. 359;
    stridulation of the, and Homoptera, discussed, i. 360.

  _Ortygornis gularis_, pugnacity of the male, ii. 44.

  _Oryctes_, stridulation of, i. 381;
    sexual differences in the stridulant organs of, i. 383.

  _Oryx leucoryx_, use of the horns of, ii. 251, 263.

  _Osphranter rufus_, sexual difference in the colour of, ii. 286.

  OSTRICH, African, sexes and incubation of the, ii. 205.

  OSTRICHES, stripes of young, ii. 184.

  _Otaria jubata_, mane of the male, ii. 267.

  _Otaria nigrescens_, difference in the coloration of the sexes of,
    ii. 287.

  _Otis bengalensis_, love-antics of the male, ii. 68.

  _Otis tarda_, polygamous, i. 269;
    throat-pouch of the male, ii. 58.

  OUZEL, ring-, colours and nidification of the, ii. 179.

  OUZEL, water-, colours and nidification of the, ii. 170.

  _Ovibos moschatus_, horns of, ii. 247.

  OVIPOSITOR of insects, i. 254.

  _Ovis cycloceros_, mode of fighting of, ii. 249.

  OVULE of man, i. 14.

  OWEN, Prof., on the Corpora Wolffiana, i. 16;
    on the great toe in man, i. 16;
    on the nictitating membrane and semilunar fold, i. 23;
    on the development of the posterior molars in different races
      of man, i. 26;
    on the length of the cæcum in the Koala, i. 27;
    on the coccygeal vertebræ, i. 29;
    on rudimentary structures belonging to the reproductive system,
      i. 31;
    on abnormal conditions of the human uterus, i. 123;
    on the number of digits in the Ichthyopterygia, i. 125;
    on the canine teeth in man, i. 126;
    on the walking of the chimpanzee and orang, i. 139;
    on the mastoid processes in the higher apes, i. 143;
    on the hairiness of elephants in elevated districts, i. 149;
    on the caudal vertebræ of monkeys, i. 150;
    classification of mammalia, i. 187;
    on the hair in monkeys, i. 194;
    on the piscine affinities of the Ichthyosaurians, i. 204;
    on polygamy and monogamy among the antelopes, i. 267;
    on the horns of _Antilocapra americana_, i. 289;
    on the musky odour of crocodiles during the breeding season, ii. 29;
    on the scent-glands of snakes, ii. 30;
    on the Dugong, Cachalot and _Ornithorhynchus_, ii. 242;
    on the antlers of the red deer, ii. 252;
    on the dentition of the camelidæ, ii. 257;
    on the tusks of the Mammoth, ii. 258;
    on the horns of the Irish elk, ii. 259;
    on the voice in the giraffe, porcupine, and stag, ii. 274;
    on the laryngeal sac of the gorilla and orang, ii. 276;
    on the odoriferous glands of mammals, ii. 279, 280;
    on the effects of emasculation on the vocal organs of men, ii. 330;
    on the voice of _Hylobates agilis_, ii. 332;
    on American monogamous monkeys, ii. 362.

  OWLS, white, new mates found by, ii. 105.

  _Oxynotus_, difference of the females of two species of, ii. 193.


  P.

  PACHYDERMATA, i. 268.

  PAGET, on the abnormal development of hairs in man, i. 25;
    on the thickness of the skin on the soles of the feet of infants,
      i. 118.

  PAINTING, i. 232.

  _Palæmon_, chelæ of a species of, i. 331.

  _Palæornis_, sexual differences of colour in, ii. 231.

  _Palæornis Javanicus_, colour of beak of, ii. 179.

  _Palæornis rosa_, young of, ii. 188.

  _Palamedea cornuta_, spurs on the wings, ii. 47.

  PALEOLITHIC period, i. 183.

  PALESTINE, habits of the chaffinch in, i. 307.

  PALLAS, on the perfection of the senses in the Mongolians, i. 119;
    on the want of connexion between climate and the colour of the skin,
      i. 241;
    on the polygamous habits of _Antilope saiga_, i. 267;
    on the lighter colour of horses and cattle in winter in Siberia,
      i. 282;
    on the tusks of the musk-deer, ii. 256, 258;
    on the odoriferous glands of mammals, ii. 279;
    on the odoriferous glands of the musk-deer, ii. 280;
    on winter changes of colour in mammals, ii. 298;
    on the ideal of female beauty in North China, ii. 344.

  _Palmaris accessorius_ muscle, variations of the, i. 109.

  PAMPAS, horses of the, i. 236.

  PANGENESIS, hypothesis of, i. 280, 284.

  PANNICULUS carnosus, i. 19.

  _Papilio_, sexual differences of colouring in species of, i. 389;
    proportion of the sexes in North American species of, i. 309;
    coloration of the wings in species of, i. 396.

  _Papilio ascanius_, i. 389.

  _Papilio Sesostris_ and _Childrenæ_, variability of, i. 402.

  _Papilio Turnus_, i. 310.

  _Papilionidæ_, variability in the, i. 402.

  PAPUANS, line of separation between the, and the Malays, i. 218;
    beards of the, ii. 322;
    hair of, ii. 340.

  PAPUANS and Malays, contrast in characters of, i. 216.

  PARADISE, Birds of, ii. 100, 181;
    supposed by Lesson to be polygamous, i. 260;
    rattling of their quills by, ii. 61;
    racket-shaped feathers in, ii. 73;
    sexual differences in colour of, ii. 76;
    decomposed feathers in, ii. 74, 97;
    display of plumage by the male, ii. 88.

  _Paradisea apoda_, barbless feathers in the tail of, ii. 74;
    plumage of, ii. 78;
    and _P. papuana_, divergence of the females of, ii. 192.

  _Paradisea rubra_, ii. 75, 78.

  PARAGUAY, Indians of, eradication of eyebrows and eyelashes by,
    ii. 348.

  PARAKEET, Australian, variation in the colour of the thighs
    of a male, ii. 126.

  PARALLELISM of development of species and languages, i. 59.

  PARASITES on man and animals, i. 12;
    as evidence of specific identity or distinctness, i. 219;
    immunity from, correlated with colour, i. 242.

  PARENTAL affection, partly a result of natural selection, i. 81.

  PARENTS, age of, influence upon sex of offspring, i. 302.

  PARINÆ, sexual difference of colour in, ii. 174.

  PARK, Mungo, negro-women teaching their children to love the truth,
      i. 95;
    his treatment by the negro-women, i. 95, 326;
    on negro opinions of the appearance of white men, ii. 346.

  PARROT, racket-shaped feathers in the tail of a, ii. 73;
    instance of benevolence in a, ii. 109.

  PARROTS, imitative faculties of, i. 44;
    change of colour in, i. 152;
    living in triplets, ii. 106;
    affection of, ii. 108;
    colours of, ii. 223;
    sexual differences of colour in, ii. 231;
    colours and nidification of the, ii. 171, 174, 176;
    immature plumage of the, ii. 188;
    musical powers of, ii. 335.

  PARTHENOGENESIS in the Tenthredinæ, i. 314;
    in Cynipidæ, i. 314;
    in Crustacea, i. 315.

  PARTRIDGE, monogamous, i. 269;
    proportion of the sexes in the, i. 306;
    female, ii. 194.

  “PARTRIDGE-DANCES,” ii. 68.

  PARTRIDGES, living in triplets, ii. 106;
    spring coveys of male, ii. 107;
    distinguishing persons, ii. 110.

  _Parus cæruleus_, ii. 174.

  _Passer_, sexes and young of, ii. 212.

  _Passer brachydactylus_, ii. 212.

  _Passer domesticus_, ii. 170, 212.

  _Passer montanus_, ii. 170, 212.

  PATAGONIANS, self-sacrifice by, i. 88.

  PATTERSON, Mr., on the _Agrionidæ_, i. 362.

  PAULISTAS of Brazil, i. 225.

  _Pavo cristatus_, i. 290; ii. 136.

  _Pavo muticus_, i. 290, ii. 136;
    possession of spurs by the female, ii. 46, 162.

  _Pavo nigripennis_, ii. 120.

  PAYAGUAS Indians, thin legs and thick arms of the, i. 117.

  PAYAN, Mr., on the proportion of the sexes in sheep, i. 305.

  PEACOCK, polygamous, i. 269;
    sexual characters of, i. 290;
    pugnacity of the, ii. 46;
    rattling of the quills by, ii. 61;
    elongated tail-coverts of the, ii. 72, 97;
    love of display of the, ii. 135; 68, 87;
    ocellated spots of the, ii. 135;
    inconvenience of long tail of the, to the female, ii. 154, 164, 165;
    continued increase of beauty of the, ii. 216.

  PEACOCK-BUTTERFLY, i. 392.

  PEAFOWL, preference of females for a particular male, ii. 120;
    first advances made by the female, ii. 120.

  _Pediculi_ of domestic animals and man, i. 219.

  PEDIGREE of man, i. 213.

  _Pedionomus torquatus_, sexes of, ii. 201.

  PEEWIT, wing-tubercles of the male, ii. 48.

  PELAGIC animals, transparency of, i. 323.

  _Pelecanus erythrorhynchus_, horny crest on the beak of the male,
    during the breeding season, ii. 80.

  _Pelecanus onocrotalus_, spring plumage of, ii. 85.

  PELELÉ, ii. 341.

  PELICAN, blind, fed by his companions, i. 77;
    young, guided by old birds, i. 77;
    pugnacity of the male, ii. 43.

  PELICANS, fishing in concert, i. 75.

  _Pelobius Hermanni_, stridulation of, i. 380, 382.

  PELVIS, alteration of, to suit the erect attitude of man, i. 143;
    differences of the, in the sexes in man, ii. 317.

  _Penelope nigra_, sound produced by the male, ii. 64.

  PENNANT, on the battles of seals, ii. 240;
    on the bladder-nose seal, ii. 278.

  _Penthe_, antennal cushions of the male, i. 343.

  PERCH, brightness of male, during breeding season, ii. 13.

  PEREGRINE Falcon, new mate found by, ii. 104.

  PERIOD of variability, relation of, to sexual selection, i. 296.

  PERIODICITY, vital, Dr. Laycock on, i. 12.

  PERIODS, lunar, followed by functions in man and animals, i. 12, 212.

  PERIODS of life, inheritance at corresponding, i. 280, 285.

  _Perisoreus canadensis_, young of, ii. 209.

  _Peritrichia_, difference of colour in the sexes of a species of,
    i. 367.

  PERIWINKLE, i. 324.

  _Pernis cristata_, ii. 126.

  PERSEVERANCE, a characteristic of man, ii. 328.

  PERSIANS, said to be improved by intermixture with Georgians
    and Circassians, ii. 357.

  PERSONNAT, M., on _Bombyx Yamamai_, i. 310.

  PERUVIANS, civilisation of the, not foreign, i. 183.

  PETRELS, colours of, ii. 230.

  _Petrocincla cyanea_, young of, ii. 219.

  _Petronia_, ii. 212.

  PFEIFFER, Ida, on Javanese ideas of beauty, ii. 347.

  _Phacochœrus æthiopicus_, tusks and pads of, ii. 265.

  PHALANGER, Vulpine, black varieties of the, ii. 294.

  _Phalaropus fulicarius_, ii. 203.

  _Phalaropus hyperboreus_, ii. 203.

  _Phanæus_, i. 373.

  _Phanæus carnifex_, variation of the horns of the male, i. 370.

  _Phanæus faunus_, sexual differences of, i. 369.

  _Phanæus lancifer_, i. 370.

  _Phasgonura viridissima_, stridulation of, i. 354, 356.

  _Phasianus Sœmmerringii_, ii. 157.

  _Phasianus versicolor_, ii. 89.

  _Phasianus Wallichii_, ii. 93, 196.

  PHASMIDÆ, mimickry of leaves by the, i. 414.

  PHEASANT, polygamous, i. 269;
    production of hybrids with the common fowl, ii. 122;
    and black grouse, hybrids of, ii. 113;
    immature plumage of the, ii. 188.

  PHEASANT, Argus, ii. 72, 181;
    display of plumage by the male, ii. 91;
    ocellated spots of the, ii. 134, 141;
    gradation of characters in the, ii. 141.

  PHEASANT, Blood-, ii. 46.

  PHEASANT, Cheer, ii. 93, 195.

  PHEASANT, Eared, i. 290, ii. 93, 195;
    sexes alike in the, ii. 178;
    length of the tail in the, ii. 166.

  PHEASANT, Golden, display of plumage by the male, ii. 89;
    sex of young, ascertained by pulling out head-feathers, ii. 214;
    age of mature plumage in the, ii. 213.

  PHEASANT, Kalij, drumming of the male, ii. 62.

  PHEASANT, Reeve’s, length of the tail in, ii. 166.

  PHEASANT, Silver, sexual coloration of the, ii. 228;
    triumphant male, deposed on account of spoiled plumage, ii. 120.

  PHEASANT, Sœmmerring’s, ii. 156, 166.

  PHEASANT, Tragopan, ii. 72;
    display of plumage by the male, ii. 91;
    markings of the sexes of the, ii. 134.

  PHEASANTS, period of acquisition of male characters in the family
      of the, i. 290;
    proportion of sexes in chicks of, i. 306;
    length of the tail in, ii. 156, 164, 166.

  _Philodromus_, i. 337.

  PHILTERS, worn by women, ii. 344.

  _Phoca grœnlandica_, sexual difference in the coloration of, ii. 287.

  _Phœnicura ruticilla_, ii. 105.

  PHOSPHORESCENCE of insects, i. 345.

  PHRYGANIDÆ, copulation of distinct species of, i. 342.

  _Phryniscus nigricans_, ii. 25.

  PHYSICAL inferiority, supposed, of man, i. 156.

  PICKERING, on the number of species of man, i. 226.

  PICTON, J. A., on the soul of man, ii. 395.

  _Picus auratus_, ii. 43.

  PIERIDÆ, mimickry by female, i. 413.

  _Pieris_, i. 393.

  PIGEON, carrier, late development of the wattle in, i. 293;
    domestic, breeds and sub-breeds of, ii. 178;
    pouter, late development of the crop in, i. 293;
    female, deserting a weakened mate, i. 262.

  PIGEONS, nestling, fed by the secretion of the crop of both parents,
      i. 210;
    changes of plumage in, i. 281;
    transmission of sexual peculiarities in, i. 283;
    changing colour after several moultings, i. 294;
    numerical proportion of the sexes in, i. 306;
    cooing of, ii. 60;
    variations in plumage of, ii. 74;
    display of plumage by male, ii. 96;
    local memory of, ii. 109;
    antipathy of female, to certain males, ii. 118;
    pairing of, ii. 118, 119;
    profligate male and female, ii. 119;
    wing-bars and tail-feathers of, ii. 131;
    supposititious breed of, ii. 155;
    pouter and carrier, peculiarities of predominant in males, ii. 158;
    nidification of, ii. 168;
    immature plumage of the, ii. 188;
    Australian, ii. 175;
    Belgian, with black-streaked males, i. 285, 293; ii. 157.

  PIGS, origin of the improved breeds of, i. 230;
    numerical proportion of the sexes in, i. 305;
    stripes of young, ii. 184, 303;
    sexual preference shown by, ii. 273.

  PIKE, American, brilliant colours of the male, during the breeding
    season, ii. 14.

  PIKE, male, devoured by females, i. 308.

  PIKE, L. O., on the psychical elements of religion, i. 68.

  _Pimelia striata_, sounds produced by the female, i. 385.

  PINTAIL Drake, plumage of, ii. 84;
    pairing with a wild duck, ii. 115.

  PINTAIL Duck, pairing with a Wigeon, ii. 114.

  PIPE-FISH, filamentous, ii. 18;
    marsupial receptacles of the male, ii. 21.

  PIPITS, moulting of the, ii. 83.

  _Pipra_, modified secondary wing-feathers of male, ii. 65.

  _Pipra deliciosa_, ii. 65, 66.

  _Pirates stridulus_, stridulation of, i. 350.

  _Pithecia leucocephala_, sexual differences of colour in, ii. 290.

  _Pithecia Satanas_, beard of, ii. 283, 284, 285;
    resemblance of, to a negro, ii. 381.

  PITS, suborbital, of Ruminants, ii. 280.

  PITTIDÆ, nidification of, ii. 167.

  PLACENTATA, i. 202.

  PLAGIOSTOMOUS fishes, ii. 1.

  PLAIN-WANDERER, Australian, ii. 201.

  _Planariæ_, bright colours of some, i. 322.

  PLANTAIN-EATERS, colours and nidification of the, ii. 171;
    both sexes of, equally brilliant, ii. 177.

  PLANTS, cultivated, more fertile than wild, i. 132;
    Nägeli, on natural selection in, i. 152;
    male flowers of, mature before the female, i. 260;
    phenomena of fertilisation in, i. 273;
    relation between number and size of seeds in, i. 317.

  _Platalea_, ii. 60;
    change of plumage in, ii. 179.

  _Platyblemnus_, i. 361.

  _Platycercus_, young of, ii. 209.

  _Platyphyllum concavum_, i. 352, 356.

  PLATYRRHINE monkeys, i. 196.

  PLATYSMA _myoides_, i. 19.

  _Plecostomus_, head-tentacles of the male of a species of, ii. 10.

  _Plecostomus barbatus_, peculiar beard of the male, ii. 10.

  _Plectropterus gambensis_, spurred wings of, ii. 46.

  _Ploceus_, ii. 54.

  PLOVERS, wing-spurs of, ii. 48;
    double moult in, ii. 83.

  PLUMAGE, changes of, inheritance of, by fowls, i. 281;
    tendency to analogous variation in, ii. 74;
    display of, by male birds, ii. 86, 96;
    changes of, in relation to season, ii. 180;
    immature, of birds, ii. 183, 187;
    colour of, in relation to protection, ii. 223.

  PLUMES on the head in birds, difference of, in the sexes, ii. 164.

  _Pneumora_, structure of, i. 357.

  _Podica_, sexual difference in the colour of the irides of, ii. 128.

  POEPPIG, on the contact of civilised and savage races, i. 239.

  POISON, avoidance of, by animals, i. 49.

  POISONOUS fruits and herbs avoided by animals, i. 36.

  POISONS, immunity from, correlated with colour, i. 242.

  POLISH fowls, origin of the crest in, i. 284.

  POLLEN and van Dam, on the colours of _Lemur macaco_, ii. 290.

  POLYANDRY, ii. 365;
    in certain cyprinidæ, i. 309;
    among the elateridæ, i. 313.

  POLYDACTYLISM in man, i. 125.

  POLYGAMY, influence of, upon sexual selection, i. 265;
    superinduced by domestication, i. 270;
    supposed increase of female births by, i. 303;
    in the stickleback, ii. 2.

  POLYGENISTS, i. 228.

  POLYNESIA, prevalence of infanticide in, ii. 364.

  POLYNESIANS, aversion of, to hairs on the face, ii. 349;
    wide geographical range of, i. 112;
    difference of stature among the, i. 115;
    crosses of, i. 225;
    variability of, i. 225;
    heterogeneity of the, i. 241.

  _Polyplectron_, display of plumage by the male, i. 89;
    number of spurs in, ii. 46;
    gradation of characters in, ii. 137;
    female of, ii. 194.

  _Polyplectron chinquis_, ii. 90, 138, 139.

  _Polyplectron Hardwickii_, ii. 138, 139.

  _Polyplectron malaccense_, ii. 139, 140.

  _Polyplectron Napoleonis_, ii. 138, 140.

  POLYZOA, i. 324.

  _Pontoporeia affinis_, i. 329.

  PORCUPINE, mute, except in the rutting season, ii. 274.

  PORES, excretory, numerical relation of, to the hairs in sheep,
    i. 248.

  _Porpitæ_, bright colours of some, i. 322.

  _Portax picta_, dorsal crest and throat-tuft of, ii. 282;
    sexual differences of colour in, ii. 287, 299.

  _Portunus puber_, pugnacity of, i. 332.

  _Potamochoerus penicillatus_, tusks and facial knobs of the, ii. 266.

  POUCHET, G., on the ratio of instinct and intelligence, i. 37;
    on the instincts of ants, i. 187;
    on the caves of Abou-Simbel, i. 217;
    on the immunity of negroes from yellow fever, i. 243.

  POUTER pigeon, late development of the large crop in, i. 293.

  POWER, Dr., on the different colours of the sexes in a species
    of _Squilla_, i. 335.

  POWYS, Mr., on the habits of the chaffinch in Corfu, i. 307.

  PRE-EMINENCE of man, i. 137.

  PREFERENCE for males by female birds, ii. 113, 122;
    shown by mammals, in pairing, ii. 268.

  PREHENSILE organs, i. 256.

  _Presbytis entellus_, fighting of the male, ii. 324.

  PREYER, Dr., on supernumerary mammæ in women, i. 125.

  PRICHARD, on the difference of stature among the Polynesians, i. 115;
    on the connection between the breadth of the skull in the
      Mongolians and the perfection of their senses, i. 119;
    on the capacity of British skulls of different ages, i. 146;
    on the flattened heads of the Colombian savages, ii. 340;
    on Siamese notions of beauty, ii. 345;
    on the beardlessness of the Siamese, ii. 349;
    on the deformation of the head among American tribes and
      the natives of Arakhan, ii. 352.

  PRIMARY sexual organs, i. 254.

  PRIMATES, i. 190;
    sexual differences of colour in, ii. 290.

  PRIMOGENITURE, evils of, i. 170.

  _Primula_, relation between number and size of seeds in, i. 317.

  PRIONIDÆ, difference of the sexes in colour, i. 367.

  _Proctotretus multimaculatus_, ii. 26, 37.

  _Proctotretus tenuis_, sexual difference in the colour of, ii. 37.

  PROFLIGACY, i. 173.

  PROGENITORS, early, of man, i. 206.

  PROGRESS, not the normal rule in human society, i. 166;
    elements of, i. 177.

  PRONG-HORN, horns of, i. 289.

  PROPORTIONS, difference of, in distinct races, i. 216.

  PROTECTIVE colouring in butterflies, i. 392;
    in lizards, ii. 37;
    in birds, ii. 197, 223;
    in mammals, ii. 298, 299.

  PROTECTIVE nature of the dull colouring of female Lepidoptera, i. 403,
    405, 414.

  PROTECTIVE resemblances in fishes, ii. 18.

  PROTOZOA, absence of secondary sexual characters in, i. 321.

  PRUNER-BEY, on the occurrence of the supra-condyloid foramen
      in the humerus of man, i. 29;
    on the colour of negro infants, ii. 318.

  PRUSSIA, numerical proportion of male and female births in, i. 301.

  _Psocus_, proportions of the sexes in, i. 314.

  PTARMIGAN, monogamous, i. 269;
    summer and winter plumage of the, ii. 81, 83;
    nuptial assemblages of, ii. 101;
    triple moult of the, ii. 181;
    protective coloration of, ii. 198.

  PUFF-BIRDS, colours and nidification of the, ii. 171.

  PUGNACITY of fine-plumaged male birds, ii. 93.

  PUMAS, stripes of young, ii. 183.

  PUPPIES learning from cats to clean their faces, i. 44.

  _Pycnonotus hæmorrhous_, pugnacity of the male, ii. 41;
    display of under tail coverts by the male, ii. 96.

  _Pyranga æstiva_, male aiding in incubation, ii. 167.

  _Pyrodes_, difference of the sexes in colour, i. 367.


  Q.

  QUADRUMANA, hands of, i. 139;
    differences between man and the, i. 190;
    dependence of, on climate, i. 218;
    sexual differences of colour in, ii. 290;
    ornamental characters of, ii. 306;
    analogy of sexual differences of, with those of man, ii. 318;
    fighting of males for the females, ii. 324;
    monogamous habits of, ii. 361;
    beards of the, ii. 378.

  QUAIN, R., on the variation of the muscles in man, i. 109.

  QUATREFAGES, A. de, on the occurrence of a rudimentary tail in man,
      i. 29;
    on the moral sense as a distinction between man and animals, i. 70;
    on variability, i. 112;
    on the fertility of Australian women with white men, i. 221;
    on the Paulistas of Brazil, i. 225;
    on the evolution of the breeds of cattle, i. 230;
    on the Jews, i. 242;
    on the liability of negroes to tropical fevers after residence
      in a cold climate, i. 243;
    on the difference between field- and house-slaves, i. 246;
    on the influence of climate on colour, i. 246;
    on the Ainos, ii. 321;
    on the women of San-Giuliano, ii. 357.

  QUECHUA Indians, i. 119;
    local variation of colour in the, i. 246;
    no grey hair among the, ii. 320;
    hairlessness of the, ii. 322;
    long hair of the, ii. 348.

  _Querquedula acuta_, ii. 114.

  _Quiscalus major_, proportions of the sexes of, in Florida
    and Honduras, i. 307.


  R.

  RABBIT, white tail of the, ii. 298.

  RABBITS, danger-signals of, i. 74;
    domestic, elongation of the skull in, i. 147;
    modification of the skull in, by the lopping of the ear, i. 147;
    numerical proportion of the sexes in, i. 305.

  RACES, distinctive characters of, i. 215;
    or species of man, i. 217;
    crossed, fertility or sterility of, i. 220;
    of man, variability of the, i. 225;
    of man, resemblance of, in mental characters, i. 232;
    formation of, i. 235;
    of man, extinction of, i. 236;
    effects of the crossing of, i. 240;
    of man, formation of the, i. 240;
    of man, children of the, ii. 318;
    beardless, aversion of, to hairs on the face, ii. 349.

  RAFFLES, Sir S., on the Banteng, ii. 290.

  RAFTS, use of, i. 137, 234.

  RAGE, manifested by animals, i. 40.

  _Raia batis_, teeth of, ii. 6.

  _Raia clavata_, female spined on the back, ii. 2;
    sexual difference in the teeth of, ii. 6.

  _Raia maculata_, teeth of, ii. 6.

  RAILS, spur-winged, ii. 48.

  RAM, mode of fighting of the, ii. 249;
    African, mane of an, ii. 284;
    fat-tailed, ii. 284.

  RAMESES II., i. 217.

  RAMSAY, Mr., on the Australian Musk-duck, ii. 38;
    on the Regent-bird, ii. 113;
    on the incubation of _Menura superba_, ii. 165.

  _Rana esculenta_, vocal sacs of, ii. 28.

  RAT, common, general dispersion of, a consequence of superior cunning,
      i. 50;
    supplantation of the native, in New Zealand, by the European rat,
      i. 240;
    common, said to be polygamous, i. 268;
    numerical proportion of the sexes in, i. 305.

  RATS, enticed by essential oils, ii. 281.

  RATIONALITY of birds, ii. 108.

  RATTLE-SNAKES, difference of the sexes in the, ii. 29;
    said to use their rattles as a sexual call, ii. 30.

  RAVEN, vocal organs of the, ii. 55;
    stealing bright objects, ii. 112;
    pied, of the Feroe Islands, ii. 120.

  RAYS, prehensile organs of male, ii. 1.

  RAZOR-BILL, young of the, ii. 217.

  READE, Winwood, on the Guinea sheep, i. 289;
    non-development of horns in castrated male Guinea sheep, ii. 247;
    on the occurrence of a mane in an African ram, ii. 285;
    on the negroes’ appreciation of the beauty of their women, ii. 344;
    on the admiration of negroes for a black skin, ii. 346;
    on the idea of beauty among negroes, ii. 350;
    on the Jollofs, ii. 357;
    on the marriage-customs of the negroes, ii. 374.

  REASON, in animals, i. 46.

  REDSTART, American, breeding in immature plumage, ii. 214.

  REDSTARTS, new mates found by, ii. 105.

  REDUVIDÆ, stridulation of, i. 350.

  REED-BUNTING, head-feathers of the male, ii. 95;
    attacked by a bullfinch, ii. 111.

  REEFS, fishes frequenting, ii. 17.

  REGENERATION, partial, of lost parts in man, i. 13.

  REGENT-BIRD, ii. 112.

  REINDEER, antlers of, with numerous points, ii. 252;
    sexual preferences shown by, ii. 273;
    horns of the, i. 288;
    winter change of the, ii. 299;
    battles of, ii. 240;
    horns of the female, ii. 243.

  RELATIONSHIP, terms of, ii. 360.

  RELIGION, deficiency of, among certain races, i. 65;
    psychical elements of, i. 68.

  REMORSE, i. 91;
    deficiency of, among savages, i. 164.

  RENGGER, on the diseases of _Cebus Azaræ_, i. 11;
    on maternal affection in a _Cebus_, i. 40;
    revenge taken by monkeys, i. 40;
    on the reasoning powers of American monkeys, i. 47;
    on the use of stones by monkeys for cracking hard nuts, i. 51;
    on the sounds uttered by _Cebus Azaræ_, i. 54;
    on the signal-cries of monkeys, i. 57;
    on the diversity of the mental faculties of monkeys, i. 110;
    on the Payaguas Indians, i. 117;
    on the inferiority of Europeans to savages in their senses, i. 118;
    on the polygamous habits of _Mycetes caraya_, i. 266;
    on the voice of the howling monkeys, ii. 277;
    on the odour of _Cervus campestris_, ii. 279;
    on the beards of _Mycetes caraya_ and _Pithecia Satanas_, ii. 283;
    on the colours of _Felis mitis_, ii. 287;
    on the colours of _Cervus paludosus_, ii. 290;
    on sexual differences of colour in _Mycetes_, ii. 291;
    on the colour of the infant Guaranys, ii. 318;
    on the early maturity of the female of _Cebus azaræ_, ii. 318;
    on the beards of the Guaranys, ii. 322, 323;
    on the emotional notes employed by monkeys, ii. 336;
    on American polygamous monkeys, ii. 362.

  REPRESENTATIVE species, of birds, ii. 190, 191.

  REPRODUCTION, unity of phenomena of, throughout the mammalia, i. 13;
    period of, in birds, ii. 214.

  REPRODUCTIVE system, rudimentary structures in the, i. 30;
    accessory parts of, i. 207.

  REPTILES, ii. 28.

  REPTILES and birds, alliance of, i. 213.

  RESEMBLANCES, small, between man and the apes, i. 191.

  RETRIEVERS, exercise of reasoning faculties by, i. 48.

  REVENGE, manifested by animals, i. 40.

  REVERSION, i. 122;
    perhaps the cause of some bad dispositions, i. 173.

  _Rhagium_, difference of colour in the sexes of a species of, i. 367.

  _Ramphastos carinatus_, ii. 227.

  RHINOCEROS, nakedness of, i. 148;
    horns of, ii. 247;
    horns of, used defensively, ii. 263;
    attacking white or grey horses, ii. 295.

  _Rhynchæa_, sexes and young of, ii. 202.

  _Rhynchæa australis_, ii. 203.

  _Rhynchæa bengalensis_, ii. 203.

  _Rhynchæa capensis_, ii. 202.

  RHYTHM, perception of, by animals, ii. 333.

  RICHARD, M., on rudimentary muscles in man, i. 19.

  RICHARDSON, Sir J., on the pairing of _Tetrao umbellus_, ii. 49;
    on _Tetrao urophasianus_, ii. 58;
    on the drumming of grouse, ii. 63;
    on the dances of _Tetrao phasianellus_, ii. 69;
    on assemblages of grouse, ii. 101;
    on the battles of male deer, ii. 240;
    on the reindeer, ii. 244;
    on the horns of the musk-ox, ii. 247;
    on antlers of the reindeer with numerous points, ii. 252;
    on the moose, ii. 259.

  RICHARDSON, on the Scotch deerhound, ii. 261.

  RICHTER, Jean Paul, on imagination, i. 45.

  RIEDEL, on profligate female pigeons, ii. 119.

  RING-OUZEL, colours and nidification of the, ii. 170.

  RIPA, Father, on the difficulty of distinguishing the races
    of the Chinese, i. 215.

  RIVALRY, in singing, between male birds, ii. 53.

  RIVER-HOG, African, tusks and knobs of the, ii. 266.

  RIVERS, analogy of, to islands, i. 204.

  ROACH, brightness of male during breeding-season, ii. 13.

  ROBBERY, of strangers, considered honourable, i. 94.

  ROBERTSON, Mr., remarks on the development of the horns
    in the roebuck and red-deer, i. 288.

  ROBIN, pugnacity of the male, ii. 40;
    autumn song of the, ii. 54;
    female, singing of the, ii. 54;
    attacking other birds with red in their plumage, ii. 111;
    young of the, ii. 208.

  ROBINET, on the difference of size of the male and female cocoons
    of the silk-moth, i. 346.

  RODENTS, uterus in the, i. 123;
    absence of secondary sexual characters in, i. 268;
    sexual differences in the colours of, ii. 286.

  ROE, winter change of the, ii. 299.

  ROLLE, F., on the origin of man, i. 4;
    on a change in German families settled in Georgia, i. 246.

  ROLLER, ii. 56.

  ROMANS, ancient, gladiatorial exhibitions of the, i. 101.

  ROOK, voice of the, ii. 61.

  RÖSSLER, Dr., on the resemblance of the lower surface of butterflies
    to the bark of trees, i. 392.

  ROSTRUM, sexual difference in the length of, in some weevils, i. 255.

  RUDIMENTARY organs, i. 17;
    origin of, i. 32.

  RUDIMENTS, presence of, in languages, i. 60.

  RUDOLPH, on the want of connexion between climate and the colour
    of the skin, i. 241.

  RUFF, supposed to be polygamous, i. 270;
    proportion of the sexes in the, i. 306;
    pugnacity of the, ii. 41, 48;
    double moult in, ii. 81, 84;
    duration of dances of, ii. 100;
    attraction of the, to bright objects, ii. 111.

  RUMINANTS, male, disappearance of canine teeth in, i. 144, ii. 325;
    generally polygamous, i. 266;
    analogy of Lamellicorn beetles to, i. 373;
    suborbital pits of, ii. 280;
    sexual differences of colour in, ii. 287.

  _Rupicola crocea_, display of plumage by the male, ii. 87.

  RÜPPELL, on canine teeth in deer and antelopes, ii. 258.

  RUSSIA, numerical proportion of male and female births in, i. 301.

  _Ruticilla_, ii. 180.

  RÜTIMEYER, Prof., on the physiognomy of the apes, i. 149;
    on the sexual differences of monkeys, ii. 323.

  RUTLANDSHIRE, numerical proportion of male and female births in,
    i. 301.


  S.

  SACHS, Prof., on the behaviour of the male and female elements
    in fertilisation, i. 274.

  SACRIFICES, Human, i. 182.

  SAGITTAL crest in male apes and Australians, ii. 319.

  SAHARA, birds of the, ii. 172;
    animal inhabitants of the, ii. 224.

  SAILORS, growth of, delayed by conditions of life, i. 114;
    long-sighted, i. 118.

  SAILORS and soldiers, difference in the proportions of, i. 116.

  ST. JOHN, Mr., on the attachment of mated birds, ii. 108.

  ST. KILDA, beards of the inhabitants of, ii. 321.

  _Salmo eriox_, and _S. umbla_, colouring of the male, during
     the breeding season, ii. 14.

  _Salmo lycaodon_, ii. 4.

  _Salmo salar_, ii. 4.

  SALMON, leaping out of fresh water, i. 83;
    male, ready to breed before the female, i. 260;
    proportion of the sexes in, i. 308;
    male, pugnacity of the, ii. 3;
    male, characters of, during the breeding season, ii. 3, 14;
    spawning of the, ii. 19;
    breeding of immature male, ii. 215.

  SALVIN, O., on the Humming-birds, i. 269, ii. 168;
    on the numerical proportion of the sexes in Humming-birds,
      i. 307, ii. 221;
    on _Chamæpetes_ and _Penelope_, ii. 64;
    on _Selasphorus platycercus_, ii. 65;
    on _Pipra deliciosa_, ii. 66;
    on _Chasmorhynchus_, ii. 79.

  SAMOA Islands, beardlessness of the natives of, ii. 322, 349.

  SAND-SKIPPER, i. 334.

  SANDWICH Islands, variation in the skulls of the natives of the,
      i. 108;
    superiority of the nobles in the, ii. 356.

  SANDWICH Islanders, lice of, i. 219.

  SAN-GIULIANO, women of, ii. 357.

  SANTALI, recent rapid increase of the, i. 133;
    Mr. Hunter on the, i. 241.

  _Saphirina_, characters of the males of, i. 335.

  _Sarkidiornis melanonotus_, characters of the young, ii. 185.

  SARS, O., on _Pontoporeia offinis_, i. 329.

  _Saturnia carpini_, attraction of males by the female, i. 311.

  _Saturnia Io_, difference of coloration in the sexes of, i. 398.

  _Saturniidæ_, coloration of the, i. 396, 398.

  SAVAGE, Dr., on the fighting of the male gorillas, ii. 324;
    on the habits of the gorilla, ii. 363.

  SAVAGE and Wyman, on the polygamous habits of the gorilla, i. 266.

  SAVAGES, imitative faculties of, i. 57, 161;
    causes of low morality of, i. 97;
    uniformity of, exaggerated, i. 111;
    long-sighted, i. 118;
    rate of increase among, usually small, i. 132;
    retention of the prehensile power of the feet by, i. 142;
    tribes of, supplanting one another, i. 160;
    improvements in the arts among, i. 182;
    arts of, i. 234;
    fondness of, for rough music, ii. 67;
    attention paid by, to personal appearance, ii. 338;
    relation of the sexes among, ii. 363.

  SAW-FLY, pugnacity of a male, i. 364.

  SAW-FLIES, proportions of the sexes in, i. 314.

  _Saxicola rubicola_, young of, ii. 220.

  SCALP, motion of the, i. 20.

  SCENT-GLANDS in snakes, ii. 30.

  SCHAAFFHAUSEN, Prof., on the development of the posterior molars
      in different races of man, i. 26;
    on the jaw from La Naulette, i. 126;
    on the correlation between muscularity and prominent supra-orbital
      ridges, i. 130;
    on the mastoid processes of man, i. 143;
    on modifications of the cranial bones, i. 147;
    on human sacrifices, i. 182;
    on the probable speedy extermination of the anthropomorphous apes,
      i. 201;
    on the ancient inhabitants of Europe, i. 237;
    on the effects of use and disuse of parts, i. 247;
    on the superciliary ridge in man, ii. 316;
    on the absence of race-differences in the infant skull in man,
      ii. 318;
    on ugliness, ii. 354.

  SCHAUM, H., on the elytra of _Dytiscus_ and _Hydroporus_, i. 343.

  SCHELVER, on dragon-flies, i. 363.

  SCHIODTE, on the stridulation of _Heterocerus_, i. 379.

  SCHLEGEL, F. von, on the complexity of the languages of uncivilised
    peoples, i. 61.

  SCHLEGEL, Prof., on _Tanysiptera_, ii. 190.

  SCHLEICHER, Prof., on the origin of language, i. 56.

  SCHLEIDEN, Prof., on the rattle-snake, ii. 30.

  SCHOMBURGK, Sir R., on the pugnacity of the male musk-duck
      of Guiana, ii. 43;
    on the courtship of _Rupicola crocea_, ii. 87.

  SCHOOLCRAFT, Mr., on the difficulty of fashioning stone implements,
    i. 138.

  SCLATER, P. L., on modified secondary wing-feathers in the males
      of _Pipra_, ii. 65;
    on elongated feathers in nightjars, ii. 73;
    on the species of _Chasmorhynchus_, ii. 79;
    on the plumage of _Pelecanus onocrotalus_, ii. 85;
    on the plantain-eaters, ii. 177;
    on the sexes and young of _Tadorna variegata_, ii. 206;
    on the colours of _Lemur macaco_, ii. 290;
    on the stripes in asses, ii. 305.

  SCOLECIDA, absence of secondary sexual characters in, i. 321.

  _Scolopax frenata_, tail-feathers of, ii. 64.

  _Scolopax gallinago_, drumming of, ii. 63.

  _Scolopax javensis_, tail-feathers of, ii. 64.

  _Scolopax major_, assemblies of, ii. 101.

  _Scolopax Wilsonii_, sound produced by, ii. 64.

  _Scolytus_, stridulation of, i. 379.

  SCOTER-DUCK, black, sexual difference in coloration of the, ii. 226;
    bright beak of male, ii. 227.

  SCOTT, J., on the colour of the beard in man, ii. 319.

  SCROPE, on the pugnacity of the male salmon, ii. 3;
    on the battles of stags, ii. 240.

  SCUDDER, S. H., imitation of the stridulation of the Orthoptera,
      i. 353;
    on the stridulation of the _Acridiidæ_, i. 356;
    on a Devonian insect, i. 360;
    on stridulation, ii. 331.

  SCULPTURE, expression of the ideal of beauty by, ii. 350.

  SEA-ANEMONIES, bright colours of, i. 322.

  SEA-BEAR, polygamous, i. 268.

  SEA-ELEPHANT, male, structure of the nose of the, ii. 278;
    polygamous, i. 268.

  SEA-LION, polygamous, i. 268.

  SEAL, bladder-nose, ii. 278.

  SEALS, their sentinels generally females, i. 74;
    evidence furnished by, on classification, i. 190;
    sexual differences in the coloration of, ii. 287;
    appreciation of music by, ii. 333;
    battles of male, ii. 240;
    canine teeth of male, ii. 241;
    polygamous habits of, i. 268;
    pairing of, ii. 269;
    sexual peculiarities of, ii. 277.

  SEA-SCORPION, sexual differences in, ii. 9.

  SEASON, changes of colour in birds, in accordance with the, ii. 80;
    changes of plumage of birds in relation to, ii. 180.

  SEASONS, inheritance at corresponding, i. 282.

  SEBITUANI, ii. 340.

  SEBRIGHT Bantam, i. 294.

  SECONDARY sexual characters, i. 253;
    relations of polygamy to, i. 266;
    gradation of, in birds, ii. 135;
    transmitted through both sexes, i. 279.

  SEDGWICK, W., on hereditary tendency to produce twins, i. 133.

  SEEMANN, Dr., on the different appreciation of music by different
      peoples, ii. 334;
    on the effects of music, ii. 335.

  _Selasphorus platycercus_, acuminate first primary of the male,
     ii. 65.

  SELBY, P. J., on the habits of the black and red grouse, i. 269.

  SELECTION, double, i. 276.

  SELECTION of male by female birds, ii. 99, 122.

  SELECTION, methodical, of Prussian grenadiers, i. 112.

  SELECTION, sexual, influence of, on the colouring of Lepidoptera,
      i. 403;
    explanation of, i. 256, 260, 271.

  SELECTION, sexual and natural, contrasted, i. 278.

  SELF-COMMAND, habit of, inherited, i. 92;
    estimation of, i. 95.

  SELF-CONSCIOUSNESS, i. 62.

  SELF-PRESERVATION, instinct of, i. 89.

  SELF-SACRIFICE, by savages, i. 88;
    estimation of, i. 95.

  SEMILUNAR fold, i. 23.

  _Semnopithecus_, i. 197;
    long hair on the heads of species of, i. 192; ii. 380.

  _Semnopithecus chrysomelas_, sexual differences of colour in ii. 291.

  _Semnopithecus comatus_, ornamental hair on the head of, ii. 307.

  _Semnopithecus frontatus_, beard, &c., of, ii. 308.

  _Semnopithecus nasica_, nose of, i. 192.

  _Semnopithecus nemæus_, colouring of, ii. 310.

  _Semnopithecus rubicundus_, ornamental hair on the head of, ii. 306.

  SENSES, inferiority of Europeans to savages in the, i. 118.

  SENTINELS, i. 74, 82.

  SERPENTS, instinctively dreaded by apes and monkeys, i. 37, 42.

  _Serranus_, hermaphroditism in, i. 208.

  SEX, inheritance limited by, i. 282.

  SEXES, relative proportions of, in man, i. 300, ii. 320;
    probable relation of the, in primeval man, ii. 362.

  SEXUAL characters, secondary, i. 253;
    relations of polygamy to, i. 266;
    transmitted through both sexes, i. 279;
    gradation of, in birds, ii. 135.

  SEXUAL and natural selection, contrasted, i. 278.

  SEXUAL characters, effects of the loss of, i. 284;
    limitation of, i. 284.

  SEXUAL differences in man, i. 14.

  SEXUAL selection, explanation of, i. 256, 260, 271;
    influence of, on the colouring of Lepidoptera, i. 403;
    action of, in mankind, ii. 368.

  SEXUAL similarity, i. 277.

  SHARKS, prehensile organs of male, ii. 1.

  SHARPE, R. B., on _Tanysiptera sylvia_, ii. 165;
    on _Ceryle_, ii. 173;
    on the young male of _Dacelo Gaudichaudi_, ii. 188.

  SHAW, Mr., on the pugnacity of the male salmon, ii. 3.

  SHAW, J., on the decorations of birds, ii. 71.

  SHEEP, danger-signals of, i. 74;
    sexual differences in the horns of, i. 283;
    horns of, i. 289, ii. 246, 259;
    domestic, sexual differences of, late developed, i. 293;
    numerical proportion of the sexes in, i. 304;
    mode of fighting of, ii. 249;
    arched foreheads of some, ii. 284.

  SHEEP, Merino, loss of horns in females of, i. 284;
    horns of, i. 289.

  SHELLS, difference in form of, in male and female Gasteropoda, i. 324;
    beautiful colours and shapes of, i. 326.

  SHIELD-DRAKE, pairing with a common duck, ii. 114;
    New Zealand, sexes and young of, ii. 206.

  SHOOTER, J., on the Kafirs, ii. 347;
    on the marriage-customs of the Kafirs, ii. 373.

  SHREW-MICE, odour of, ii. 279.

  SHRIKE, Drongo, ii. 179.

  SHRIKES, characters of young, ii. 185.

  SHUCKARD, W. E., on sexual differences in the wings of Hymenoptera,
    i. 435.

  SHYNESS of adorned male birds, ii. 97.

  _Siagonium_, proportions of the sexes in, i. 314;
    dimorphism in males of, i. 374.

  SIAM, proportion of male and female births in, i. 303.

  SIAMESE, general beardlessness of the, ii. 321;
    notions of beauty of the, ii. 345;
    hairy family of, ii. 378.

  SIEBOLD, C. T. von, on the auditory apparatus of the stridulant
    orthoptera, i. 353.

  SIGHT, inheritance of long and short, i. 118.

  SIGNAL-CRIES of monkeys, i. 57.

  SILK-MOTH, difference of size of the male and female cocoons
      of the, i. 346;
    pairing of the, i. 401;
    male, fertilising two or three females, i. 406;
    proportion of the sexes in, i. 309, 311;
    Ailanthus, Prof. Canestrini, on the destruction of its larvæ
      by wasps, i. 311.

  SIMIADÆ, i. 195;
    their origin and divisions, i. 213.

  SIMILARITY, sexual, i. 277.

  SINGING of the Cicadæ and Fulgoridæ, i. 351;
    of tree-frogs, ii. 27;
    of birds, object of the, ii. 52.

  SIRENIA, nakedness of, i. 148.

  _Sirex juvencus_, i. 365.

  SIRICIDÆ, difference of the sexes in, i. 365.

  SISKIN, ii. 85;
    pairing with a canary, ii. 115.

  _Sitana_, throat-pouch of the males of, ii. 33, 36.

  SIZE, relative, of the sexes of insects, i. 345.

  SKIN, movement of the, i. 19;
    nakedness of, in man, i. 148;
    colour of the, i. 241.

  SKIN and hair, correlation of colour of, i. 248.

  SKULL, variation of, in man, i. 108;
    cubic contents of, no absolute test of intellect, i. 145;
    Neanderthal, capacity of the, i. 146;
    causes of modification of the, i. 147;
    difference of, in form and capacity, in different races of men,
      i. 216;
    variability of the shape of the, i. 226;
    differences of, in the sexes in man, ii. 317;
    artificial modifications of the shape of, ii. 340.

  SKUNK, odour emitted by the, ii. 279.

  SLAVERY, prevalence of, i. 94;
    of women, ii. 366.

  SLAVES, difference between those of field and house, i. 246.

  SMELL, sense of, in man and animals, i. 23.

  SMITH, Adam, on the basis of sympathy, i. 82.

  SMITH, Sir A., on the recognition of women by male _Cynocephali_,
      i. 13;
    on an instance of memory in a baboon, i. 45;
    on the retention of their colour by the Dutch in South Africa,
      i. 242;
    on the polygamy of the South African antelopes, i. 267;
    on the proportion of the sexes in _Kobus ellipsiprymnus_, i. 305;
    on _Bucephalus capensis_, ii. 29;
    on South African lizards, ii. 37;
    on fighting gnus, ii. 240;
    on the horns of rhinoceroses, ii. 248;
    on the fighting of lions, ii. 266;
    on the colours of the Cape Eland, ii. 288;
    on the colours of the gnu, ii. 289;
    on Hottentot notions of beauty, ii. 345.

  SMITH, F., on the Cynipidæ and Tenthredinidæ, i. 314;
    on the relative size of the sexes of Aculeate Hymenoptera, i. 347;
    on the difference between the sexes of ants and bees, i. 365;
    on the stridulation of _Trox sabulosus_, i. 380;
    on the stridulation of _Mononychus pseudacori_, i. 382.

  _Smynthurus luteus_, courtship of, i. 348.

  SNAKES, sexual differences of, ii. 29;
    male, ardency of, ii. 30.

  “SNARLING MUSCLES,” i. 127.

  SNIPE, drumming of the, ii. 63;
    coloration of the, ii. 226.

  SNIPE, painted, sexes and young of, ii. 202.

  SNIPE, solitary, assemblies of, ii. 101.

  SNIPES, arrival of male before the female, i. 260;
    pugnacity of male, ii. 43;
    double moult in, ii. 80.

  SNOW-GOOSE, whiteness of the, ii. 228.

  SOCIAL animals, affection of, for each other, i. 76;
    defence of, by the males, i. 83.

  SOCIABILITY, the sense of duty connected with, i. 71;
    impulse to, in animals, i. 79, 80;
    manifestations of, in man, i. 84;
    instinct of, in animals, i. 86.

  SOCIALITY, probable, of primeval men, i. 155;
    influence of, on the development of the intellectual faculties,
      i. 160;
    origin of, in man, i. 161.

  SOLDIERS, American, measurements of, i. 114.

  SOLDIERS and sailors, difference in the proportions of, i. 116.

  _Solenostoma_, bright colours and marsupial sack of the females
     of, ii. 22.

  SONG of male birds appreciated by their females, i. 63;
    want of, in brilliant plumaged birds, ii. 94;
    of birds, ii. 163.

  _Sorex_, odour of, ii. 279.

  SOUNDS admired alike by man and animals, i. 64;
    produced by fishes, ii. 23;
    produced by male frogs and toads, ii. 27;
    instrumentally produced by birds, ii. 63 _et seqq._

  SPAIN, decadence of, i. 178.

  _Sparassus smaragdulus_, difference of colour in the sexes of, i. 337,
    338.

  SPARROW, pugnacity of the male, ii. 40;
    acquisition of the Linnet’s song by a, ii. 55;
    coloration of the, ii. 198;
    immature plumage of the, ii. 188.

  SPARROW, white-crowned, young of the, ii. 217.

  SPARROWS, house- and tree-, ii. 170.

  SPARROWS, new mates found by, ii. 105.

  SPARROWS, sexes and young of, ii. 212;
    learning to sing, ii. 334.

  _Spathura Underwoodi_, ii. 77.

  SPAWNING of fishes, ii. 15, 19.

  SPEAR, origin of the, i. 234.

  SPECIES, causes of the advancement of, i. 172;
    distinctive characters of, i. 214;
    or races of man, i. 217;
    sterility and fertility of, when crossed, i. 122;
    supposed, of man, i. 226;
    gradation of, i. 227;
    difficulty of defining, i. 228;
    representative, of birds, ii. 190, 191;
    of birds, comparative differences between the sexes of distinct,
      ii. 192.

  SPECTRE-INSECTS, mimickry of leaves by, i. 414.

  _Spectrum femoratum_, difference of colour in the sexes of, i. 361.

  SPEECH, connection between the brain and the faculty of, i. 58.

  “SPEL” of the black-cock, ii. 60.

  SPENCER, Herbert, on the dawn of intelligence, i. 37;
    on the origin of the belief in spiritual agencies, i. 66;
    on the origin of the moral sense, i. 101;
    on the influence of food on the size of the jaws, i. 118;
    on the ratio between individuation and genesis, i. 318;
    on music, ii. 336.

  SPERM-WHALES, battles of male, ii. 240.

  SPHINGIDÆ, coloration of the, i. 396.

  SPHINX, Humming-bird, i. 399.

  _Sphinx_, Mr. Bates on the caterpillar of a, i. 416.

  SPIDERS, i. 337;
    male, more active than female, i. 272;
    proportion of the sexes in, i. 314;
    male, small size of, i. 338.

  _Spilosoma menthrasti_, rejected by turkeys, i. 398.

  SPINE, alteration of, to suit the erect attitude of man, i. 143.

  SPIRITS, fondness of monkeys for, i. 12.

  SPIRITUAL agencies, belief in, almost universal, i. 65.

  SPOONBILL, ii. 60;
    Chinese, change of plumage in, ii. 179.

  SPOTS, retained throughout groups of birds, ii. 131;
    disappearance of, in adult mammals, ii. 303.

  SPRENGEL, C. K., on the sexuality of plants, i. 260.

  SPRING-BOC, horns of the, ii. 251.

  SPROAT, Mr., on the extinction of savages in Vancouver Island,
      i. 239;
    on the eradication of facial hair by the natives of Vancouver
      Island, ii. 348;
    on the eradication of the beard by the Indians of Vancouver Island,
      ii. 380.

  SPURS, occurrence of, in female fowls, i. 280, 284;
    development of, in various species of Phasianidæ, i. 290;
    of Gallinaceous birds, ii. 44, 46;
    development of, in female Gallinaceæ, ii. 162.

  _Squilla_, different colours of the sexes of a species of, i. 335.

  SQUIRRELS, battles of male, ii. 239;
    African, sexual differences in the colouring of, ii. 286;
    black, ii. 294.

  STAG, long hairs of the throat of, ii. 268;
    horns of the, i. 279, 282;
    battles of, ii. 240;
    horns of the, with numerous branches, ii. 252;
    bellowing of the, ii. 274;
    crest of the, ii. 282.

  STAG-BEETLE, large size of male, i. 347;
    weapons of the male, i. 375;
    numerical proportion of sexes of, i. 313.

  STAINTON, H. T., on the numerical proportion of the sexes
      in the smaller moths, i. 310;
    habits of _Elachista rufocinerea_, i. 311;
    on the coloration of moths, i. 397;
    on the rejection of _Spilosoma menthrasti_, by turkeys, i. 398;
    on the sexes of _Agrotis exclamationis_, i. 399.

  STALLION, mane of the, ii. 268.

  STALLIONS, two, attacking a third, i. 75;
    fighting, ii. 241;
    small canine teeth of, ii. 258.

  STANSBURY, Capt., observations on pelicans, i. 77.

  STAPHYLINIDÆ, hornlike processes in male, i. 374.

  STARFISHES, bright colours of some, i. 322.

  STARK, Dr., on the death-rate in towns and rural districts, i. 175;
    on the influence of marriage on mortality, i. 176;
    on the higher mortality of males in Scotland, i. 302.

  STARLING, American field, pugnacity of male, ii. 51.

  STARLING, red-winged, selection of a mate by the female, ii. 116.

  STARLINGS, three, frequenting the same nest, i. 269, ii. 106;
    new mates found by, ii. 105.

  STATUES, Greek, Egyptian, Assyrian, &c., contrasted, ii. 350.

  STATURE, dependence of, upon local influences, i. 114.

  STAUDINGER, Dr., his list of Lepidoptera, i. 312;
    on breeding Lepidoptera, i. 311.

  STAUNTON, Sir G., hatred of indecency a modern virtue, i. 96.

  STEALING of bright objects by birds, ii. 112.

  STEBBING, T. R., on the nakedness of the human body, ii. 375.

  _Stemmatopus_, ii. 278.

  _Stenobothrus pratorum_, stridulating organs of, i. 357.

  STERILITY, general, of sole daughters, i. 170;
    when crossed, a distinctive character of species, i. 214.

  _Sterna_, seasonal change of plumage in, ii. 228.

  STICKLEBACK, polygamous, i. 271;
    male, courtship of the, ii. 2;
    male, brilliant colouring of, during the breeding season, ii. 14;
    nidification of the, ii. 20.

  STICKS used as implements and weapons by monkeys, i. 51.

  STING in bees, i. 254.

  STOKES, Capt., on the habits of the great Bower-bird, ii. 70.

  STONECHAT, young of the, ii. 220.

  STONE IMPLEMENTS, difficulty of making, i. 138;
    as traces of extinct tribes, i. 237.

  STONES, used by monkeys for breaking hard fruits and as missiles,
      i. 140;
    piles of, i. 233.

  STORK, black, sexual differences in the bronchi of the, ii. 60;
    red beak of the, ii. 227.

  STORKS, ii. 226, 230;
    sexual difference in the colour of the eyes of, ii. 128.

  STRANGE, Mr., on the Satin Bower-bird, ii. 69.

  STRETCH, Mr., on the numerical proportion in the sexes of chickens,
    i. 306.

  _Strepsiceros kudu_, horns of, ii. 255;
    markings of, ii. 300.

  STRIDULATION, by males of _Theridion_, i. 339;
    of the Orthoptera and Homoptera discussed, i. 360;
    of beetles, i. 378.

  STRIPES, retained throughout groups of birds, ii. 131;
    disappearance of, in adult mammals, ii. 303.

  _Strix flammea_, ii. 105.

  STRUCTURE, existence of unserviceable modifications of, i. 153.

  STRUGGLE for existence, in man, i. 180, 185.

  STRUTHERS, Dr., on the occurrence of the supra-condyloid foramen
    in the humerus of man, i. 28.

  _Sturnella ludoviciana_, pugnacity of the male, ii. 51.

  _Sturnus vulgaris_, ii. 105.

  SUB-SPECIES, i. 227.

  SUFFERING, in strangers, indifference of savages to, i. 94.

  SUICIDE, i. 172;
    formerly not regarded as a crime, i. 94;
    rarely practised among the lowest savages, i. 94.

  SUIDÆ, stripes of young, ii. 184.

  SUMATRA, compression of the nose by the Malays of, ii. 352.

  SUMNER, Archb., man alone capable of progressive improvement, i. 49.

  SUN-BIRDS, nidification of, ii. 169.

  SUPERSTITIONS, i. 182;
    prevalence of, i. 99.

  SUPERSTITIOUS customs, i. 68.

  SUPERCILIARY ridge in man, ii. 316, 318.

  SUPERNUMERARY digits, more frequent in men than in women, i. 276;
    inheritance of, i. 285;
    early development of, i. 292.

  SUPRA-CONDYLOID foramen in the early progenitors of man, i. 206.

  SUSPICION, prevalence of, among animals, i. 39.

  SULIVAN, Sir B. J., on two stallions attacking a third, ii. 241.

  SWALLOW-TAIL Butterfly, i. 393.

  SWALLOWS deserting their young, i. 84, 90.

  SWAN, black, red beak of the, ii. 227;
    black-necked, ii. 230;
    white, young of, ii. 211;
    wild, trachea of the, ii. 59.

  SWANS, ii. 226, 230;
    young, ii. 208.

  SWAYSLAND, Mr., on the arrival of migratory birds, i. 259.

  SWINHOE, R., on the common rat in Formosa and China, i. 50;
    on the sounds produced by the male Hoopoe, ii. 62;
    on _Dicrurus macrocercus_ and the Spoonbill, ii. 179;
    on the young of _Ardeola_, ii. 190;
    on the habits of _Turnix_, ii. 202;
    on the habits of _Rhynchæa bengalensis_, ii. 203;
    on Orioles breeding in immature plumage, ii. 214, 215.

  _Sylvia atricapilla_, young of, ii. 219.

  _Sylvia cinerea_, aerial love-dance of the male, ii. 68.

  SYMPATHY, i. 168;
    among animals, i. 77;
    its supposed basis, i. 82.

  SYMPATHIES, gradual widening of, i. 100.

  SYNGNATHOUS fishes, abdominal pouch in male, i. 210.

  _Sypheotides auritus_, acuminated primaries of the male, ii. 64;
    ear-tufts of, ii. 73.


  T.

  TABANIDÆ, habits of, i. 254.

  _Tadorna variegata_, sexes and young of, ii. 206.

  _Tadorna vulpanser_, ii. 114.

  TAHITIANS, i. 183;
    compression of the nose by the, ii. 352.

  TAIL, rudimentary, occurrence of, in man, i. 29;
    convoluted body in the extremity of the, i. 30;
    absence of, in man and the higher apes, i. 150, 194;
    variability of, in species of _Macacus_ and in baboons, i. 150;
    presence of, in the early progenitors of man, i. 206;
    length of, in pheasants, ii. 156, 164, 166;
    difference of length of the, in the two sexes of birds, ii. 164.

  TAIT, Lawson, on the effects of natural selection on civilised
    nations, i. 168.

  TANAGER, scarlet, variation in the male, ii. 126.

  _Tanagra æstiva_, ii. 180;
    age of mature plumage in, ii. 213.

  _Tanagra rubra_, ii. 126;
     young of, ii. 220.

  _Tanais_, absence of mouth in the males of some species of, i. 255;
    relations of the sexes in, i. 315;
    dimorphic males of a species of, i. 328.

  TANKERVILLE, Earl, on the battles of wild bulls, ii. 240.

  _Tanysiptera_, races of, determined from adult males, ii. 190.

  _Tanysiptera sylvia_, long tail-feathers of, ii. 165.

  _Taphroderes distortus_, enlarged left mandible of the male, i. 344.

  TAPIRS, longitudinal stripes of young, ii. 184, 303.

  TARSI, dilatation of front, in male beetles, i. 343.

  _Tarsius_, i. 200.

  TASMANIA, half-castes killed by the natives of, i. 220.

  TATTOOING, i. 232;
    universality of, ii. 339.

  TASTE, in the Quadrumana, ii. 296.

  TAYLOR, G. on _Quiscalus major_, i. 307.

  TEA, fondness of monkeys for, i. 12.

  TEAR-SACKS, of Ruminants, ii. 280.

  TEEBAY, Mr., on changes of plumage in spangled Hamburgh fowls, i. 281.

  TEETH, rudimentary incisor, in Ruminants, i. 17;
    posterior molar, in man, i. 25;
    wisdom, i. 26;
    diversity of, i. 108;
    canine, in the early progenitors of man, i. 206;
    canine, of male mammals, ii. 241;
    in man, reduced by correlation, ii. 325;
    staining of the, ii. 339;
    front, knocked out or filed by some savages, ii. 340.

  TEGETMEIER, Mr., on the abundance of male pigeons, i. 306;
    on the wattles of game-cocks, ii. 98;
    on the courtship of fowls, ii. 117;
    on dyed pigeons, ii. 118.

  TEMBETA, ii. 341.

  TEMPER, in dogs and horses, inherited, i. 40.

  TENCH, proportions of the sexes in the, i. 308, 309;
    brightness of male, during breeding season, ii. 13.

  TENEBRIONIDÆ, stridulation of, i. 379.

  TENNENT, Sir J. E., on the tusks of the Ceylon Elephant, ii. 248, 258;
    on the frequent absence of beard in the natives of Ceylon, ii. 321;
    on the Chinese opinion of the aspect of the Cingalese, ii. 345.

  TENNYSON, A., on the control of thought, i. 101.

  TENTHREDINIDÆ, proportions of the sexes in, i. 314;
    fighting habits of male, i. 364;
    difference of the sexes in, i. 365.

  _Tephrodornis_, young of, ii. 190.

  TERAI, i. 237.

  _Termites_, habits of, i. 364.

  TERNS, white, ii. 228;
    and black, ii. 230.

  TERNS, seasonal change of plumage in, ii. 228.

  TERROR, common action of, upon the lower animals and man, i. 39.

  _Testudo nigra_, ii. 28.

  _Tetrao cupido_, battles of, ii. 50;
    sexual difference in the vocal organs of, ii. 56.

  _Tetrao phasianellus_, dances of, ii. 68;
    duration of dances of, ii. 100.

  _Tetrao scoticus_, ii. 170, 185, 194.

  _Tetrao tetrix_, ii. 170, 185, 194;
     pugnacity of the male, ii. 45.

  _Tetrao umbellus_, pairing of, ii. 49;
    battles of, ii. 50;
    drumming of the male, ii. 61.

  _Tetrao urogalloides_, dances of, ii. 100.

  _Tetrao urogallus_, pugnacity of the male, ii. 45.

  _Tetrao urophasianus_, inflation of the œsophagus in the male,
    ii. 57.

  _Thamnobia_, young of, ii. 190.

  _Thaumalea picta_, display of plumage by the male, ii. 89.

  _Thecla_, sexual differences of colouring in species of, i. 389.

  _Thecla rubi_, protective colouring of, i. 392.

  _Theridion_, i. 337;
    stridulation of males of, i. 339.

  _Theridion lineatum_, variability of, i. 338.

  _Thomisus citreus_, and _T. floricolens_, difference of colour
    in the sexes of, i. 337.

  THOMPSON, J. H., on the battles of sperm-whales, ii. 240.

  THOMPSON, W., on the colouring of the male char during the breeding
      season, ii. 14;
    on the pugnacity of the males of _Gallinula chloropus_, ii. 41;
    on the finding of new mates by magpies, ii. 103;
    on the finding of new mates by Peregrine falcons, ii. 104.

  THORAX, processes of, in male beetles, i. 370.

  THORELL, T., on the proportion of the sexes in spiders, i. 315.

  THORNBACK, difference in the teeth of the two sexes of the, ii. 6.

  THOUGHTS, control of, i. 101.

  THRUSH, pairing with a blackbird, ii. 113;
    colours and nidification of the, ii. 170.

  THRUSHES, characters of young, ii. 185, 269.

  THUG, his regrets, i. 94.

  THUMB, absence of, in _Ateles_ and _Hylobates_, i. 140.

  THURY, M., on the numerical proportion of male and female births
    among the Jews, i. 301.

  _Thylacinus_, possession of the marsupial sack by the male, i. 208.

  THYSANURA, i. 348.

  TIBIA, dilated, of the male _Crabro cribrarius_, i. 343.

  TIBIA and femur, proportions of, in the Aymara Indians, i. 119.

  TIERRA del Fuego, marriage-customs of, ii. 373.

  TIGER, colours and markings of the, ii. 302.

  TIGERS, depopulation of districts by, in India, i. 134.

  _Tillus elongatus_, difference of colour in the sexes of, i. 368.

  TIMIDITY, variability of, in the same species, i. 40.

  TINEINA, proportion of the sexes in, i. 310.

  _Tipula_, pugnacity of male, i. 349.

  TITS, sexual difference of colour in, ii. 174.

  TOADS, ii. 25;
    male, treatment of ova by some, i. 210;
    male, ready to breed before the female, i. 260.

  TOE, great, condition of, in the human embryo, i. 17.

  TOMTIT, blue, sexual difference of colour in the, ii. 174.

  TONGA Islands, beardlessness of the natives of, ii. 322, 349.

  TOOKE, Horne, on language, i. 55.

  TOOLS, flint, i. 183;
    used by monkeys, i. 51;
    use of, i. 137.

  TOP-KNOTS in birds, ii. 74.

  _Tomicus villosus_, proportion of the sexes in, i. 314.

  TORTOISE, voice of the male, ii. 331.

  TORTURES, submitted to by American savages, i. 95.

  _Totanus_, double moult in, ii. 81.

  TOUCANS, colours and nidification of the, ii. 171;
    beaks and ceres of the, ii. 227.

  TOWNS, residence in, a cause of diminished stature, i. 115.

  TOYNBEE, J., on the external shell of the ear in man, i. 21.

  TRACHEA, convoluted and imbedded in the sternum, in some birds,
      ii. 59;
    structure of the, in Rhynchæa, ii. 203.

  TRADES, affecting the form of the skull, i. 147.

  _Tragelaphus_, sexual differences of colour in, ii. 288.

  _Tragelaphus scriptus_, dorsal crest of, ii. 282;
    markings of, ii. 299, 300.

  TRAGOPAN, i. 270;
    swelling of the wattles of the male, during courtship, ii. 72;
    display of plumage by the male, ii. 91;
    markings of the sexes of the, ii. 134.

  _Tragops dispar_, sexual difference in the colour of, ii. 30.

  TRAINING, effect of, on the mental difference between the sexes
    of man, ii. 329.

  TRANSFER of male characters to female birds, ii. 193.

  TRANSMISSION, equal, of ornamental characters, to both sexes
    in mammals, ii. 297.

  TRAPS, avoidance of, by animals, i. 49;
    use of, i. 137.

  TREACHERY, to comrades, avoidance of, by savages, i. 88.

  _Tremex columbæ_, i. 365.

  TRIBES, extinct, i. 160;
    extinction of, i. 236.

  _Trichius_, difference of colour in the sexes of a species of,
    i. 368.

  TRIMEN, R., on the proportion of the sexes in South African
      butterflies, i. 310;
    on the attraction of males by the female of _Lasiocampa quercus_,
      i. 312;
    on _Pneumora_, i. 358;
    on difference of colour in the sexes of beetles, i. 367;
    on moths brilliantly coloured beneath, i. 397;
    on mimickry in butterflies, i. 412;
    on _Gynanisa Isis_, and on the ocellated spots of Lepidoptera,
      ii. 132;
    on _Cyllo Leda_, ii. 133.

  _Tringa_, sexes and young of, ii. 216.

  _Tringa canutus_, ii. 82.

  _Triphæna_, coloration of the species of, i. 395.

  TRISTRAM, H. B., on unhealthy districts in North Africa, i. 244;
    on the habits of the chaffinch in Palestine, i. 307;
    on the birds of the Sahara, ii. 172;
    on the animals inhabiting the Sahara, ii. 224.

  _Triton cristatus_, ii. 24.

  _Triton palmipes_, ii. 24.

  _Triton punctatus_, ii. 24, 25.

  _Troglodytes vulgaris_, ii. 198.

  TROGONS, colours and nidification of the, ii. 171, 173.

  TROPIC-BIRDS, white only when mature, ii. 228.

  TROPICS, freshwater fishes of the, ii. 17.

  TROUT, proportion of the sexes in, i. 308;
    male, pugnacity of the, ii. 3.

  _Trox sabulosus_, stridulation of, i. 380.

  TRUTH, not rare between members of the same tribe, i. 95;
    more highly appreciated by certain tribes, i. 100.

  TULLOCH, Major, on the immunity of the negro from certain fevers,
    i. 243.

  TUMBLER, almond, change of plumage in the, i. 294.

  _Turdus merula_, ii. 170;
    young of, ii. 219.

  _Turdus migratorius_, ii. 185.

  _Turdus musicus_, ii. 170.

  _Turdus polyglottus_, young of, ii. 219.

  _Turdus torquatus_, ii. 170.

  TURKEY, swelling of the wattles of the male, ii. 72;
    variety of, with a top-knot, ii. 74;
    recognition of a dog by a, ii. 110;
    wild, pugnacity of young male, ii. 48;
    wild, notes of the, ii. 60;
    male, wild, acceptable to domesticated females, ii. 119;
    wild, first advances made by older females, ii. 121;
    wild, breast-tuft of bristles of the, ii. 179.

  TURKEY-COCK, scraping of the wings of, upon the ground, ii. 61;
    wild, display of plumage by, ii. 87;
    fighting habits of, ii. 98.

  TURNER, Prof. W., on muscular fasciculi in man referable to
      the panniculus carnosus, i. 19;
    on the occurrence of the supra-condyloid foramen in the human
      humerus, i. 28;
    on muscles attached to the coccyx in man, i. 29;
    on the _filum terminale_ in man, i. 30;
    on the variability of the muscles, i. 109;
    on abnormal conditions of the human uterus, i. 123;
    on the development of the mammary glands, i. 209;
    on male fishes hatching ova in their mouths, i. 210.

  _Turnix_, sexes of some species of, ii. 201, 207.

  TURTLE-DOVE, cooing of the, ii. 60.

  TUTTLE, H., on the number of species of man, i. 226.

  TYLOR, E. B., on emotional cries, gestures, &c., of man, i. 54;
    on the origin of the belief in spiritual agencies, i. 66;
    on the primitive barbarism of civilised nations, i. 181;
    on the origin of counting, i. 181;
    on resemblances of the mental characters in different races of man,
      i. 232.

  TYPE of structure, prevalence of, i. 211.

  _Typhœus_, stridulating organs of, i. 378;
    stridulation of, i. 380.

  TWINS, tendency to produce, hereditary, i. 133.

  TWITE, proportion of the sexes in the, i. 307.


  U.

  UGLINESS, said to consist in an approach to the lower animals,
    ii. 354.

  UMBRELLA-BIRD, ii. 58, 59.

  _Umbrina_, sounds produced by, ii. 23.

  UNITED States, rate of increase in, i. 131;
    influence of natural selection on the progress of, i. 179;
    change undergone by Europeans in the, i. 246.

  _Upupa epops_, sounds produced by the male, ii. 62.

  URANIIDÆ, coloration of the, i. 396.

  _Uria troile_, variety of, (= _U. lacrymans_), ii. 127.

  URODELA, ii. 24.

  _Urosticte Benjamini_, sexual differences in, ii. 151.

  USE and disuse of parts, effects of, i. 116;
    influence of, on the races of man, i. 247.

  UTERUS, reversion in the, i. 123;
    more or less divided, in the human subject, i. 123, 130;
    double, in the early progenitors of man, i. 206.


  V.

  VACCINATION, influence of, i. 168.

  VANCOUVER Island, Mr. Sproat on the savages of, i. 239;
    natives of, eradication of facial hair by the, ii. 348.

  _Vanellus cristatus_, wing tubercles of the male, ii. 48.

  _Vanessæ_, i. 387;
    resemblance of lower surface of, to bark of trees, i. 392.

  VARIABILITY, causes of, i. 111;
    in man, analogous to that in the lower animals, i. 112;
    of the races of man, i. 225;
    greater in men than in women, i. 275;
    period of, relation of the, to sexual selection, i. 296;
    of birds, ii. 124;
    of secondary sexual characters in man, ii. 320.

  VARIATION, correlated, i. 30;
    laws of, i. 113;
    in man, i. 185;
    analogous, i. 194;
    analogous, in plumage of birds, ii. 74.

  VARIATIONS, spontaneous, i. 131.

  VARIETIES, absence of, between two species, evidence of their
    distinctness, i. 215.

  VARIETY, an object in nature, ii. 230.

  VARIOLA, communicable between man and the lower animals, i. 11.

  VAURÉAL, i. 29.

  VEDDAHS, monogamous habits of, ii. 363.

  VEITCH, Mr., on the aversion of Japanese ladies to whiskers, ii. 349.

  VENGEANCE, instinct of, i. 89.

  VENUS Erycina, priestesses of, ii. 357.

  VERMES, i. 327.

  VERMIFORM appendage, i. 27.

  VERREAUX, M., on the attraction of numerous males by the female
    of an Australian _Bombyx_, i. 312.

  Vertebræ, caudal, number of, in macaques and baboons, i. 150;
    of monkeys, partly imbedded in the body, i. 151.

  VERTEBRATA, ii. 1;
    common origin of the, i. 203;
    most ancient progenitors of, i. 212;
    origin of the voice in air-breathing, ii. 331.

  _Vesicula prostatica_, the homologue of the uterus, i. 31, 208.

  VIBRISSÆ, represented by long hairs in the eyebrows, i. 25.

  _Vidua_, ii. 181.

  _Vidua axillaris_, i. 269.

  VILLERME, M., on the influence of plenty upon stature, i. 115.

  VINSON, Aug., on the male of _Epeira nigra_, i. 338.

  VIPER, difference of the sexes in the, ii. 29.

  VIREY, on the number of species of man, i. 226.

  VIRTUES, originally social only, i. 93;
    gradual appreciation of, i. 165.

  VISCERA, variability of, in man, i. 109.

  VITI Archipelago, population of the, i. 225.

  VLACOVICH, Prof., on the ischio-pubic muscle, i. 127.

  VOCAL music of birds, ii. 51.

  VOCAL organs of man, i. 58;
    of birds, i. 59; ii. 163;
    of frogs, ii. 28;
    of the Insessores, ii. 55;
    difference of, in the sexes of birds, ii. 56;
    primarily used in relation to the propagation of the species,
      ii. 330.

  VOGT, Carl, on the origin of species, i. 1;
    on the origin of man, i. 4;
    on the semilunar fold in man, i. 23;
    on the imitative faculties of microcephalous idiots, i. 57;
    on microcephalous idiots, i. 121;
    on skulls from Brazilian caves, i. 218;
    on the evolution of the races of man, i. 230;
    on the formation of the skull in women, ii. 317;
    on the Ainos and negroes, ii. 321;
    on the increased cranial difference of the sexes in man with
      race-development, ii. 329;
    on the obliquity of the eye in the Chinese and Japanese, ii. 344.

  VOICE in mammals, ii. 274;
    in monkeys and man, ii. 319;
    in man, ii. 330;
    origin of, in air-breathing vertebrates, ii. 331.

  VON BAER, definition of advancement in the organic scale, i. 211.

  VULPIAN, Prof., on the resemblance between the brains of man and
    of the higher apes, i. 11.

  VULTURES, selection of a mate by the female, ii. 116;
    colours of, ii. 229.


  W.

  WADERS, young of, ii. 217.

  WAGNER, R., on the occurrence of the diastema in a Kafir skull,
      i. 126;
    on the bronchi of the black stork, ii. 60.

  WAGTAIL, Ray’s, arrival of the male before the female, i. 260.

  WAGTAILS, Indian, young of, ii. 190.

  WAIST, proportions of, in soldiers and sailors, i. 117.

  WAITZ, Prof., on the number of species of man, i. 226;
    on the colour of Australian infants, ii. 318;
    on the beardlessness of negroes, ii. 321;
    on the fondness of mankind for ornaments, ii. 338;
    on the liability of negroes to tropical fevers after residence
      in a cold climate, i. 243;
    on negro ideas of female beauty, ii. 346;
    on Javanese and Cochin Chinese ideas of beauty, ii. 347.

  WALCKENAER and Gervais, on the Myriapoda, i. 340.

  WALDEYER, M., on the hermaphroditism of the vertebrate embryo, i. 207.

  WALES, North, numerical proportion of male and female births in,
    i. 301.

  WALKER, Alex., on the large size of the hands of labourers’ children,
    i. 117.

  WALKER, F., on sexual differences in the diptera, i. 348.

  WALLACE, Dr. A., on the prehensile use of the tarsi in male moths,
      i. 256;
    on the rearing of the Ailanthus silk-moth, i. 311;
    on breeding Lepidoptera, i. 311;
    proportion of sexes of _Bombyx cynthia_, _B. yamamai_,
      and _B. Pernyi_, reared by, i. 313;
    on the development of _Bombyx cynthia_ and _B. yamamai_, i. 346;
    on the pairing of _Bombyx cynthia_, i. 401;
    on the fertilisation of moths, i. 406.

  WALLACE, A. R., on the origin of man, i. 4;
    on the power of imitation in man, i. 39;
    on the use of missiles by the orang, i. 52;
    on the varying appreciation of truth among different tribes, i. 100;
    on the limits of natural selection in man, i. 137, 158;
    on the occurrence of remorse among savages, i. 165;
    on the effects of natural selection on civilised nations, i. 168;
    on the use of the convergence of the hair at the elbow in the orang,
      i. 193;
    on the contrast in the characters of the Malays and Papuans, i. 216;
    on the line of separation between the Papuans and Malays, i. 218;
    on the sexes of _Ornithoptera Croesus_, i. 310;
    on protective resemblances, i. 322;
    on the relative sizes of the sexes of insects, i. 346;
    on _Elaphomyia_, i. 349;
    on the Birds of Paradise, i. 269;
    on the pugnacity of the males of _Leptorhynchus angustatus_, i. 375;
    on sounds produced by _Euchirus longimanus_, i. 381;
    on the colours of _Diadema_, i. 388;
    on _Kallima_, i. 392;
    on the protective colouring of moths, i. 394;
    on bright coloration as protective in butterflies, i. 395;
    on variability in the Papilionidæ, i. 402;
    on male and female butterflies inhabiting different stations, i. 403;
    on the protective nature of the dull colouring of female butterflies,
      i. 403, 405, 414;
    on mimickry in butterflies, i. 412;
    on the mimickry of leaves by Phasmidæ, i. 414;
    on the bright colours of caterpillars, i. 416;
    on brightly-coloured fishes frequenting reefs, ii. 17;
    on the coral snakes, ii. 31;
    on _Paradisea apoda_, ii. 74, 78;
    on the display of plumage by male Birds of Paradise, ii. 88;
    on assemblies of Birds of Paradise, ii. 101;
    on the instability of the ocellated spots in _Hipparchia Janira_,
      ii. 132;
    on sexually limited inheritance, ii. 155;
    on the sexual coloration of birds, ii. 166, 196, 197, 200, 206;
    on the relation between the colours and nidification of birds,
      ii. 166, 171;
    on the coloration of the Cotingidæ, ii. 177;
    on the females of _Paradisea apoda_ and _papuana_, ii. 193;
    on the incubation of the cassowary, ii. 204;
    on protective coloration in birds, ii. 223;
    on the hair of the Papuans, ii. 340;
    on the Babirusa, ii. 264;
    on the markings of the tiger, ii. 302;
    on the beards of the Papuans, ii. 322;
    on the distribution of hair on the human body, ii. 375.

  WALRUS, development of the nictitating membrane in the, i. 23;
    tusks of the, ii. 241, 248;
    use of the tusks by the, ii. 257.

  WALSH, B. D., on the proportion of the sexes in _Papilio Turnus_,
      i. 310;
    on the Cynipidæ and Cecidomyidæ, i. 314;
    on the jaws of _Ammophila_, i. 342;
    on _Corydalis cornutus_, i. 342;
    on the prehensile organs of male insects, i. 342;
    on the antennæ of _Penthe_, i. 343;
    on the caudal appendages of dragon-flies, i. 344;
    on _Platyphyllum concavum_, i. 356;
    on the sexes of the Ephemeridæ, i. 361;
    on the difference of colour in the sexes of _Spectrum femoratum_,
      i. 361;
    on sexes of dragon-flies, i. 361;
    on the difference of the sexes in the Ichneumonidæ, i. 365;
    on the sexes of _Orsodacna atra_, i. 368;
    on the variation of the horns of the male _Phanæus carnifex_,
      i. 370;
    on the coloration of the species of _Anthocharis_, i. 393.

  WAPITI, battles of, ii. 240;
    traces of horns in the female, ii. 245;
    attacking a man, ii. 253;
    crest of the male, ii. 282;
    sexual difference in the colour of the, ii. 289.

  WARBLER, Hedge-, ii. 198;
    young of the, ii. 209.

  WARBLERS, Superb, nidification of, ii. 169.

  WARINESS, acquired by animals, i. 50.

  WARINGTON, R., on the habits of the sticklebacks, ii. 2, 20;
    on the brilliant colours of the male stickleback during
      the breeding season, ii. 14.

  WART-HOG, tusks and pads of the, ii. 265.

  WATCHMAKERS, short-sighted, i. 118.

  WATER-HEN, ii. 40.

  WATERHOUSE, C. O., on blind beetles, i. 367;
    on difference of colour in the sexes of beetles, i. 367.

  WATERHOUSE, G. R., on the voice of _Hylobates agilis_, ii. 332.

  WATER-OUZEL, autumn song of the, ii. 54.

  WATERTON, C., on the pairing of a Canada goose with a Bernicle gander,
      ii. 114;
    on hares fighting, ii. 239;
    on the Bell-bird, ii. 79.

  WATTLES, disadvantageous to male birds in fighting, ii. 98.

  WEALTH, influence of, i. 169.

  WEALE, J. Mansel, on a South African caterpillar, i. 416.

  WEAPONS, employed by monkeys, i. 51;
    use of, i. 137;
    offensive, of males, i. 257;
    of mammals, ii. 241 _et seq._

  WEAVER-BIRD, ii. 54.

  WEAVER-BIRDS, rattling of the wings of, ii. 62;
    assemblies of, ii. 101.

  WEBB, Dr., on the wisdom teeth, i. 25.

  WEDGWOOD, Hensleigh, on the origin of language, i. 56.

  WEEVILS, sexual difference in length of snout in some, i. 255.

  WEIR, Harrison, on the numerical proportion of the sexes in pigs
      and rabbits, i. 305;
    on the sexes of young pigeons, i. 306;
    on the songs of birds, ii. 52;
    on pigeons, ii. 109;
    on the dislike of blue pigeons to other coloured varieties, ii. 118;
    on the desertion of their mates by female pigeons, ii. 119.

  WEIR, J. Jenner, on the nightingale and blackcap, i. 259;
    on the relative sexual maturity of male birds, i. 261;
    on female pigeons deserting a feeble mate, i. 262;
    on three starlings frequenting the same nest, i. 269;
    on the proportion of the sexes in _Machetes pugnax_ and other birds,
      i. 306, 307;
    on the coloration of the _Triphænæ_, i. 395;
    on the rejection of certain caterpillars by birds, i. 417;
    on sexual differences of the beak in the goldfinch, ii. 40;
    on a piping bullfinch, ii. 52;
    on the object of the nightingale’s song, ii. 52;
    on song-birds, ii. 53;
    on the pugnacity of male fine-plumaged birds, ii. 93;
    on the courtship of birds, ii. 94;
    on the finding of new mates by Peregrine-falcons and Kestrels,
      ii. 104;
    on the bullfinch and starling, ii. 105;
    on the cause of birds remaining unpaired, ii. 107;
    on starlings and parrots living in triplets, ii. 107;
    on recognition of colour by birds, ii. 110;
    on hybrid birds, ii. 113;
    on the selection of a greenfinch by a female canary, ii. 115;
    on a case of rivalry of female bullfinches, ii. 121;
    on the maturity of the Golden pheasant, ii. 213.

  WEISBACH, Dr., measurement of men of different races, i. 216;
    on the greater variability of men than of women, i. 275;
    on the relative proportions of the body in the sexes of different
      races of man, ii. 320.

  WELCKER, M., on Brachycephaly and Dolichocephaly, i. 148;
    on sexual differences in the skull in man, ii. 317.

  WELLS, Dr., on the immunity of coloured races from certain poisons,
    i. 243.

  WESTRING, on the stridulation of _Reduvius personatus_, i. 350;
    on the stridulating organs of the Coleoptera, i. 382;
    on sounds produced by _Cychrus_, i. 382;
    on the stridulation of males of _Theridion_, i. 339;
    on the stridulation of beetles, i. 379;
    on the stridulation of _Omaloplia brunnea_, i. 381.

  WESTPHALIA, greater proportion of female illegitimate children in,
    i. 301.

  WESTROPP, H. M., on the prevalence of certain forms of ornamentation,
    i. 233.

  WESTWOOD, J. O., on the classification of the Hymenoptera, i. 188;
    on the Culicidæ and Tabanidæ, i. 254;
    on a Hymenopterous parasite with a sedentary male, i. 272;
    on the proportions of the sexes in _Lucanus cervus_ and _Siagonium_,
      i. 313;
    on the absence of ocelli in female mutillidæ, i. 341;
    on the jaws of _Ammophila_, i. 342;
    on the copulation of insects of distinct species, i. 342;
    on the male of _Crabro cribrarius_, i. 343;
    on the pugnacity of male _Tipulæ_ i. 349;
    on the stridulation of _Pirates stridulus_, i. 350;
    on the Cicadæ, i. 351;
    on the stridulating organs of the crickets, i. 354;
    on _Pneumora_, i. 357;
    on _Ephippiger vitium_, i. 355, 358;
    on the pugnacity of the Mantides, i. 360;
    on _Platyblemnus_, i. 361;
    on difference in the sexes of the Agrionidæ, i. 362;
    on the pugnacity of the males of a species of Tenthredinæ, i. 364;
    on the pugnacity of the male stag-beetle, i. 375;
    on _Bledius taurus_ and _Siagonium_, i. 375;
    on lamellicorn beetles, i. 378;
    on the coloration of _Lithosia_, i. 396.

  WHALE, Sperm-, battles of male, ii. 240.

  WHALES, nakedness of, i. 148.

  WHATELY, Archb., language not peculiar to man, i. 53;
    on the primitive civilisation of man, i. 181.

  WHEWELL, Prof., on maternal affection, i. 40.

  WHISKERS, in monkeys, i. 192.

  WHITE, Gilbert, on the proportion of the sexes in the partridge,
      i. 306;
    on the house-cricket, i. 352;
    on the object of the song of birds, ii. 52;
    on the finding of new mates by white owls, ii. 105;
    on spring coveys of male partridges, ii. 107.

  WHITENESS, a sexual ornament in some birds, ii. 232;
    of mammals inhabiting snowy countries, ii. 298.

  WHITE-THROAT, aerial love-dance of the male, ii. 68.

  WIDOW-BIRD, polygamous, i. 269;
    breeding plumage of the male, ii. 84, 97;
    female, rejecting the unadorned male, ii. 120.

  WIDOWS and widowers, mortality of, i. 176.

  WIGEON, pairing with a pintail duck, ii. 114.

  WILCKENS, Dr., on the modification of domestic animals in mountainous
      regions, i. 120;
    on a numerical relation between the hairs and excretory pores
      in sheep, i. 248.

  WILDER, Dr. Burt, on the greater frequency of supernumerary digits
    in men than in women, i. 276.

  WILLIAMS, on the marriage-customs of the Fijians, ii. 374.

  WILSON, Dr., on the conical heads of the natives of North-Western
      America, ii. 351;
    on the Fijians, ii. 352;
    on the persistence of the fashion of compressing the skull, ii. 353.

  WING-SPURS, ii. 162.

  WINGS, differences of, in the two sexes of butterflies
      and Hymenoptera, i. 345;
    play of, in the courtship of birds, ii. 95.

  WINTER, change of colour of mammals in, ii. 298.

  WITCHCRAFT, i. 68.

  WIVES, traces of the forcible capture of, i. 182.

  WOLF, winter change of the, ii. 298.

  WOLFF, on the variability of the viscera in man, i. 109.

  WOLLASTON, T. V., on _Eurygnathus_, i. 344;
    on musical curculionidæ, i. 378;
    on the stridulation of _Acalles_, i. 384.

  WOLVES learning to bark from dogs, i. 44;
    hunting in packs, i. 75.

  WOLVES, black, ii. 294.

  WOMBAT, black varieties of the, ii. 294.

  WOMEN distinguished from men by male monkeys, i. 13;
    preponderance of, in numbers, i. 302;
    effects of selection of, in accordance with different standards
      of beauty, ii. 355;
    practice of capturing, ii. 360, 364;
    early betrothals and slavery of, ii. 366;
    selection of, for beauty, ii. 372;
    freedom of selection by, in savage tribes, ii. 372.

  WONDER, manifestations of, by animals, i. 42.

  WONFOR, Mr., on sexual peculiarities in the wings of butterflies,
    i. 345.

  WOOLNER, Mr., observations on the ear in man, i. 22.

  WOOD, J., on muscular variations in man, i. 109, 128, 129;
    on the greater variability of the muscles in men than in women,
      i. 275.

  WOOD, T. W., on the colouring of the orange-tip butterfly, i. 394;
    on the habits of the Saturniidæ, i. 398;
    on the habits of _Menura Alberti_, ii. 56;
    on _Tetrao cupido_, ii. 56;
    on the display of plumage by male pheasants, ii. 89;
    on the ocellated spots of the Argus pheasant, ii. 144;
    on the habits of the female Cassowary, ii. 204.

  WOODCOCK, coloration of the, ii. 226.

  WOODPECKER, selection of a mate by the female, ii. 116.

  WOODPECKERS, ii. 56;
    tapping of, ii. 62;
    colours and nidification of the, ii. 171, 174, 223;
    characters of young, ii. 185, 199, 209.

  WORMALD, Mr., on the coloration of _Hypopyra_, i. 397.

  WOUNDS, healing of, i. 13.

  WREN, ii. 198;
    young of the, ii. 209.

  WRIGHT, C. A., on the young of _Orocetes_ and _Petrocincla_, ii. 220.

  WRIGHT, Chauncey, on correlative acquisition, ii. 335;
    on the enlargement of the brain in man, ii. 391.

  WRIGHT, Mr., on the Scotch deerhound, ii. 261;
    on sexual preference in dogs, ii. 271;
    on the rejection of a horse by a mare, ii. 272.

  WRIGHT, W. von, on the protective plumage of the Ptarmigan, ii. 81.

  WRITING, i. 182.

  WYMAN, Prof., on the prolongation of the coccyx in the human embryo,
      i. 16;
    on the condition of the great toe in the human embryo, i. 17;
    on variation in the skulls of the natives of the Sandwich Islands,
      i. 108;
    on the hatching of the eggs in the mouths and branchial cavities
      of male fishes, i. 210, ii. 20.


  X.

  XENARCHUS, on the Cicadæ, i. 350.

  _Xenorhynchus_, sexual difference in the colour of the eyes in,
    ii. 129.

  _Xiphophorus Hellerii_, peculiar anal fin of the male, ii. 9, 10.

  _Xylocopa_, difference of the sexes in, i. 366.


  Y.

  YARRELL, W., on the habits of the Cyprinidæ, i. 309;
    on _Raia clavata_, ii. 2;
    on the characters of the male salmon during the breeding season,
      ii. 4, 14;
    on the characters of the rays, ii. 6;
    on the gemmeous dragonet, ii. 8;
    on the spawning of the salmon, ii. 19;
    on the incubation of the Lophobranchii, ii. 21;
    on rivalry in song-birds, ii. 53;
    on the trachea of the swan, ii. 60;
    on the moulting of the anatidæ, ii. 85;
    on an instance of reasoning in a gull, ii. 108;
    on the young of the waders, ii. 217.

  YELLOW fever, immunity of negroes and mulattoes from, i. 243.

  YOUATT, Mr., on the development of the horns in cattle, i. 284.

  YURA-CARAS, their notions of beauty, ii. 347.


  Z.

  ZEBRA, rejection of an ass by a female, ii. 295;
    stripes of the, ii. 302.

  ZEBUS, humps of, i. 284.

  ZIGZAGS, prevalence of, as ornaments, i. 233.

  ZINCKE, Mr., on European emigration to America, i. 179.

  _Zootoca vivipara_, sexual difference in the colour of, ii. 36.

  ZYGÆNIDÆ, coloration of the, i. 396.


THE END.




LONDON:

PRINTED BY WILLIAM CLOWES AND SONS, DUKE STREET, STAMFORD STREET,
AND CHARING CROSS.


50A, ALBEMARLE STREET, LONDON
_January, 1871._


MR. MURRAY’S

LIST OF STANDARD WORKS.


  AIDS TO FAITH; a Series of Theological Essays. By various Writers.
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  _Miracles._—DEAN MANSEL.

  _Evidences of Christianity._—BISHOP OF KILLALOE.

  _Prophecy—and the Mosaic Record of Creation._—Rev. Dr. M’CAUL.

  _Ideology and Subscription._—Canon F. C. COOK.

  _The Pentateuch._—Rev. GEORGE RAWLINSON.

  _Inspiration._—BISHOP OF ELY.

  _Death of Christ._—ARCHBISHOP OF YORK.

  _Scripture and its Interpretation._—BISHOP OF GLOUCESTER AND BRISTOL.


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