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DARWIN, AND AFTER DARWIN

II

Post-Darwinian Questions

Heredity and Utility

       *       *       *       *       *


BY THE SAME AUTHOR.


    DARWIN AND AFTER DARWIN. An Exposition of the Darwinian Theory and a
        Discussion of Post-Darwinian Questions.
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[Illustration: Frontispiece]


DARWIN, AND AFTER DARWIN

AN EXPOSITION OF THE DARWINIAN THEORY
AND A DISCUSSION OF POST-DARWINIAN QUESTIONS

by the Late

GEORGE JOHN ROMANES, M.A., LL.D., F.R.S.
Honorary Fellow of Gonville and Caius College, Cambridge

II

Post-Darwinian Questions
Heredity and Utility

FOURTH EDITION







Chicago London
The Open Court Publishing Company
1916

Chapter 1 Copyrighted by
The Open Court Publishing Co.
Chicago, Ill., 1895

Printed in the
United States of America




PREFACE


As its sub-title announces, the present volume is mainly devoted to a
consideration of those Post-Darwinian Theories which involve fundamental
questions of Heredity and Utility.

As regards Heredity, I have restricted the discussion almost exclusively
to Professor Weismann's views, partly because he is at present by far
the most important writer upon this subject, and partly because his
views with regard to it raise with most distinctness the issue which
lies at the base of all Post-Darwinian speculation touching this
subject--the issue as to the inheritance or non-inheritance of acquired
characters.

My examination of the Utility question may well seem to the general
reader needlessly elaborate; for to such a reader it can scarcely fail
to appear that the doctrine which I am assailing has been broken to
fragments long before the criticism has drawn to a close. But from my
previous experience of the hardness with which this fallacious doctrine
dies, I do not deem it safe to allow even one fragment of it to remain,
lest, hydra-like, it should re-develop into its former proportions. And
I can scarcely think that naturalists who know the growing prevalence of
the doctrine, and who may have followed the issues of previous
discussions with regard to it, will accuse me of being more over-zealous
in my attempt to make a full end thereof.

One more remark. It is a misfortune attending the aim and scope of Part
II that they bring me into frequent discord with one or other of the
most eminent of Post-Darwinian writers--especially with Mr. Wallace. But
such is the case only because the subject-matter of this volume is
avowedly restricted to debateable topics, and because I choose those
naturalists who are deservedly held in most esteem to act spokesmen on
behalf of such Post-Darwinian views as appear to me doubtful or
erroneous. Obviously, however, differences of opinion on particular
points ought not to be taken as implying any failure on my part to
recognize the general scientific authority of these men, or any
inability to appreciate their labours in the varied fields of Biology.

G. J. R.
CHRIST CHURCH, OXFORD.




NOTE

Some time before his death Mr. Romanes decided to publish those sections
of his work which deal with Heredity and Utility, as a separate volume,
leaving Isolation and Physiological Selection for the third and
concluding part of _Darwin, and after Darwin_.

Most of the matter contained in this part was already in type, but was
not finally corrected for the press. The alterations made therein are
for the most part verbal.

Chapter IV was type-written; in it, too, no alterations of any moment
have been made.

For Chapters V and VI there were notes and isolated paragraphs not yet
arranged. I had promised during his life to write for Mr. Romanes
Chapter V on the basis of these notes, extending it in such ways as
seemed to be desirable. In that case it would have been revised and
amended by the author and received his final sanction. Death annulled
this friendly compact; and since, had I written the chapter myself, it
could not receive that imprimatur which would have given its chief
value, I have decided to arrange the material that passed into my hands
without adding anything of importance thereto. The substance of Chapters
V and VI is therefore entirely the author's: even the phraseology is
his; the arrangement only is by another hand.

Such parts of the Preface as more particularly refer to Isolation and
Physiological Selection are reserved for publication in Part III. A year
or more must elapse before that part will be ready for publication.

Mr. F. Howard Collins has, as a kindly tribute to the memory of the
author, read through the proofs. Messrs. F. Darwin, F. Galton, H.
Seebohm, and others, have rendered incidental assistance. After much
search I am unable to give the references to one or two passages.

I have allowed a too flattering reference to myself to stand, in
accordance with a particular injunction of Mr. Romanes given shortly
before that sad day on which he died, leaving many to mourn the loss of
a personal friend most bright, lovable, and generous-hearted, and
thousands to regret that the hand which had written so much for them
would write for them no more.

C. LL. M.

UNIVERSITY COLLEGE, BRISTOL,
_April, 1894_.




CONTENTS

                                                                    PAGE
CHAPTER I.
INTRODUCTORY: THE DARWINISM OF DARWIN AND OF THE
POST-DARWINIAN SCHOOLS                                                 1

CHAPTER II.
CHARACTERS AS HEREDITARY AND ACQUIRED (_Preliminary_)                 39

CHAPTER III.
CHARACTERS AS HEREDITARY AND ACQUIRED (_Continued_)
    A. _Indirect evidence in favour of the Inheritance of Acquired
        Characters_                                                   60
    B. _Inherited effects of Use and of Disuse_                       95

CHAPTER IV.
CHARACTERS AS HEREDITARY AND ACQUIRED (_Continued_)
    C. _Experimental evidence in favour of the Inheritance of Acquired
        Characters_                                                  103

CHAPTER V.
CHARACTERS AS HEREDITARY AND ACQUIRED (_Continued_)
    A. and B. _Direct and Indirect Evidence in favour of the
        Non-inheritance of Acquired Characters_                      133

    C. _Experimental Evidence as to the Non-inheritance of Acquired
        Characters_                                                  142

CHAPTER VI.
CHARACTERS AS HEREDITARY AND ACQUIRED (_Conclusion_)                 150

CHAPTER VII.
CHARACTERS AS ADAPTIVE AND SPECIFIC                                  159

CHAPTER VIII.
CHARACTERS AS ADAPTIVE AND SPECIFIC (_Continued_)
    I. _Climate_                                                     200
    II. _Food_                                                       217
    III. _Sexual Selection_                                          219
    IV. _Isolation_                                                  223
    V. _Laws of Growth_                                              226

CHAPTER IX.
CHARACTERS AS ADAPTIVE AND SPECIFIC (_Continued_)                    228

CHAPTER X.
CHARACTERS AS ADAPTIVE AND SPECIFIC (_Concluded_)                    251
    SUMMARY                                                          274

APPENDIX I. ON PANMIXIA                                              291

APPENDIX II. ON CHARACTERS AS ADAPTIVE AND SPECIFIC                  307

NOTE A TO PAGE 57                                                    333

NOTE B TO PAGE 89                                                    337




LIST OF ILLUSTRATIONS

                                                                    PAGE

Portrait of George John Romanes                           _Frontispiece_

Diagram of Prof. Weismann's Theories                                  43

FIG. 1. Guinea pigs, showing gangrene of ears due to injury of
           restiform bodies                                          118

FIG. 2. Old Irish Pig (after Richardson)                             188

FIG. 3. Skulls of Niata Ox and of Wild White Ox                      192

FIG. 4. Lower teeth of Orang (after Tomes)                           261




CHAPTER I.

INTRODUCTORY: THE DARWINISM OF DARWIN, AND OF THE POST-DARWINIAN
SCHOOLS.


It is desirable to open this volume of the treatise on _Darwin and after
Darwin_ by taking a brief survey of the general theory of descent,
first, as this was held by Darwin himself, and next, as it is now held
by the several divergent schools of thought which have arisen since
Darwin's death.

The most important of the questions in debate is one which I have
already had occasion to mention, while dealing, in historical order,
with the objections that were brought against the theory of natural
selection during the life-time of Darwin[1]. Here, however, we must
consider it somewhat more in detail, and justify by quotation what was
previously said regarding the very definite nature of his utterances
upon the matter. This question is whether natural selection has been the
sole, or but the main, cause of organic evolution.

    [1] Part I, pp. 253-256.

Must we regard survival of the fittest as the one and only principle
which has been concerned in the progressive modification of living
forms, or are we to suppose that this great and leading principle has
been assisted by other and subordinate principles, without the
co-operation of which the results, as presented in the animal and
vegetable kingdoms, could not have been effected? Now Darwin's answer to
this question was distinct and unequivocal. He stoutly resisted the
doctrine that natural selection was to be regarded as the only cause of
organic evolution. On the other hand, this opinion was--and still
continues to be--persistently maintained by Mr. Wallace; and it
constitutes the source of all the differences between his views and
those of Darwin. Moreover, up to the time of Darwin's death, Mr. Wallace
was absolutely alone in maintaining this opinion: the whole body of
scientific thought throughout the world being against him; for it was
deemed improbable that, in the enormously complex and endlessly varied
processes of organic evolution, only a single principle should be
everywhere and exclusively concerned[2]. But since Darwin's death there
has been a great revolution of biological thought in favour of Mr.
Wallace's opinion. And the reason for this revolution has been, that his
doctrine of natural selection as the sole cause of organic evolution has
received the corroborative support of Professor Weismann's theory of
heredity--which has been more or less cordially embraced by a certain
section of evolutionists, and which appears to carry the doctrine in
question as a logical corollary, so far, at all events, as adaptive
structures are concerned.

    [2] _Contributions to the Theory of Natural Selection_, p. 47.

Now in this opening chapter we shall have to do merely with a setting
forth of Darwin's opinion: we are not considering how far that opinion
ought to be regarded as having been in any measure displaced by the
results of more recent progress. Such, then, being the only matter which
here concerns us, I will supply a few brief quotations, to show how
unequivocally Darwin has stated his views. First, we may take what he
says upon the "Lamarckian factors[3];" and next we may consider what he
says with regard to other factors, or, in general, upon natural
selection not being the sole cause of organic evolution.

    [3] So far as we shall be concerned with them throughout this
        treatise, the "Lamarckian factors" consist in the supposed
        transmission of acquired characters, whether the latter be due
        to the direct influence of external conditions of life on the
        one hand, or to the inherited effects of use and disuse on the
        other. For the phrase "inherited effects of use and disuse," I
        shall frequently employ the term "use-inheritance," which has
        been coined by Mr. Platt Ball as a more convenient expression.

     "Changed habits produce an inherited effect, as in the period of
     the flowering of plants when transported from one climate to
     another. With animals the increased use or disuse of parts has had
     a more marked influence[4]."

    [4] _Origin of Species_, 6th ed. p. 8.

     "There can be no doubt, from the facts given in this chapter, that
     extremely slight changes in the conditions of life sometimes,
     probably often, act in a definite manner on our domesticated
     productions; and, as the action of changed conditions in causing
     indefinite variability is accumulative, so it may be with their
     definite action. Hence considerable and definite modifications of
     structure probably follow from altered conditions acting during
     long series of generations[5]."

    [5] _Variation_ &c. 2nd ed. ii. p. 280.

     "How, again, can we explain the inherited effects of the use and
     disuse of particular organs? The domesticated duck flies less and
     walks more than the wild duck, and its limb bones have become
     diminished and increased in a corresponding manner in comparison
     with those of the wild duck. A horse is trained to certain paces,
     and the colt inherits similar consensual movements. The
     domesticated rabbit becomes tame from close confinement; the dog,
     intelligent from associating with man; the retriever is taught to
     fetch and carry; and these mental endowments and bodily powers are
     all inherited. Nothing in the whole circuit of physiology is more
     wonderful. How can the use or disuse of a particular limb or of the
     brain affect a small aggregate of reproductive cells, seated in a
     distant part of the body, in such a manner that the being developed
     from these cells inherits the characters of either one or both
     parents?... In the chapters devoted to inheritance, it was shown
     that a multitude of newly acquired characters, whether injurious or
     beneficial, whether of the lowest or highest vital importance, are
     often faithfully transmitted[6]."

    [6] _Variation_ &c. ii. p. 367.

     "When discussing special cases, Mr. Mivart passes over the effects
     of the increased use and disuse of parts, which I have always
     maintained to be highly important, and have treated in my
     'Variation under Domestication' at greater length than, as I
     believe, any other writer[7]."

    [7] _Origin of Species_, p. 176.

So much for the matured opinion of Darwin touching the validity of the
theory of use-inheritance. Turning now to his opinion on the question
whether or not there are yet any further factors concerned in the
process of organic evolution, I think it will be sufficient to quote a
single passage from the _Origin of Species_. The first paragraph of the
"Conclusion" is devoted to a _résumé_ of his views upon this matter, and
consists of the following most emphatic words.

     "I have now recapitulated the facts and considerations which have
     thoroughly convinced me that species have been modified, during a
     long course of descent. This has been effected chiefly through the
     natural selection of numerous successive, slight, favourable
     variations; aided in an important manner by the inherited effects
     of the use and disuse of parts; and in an unimportant manner, that
     is in relation to adaptive structures, whether past or present, by
     the direct action of external conditions, and by variations which
     seem to us in our ignorance to arise spontaneously. It appears that
     I formerly underrated the frequency and value of these latter forms
     of variation, as leading to permanent modifications of structure
     independently of natural selection. But as my conclusions have
     lately been much misrepresented, and it has been stated that I
     attribute the modification of species exclusively to natural
     selection, I may be permitted to remark that in the first edition
     of this work, and subsequently, I placed in a most conspicuous
     position--namely, at the close of the Introduction--the following
     words: 'I am convinced that natural selection has been the main,
     but not the exclusive means of modification.' This has been of no
     avail. Great is the power of steady misrepresentation; but the
     history of science shows that fortunately this power does not long
     endure."

In the whole range of Darwin's writings there cannot be found a passage
so strongly worded as this: it presents the only note of bitterness in
all the thousands of pages which he has published. Therefore I do not
think it is necessary to supply any further quotations for the purpose
of proving the state of his opinion upon the point in question. But, be
it carefully noted, from this great or radical difference of opinion
between the joint originators of the theory of natural selection, all
their other differences of opinion arise; and seeing that since the
death of Darwin a large number of naturalists have gone over to the side
of Wallace, it seems desirable here to state categorically what these
other or sequent points of difference are. Without at present discussing
them, therefore, I will merely set them out in a tabular form, in order
that a clear perception may be gained of their logical connexion with
this primary point of difference.

     |_The Theory of Natural      |_The theory of Natural      |
     |Selection according to      |Selection according to      |
     |Darwin._                    |Wallace._                   |
     |                            |                            |
     |Natural Selection has been  |Natural Selection has been  |
     |the main means of           |the sole means of           |
     |modification, not excepting |modification, excepting in  |
     |the case of Man.            |the case of Man.            |
     |                            |                            |
     |(_a_) Therefore it is a     |(_a_) Therefore it is       |
     |question of evidence        |antecedently impossible     |
     |whether the Lamarckian      |that the Lamarckian factors |
     |factors have co-operated.   |can have co-operated.       |
     |                            |                            |
     |(_b_) Neither all species,  |(_b_) Not only all species, |
     |nor, _a fortiori_, all      |but all specific            |
     |specific characters, have   |characters, must            |
     |been due to natural         |necessarily have been due   |
     |selection.                  |to natural selection.       |
     |                            |                            |
     |(_c_) Thus the principle of |(_c_) Thus the principle of |
     |Utility is not of universal |Utility must necessarily be |
     |application, even where     |of universal application,   |
     |species are concerned.      |where species are           |
     |                            |concerned.                  |
     |                            |                            |
     |(_d_) Thus, also, the       |(_d_) Thus, also, the       |
     |suggestion as to Sexual     |suggestion as to Sexual     |
     |Selection, or any other     |Selection, or of any other  |
     |supplementary cause of      |supplementary cause of      |
     |modification, may be        |modification, must be ruled |
     |entertained; and, as in the |out; and, as in the case of |
     |case of the Lamarckian      |the Lamarckian factors,     |
     |factors, it is a question   |their co-operation deemed   |
     |of evidence whether, or how |impossible.                 |
     |far, they have co-operated. |                            |
     |                            |                            |
     |(_e_) No detriment arises   |(_e_) The possibility--and, |
     |to the theory of natural    |_a fortiori_ the            |
     |selection as a theory of    |probability--of any         |
     |the origin of species by    |supplementary factors       |
     |entertaining the            |cannot be entertained       |
     |possibility, or the         |without serious detriment   |
     |probability, of             |to the theory of natural    |
     |supplementary factors.      |selection, as a theory of   |
     |                            |the origin of species.      |
     |                            |                            |
     |(_f_) Cross-sterility in    |(_f_) Cross-sterility in    |
     |species cannot possibly be  |species is probably due to  |
     |due to natural selection.   |natural selection[8].       |

    [8] This, to the best of my judgement, is the fairest extract that I
        can give of Mr. Wallace's most recently published opinions on
        the points in question. [In particular as regards (_a_) see
        _Darwinism_ pp. 435-6.] But with regard to some of them, his
        expression of opinion is not always consistent, as we shall find
        in detail later on. Besides, I am here taking Mr. Wallace as
        representative of the Neo-Darwinian school, one or other
        prominent member of which has given emphatic expression to each
        of the above propositions.

As it will be my endeavour in the ensuing chapters to consider the
rights and the wrongs of these antithetical propositions, I may reserve
further quotations from Darwin's works, which will show that the above
is a correct epitome of his views as contrasted with those of Wallace
and the Neo-Darwinian school of Weismann. But here, where the object is
merely a statement of Darwin's theory touching the points in which it
differs from those of Wallace and Weismann, it will be sufficient to set
forth these points of difference in another and somewhat fuller form. So
far then as we are at present concerned, the following are the matters
of doctrine which have been clearly, emphatically, repeatedly, and
uniformly expressed throughout the whole range of Darwin's writings.

1. That natural selection has been the main means of modification.

2. That, nevertheless, it has not been the only means; but has been
supplemented or assisted by the co-operation of other causes.

3. That the most "important" of these other causes has been the
inheritance of functionally-produced modifications (use-inheritance);
but this only because the transmission of such modifications to progeny
must always have had immediate reference to _adaptive_ ends, as
distinguished from merely useless change.

4. That there are sundry other causes which lead to merely useless
change--in particular, "the direct action of external conditions, and
variations which seem to us in our ignorance to arise spontaneously."

5. Hence, that the "principle of utility," far from being of universal
occurrence in the sphere of animate nature, is only of what may be
termed highly general occurrence; and, therefore, that certain other
advocates of the theory of natural selection were mistaken in
representing the universality of this principle as following by way of
necessary consequence from that theory.

6. Cross-sterility in species cannot possibly be due to natural
selection; but everywhere arises as a result of some physiological
change having exclusive reference to the sexual system--a change which
is probably everywhere due to the same cause, although what this cause
could be Darwin was confessedly unable to suggest.

Such, then, was the theory of evolution as held by Darwin, so far as the
points at present before us are concerned. And, it may now be added,
that the longer he lived, and the more he pondered these points, the
less exclusive was the _rôle_ which he assigned to natural selection,
and the more importance did he attribute to the supplementary factors
above named. This admits of being easily demonstrated by comparing
successive editions of his works; a method adopted by Mr. Herbert
Spencer in his essay on the _Factors of Organic Evolution_.

My object in thus clearly defining Darwin's attitude regarding these
sundry points is twofold.

In the first place, with regard to merely historical accuracy, it
appears to me undesirable that naturalists should endeavour to hide
certain parts of Darwin's teaching, and give undue prominence to others.
In the second place, it appears to me still more undesirable that this
should be done--as it usually is done--for the purpose of making it
appear that Darwin's teaching did not really differ very much from that
of Wallace and Weismann on the important points in question. I myself
believe that Darwin's judgement with regard to all these points will
eventually prove more sound and accurate than that of any of the recent
would-be improvers upon his system; but even apart from this opinion of
my own it is undesirable that Darwin's views should be misrepresented,
whether the misrepresentation be due to any unfavourable bias against
one side of his teaching, or to sheer carelessness in the reading of his
books. Yet the new school of evolutionists, to which allusion has now so
frequently been made, speak of their own modifications of Darwin's
teaching as "pure Darwinism," in contradistinction to what they call
"Lamarckism." In other words, they represent the principles of
"Darwinism" as standing in some kind of opposition to those of
"Lamarckism": the Darwinian principle of natural selection, they think,
is in itself enough to account for all the facts of adaptation in
organic nature. Therefore they are eager to dispense with the Lamarckian
principle of the inherited effects of use and disuse, together with the
direct influence of external conditions of life, and all or any other
causes of modification which either have been, or in the future may
possibly be, suggested. Now, of course, there is no reason why any one
should not hold these or any other opinions to which his own
independent study of natural science may lead him; but it appears to me
that there is the very strongest reason why any one who deviates from
the carefully formed opinions of such a man as Darwin, should above all
things be careful to be absolutely fair in his representations of them;
he should be scrupulously jealous, so to speak, of not letting it appear
that he is unjustifiably throwing over his own opinions the authority of
Darwin's name.

But in the present case, as we have seen, not only do the Neo-Darwinians
strain the teachings of Darwin; they positively reverse those
teachings--representing as anti-Darwinian the whole of one side of
Darwin's system, and calling those who continue to accept that system in
its entirety by the name "Lamarckians." I know it is sometimes said by
members of this school, that in his utilization of Lamarckian principles
as accessory to his own, Darwin was actuated by motives of "generosity."
But a more preposterous suggestion could not well be made. We may
fearlessly challenge any one who speaks or writes in such a way, to show
any other instance where Darwin's great generosity of disposition had
the effect of influencing by one hair's breadth his still greater
loyalty to truth. Moreover, and with special regard to this particular
case, I would point out that in no one of his many allusions to, and
often lengthy discussions of, these so-called Lamarckian principles,
does he ever once introduce the name of Lamarck; while, on the other
hand, in the only places where he does so--whether in his books or in
his now published letters--he does so in order to express an almost
contemptuous dissatisfaction, and a total absence of obligation. Hence,
having regard to the "generosity" with which he always acknowledged
obligations, there can be no reasonable doubt that Darwin was not in the
smallest degree influenced by the speculative writings of Lamarck; or
that, even if Lamarck had never lived, the _Origin of Species_ would
have differed in any single particular from the form in which it now
stands. Finally, it must not be forgotten that Darwin's acceptance of
the theory of use-inheritance was vitally essential to his theory of
Pangenesis--that "beloved child" over which he had "thought so much as
to have lost all power of judging it[9]."

    [9] _Life and Letters_, vol. iii. pp. 72 and 75.

What has just been said touching the relations between Darwin's theory
and that of Lamarck, applies with equal force to the relations between
Darwin's theory and any other theory appertaining to evolution which has
already been, or may hereafter be propounded. Yet so greatly have some
of the Neo-Darwinians misunderstood the teachings of Darwin, that they
represent as "Darwinian heresy" any suggestions in the way of factors
"supplementary to," or "co-operative with" natural selection. Of course,
if these naturalists were to avow themselves followers of Wallace,
instead of followers of Darwin, they would be perfectly justified in
repudiating any such suggestions as, _ipso facto_ heretical. But, as we
have now seen, through all his life Darwin differed from Wallace with
regard to this very point; and therefore, unlike Wallace, he was always
ready to entertain "additional suggestions" regarding the causes of
organic evolution--several of which, indeed, he himself supplied. Hence
we arrive at this curious state of matters. Those biologists who of late
years have been led by Weismann to adopt the opinions of Wallace,
represent as anti-Darwinian the opinions of other biologists who still
adhere to the unadulterated doctrines of Darwin. Weismann's _Essays on
Heredity_ (which argue that natural selection is the only possible cause
of adaptive modification) and Wallace's work on _Darwinism_ (which in
all the respects where any charge of "heresy" is concerned directly
contradicts the doctrine of Darwin)--these are the writings which are
now habitually represented by the Neo-Darwinians as setting forth the
views of Darwin in their "pure" form. The result is that, both in
conversation and in the press, we habitually meet with complete
inversions of the truth, which show the state of confusion into which a
very simple matter has been wrought by the eagerness of certain
naturalists to identify the views of Darwin with those of Wallace and
Weismann. But we may easily escape this confusion, if we remember that
wherever in the writings of these naturalists there occur such phrases
as "pure Darwinism" we are to understand pure _Wallaceism_, or the pure
theory of natural selection to the exclusion of any supplementary
theory. Therefore it is that for the sake of clearness I coined, several
years ago, the terms "Neo-Darwinian" and "Ultra-Darwinian" whereby to
designate the school in question.

       *       *       *       *       *

So much, then, for the Darwinism of Darwin, as contrasted with the
Darwinism of Wallace, or, what is the same thing, of the Neo-Darwinian
school of Weismann. Next we may turn, by way of antithesis, to the
so-called "Neo-Lamarckian" school of the United States. For, by a
curious irony of fate, while the Neo-Darwinian school is in Europe
seeking to out-Darwin Darwin by assigning an exclusive prerogative to
natural selection in both kingdoms of animate nature, the Neo-Lamarckian
school is in America endeavouring to reform Darwinism in precisely the
opposite direction--viz. by transferring the sovereignty from natural
selection to the principles of Lamarck. Without denying to natural
selection a more or less important part in the process of organic
evolution, members of this school believe that much greater importance
ought to be assigned to the inherited effects of use and disuse than was
assigned to these agencies by Darwin. Perhaps this noteworthy state of
affairs, within a decade of Darwin's death, may lead us to anticipate
that his judgement--standing, as it does, between these two
extremes--will eventually prove the most accurate of all, with respect
to the relative importance of these factors of evolution. But, be this
as it may, I must now offer a few remarks upon the present position of
the matter.

In the first place, to any one who (with Darwin and against Weismann)
admits not only the abstract possibility, but an actual working, of the
Lamarckian factors, it becomes difficult to determine, even
approximately, the degrees of value which ought to be ascribed to them
and to natural selection respectively. For, since the results are in
both cases identical in kind (as, adaptive changes of organic types),
where both sets of causes are supposed to be in operation together, we
have no means of estimating the relative shares which they have had in
bringing about these results. Of course there are large numbers of cases
where it cannot possibly be supposed that the Lamarckian factors have
taken any part at all in producing the observed effects; and therefore
in such cases there is almost full agreement among evolutionists in
theoretically ascribing such effects to the exclusive agency of natural
selection. Of such, for instance, are the facts of protective colouring,
of mimicry, of the growth of parts which, although _useful_, are never
_active_ (e.g. shells of mollusks, hard coverings of seeds), and so on.
But in the majority of cases where adaptive structures are concerned,
there is no means of discriminating between the influences of the
Lamarckian and the Darwinian factors. Consequently, if by the
Neo-Lamarckian school we understand all those naturalists who assign any
higher importance to the Lamarckian factors than was assigned to them by
Darwin, we may observe that members of this school differ very greatly
among themselves as to the degree of importance that ought to be
assigned. On the one hand we have, in Europe, Giard, Perrier, and Eimer,
who stand nearer to Darwin than do a number of the American
representatives--of whom the most prominent are Cope, Osborn, Packard,
Hyatt, Brooks, Ryder, and Dall. The most extreme of these is Professor
Cope, whose collection of essays entitled _The Origin of the Fittest_,
as well as his more recent and elaborate monograph on _The Development
of the Hard Parts of the Mammalia_, represent what appears even to some
other members of his school an extravagant estimate of the importance
of Lamarckian principles.

But the most novel, and in many respects the most remarkable school of
what may be termed Anti-selectionists is one which is now (1894) rapidly
increasing both in numbers and in weight, not only in the New World, but
also in Germany, and to a lesser extent, in Great Britain.

This school, without being either Lamarckian or Darwinian (for its
individual members differ widely from one another in these respects)
maintains a principle which it deems of more importance than either
use-inheritance or natural selection. This principle it calls
Self-adaptation. It is chiefly botanists who constitute this school, and
its principal representatives, in regard to authority, are Sachs,
Pfeffer and Henslow.

Apart from topics which are to be dealt with in subsequent chapters, the
only matters of much importance which have been raised in the
Post-Darwinian period are those presented by the theories of Geddes,
Cope, Hyatt, and others, and certain more or less novel ideas set forth
in Wallace's _Darwinism_.

Mr. Geddes has propounded a new theory of the origin of species, which
in his judgement supersedes to a large extent the theory of natural
selection. He has also, in conjunction with Mr. Thomson, propounded a
theory of the origin of sex. For my own part, I cannot see that these
views embody any principles or suggestions of a sufficiently definite
kind to constitute them theories at all. In this respect the views of
Mr. Geddes resemble those of Professors Cope, Hyatt, and others, on what
they term "the law of acceleration and retardation." In all these
cases, so far as I can see, the so-called explanations are not in fact
any explanations; but either a mere re-statement of the facts, or else
an enunciation of more or less meaningless propositions. Thus, when it
is said that the evolution of any given type has been due to the
"acceleration of growth-force" with respect to some structures, and the
"retardation of growth-force" with respect to others, it appears evident
that we have not any real explanation in terms of causality; we have
only the form of an explanation in the terms of a proposition. All that
has been done is to express the fact of evolution in somewhat obscure
phraseology, since the very thing we want to know about this fact
is--What are the causes of it as a fact, or the reasons which have led
to the increase of some of the parts of any given type, and the
concomitant decrease of others? It is merely the facts themselves that
are again presented by saying that the development has been in the one
case accelerated, while in the other it has been retarded[10].

    [10] Take, for example, the following, which is a fair epitome of
         the whole:--"I believe that this is the simplest mode of
         stating and explaining the law of variation; that some forms
         acquire something which their parents did not possess; and that
         those which acquire something additional have to pass through
         more numerous stages than their ancestors; and those which lose
         something pass through fewer stages than their ancestors; and
         these processes are expressed by the terms 'acceleration' and
         'retardation'" (_Origin of the Fittest_, pp. 125, 226, and
         297). Even if this be "the simplest mode of _stating_ the law
         of variation," it obviously does nothing in the way of
         _explaining_ the law.

So much for what may be termed this New World theory of the origin of
species: it is a mere re-statement of the facts. Mr. Geddes' theory, on
the other hand, although more than a mere re-statement of the facts,
appears to me too vague to be of any explanatory service. His view is
that organic evolution has everywhere depended upon an antagonism,
within the limits of the same organism, between the processes of
nutrition and those of reproduction. But although he is thus able
hypothetically to explain certain facts--such as the shortening of a
flower-spike into a composite flower--the suggestion is obviously
inadequate to meet, even hypothetically, most of the facts of organic
evolution, and especially the development of _adaptive_ structures.
Therefore, it seems to me, we may dismiss it even as regards the
comparatively few facts which it might conceivably explain--seeing that
these same facts may be equally well explained by the causes which are
already known to operate in other cases. For it is the business of
natural selection to ensure that there shall nowhere be any needless
expenditure of vital energy, and, consequently, that everywhere the
balance between nutrition and reproduction shall be most profitably
adjusted.

Similarly with respect to the theory of the _Origin of Sex_, I am unable
to perceive even this much of scientific relevancy. As stated by its
authors the theory is, that the female is everywhere "anabolic," as
compared with the male, which is "katabolic." By anabolic is meant
comparative inactivity of protoplasmic change due to a nutritive winding
up of molecular constitution, while by katabolic is meant the opposite
condition of comparative activity due to a dynamic running down of
molecular constitution. How, then, can the _origin_ of sex be explained,
or the _causes_ which led to the differentiation of the sexes be shown
by saying that the one sex is anabolic and the other katabolic? In so
far as these verbal statements serve to express what is said to be a
general fact--namely, that the female sexual elements are less mobile
than the male--they merely serve to re-state this general fact in
terminology which, as the authors themselves observe, is "unquestionably
ugly." But in so far as any question of _origin_ or _causality_ is
concerned, it appears to me that there is absolutely no meaning in such
statements. They belong to the order of merely formal explanations, as
when it is said that the toxic qualities of morphia are due to this drug
possessing a soporific character.

Much the same, in my opinion, has to be said of the Rev. G. Henslow's
theory of the origin of species by what he terms "self-adaptation."
Stated briefly his view is that there is no sufficient evidence of
natural selection as a _vera causa_, while there is very abundant
evidence of adjustments occurring without it, first in individual
organisms, and next, by inheritance of acquired characters, in species.
Now, much that he says in criticism of the selection theory is of
considerable interest as such; but when we pass from the critical to the
constructive portions of his books and papers, we again meet with the
want of clearness in thought between a statement of facts in terms of a
proposition, and an explanation of them in those of causality. Indeed, I
understand from private correspondence, that Mr. Henslow himself admits
the validity of this criticism; for in answer to my questions,--"How
does Self-adaptation work in each case, and why should protoplasm be
able to _adapt itself_ into the millions of diverse mechanisms in
nature?"--he writes. "Self-adaptation does not profess to be a _vera
causa_ at all; for the true causes of variation can only be found in the
answer to your [above] questions, and I must say at once, _these
questions cannot be answered_." That is, they cannot be answered on the
hypothesis of self-adaptation, which is therefore a statement of the
facts of adaptation as distinguished from an explanation of them.
Nevertheless, two things have here to be noted. In the first place, the
statement of facts which Mr. Henslow has collected is of considerable
theoretical importance as tending to show that there are probably causes
of an internal kind (i. e. other than natural selection) which have been
largely concerned in the adaptive modification of plants. And, in the
second place, it is not quite true that the theory of self-adaptation
is, as its author says in the sentences above quoted, a mere statement
of the facts of adaptation, without any attempt at explaining their
causes. For in his published words he does attempt to do so[11]. And,
although I think his attempt is a conspicuous failure, I ought in
fairness to give examples of it. His books are almost exclusively
concerned in an application of his theory to the mechanisms of flowers
for securing their own fertilization. These mechanisms he ascribes, in
the case of entomophylous flowers, to the "thrusts," "strains," and
other "irritations" supplied to the flowers by their insect visitors,
and consequent "reactions" of the vegetable "protoplasm." But no attempt
is made to show why these "reactions" should be of an _adaptive_ kind,
so as to build up the millions of diverse and often elaborate mechanisms
in question--including not only forms and movements, but also colours,
odours, and secretions. For my own part I confess that, even granting to
an ultra-Lamarckian extent the inheritance of acquired characters, I
could conceive of "self-adaptation" alone producing all such innumerable
and diversified adjustments only after seeing, with Cardinal Newman, an
angel in every flower. Yet Mr. Henslow somewhat vehemently repudiates
any association between his theory and that of teleology.

    [11] _Floral Structures_ (Internat. Sc. Ser. lxiv. 1888): _The
         Making of Flowers_ (Romance of Science Ser. 1891); and Linn.
         Soc. Papers 1893-4.

On the whole, then, I regard all the works which are here classed
together (those by Cope, Geddes, and Henslow), as resembling one another
both in their merits and defects. Their common merits lie in their
erudition and much of their criticism, while their common defects
consist on the one hand in not sufficiently distinguishing between mere
statements and real explanations of facts, and, on the other, in not
perceiving that the theories severally suggested as substitutes for that
of natural selection, even if they be granted true, could be accepted
only as co-operative factors, and by no stretch of logic as substitutes.

       *       *       *       *       *

Turning now to Mr. Wallace's work on _Darwinism_, we have to notice, in
the first place, that its doctrine differs from "Darwinism" in regard to
the important dogma which it is the leading purpose of that work to
sustain--namely, that "the law of utility" is, to all intents and
purposes, universal, with the result that natural selection is virtually
the only cause of organic evolution. I say "to all intents and
purposes," or "virtually," because Mr. Wallace does not expressly
maintain the abstract impossibility of laws and causes other than those
of utility and natural selection; indeed, at the end of his treatise, he
quotes with approval Darwin's judgement, that "natural selection has
been the most important, but not the exclusive means of modification."
Nevertheless, as he nowhere recognizes any other law or cause of
adaptive evolution[12], he practically concludes that, on inductive or
empirical grounds, there _is_ no such other law or cause to be
entertained--until we come to the particular case of the human mind. But
even in making this one particular exception--or in representing that
some other law than that of utility, and some other cause than that of
natural selection, must have been concerned in evolving the mind of
man--he is not approximating his system to that of Darwin. On the
contrary, he is but increasing the divergence, for, of course, it was
Darwin's view that no such exception could be legitimately drawn with
respect to this particular instance. And if, as I understand must be the
case, his expressed agreement with Darwin touching natural selection not
being the only cause of adaptive evolution has reference to this point,
the quotation is singularly inapt.

    [12] "The law of correlation," and the "laws of growth," he does
         recognize; and shows that they furnish an explanation of the
         origin of many characters, which cannot be brought under "the
         law of utility."

Looking, then, to these serious differences between his own doctrine of
evolution--both organic and mental--and that of Darwin, I cannot think
that Mr. Wallace has chosen a suitable title for his book; because, in
view of the points just mentioned, it is unquestionable that _Darwinism_
differs more widely from the _Origin of Species_ than does the _Origin
of Species_ from the writings of the Neo-Lamarckians. But, passing over
this merely nominal matter, a few words ought to be added on the very
material question regarding the human mind. In subsequent chapters the
more general question, or that which relates to the range of utility and
natural selection elsewhere will be fully considered.

Mr. Wallace says,--

     "The immense interest that attaches to the origin of the human
     race, and the amount of misconception which prevails regarding the
     essential teachings of Darwin's theory on the question, as well as
     regarding my own special views upon it, induce me to devote a final
     chapter to its discussion."

Now I am not aware that there is any misconception in any quarter as to
the essential teachings of Darwin's theory on this question. Surely it
is rather the case that there is a very general and very complete
understanding on this point, both by the friends and the foes of
Darwin's theory--so much so, indeed, that it is about the only point of
similar import in all Darwin's writings of which this can be said. Mr.
Wallace's "special views" on the other hand are, briefly stated, that
certain features, both of the morphology and the psychology of man, are
inexplicable by natural selection--or indeed by any other cause of the
kind ordinarily understood by the term natural: they can be explained
only by supposing "the intervention of some distinct individual
intelligence," which, however, need not necessarily be "one Supreme
Intelligence," but some other order of Personality standing anywhere in
"an infinite chasm between man and the Great Mind of the universe[13]."
Let us consider separately the corporeal and the mental peculiarities
which are given as justifying this important conclusion.

    [13] _Natural Selection and Tropical Nature_, p. 205; 1891.

The bodily peculiarities are the feet, the hands, the brain, the voice,
and the naked skin.

As regards the feet Mr. Wallace writes, "It is difficult to see why the
prehensile power [of the great toe] should have been taken away,"
because, although "it may not be compatible with perfectly easy erect
locomotion," "how can we conceive that early man, _as an animal_, gained
anything by purely erect locomotion[14]?" But surely it is not difficult
to conceive this. In the proportion that our simian progenitors ceased
to be arboreal in their habits (and there may well have been very good
utilitarian reasons for such a change of habitat, analogous to those
which are known to have occurred in the phylogenesis of countless other
animals), it would clearly have been of advantage to them that their
already semi-erect attitude should have been rendered more and more
erect. To name one among several probabilities, the more erect the
attitude, and the more habitually it was assumed, the more would the
hands have been liberated for all the important purposes of
manipulation. The principle of the physiological division of labour
would thus have come more and more into play: natural selection would
therefore have rendered the upper extremities more and more suited to
the execution of these purposes, while at the same time it would have
more and more adapted the lower ones to discharging the sole function of
locomotion. For my own part, I cannot perceive any difficulty about
this: in fact, there is an admirable repetition of the process in the
ontogeny of our own children[15].

    [14] _Ibid._ pp. 197-8.

    [15] For an excellent discussion on the ontogeny of the child in
         this connexion, see _Some Laws of Heredity_, by Mr. S. S.
         Buckman, pp. 290, _et seq._ (Proc. Cotteswold Nat. Field Club,
         vol. x. p. 3, 1892).

Next, with regard to the hand, Mr. Wallace says, that it "contains
latent capacities which are unused by savages, and must have been even
less used by palaeolithic man and his still ruder predecessors." Thus,
"it has all the appearance of an organ prepared for the use of civilized
man[16]." Even if this be true, however, it would surely be a dangerous
argument to rely upon, seeing that we cannot say of how much importance
it may have been for early man--or even apes--to have had their power of
manipulation progressively improved. But is the statement true? It
appears to me that if Mr. Wallace had endeavoured to imitate the
manufactures that were practised by "palaeolithic man," he would have
found the very best of reasons for cancelling his statement. For it is
an extremely difficult thing to chip a flint into the form of an
arrow-head: when made, the suitable attachment of it to a previously
prepared arrow is no easy matter: neither a bow nor a bow-string could
have been constructed by hands of much less perfection than our own: and
the slaying of game with the whole apparatus, when it has been
constructed, requires a manual dexterity which we may be perfectly
certain that Mr. Wallace--unless he has practised the art from
boyhood--does not possess.

    [16] _loc. cit._ p. 198.

So it is with his similar argument that the human voice is more
"powerful," more "flexible," and presents a greater "range" and
"sweetness" than the needs of savage life can be held to require. The
futility of this argument is self-evident as regards "power." And
although its weakness is not so obvious with respect to the other three
qualities which are named, need we go further than the closely analogous
case of certain birds to show the precariousness of arguing from such
facts of organic nature to the special operation of "a superior
intelligence"? I can hardly suppose that Mr. Wallace will invoke any
such agency for the purpose of explaining the "latent capacities" of the
voice of a parrot. Yet, in many respects, these are even more wonderful
than those of the human voice, albeit in a wild state they are "never
required or used[17]."

    [17] For a discussion of this remarkable case, see _Mental Evolution
         in Animals_, pp. 222-3. It appears to me that if Mr. Wallace's
         argument from the "latent capacities of the voice of Man" is
         good for anything, _a fortiori_ it must be taken to prove that,
         in the case of the Parrot, "the organ has been prepared in
         anticipation" of the amusement which the cultivation of its
         latent capacities arouses in "civilized man."

Once more, with regard to the naked skin, it seems sufficient to quote
the following passage from the first edition of the _Descent of Man_.

     "The Rev. T. R. Stebbing, in commenting on this view, 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 civilization through the
     practice of various arts, in the manner indicated by Mr.
     Wallace[18]."

    [18] _Descent of Man_, 1st Ed. ch. xx. (Trans. Dev. Assoc. for
         Science, 1890).

To this it may be added that the Chimpanzee "Sally" was largely denuded
of hair, especially on the back, or the part of "man's organization" on
which Mr. Wallace lays special stress, as being in this respect out of
analogy with other mammalia[19].

    [19] The late Prof. Moseley informed me that, during his voyage on
         the _Challenger_, he had seen many men whose backs were well
         covered with hair.--For an excellent discussion of the whole
         question, chiefly in the light of embryology, see the paper by
         Buckman already alluded to, pp. 280-289. Also, for an account
         of an extraordinary hairy race of men, see _Alone with the
         Hairy Ainu_, by A. H. Savage Landor, 1893.

Lastly, touching his statement that the brain of savage man is both
quantitatively and qualitatively in advance of his requirements, it is
here also sufficient to refer to Darwin's answer, as given in the
_Descent of Man_. Mr. Wallace, indeed, ignores this answer in his recent
re-publication of the argument; but it is impossible to understand why
he should have done so. To me, at all events, it seems that one out of
several considerations which Darwin advances is alone sufficient to show
the futility of this argument. I allude to the consideration that the
power of forming abstract ideas with the complex machinery of language
as the vehicle of their expression, is probably of itself enough to
account for both the mass and the structure of a savage's brain. But
this leads us to the second division of Mr. Wallace's argument, or that
derived from the mental endowments of mankind.

Here the peculiarities called into evidence are, "the Mathematical
Faculty," "the Artistic Faculties," and "the Moral Sense." With regard
to the latter, he avows himself a member of the intuitional school of
ethics; but does not prove a very powerful advocate as against the
utilitarian[20].

    [20] E.g. "The special faculties we have been discussing clearly
         point to the existence in man of something which he has not
         derived from his animal progenitors--something which we may
         best refer to as being of a spiritual essence or nature,
         capable of progressive development under favourable conditions.
         On the hypothesis of this spiritual nature, superadded to the
         animal nature of man, we are able to understand much that is
         otherwise mysterious or unintelligible in regard to him,
         especially the enormous influence of ideas, principles, and
         beliefs over his whole life and action. Thus alone can we
         understand the constancy of the martyr, the unselfishness of
         the philanthropist, the devotion of the patriot, the enthusiasm
         of the artist, and the resolute and persevering search of the
         scientific worker after nature's secrets. Thus we may perceive
         that the love of truth, the delight in beauty, the passion for
         justice, and the thrill of exultation with which we hear of any
         act of courageous self-sacrifice, are the workings within us of
         a higher nature which has not been developed by means of the
         struggle for material existence." (_Darwinism_, p. 474.) I have
         quoted this whole paragraph, because it is so inconsistent with
         the rest of Mr. Wallace's system that a mere epitome of it
         might well have been suspected of error. Given an intellectual
         being, howsoever produced, and what is there "mysterious or
         unintelligible" in "the enormous influence of ideas,
         principles, and beliefs over his whole life and action"? Or
         again, if he be also a social being, what is the relevancy of
         adducing "the constancy of the martyr," "the unselfishness of
         the philanthropist," "the devotion of the patriot," "the love
         of truth," "the passion for justice," "the thrill of exultation
         when we hear of any act of courageous self-sacrifice," in
         evidence _against_ the law of _utility_, or in order to prove
         that a "nature" thus endowed has "_not_ been developed by means
         of the struggle for existence," when once this struggle has
         been transferred from individuals to communities? The whole
         passage reads like an ironical satire in favour of "Darwinism,"
         rather than a serious argument against it.

It comes, then, to this. According to Mr. Wallace's eventual
conclusion, man is to be separated from the rest of organic nature, and
the steady progress of evolution by natural causes is to be regarded as
stopped at its final stage, because the human mind presents the
faculties of mathematical calculation and aesthetic perception. Surely,
on antecedent grounds alone, it must be apparent that there is here no
kind of proportion between the conclusion and the _data_ from which it
is drawn. That we are not confined to any such grounds, I will now try
to show.

Let it be remembered, however, that in the following brief criticism I
am not concerned with the issue as to whether, or how far, the
"faculties" in question have owed their origin or their development to
_natural selection_. I am concerned only with the doctrine that in order
to account for such and such particular "faculty" of the human mind,
some order of causation must be supposed other than what we call
natural. I am not a Neo-Darwinist, and so have no desire to make
"natural selection" synonymous with "natural causation" throughout the
whole domain of life and of mind. And I quite agree with Mr. Wallace
that, at any rate, the "aesthetic faculty" cannot conceivably have been
produced by natural selection--seeing that it is of no conceivable
life-serving value in any of the stages of its growth. Moreover, it
appears to me that the same thing has to be said of the play instincts,
sense of the ludicrous, and sundry other "faculties" of mind among the
lower animals. It being thus understood that I am not differing from Mr.
Wallace where he imposes "limits" on the powers of natural selection,
but only where he seems to take for granted that this is the same thing
as imposing limits on the powers of natural causation, my criticism is
as follows.

In the first place, it is a psychological fallacy to regard the
so-called "faculties" of mind as analogous to "organs" of the body. To
classify the latter with reference to the functions which they severally
perform is to follow a natural method of classification. But it is an
artificial method which seeks to partition mental _faculty_ into this,
that, and the other mental _faculties_. Like all other purely artificial
classifications, this one has its practical uses; but, also like them,
it is destitute of philosophical meaning. This statement is so well
recognized by psychologists, that there is no occasion to justify it.
But I must remark that any cogency which Mr. Wallace's argument may
appear to present, arises from his not having recognized the fact which
the statement conveys. For, had he considered the mind as a whole,
instead of having contemplated it under the artificial categories of
constituent "faculties," he would probably not have laid any such
special stress upon some of the latter. In other words, he would have
seen that the general development of the human mind as a whole has
presumably involved the growth of those conventionally abstracted parts,
which he regards as really separate endowments. Or, if he should find it
easier to retain the terms of his metaphor, we may answer him by saying
that the "faculties" of mind are "correlated," like "organs" of the
body; and, therefore, that any general development of the various other
"faculties" have presumably entailed a collateral development of the two
in question.

Again, in the second place, it would seem that Mr. Wallace has not
sufficiently considered the co-operation of either well-known natural
causes, which must have materially assisted the survival of the fittest
where these two "faculties" are concerned. For, even if we disregard the
inherited effects of use--which, however, if entertained as possible in
any degree at all, must have here constituted an important
factor,--there remain on the one hand, the unquestionable influences of
individual education and, on the other hand, of the selection principle
operating in the mind itself.

Taking these two points separately, it is surely sufficiently well known
that individual education--or special training, whether of mind or
body--usually raises congenital powers of any kind to a more or less
considerable level above those of the normal type. In other words,
whatever doubt there may be touching the _inherited_ effects of use,
there can be no question touching the immense _developmental_ effects
thereof in the individual life-time. Now, the conditions of savage life
are not such as lead to any deliberate cultivation of the "faculties"
either of the mathematical or aesthetic order. Consequently, as might be
expected, we find both of them in what Mr. Wallace regards as but a
"latent" stage of development. But in just the same way do we find that
the marvellous powers of an acrobat when specially trained from
childhood--say to curve his spine backwards until his teeth can bite his
heels--are "latent" in all men. Or, more correctly, they are _potential
in every child_. So it is with the prodigious muscular development of a
trained athlete, and with any number of other cases where either the
body or the mind is concerned. Why then should Mr. Wallace select the
particular instances of the mathematical and aesthetic powers in savages
as in any special sense "prophetic" of future development in trained
members of civilized races? Although it is true that these "latent
capacities and powers are unused by savages," is it not equally true
that savages fail to use their latent capacities and powers as tumblers
and athletes? Moreover, is it not likewise true that _as_ used by
savages, or as occurring normally in man, such capacities and powers are
no less poorly developed than are those of the "faculties" on which Mr.
Wallace lays so much stress? In other words, are not "latent capacities
and powers" of all kinds more or less equally in excess of anything that
is ever required of them by man in a state of nature? Therefore, if we
say that where mathematics and the fine arts are concerned the potential
capacities of savage man are in some mystical sense "prophetic" of a
Newton or a Beethoven, so in consistency ought we to say that in these
same capacities we discern a similar prophecy of those other uses of
civilized life which we have in a rope-dancer or a clown.

Again, and in addition to this, it should be remembered that, even if we
do suppose any prophecy of this kind where the particular capacities in
question are concerned, we must clearly extend the reference to the
lower animals. Not a few birds display aesthetic feelings in a measure
fairly comparable with those of savages; while we know that some animals
present the germs of a "faculty" of computation[21]. But, it is
needless to add, this fact is fatal to Mr. Wallace's argument as I
understand it--viz. that the "faculties" in question have been in some
special manner communicated by some superior intelligence to _man_.

    [21] See _Proc. Zool. Soc._ June 4, 1889, for an account of the
         performances in this respect of the Chimpanzee "Sally." Also,
         for some remarks on the psychology of the subject, in _Mental
         Evolution in Man_, p. 215. I should like to take this
         opportunity of stating that, after the two publications above
         referred to, this animal's instruction was continued, and that,
         before her death, her "counting" extended as far as ten. That
         is to say, any number of straws asked for from one to ten would
         always be correctly given.

Once more, it is obviously unfair to select such men as a "Newton, a La
Place, a Gauss, or a Cayley" for the purpose of estimating the
difference between savages and civilized man in regard to the latter
"faculty." These men are the picked mathematicians of centuries.
Therefore they are men who not only enjoyed all the highest possible
benefits of individual culture, but likewise those who have been most
endowed with mathematical power congenitally. So to speak, they are the
best variations in this particular direction which our race is known to
have produced. But had such variations arisen among savages it is
sufficiently obvious that they could have come to nothing. Therefore, it
is the _normal average_ of "mathematical faculty" in civilized man that
should be contrasted with that of savage man; and, when due regard is
paid to the all-important consideration which immediately follows, I
cannot feel that the contrast presents any difficulty to the theory of
human evolution by natural causation.

Lastly, the consideration just alluded to is, that civilized man enjoys
an advantage over savage man far in advance even of those which arise
from a settled state of society, incentives to intellectual training,
and so on. This inestimable advantage consists in the art of writing,
_and the consequent transmission of the effects of culture from
generation to generation_. Quite apart from any question as to the
hereditary transmission of acquired characters, we have in this
_intellectual_ transmission of acquired _experience_ a means of
accumulative cultivation quite beyond our powers to estimate. For,
unlike all other cases where we recognize the great influence of
individual use or practice in augmenting congenital "faculties" (such as
in the athlete, pianist, &c.), in this case the effects of special
cultivation do not end with the individual life, but are carried on and
on through successive generations _ad infinitum_. Hence, a civilized man
inherits mentally, if not physically, the effects of culture for ages
past, and this in whatever direction he may choose to profit therefrom.
Moreover--and I deem this an immensely important addition--in this
unique department of purely intellectual transmission, a kind of
non-physical natural selection is perpetually engaged in producing the
best results. For here a struggle for existence is constantly taking
place among "ideas," "methods," and so forth, in what may be termed a
psychological environment. The less fit are superseded by the more fit,
and this not only in the mind of the individual, but, through language
and literature, still more in the mind of the race. "A Newton, a La
Place, a Gauss, or a Cayley," would all alike have been impossible, but
for a previously prolonged course of mental evolution due to the
selection principle operating in the region of mathematics, by means of
continuous survivals of the best products in successive generations.
And, of course, the same remark applies to art in all its branches[22].

    [22] In Prof. Lloyd Morgan's _Animal Life and Intelligence_ there is
         an admirable discussion on this subject, which has been
         published since the above was written. The same has to be said
         of Weismann's Essay on Music, where much that I have here said
         is anticipated. With the views and arguments which Mr. Mivart
         has forcibly set forth I have already dealt to the best of my
         ability in a work on _Mental Evolution in Man_.

Quitting then the last, and in my opinion the weakest chapter of
_Darwinism_, the most important points presented by other portions of
this work are--to quote its author's own enumeration of them--an
attempted "proof that all specific characters are (or once have been)
either useful in themselves or correlated with useful characters": an
attempted "proof that natural selection can, in certain cases, increase
the sterility of crosses": an attempted "proof that the effects of use
and disuse, even if inherited, must be overpowered by natural
selection": an attempted proof that the facts of variation in nature are
in themselves sufficient to meet the difficulty which arises against the
theory of natural selection, as held by him, from the swamping effects
of free intercrossing: and, lastly, "a fuller discussion on the colour
relations of animals, with additional facts and arguments on the origin
of sexual differences of colour." As I intend to deal with all these
points hereafter, excepting the last, it will be sufficient in this
opening chapter to remark, that in as far as I disagree with Mr. Wallace
(and agree with Darwin), on the subject of "sexual differences of
colour," my reasons for doing so have been already sufficiently stated
in Part I. But there is much else in his treatment of this subject which
appears to me highly valuable, and therefore presenting an admirable
contribution to the literature of Darwinism. In particular, it appears
to me that the most important of his views in this connexion probably
represents the truth--namely, that, among the higher animals, more or
less conspicuous peculiarities of colour have often been acquired for
the purpose of enabling members of the same species quickly and
certainly to recognize one another. This theory was first published by
Mr. J. E. Todd, in 1888, and therefore but a short time before its
re-publication by Mr. Wallace. As his part in the matter has not been
sufficiently recognized, I should like to conclude this introductory
chapter by drawing prominent attention to the merits of Mr. Todd's
paper. For not only has it the merit of priority, but it deals with the
whole subject of "recognition colours"--or, as he calls them, "directive
colours"--in a more comprehensive manner than has been done by any of
his successors. In particular, he shows that the principle of
recognition-marking is not restricted to facilitating sexual
intercourse, but extends also to several other matters of importance in
the economy of animal life[23].

    [23] _American Naturalist_, xxii. pp. 201-207.

       *       *       *       *       *

Having thus briefly sketched the doctrines of the sundry Post-Darwinian
Schools from a general point of view, I shall endeavour throughout the
rest of this treatise to discuss in appropriate detail the questions
which have more specially come to the front in the post-Darwinian
period. It can scarcely be said that any one of these questions has
arisen altogether _de novo_ during this period; for glimmerings, more or
less conspicuous, of all are to be met with in the writings of Darwin
himself. Nevertheless it is no less true that only after his death have
they been lighted up to the full blaze of active discussion[24]. By far
the most important of them are those to which the rest of this treatise
will be confined. They are four in number, and it is noteworthy that
they are all intimately connected with the great question which Darwin
spent the best years of his life in contemplating, and which has
therefore, in one form or another, occupied the whole of the present
chapter--the question as to whether natural selection has been the sole
cause, or but the chief cause of modification.

    [24] It is almost needless to say that besides the works mentioned
         in this chapter, many others have been added to the literature
         of Darwinism since Darwin's death. But as none of these profess
         to contain much that is original, I have not thought it
         necessary to consider any of them in this merely general review
         of the period in question. In subsequent chapters, however,
         allusions will be made to those among them which I deem of most
         importance.

         [Since this note was written and printed the following works
         have been published to which it does not apply: _Animal Life
         and Intelligence_, by Professor Lloyd Morgan; _The Colours of
         Animals_, by Professor Poulton; and _Materials for the Study of
         Variation_, by Mr. Bateson. All these works are of high value
         and importance. Special reference should also be made to
         Professor Weismann's Essays.]

The four questions above alluded to appertain respectively to Heredity,
Utility, Isolation, and Physiological Selection. Of these the first two
will form the subject-matter of the present volume, while the last two
will be dealt with in the final instalment of _Darwin, and after
Darwin_.




SECTION I

_HEREDITY_




CHAPTER II.

CHARACTERS AS HEREDITARY AND ACQUIRED (PRELIMINARY).


We will proceed to consider, throughout Section I of the present work,
the most important among those sundry questions which have come to the
front since the death of Darwin. For it was in the year after this event
that Weismann published the first of his numerous essays on the subject
of Heredity, and, unquestionably, it has been these essays which have
given such prominence to this subject during the last decade.

At the outset it is desirable to be clear upon certain points touching
the history of the subject; the limits within which our discussion is to
be confined; the relation in which the present essay stands to the one
that I published last year under the title _An Examination of
Weismannism_; and several other matters of a preliminary kind.

The problems presented by the phenomena of heredity are manifold; but
chief among them is the hitherto unanswered question as to the
transmission or non-transmission of acquired characters. This is the
question to which the present Section will be confined.

Although it is usually supposed that this question was first raised by
Weismann, such was not the case. Any attentive reader of the successive
editions of Darwin's works may perceive that at least from the year 1859
he had the question clearly before his mind; and that during the rest of
his life his opinion with regard to it underwent considerable
modifications--becoming more and more Lamarckian the longer that he
pondered it. But it was not till 1875 that the question was clearly
presented to the general public by the independent thought of Mr.
Galton, who was led to challenge the Lamarckian factors _in toto_ by way
of deduction from his theory of Stirp--the close resemblance of which to
Professor Weismann's theory of Germ-plasm has been shown in my
_Examination of Weismannism_. Lastly, I was myself led to doubt the
Lamarckian factors still further back in the seventies, by having found
a reason for questioning the main evidence which Mr. Darwin had adduced
in their favour. This doubt was greatly strengthened on reading, in the
following year, Mr. Galton's _Theory of Heredity_ just alluded to; and
thereupon I commenced a prolonged course of experiments upon the
subject, the general nature of which will be stated in future chapters.
Presumably many other persons must have entertained similar misgivings
touching the inheritance of acquired characters long before the
publication of Weismann's first essay upon the subject in 1883. The
question as to the inheritance of acquired characters was therefore
certainly not first raised by Weismann--although, of course, there is no
doubt that it was conceived by him independently, and that he had the
great merit of calling general attention to its existence and
importance. On the other hand, it cannot be said that he has succeeded
in doing very much towards its solution. It is for these reasons that
any attempt at dealing with Weismann's fundamental postulate--i.e. that
of the non-inheritance of acquired characters--was excluded from my
_Examination of Weismannism_. As there stated, he is justified in
assuming, for the purposes of his discussion, a negative answer to the
question of such inheritance; but evidently the question itself ought
not to be included within what we may properly understand by
"Weismannism." Weismannism, properly so called, is an elaborate system
of theories based on the fundamental postulate just mentioned--theories
having reference to the mechanism of heredity on the one hand, and to
the course of organic evolution on the other. Now it was the object of
the foregoing _Examination_ to deal with this system of theories _per
se_; and therefore we have here to take a new point of departure and to
consider separately the question of fact as to the inheritance or
non-inheritance of acquired characters. At first sight, no doubt, it
will appear that in adopting this method I am putting the cart before
the horse. For it may well appear that I ought first to have dealt with
the validity of Weismann's postulate, and not till then to have
considered the system of theories which he has raised upon it. But this
criticism is not likely to be urged by any one who is well acquainted
with the questions at issue. For, in the first place, it is notorious
that the question of fact is still open to question; and therefore it
ought to be considered separately, or apart from any theories which may
have been formed with regard to it. In the second place, our judgement
upon this question of fact must be largely influenced by the validity of
general reasonings, such as those put forward in the interests of rival
theories of heredity; and, as the theory of germ-plasm has been so
thoughtfully elaborated by Professor Weismann, I have sought to give it
the attention which it deserves as preliminary to our discussion of the
question of fact which now lies before us. Thirdly and lastly, even if
this question could be definitely answered by proving either that
acquired characters are inherited or that they are not, it would by no
means follow that Weismann's theory of heredity would be proved wholly
false in the one case, or wholly true in the other. That it need not be
wholly true, even were its fundamental postulate to be proved so, is
evident, because, although the fact might be taken to prove the theory
of Continuity, the theory of Germ-plasm is, as above stated, very much
more than this. That the theory of Germ-plasm need not be wholly false,
even if acquired characters should ever be proved heritable, a little
thought may easily show, because, in this event, the further question
would immediately arise as to the degrees and the comparative frequency
of such inheritance. For my own part, as stated in the _Examination_, I
have always been disposed to accept Mr. Galton's theory of Stirp in
preference to that of Germ-plasm on this very ground--i. e. that it does
not dogmatically exclude the possibility of an occasional inheritance of
acquired characters in faint though cumulative degrees. And whatever our
individual opinions may be touching the admissibility of such a _via
media_ between the theories of Pangenesis and Germ-plasm, at least we
may all agree on the desirability of fully considering the matter as a
preliminary to the discussion of the question of fact.

As it is not to be expected that even those who may have read my
previous essay can now carry all these points in their memories, I will
here re-state them in a somewhat fuller form.

The following diagram will serve to give a clearer view of the sundry
parts of Professor Weismann's system of theories, as well as of their
relations to one another.

[Illustration: Postulate as to the absolute non-inheritance of acquired
characters.]

Now, as just explained, the parts of this system which may be properly
and distinctively called "Weismannism" are those which go to form the
Y-like structure of deductions from the fundamental postulate.
Therefore, it was the Y-like system of deductions which were dealt with
in the _Examination of Weismannism_, while it is only his basal
postulate which has to be dealt with in the following chapters.

So much, then, for the relations of Weismann's system of theories to one
another. It is, however, of even more importance that we should gain a
clear view of the relations between his theory of _heredity_ to those of
Darwin and of Galton, as preliminary to considering the fundamental
question of fact.

As we have already seen, the theory of germ-plasm is not only a theory
of heredity: it is also, and more distinctively, a theory of evolution,
&c. As a theory of heredity it is grounded on its author's fundamental
postulate--the _continuity_ of germ-plasm. But as a theory of evolution,
it requires for its support this additional postulate, that the
continuity of germ-plasm has been _absolute_ "since the first origin of
life." It is clear that this additional postulate is not needed for his
theory of heredity, but only for his additional theory of evolution, &c.
There have been one or two other theories of heredity, prior to this
one, which, like it, have been founded on the postulate of Continuity of
the substance of heredity; but it has not been needful for any of these
theories to postulate further that this substance has been _always_ thus
isolated, or even that it is now _invariably_ so. For even though the
isolation be frequently invaded by influences of body-changes on the
congenital characters of this substance, it does not follow that this
principle of Continuity may not still be true _in the main_, even
although it is supplemented in some degree by that of use-inheritance.
Indeed, so far as the phenomena of heredity are concerned, it is
conceivable that all congenital characters were originally acquired,
and afterwards became congenital on account of their long inheritance. I
do not myself advocate this view as biologically probable, but merely
state it as logically possible, and in order to show that, so far as the
phenomena of heredity are concerned, there appears to be no reason for
Weismann's deduction that the principle of Continuity, if true at all,
must be _absolute_. And it would further appear, the only reason why he
makes this deduction (stem of the Y) is in order to provide a foundation
for his further theories of evolution, &c. (arms of the Y). It is indeed
necessary for these further theories that body-changes should never
exercise any hereditary influence on the hereditary endowments of
germ-plasm, and therefore it is that he posits the substance of heredity
as, not only continuous, but uninterruptably so "since the first origin
of life."

Now, this may be made more clear by briefly comparing Weismann's theory
with those of Darwin and of Galton. Weismann's theory of heredity, then,
agrees with its predecessors which we are considering in all the
following respects. The substance of heredity is particulate; is mainly
lodged in highly specialized cells; is nevertheless also distributed
throughout the general cellular tissues, where it is concerned in all
processes of regeneration, repair, and a-sexual reproduction; presents
an enormously complex structure, in that every constituent part of a
potentially future organism is represented in a fertilized ovum by
corresponding particles; is everywhere capable of virtually unlimited
multiplication, without ever losing its hereditary endowments; is often
capable of carrying these endowments in a dormant state through a long
series of generations until at last they reappear in what we recognize
as recursions. Thus far all three theories are in agreement. In fact,
the only matter of any great importance wherein they disagree has
reference to the doctrine of Continuity[25]. For while Darwin's theory
supposes the substance of heredity to be mainly formed anew in each
ontogeny, and therefore that the continuity of this substance is for the
most part interrupted in every generation[26], Weismann's theory
supposes this substance to be formed only during the phylogeny of each
species, and therefore to have been absolutely uninterrupted since the
first origin of life.

    [25] Originally, Weismann's further assumption as to the perpetual
         stability of germ-plasm, "since the first origin of sexual
         reproduction," was another very important point of difference,
         but this has now been withdrawn.

    [26] I say "_mainly_ formed anew," and "_for the most part_
         interrupted," because even Darwin's theory does not, as is
         generally supposed, exclude the doctrine of Continuity _in
         toto_.

But now, Galton's theory of heredity stands much nearer to Weismann's in
this matter of Continuity; for it is, as he says, a theory of "modified
pangenesis," and the modification consists in allowing very much more
for the principle of Continuity than is allowed by Darwin's theory; in
fact he expresses himself as quite willing to adopt (on adequate grounds
being shown) the doctrine of Continuity as absolute, and therefore
propounded, as logically possible, the identical theory which was
afterwards and independently announced by Weismann. Or, to quote his own
words--

     "We might almost reserve our belief that the structural [i. e.
     somatic] cells can react on the sexual elements at all, and we may
     be confident that at most they do so in a very faint degree; in
     other words, that acquired modifications are barely, if at all,
     _inherited_, in the correct sense of that word[27]."

    [27] _Theory of Heredity_ (Journ. Anthrop. Inst. 1875, p. 346).

So far Mr. Galton; but for Weismann's further theory of evolution, &c.,
it is necessary to postulate the additional doctrine in question; and it
makes a literally immeasurable difference to any theory of evolution
whether or not we entertain this additional postulate. For no matter how
faintly or how fitfully the substance of heredity may be modified by
somatic tissues, the Lamarckian principles are hypothetically allowed
some degree of play. And although this is a lower degree than Darwin
supposed, their influence in determining the course of organic evolution
may still have been enormous; seeing that their action in any degree
must always have been _directive_ of variation on the one hand, and
_cumulative_ on the other.

Thus, by merely laying this theory side by side with Weismann's we can
perceive at a glance how a _pure_ theory of _heredity_ admits of being
based on the postulate of Continuity alone, without cumbering itself by
any further postulate as to this Continuity being _absolute_. And this,
in my opinion is the truly scientific attitude of mind for us to adopt
as preliminary to the following investigation. For the whole
investigation will be concerned--and concerned only--with this question
of Continuity as absolute, or as admitting of degrees. There is, without
any question, abundant evidence to prove that the substance of heredity
is at least partly continuous (Gemmules). It may be that there is also
abundant evidence to prove this substance much more _largely_
continuous than Darwin supposed (Stirp); but be this as it may, it is
certain that any such question as to the _degree_ of continuity differs,
_toto caelo_, from that as to whether there can ever be any continuity
at all.

How, then, we may well ask, is it that so able a naturalist and so clear
a thinker as Weismann can have so far departed from the inductive
methods as to have not merely propounded the question touching
Continuity and its degrees, or even of Continuity as absolute; but to
have straightway assumed the latter possibility as a basis on which to
run a system of branching and ever-changing speculations concerning
evolution, variation, the ultimate structure of living material, the
intimate mechanism of heredity, or, in short, such a system of deductive
conjectures as has never been approached in the history of science? The
answer to this question is surely not far to seek. Must it not be the
answer already given? Must it not have been for the sake of rearing this
enormous structure of speculation that Weismann has adopted the
assumption of Continuity as absolute? As we have just seen, Galton had
well shown how a theory of heredity could be founded on the general
doctrine of Continuity, without anywhere departing from the inductive
methods--even while fully recognizing the possibility of such continuity
as absolute. But Galton's theory was a "_Theory of Heredity_," and
nothing more. Therefore, while clearly perceiving that the Continuity in
question _may_ be absolute, he saw no reason, either in fact or in
theory, for concluding that it _must_ be. On the contrary, he saw that
this question is, for the present, necessarily unripe for profitable
discussion--and, _a fortiori_, for the shedding of clouds of seed in all
the directions of "Weismannism."

Hence, what I desire to be borne in mind throughout the following
discussion is, that it will have exclusive reference to the question of
fact already stated, without regard to any superjacent theories; and,
still more, that there is a vast distinction between any question
touching the degrees in which acquired characters are transmitted to
progeny, and the question as to whether they are ever transmitted in any
degree at all. Now, the latter question, being of much greater
importance than the former, is the one which will mainly occupy our
attention throughout the rest of this Section.

We have already seen that before the subject was taken up by Weismann
the difference between acquired and congenital characters in respect to
transmissibility was generally taken to be one of degree; not one of
kind. It was usually supposed that acquired characters, although not so
fully and not so certainly inherited as congenital characters,
nevertheless were inherited in some lesser degree; so that if the same
acquired character continued to be successively acquired in a number of
sequent generations, what was at first only a slight tendency to be
inherited would become by summation a more and more pronounced tendency,
till eventually the acquired character might become as strongly
inherited as a congenital one. Or, more precisely, it was supposed that
an acquired character, in virtue of such a summation of hereditary
influence, would in time become congenital. Now, if this supposition be
true, it is evident that more or less assistance must be lent to
natural selection in its work of evolving adaptive modifications[28].
And inasmuch as we know to what a wonderful extent adaptive
modifications are secured during individual life-times--by the direct
action of the environment on the one hand, and by increased or
diminished use of special organs and mental faculties on the other--it
becomes obvious of what importance even a small measure of
transmissibility on their part would be in furnishing to natural
selection ready-made variations in required directions, as distinguished
from promiscuous variations in all directions. Contrariwise, if
functionally-produced adaptations and adaptations produced by the direct
action of the environment are never transmitted in any degree, not only
would there be an incalculable waste, so to speak, of adaptive
modifications--these being all laboriously and often most delicately
built up during life-times of individuals only to be thrown down again
as regards the interest of species--but so large an additional burden
would be thrown upon the shoulders of natural selection that it becomes
difficult to conceive how even this gigantic principle could sustain it,
as I shall endeavour to show more fully in future chapters. On the other
hand, however, Weismann and his followers not only feel no difficulty in
throwing overboard all this ready-made machinery for turning out
adaptive modifications when and as required; but they even represent
that by so doing they are following the logical maxim, _Entia non sunt
multiplicanda praeter necessitatem_--which means, in its relation to
causality, that we must not needlessly multiply hypothetical principles
to explain given results. But when appeal is here made to this logical
principle--the so-called Law of Parsimony--two things are forgotten.

    [28] Mr. Platt Ball has, indeed, argued that "use-inheritance would
         often be an evil," since, for example, "the condyle of the
         human jaw would become larger than the body of the jaw, because
         as the fulcrum of the lever it receives more pressure"; and
         similarly as regards many other hypothetical cases which he
         mentions. (_The Effects of Use and Disuse_, pp. 128-9 _et
         seq._) But it is evident that this argument proves too much.
         For if the effects of use and disuse as transmitted to progeny
         would be an evil, it could only be because these effects as
         they occur in the parents are an evil--and this they most
         certainly are not, being, on the contrary and as a general
         rule, of a high order of adaptive value. Moreover, in the race,
         there is a superadded agency always at work, which must
         effectually prevent any undue accumulation of these
         effects--namely, natural selection, which every Darwinist
         accepts as a controlling principle of all or any other
         principles of change. Therefore, if, as first produced in the
         life-time of individuals, the effects of use and disuse are not
         injurious, much less can they become so if transmitted through
         the life-time of species. Again, Mr. Wallace argues that, even
         supposing use-inheritance to occur, its adapting work in the
         individual can never extend to the race, seeing that the
         natural selection of fortuitous variations in the directions
         required must always produce the adaptations _more quickly_
         than would be possible by use-inheritance. This argument, being
         one of more weight, will be dealt with in a future chapter.

In the first place, it is forgotten that the very question in debate is
whether causes of the Lamarckian order _are_ unnecessary to explain all
the phenomena of organic nature. Of course if it could be proved that
the theory of natural selection alone is competent to explain all these
phenomena, appeal to the logical principle in question would be
justifiable. But this is precisely the point which the followers of
Darwin refuse to accept; and so long as it remains the very point at
issue, it is a mere begging the question to represent that a class of
causes which have hitherto been regarded as necessary are, in fact,
unnecessary. Or, in other words, when Darwin himself so decidedly held
that these causes are necessary as supplements to natural selection, the
burden of proof is quite as much on the side of Weismann and his
followers to show that Darwin's opinion was wrong, as it is on the side
of Darwin's followers to show that it was right. Yet, notwithstanding
the elaborate structure of theory which Weismann has raised, there is
nowhere one single fact or one single consideration of much importance
to the question in debate which was not perfectly well known to Darwin.
Therefore I say that all this challenging of Darwinists to justify their
"Lamarckian assumptions" really amounts to nothing more than a pitting
of opinion against opinion, where there is at least as much call for
justification on the one side as on the other.

Again, when these challenges are thrown down by Weismann and his
followers, it appears to be forgotten that the conditions of their own
theory are such as to render acceptance of the gauge a matter of great
difficulty. The case is very much like that of a doughty knight pitching
his glove into the sea, and then defying any antagonist to take it up.
That this is the case a very little explanation will suffice to show.

The question to be settled is whether acquired characters are ever
transmitted by heredity. Now suppose, for the sake of argument, that
acquired characters are transmitted by heredity--though not so fully and
not so certainly as congenital characters--how is this fact to be proved
to the satisfaction of Weismann and his followers? First of all they
answer,--Assuredly by adducing experimental proof of the inheritance of
injuries, or mutilations. But in making this answer they appear to
forget that Darwin has already shown its inefficiency. That the
self-styled Neo-Lamarckians have been much more unguarded in this
respect, I fully admit; but it is obviously unfair to identify Darwin's
views with those of a small section of evolutionists, who are really as
much opposed to Darwin's teaching on one side as is the school of
Weismann on the other. Yet, on reading the essays of Weismann
himself--and still more those of his followers--one would almost be led
to gather that it is claimed by him to have enunciated the distinction
between congenital and acquired characters in respect of
transmissibility; and therefore also to have first raised the objection
which lies against the theory of Pangenesis in respect of the
non-transmissibility of mutilations. In point of fact, however, Darwin
is as clear and decided on these points as Weismann. And his answer to
the obvious difficulty touching the non-transmissibility of mutilations
is, to quote his own words, "the long-continued inheritance of a part
which has been removed during many generations is no real anomaly, for
gemmules formerly derived from the part are multiplied and transmitted
from generation to generation[29]." Therefore, so far as Darwin's theory
is concerned, the challenge to produce evidence of the transmission of
injuries is irrelevant: it is no more a part of Darwin's theory than it
is of Weismann's to maintain that injuries _are_ transmitted.

    [29] _Variation under Domestication_, ii. 392.

There is, however, one point in this connexion to which allusion must
here be made. Although Darwin did not believe in the transmissibility
of mutilations when these consist merely in the amputation of parts of
an organism, he did believe in a probable tendency to transmission when
removal of the part is followed by gangrene. For, as he says, in that
case, all the gemmules of the mutilated or amputated part, as they are
gradually attracted to that part (in accordance with the law of affinity
which the theory assumes), will be successively destroyed by the morbid
process. Now it is of importance to note that Darwin made this exception
to the general rule of the non-transmissibility of mutilations, not
because his theory of pangenesis required it, but because there appeared
to be certain very definite observations and experiments--which will be
mentioned later on--proving that when mutilations are followed by
gangrene they are apt to be inherited: his object, therefore, was to
reconcile these alleged facts with his theory, quite as much as to
sustain his theory by such facts.

So much, then, for the challenge to produce direct evidence of the
transmissibility of acquired characters, so far as mutilations are
concerned: believers in Darwin's theory, as distinguished from
Weismann's, are under no obligation to take up such a challenge. But the
challenge does not end here. Show us, say the school of Weismann, a
single instance where an acquired character _of any kind_ (be it a
mutilation or otherwise) has been inherited: this is all that we
require: this is all that we wait for: and surely, unless it be
acknowledged that the Lamarckian doctrine reposes on mere assumption, at
least one such case ought to be forthcoming. Well, nothing can sound
more reasonable than this in the first instance; but as soon as we
begin to cast about for cases which will satisfy the Neo-Darwinians, we
find that the structure of their theory is such as to preclude, in
almost every conceivable instance, the possibility of meeting their
demand. For their theory begins by assuming that natural selection is
the one and only cause of organic evolution. Consequently, what their
demand amounts to is throwing upon the other side the burden of
disproving this assumption--or, in other words, of proving the negative
that in any given case of transmitted adaptation natural selection has
_not_ been the sole agent at work. Now, it must obviously be in almost
all cases impossible to prove this negative among species in a state of
nature. For, even supposing that among such species Lamarckian
principles have had a large share in the formation of hereditary and
adaptive characters, how would Weismann himself propose that we should
set about the proof of such a fact, where the proof demanded by his
assumption is, that the _abstract possibility_ of natural selection
having had anything to do with the matter must be excluded? Obviously
this is impossible in the case of inherited characters which are also
_adaptive_ characters. How then does it fare with the case of inherited
characters which are not also adaptive? Merely that this case is met by
another and sequent assumption, which constitutes an integral part of
the Neo-Darwinian creed--namely, that in nature there _can be no such
characters_. Seeing that natural selection is taken to be the only
possible cause of change in species, it follows that all changes
occurring in species must necessarily be adaptive, whether or not we are
able to perceive the adaptations. In this way apparently useless
characters, as well as obviously useful ones, are ruled out of the
question: that is to say, _all_ hereditary characters of species in a
state of nature are _assumed_ to be due to natural selection, and then
it is demanded that the validity of this assumption should be disproved
by anybody who doubts it. Yet Weismann himself would be unable to
suggest any conceivable method by which it can be disproved among
species in a state of nature--and this even supposing that the
assumption is entirely false[30].

    [30] In subsequent chapters, especially devoted to the question
         (i.e. Section II), the validity of this assumption will be
         considered on its own merits.

Consequently, the only way in which these speciously-sounding challenges
can be adequately met is by removing some individuals of a species from
a state of nature, and so from all known influences of natural
selection; then, while carefully avoiding artificial selection, causing
these individuals and their progeny through many generations unduly to
exercise some parts of their bodies, or unduly to fail in the exercise
of others. But, clearly, such an experiment is one that must take years
to perform, and therefore it is now too early in the day to reproach the
followers of Darwin with not having met the challenges which are thrown
down by the followers of Weismann[31].

    [31] I say "the followers of Weismann," because Weismann himself,
         with his clear perception of the requirements of experimental
         research, expressly states the above considerations, with the
         conclusions to which they lead. Nevertheless, he is not
         consistent in his utterances upon this matter; for he
         frequently expresses himself to the effect, "that the _onus
         probandi_ rests with my opponents, and therefore they ought to
         bring forward actual proofs" (_Essays_, i. p. 390). But, as
         above shown, the _onus_ rests as much with him as with his
         opponents; while, even if his opponents are right, he elsewhere
         recognizes that they can bring "actual proofs" of the fact only
         as a result of experiments which must take many years to
         perform.

Probably enough has now been said to show that the Neo-Darwinian
assumption precludes the possibility of its own disproof from any of the
facts of nature (as distinguished from domestication)--and this even
supposing that the assumption be false. On the other hand, of course, it
equally precludes the possibility of its own proof; and therefore it is
as idle in Darwinists to challenge Weismann for proof of his negative
(i. e. that acquired characters are not transmitted), as it is in
Weismann to challenge Darwinists for proof of the opposite negative (i.
e. that all seeming cases of such transmission are not due to natural
selection). This dead-lock arises from the fact that in nature it is
beyond the power of the followers of Darwin to exclude the abstract
possibility of natural selection in any given case, while it is equally
beyond the power of the followers of Weismann to exclude the abstract
possibility of Lamarckian principles. Therefore at present the question
must remain for the most part a matter of opinion, based upon general
reasoning as distinguished from special facts or crucial experiments.
The evidence available on either side is presumptive, not
demonstrative[32]. But it is to be hoped that in the future, when time
shall have been allowed for the performance of definite experiments on a
number of generations of domesticated plants or animals, intentionally
shielded from the influences of natural selection while exposed to those
of the Lamarckian principles, results will be gained which will finally
settle the question one way or the other.

    [32] Note A.

Meanwhile, however, we must be content with the evidence as it stands;
and this will lead us to the second division of our subject. That is to
say, having now dealt with the antecedent, or merely logical, state of
the question, we have next to consider what actual, or biological,
evidence there is at present available on either side of it. Thus far,
neither side in the debate has any advantage over the other. On grounds
of general reasoning alone they both have to rely on more or less
dogmatic assumptions. For it is equally an unreasoned statement of
opinion whether we allege that all the phenomena of organic evolution
can be, or can not be, explained by the theory of natural selection
alone. We are at present much too ignorant touching the causes of
organic evolution to indulge in dogmatism of this kind; and if the
question is to be referred for its answer to authority, it would appear
that, both in respect of number and weight, opinions on the side of
having provisionally to retain the Lamarckian factors are more
authoritative than those _per contra_[33].

    [33] For a fair and careful statement of the present balance of
         authoritative opinion upon the question, see H. F. Osborn,
         _American Naturalist_, 1892, pp. 537-67.

       *       *       *       *       *

Turning then to the question of fact, with which the following chapters
are concerned, I will conclude this preliminary one with a few words on
the method of discussion to be adopted.

First I will give the evidence in favour of Lamarckianism; this will
occupy the next two chapters. Then, in Chapter V, I will similarly give
the evidence _per contra_, or in favour of Continuity as absolute.
Lastly, I will sum up the evidence on both sides, and give my own
judgement on the whole case. But on whichever side I am thus acting as
special pleader for the time being, I will adduce only such arguments as
seem to me valid--excluding alike from both the many irrelevant or
otherwise invalid reasonings which have been but too abundantly
published. Moreover, I think it will be convenient to consider all that
has been said--or may be said--in the way of criticism to each argument
by the opposite side while such argument is under discussion--i. e. not
to wait till all the special pleading on one side shall have been
exhausted before considering the exceptions which have been (or admit of
being) taken to the arguments adduced, but to deal with such exceptions
at the time when each of these arguments shall have been severally
stated. Again, and lastly, I will arrange the evidence in each case--i.
e. on both sides--under three headings, viz. (A) Indirect, (B) Direct,
and (C) Experimental[34].

    [34] [The above paragraph is allowed to remain exactly as Mr.
         Romanes left it. Chapters V and VI were however not completed.
         _See_ note appended to Preface. C. Ll. M.]




CHAPTER III.

CHARACTERS AS HEREDITARY AND ACQUIRED
(_continued_).


(A.)
_Indirect Evidence in favour of the Inheritance of Acquired Characters._


Starting with the evidence in favour of the so-called Lamarckian
factors, we have to begin with the Indirect--and this without any
special reference to the theories, either of Weismann or of others.

It has already been shown, while setting forth in the preceding chapter
the antecedent standing of the issue, that in this respect the _prima
facie_ presumption is wholly on the side of the transmission, in greater
degree or less, of acquired characters. Even Weismann allows that all
"_appearances_" point in this direction, while there is no inductive
evidence of the action of natural selection in any one case, either as
regards germs or somas, and therefore, _a fortiori_, of the
"all-sufficiency" of this cause[35]. It is true that in some of his
earlier essays he has argued that there is no small weight of _prima
facie_ evidence in favour of his own views as to the non-inheritance of
acquired characters. This, however, will have to be considered in its
proper place further on. Meanwhile I shall say merely in general terms
that it arises almost entirely from a confusion of the doctrine of
Continuity as absolute with that of Continuity as partial, and
therefore, as admitting of degrees in different cases--which, as already
explained, are doctrines wide as the poles asunder. But, leaving aside
for the present such _prima facie_ evidence as Weismann has adduced on
his side of the issue, I may quote him as a hostile witness to the
weight of this kind of evidence _per contra_, in so far as it has
already been presented in the foregoing chapter. Indeed, Weismann is
much too logical a thinker not to perceive the cogency of the
"appearances" which lie against his view of Continuity as
absolute--although he has not been sufficiently careful in
distinguishing between such Continuity and that which admits of degrees.

    [35] See, especially, his excellent remarks on this point, _Contemp.
         Rev._ Sept. 1893.

We may take it, then, as agreed on all hands that whatever weight merely
_prima facie_ evidence may in this matter be entitled to, is on the side
of what I have termed moderated Lamarckianism: first sight "appearances"
are against the Neo-Darwinian doctrine of the absolute non-inheritance
of acquired characters.

       *       *       *       *       *

Let us now turn to another and much more important line of indirect
evidence in favour of moderated Lamarckianism.

The difficulty of _excluding the possibility_ of natural selection
having been at work in the case of wild plants and animals has already
been noticed. Therefore we may now appreciate the importance of all
facts or arguments which _attenuate the probability_ of natural
selection having been at work. This may be done by searching for cases
in nature where a congenital structure, although unquestionably
adaptive, nevertheless presents so small an amount of adaptation, that
we can scarcely suppose it to have been arrived at by natural selection
in the struggle for existence, as distinguished from the inheritance of
functionally-produced modifications. For if functionally-produced
modifications are ever transmitted at all, there is no limit to the
minuteness of adaptive values which may thus become congenital; whereas,
in order that any adaptive structure or instinct should be seized upon
and accumulated by natural selection, it must from the very first have
had an adaptive value sufficiently great to have constituted its
presence a matter of life and death in the struggle for existence. Such
structures or instincts must not only have always presented some measure
of adaptive value, but this must always have been sufficiently great to
reach what I have elsewhere called a selection-value. Hence, if we meet
with cases in nature where adaptive structures or instincts present so
low a degree of adaptive value that it is difficult to conceive how they
could ever have exercised any appreciable influence in the battle for
life, such cases may fairly be adduced in favour of the Lamarckian
theory. For example, the Neo-Lamarckian school of the United States is
chiefly composed of palaeontologists; and the reason of this seems to be
that the study of fossil forms--or of species in process of
formation--reveals so many instances of adaptations which in their
nascent condition present such exceedingly minute degrees of adaptive
value, that it seems unreasonable to attribute their development to a
survival of the fittest in the complex struggle for existence. But as
this argument is in my opinion of greatest force when it is applied to
certain facts of physiology with which I am about to deal, I will not
occupy space by considering any of the numberless cases to which the
Neo-Lamarckians apply it within the region of palaeontology[36].

    [36] There is now an extensive literature within this region. The
         principal writers are Cope, Scott and Osborn. Unfortunately,
         however, the facts adduced are not crucial as test-cases
         between the rival theories--nearly all of them, in fact, being
         equally susceptible of explanation by either.

Turning then to inherited actions, it is here that we might antecedently
expect to find our best evidence of the Lamarckian principles, if these
principles have really had any share in the process of adaptive
evolution. For we know that in the life-time of individuals it is
action, and the cessation of action, which produce nearly all the
phenomena of acquired adaptation--use and disuse in animals being merely
other names for action and the cessation of action. Again, we know that
it is where neuro-muscular machinery is concerned that we meet with the
most conclusive evidence of the remarkable extent to which action is
capable of co-ordinating structures for the ready performance of
particular functions; so that even during the years of childhood
"practice makes perfect" to the extent of organizing neuro-muscular
adjustments, so elaborate and complete as to be indistinguishable from
those which in natural species we recognized as reflex actions on the
one hand, and instinctive actions on the other. Hence, if there be any
such thing as "use-inheritance" at all, it is in the domain of reflex
actions and instinctive actions that we may expect to find our best
evidence of the fact. Therefore I will restrict the present line of
evidence--(A)--to these two classes of phenomena, as together yielding
the best evidence obtainable within this line of argument.

       *       *       *       *       *

The evidence in favour of the Lamarckian factors which may be derived
from the phenomena of reflex action has never, I believe, been pointed
out before; but it appears to me of a more cogent nature than perhaps
any other. In order to do it justice, I will begin by re-stating an
argument in favour of these factors which has already been adduced by
previous writers, and discussed by myself in published correspondence
with several leaders of the ultra-Darwinian school.

Long ago Professor Broca and Mr. Herbert Spencer pointed to the facts of
co-adaptation, or co-ordination within the limits of the same organism,
as presenting good evidence of Lamarckian principles, working in
association with natural selection. Thus, taking one of Lamarck's own
illustrations, Mr. Spencer argued that there must be numberless
changes--extending to all the organs, and even to all the tissues, of
the animal--which in the course of many generations have conspired to
convert an antelope into a giraffe. Now the point is, that throughout
the entire history of these changes their utility must always have been
dependent on their association. It would be useless that an incipient
giraffe should present the peculiar form of the hind-quarters which we
now perceive, unless at the same time it presented the correspondingly
peculiar form of the fore-quarters; and as each of these great
modifications entails innumerable subordinate modifications throughout
both halves of the creature concerned, the chances must have been
infinitely great against the required association of so many changes
happening to have arisen congenitally in the same individuals by way of
merely fortuitous variation. Yet, if we exclude the Lamarckian
interpretation, which gives an intelligible _cause_ of co-ordination, we
are required to suppose that such a happy concurrence of innumerable
independent variations must have occurred by mere accident--and this on
innumerable different occasions in the bodies of as many successive
ancestors of the existing species. For at each successive stage of the
improvement natural selection (if working alone) must have needed all,
or at any rate most, of the co-ordinated parts to occur in the same
individual organisms[37].

    [37] For another and better illustration more recently published by
         Mr. Spencer, see _The Inadequacy of Natural Selection_, p. 22.

In alluding to what I have already published upon the difficulty which
thus appears to be presented to his theory, Weismann says, "At no
distant time I hope to be able to consider this objection, and to show
that the apparent support given to the old idea [i. e. of the
transmission of functionally-produced modifications] is really insecure,
and breaks down as soon as it is critically examined[38]."

    [38] _Essays on Heredity_, vol. i. p. 389.

         [For further treatment of the subject under discussion _see_
         Weismann, _The All-sufficiency of Natural Selection_ (Contemp.
         Rev. Sept. and Oct. 1893), and _The Effect of External
         Influences upon Development_. "Romanes Lecture" 1894, and
         Spencer, _Weismannism once more_ (Cont. Rev. Oct. 1894). C. Ll.
         M.]

So much for what Weismann has said touching this matter. But the matter
has also been dealt with both by Darwin and by Wallace. Darwin very
properly distinguishes between the fallacy that "with animals such as
the giraffe, of which the whole structure is admirably co-ordinated for
certain purposes, it has been supposed that all the parts must have been
simultaneously modified[39]," and the sound argument that the
co-ordination itself cannot have been due to natural selection alone.
This important distinction may be rendered more clear as follows.

    [39] _Variation_, &c., vol. ii. p. 206.

The facts of artificial selection prove that immense modifications of
structure may be caused by a cumulative blending in the same individuals
of characters which were originally distributed among different
individuals. Now, in the parallel case of natural selection the
characters thus blended will usually--if not invariably--be of an
adaptive kind; and their eventual blending together in the same
individuals will be due to free intercrossing of the most fit. But this
_blending of adaptations_ is quite a different matter from the
_occurrence of co-ordination_. For it belongs to the essence of
co-ordination that each of the co-ordinated parts should be destitute of
adaptive value _per se_: the adaptation only begins to arise if all the
parts in question occur associated together in the same individuals
_from the very first_. In this case it is obvious that the analogy of
artificial selection can be of no avail in explaining the facts, since
the difficulty presented has nothing to do with the blending in single
individuals of adaptations previously distributed among different
individuals; it has to do with the simultaneous appearance in single
individuals of a co-adaptation of parts, none of which could ever have
been of any adaptive value had it been previously distributed among
different individuals. Consequently, where Darwin comes to consider this
particular case (or the case of co-adaptation as distinguished from the
blending of adaptations), he freely invokes the aid of the Lamarckian
principles[40].

    [40] E. g. _Origin of Species_, p. 178.

Wallace, on the other hand, refuses to do this, and says that "the best
answer to the difficulty" of supposing natural selection to have been
the only cause of co-adaptation may be "found in the fact that the very
thing said to be impossible by variation and natural selection, has been
again and again affected by variation and artificial selection[41]."
This analogy (which Darwin had already and very properly adduced with
regard to the _blending of adaptations_) he enforces by special
illustrations; but he does not appear to perceive that it misses the
whole and only point of the "difficulty" against which it is brought.
For the case which his analogy sustains is not that which Darwin,
Spencer, Broca and others, mean by _co-adaptation_: it is the case of a
blending of _adaptations_. It is not the case where adaptation is _first
initiated in spite of intercrossing_, by a fortuitous concurrence of
variations each in itself being without adaptive value: it is the case
where adaptation is _afterwards increased by means of intercrossing_,
through the blending of variations each of which has always been in
itself of adaptive value.

    [41] _Darwinism_, p. 418.

From this I hope it will be apparent that the only way in which the
"difficulty" from co-adaptation can be logically met by the
ultra-Darwinian school, is by denying that the phenomenon of
co-adaptation (as distinguished from the blending of adaptations) is
ever to be really met with in organic nature. It may be argued that in
all cases where co-adaptation _appears_ to occur, closer examination
will show that the facts are really due to a blending of adaptations.
The characters A + B + C + D, which are now found united in the same
organism, and, as thus united, all conspiring to a common end, may
originally have been distributed among different organisms, where they
_severally_ subserved some other ends--or possibly the same end, though
in a less efficient manner. Obviously, however, in this case their
subsequent combination in the same organism would not be an instance of
co-adaptation, but merely of an advantageous blending together of
already existing adaptations. This argument, or rejoinder, has in point
of fact been adopted by Professor Meldola, he believes that all cases of
seeming co-adaptation are thus due to a mere blending of
adaptations[42]. Of course, if this position can be maintained, the
whole difficulty from co-adaptation would lapse. But even then it would
lapse on the ground of _fact_. It would not have been overturned, or in
any way affected, by Wallace's _argument_ from artificial selection.
For, in that event, no such argument would be required, and, if adduced,
would be irrelevant, since no one has ever alleged that there is any
difficulty in understanding the mere confluence of adaptations by
free-intercrossing of the best adapted.

    [42] _Nature_, vol. xliii. pp. 410, 557; vol. xliv. pp. 7, 29. I say
         "adopted," because I had objected to his quoting the analogy of
         artificial selection, and stated, as above, that the only way
         to meet Mr. Spencer's "difficulty" was to deny the fact of
         co-adaptation as ever occurring in any case. It then appeared
         that Professor Meldola agreed with me as to this. But I do not
         yet understand why, if such were his view, he began by
         endorsing Mr. Wallace's analogy from artificial selection--i.
         e. confusing the case of co-adaptation with that of the
         blending of adaptations. If any one denies the fact of
         co-adaptation, he cannot assist his denial by arguing the
         totally different fact that adaptations may be blended by free
         intercrossing; for this latter fact has never been questioned,
         and has nothing to do with the one which he engaged in
         disputing.

Now, if we are agreed that the only question in debate is the question
of fact whether or not co-adaptation ever occurs in nature, it appears
to me that the best field for debating the question is furnished by the
phenomena of reflex action. I can well perceive that the instances
adduced by Broca and Spencer in support of their common argument--such
as the giraffe, the elk, &c.--are equivocal. But I think that many
instances which may be adduced of reflex action are much more to the
point. _For it belongs to the very nature of reflex action that it
cannot work unless all parts of the machinery concerned are already
present, and already co-ordinated, in the same organism._ It would be
useless, in so far as such action is concerned if the afferent and
efferent nerves, the nerve-centre, and the muscles organically grouped
together, were not all present from the very first in the same
individuals, and from the very first were not co-ordinated as a definite
piece of organic machinery.

With respect to reflex actions, therefore, it is desirable to begin by
pointing out how widely the adaptations which they involve differ from
those where no manufacture, so to speak, of special machinery is
required. Thus, it is easy to understand how natural selection alone is
capable of gradually accumulating congenital variations in the direction
of protective colouring; of mimicry; of general size, form, mutual
correlation of parts as connected with superior strength, fleetness,
agility, &c.; of greater or less development of particular parts, such
as legs, wings, tails, &c. For in all such cases the adaptation which is
in process of accumulation is from its very commencement and throughout
each of its subsequent stages, of _use_ in the struggle for existence.
And inasmuch as all the individuals of each successive generation vary
round the specific mean which characterized the preceding generation,
there will always be a sufficient number of individuals which present
congenital variations of the kind required for natural selection to
seize upon, without danger of their being swamped by free
intercrossing--as Mr. Wallace has very ably shown in his _Darwinism_.
But this law of averages can apply only to cases where single
structures--or a single group of correlated structures--are already
present, and already varying round a specific mean. The case is quite
different where a _co-ordination_ of structures is required for the
performance of a _previously non-existent_ reflex action. For some, at
least, of these structures must be _new_, as must also be the function
which all of them first conspire to perform. Therefore, neither the new
elements of structure, nor the new combination of structures, can have
been previously given as varying round a specific mean. On the contrary,
a very definite piece of machinery, consisting of many co-ordinated
parts, must somehow or other be originated in a high degree of working
efficiency, before it can be capable of answering its purpose in the
prompt performance of a particular action under particular circumstances
of stimulation. Lastly, such pieces of machinery are always of a highly
delicate character, and usually involve so immensely complex a
co-ordination of mutually dependent parts, that it is only a
physiologist who can fully appreciate the magnitude of the distinction
between "adaptations" of this kind, and "adaptations" of the kind which
arise through natural selection seizing upon congenital variations as
these oscillate round a specific mean.

Or the whole argument may be presented in another form, under three
different headings, thus:--

In the first place, it will be evident from what has just been said,
that such a piece of machinery as is concerned in even the simplest
reflex action cannot have occurred in any considerable number of
individuals of a species, _when it first began to be constructed_. On
the contrary, if its _origin_ were dependent on congenital variations
alone, the needful co-adaptation of parts which it requires can scarcely
have happened to occur in more than a very small percentage of
cases--even if it be held conceivable that by such means alone it should
ever have occurred at all. Hence, instead of preservation and subsequent
improvement having taken place _in consequence of_ free intercrossing
among all individuals of the species (as in the cases of protective
colouring, &c., where adaptation has no reference to any mechanical
co-adaptation of parts), they must have taken place _in spite of_ such
intercrossing.

In the second place, adaptations due to organic machineries of this kind
differ in another all-important respect from those due to a summation of
adaptive characters which are already present and already varying round
a specific mean. The latter depend for their summation upon the
fact--not merely, as just stated, that they are already present, already
varying round a specific mean, and therefore owe their progressive
evolution to free intercrossing, but also--_that they admit of very
different degrees of adaptation_. It is only because the degree of
adaptation in generation B is superior to that in generation A that
_gradual improvement_ in respect of adaptation is here possible. In the
case of protective resemblance, for example, a very imperfect and merely
accidental resemblance to a leaf, to another insect, &c., may at the
first start have conferred a sufficient degree of adaptive imitation to
count for something in the struggle for life; and, if so, the basis
would be given for a progressive building up by natural selection of
structures and colours in ever-advancing degrees of adaptive
resemblance. There is here no necessity to suppose--nor in point of fact
is it ever supposed, since the supposition would involve nothing short
of a miracle--that such extreme perfection in this respect as we now so
frequently admire has originated suddenly in a single generation, as a
collective variation of a congenital kind affecting simultaneously a
large proportional number of individuals. But in the case of a reflex
mechanism--which may involve even greater marvels of adaptive
adjustment, and _all_ the parts of which must occur in the same
_individuals_ to be of any use--it _is_ necessary to suppose some such
sudden and collective origin in some very high degree of efficiency, if
natural selection has been the only principle concerned in afterwards
perfecting the mechanism. For it is self-evident that a reflex action,
from its very nature, cannot admit of any great differences in its
degrees of adaptation: if it is to work at all, so as to count for
anything in the struggle for life, it must already be given in a state
of working efficiency. So that, unless we invoke either the doctrine of
"prophetic types" or the theory of sudden creations, I confess I do not
see how we are to explain either the origin, or the development, of a
reflex mechanism by means of natural selection alone.

Lastly, in the third place, _even when reflex mechanisms have been fully
formed_, it is often beyond the power of sober credence to believe that
they now are, or ever can have been, of selective value in the struggle
for existence, as I will show further on. And such cases go to fortify
the preceding argument. For if not conceivably of selective value even
when completely evolved, much less can they conceivably have been so
through all the stages of their complex evolution back to their very
origin. Therefore, supposing for the present that there are such cases
of reflex action in nature, neither their origin nor their development
can conceivably have been due to natural selection alone. The Lamarckian
factors, however, have no reference to degrees of adaptation, any more
than they have to degrees of complexity. No question of value, as
selective or otherwise, can obtain in their case: neither in their case
does any difficulty obtain as regards the co-adaptation of severally
useless parts.

Now, if all these distinctions between the Darwinian and Lamarckian
principles are valid--and I cannot see any possibility of doubt upon
this point--strong evidence in favour of the latter would be furnished
by cases (if any occur) where structures, actions, instincts, &c.,
although of some adaptive value, are nevertheless plainly not of
selective value. According to the ultra-Darwinian theory, no such cases
ought ever to occur: according to the theory of Darwin himself, they
ought frequently to occur. Therefore a good test, or criterion, as
between these different theories of organic evolution is furnished by
putting the simple question of fact--Can we, or can we not, show that
there are cases of adaptation where the degree of adaptation is so small
as to be incompatible with the supposition of its presenting a selective
value? And if we put the wider question--Are there any cases where the
co-adaptation of severally useless parts has been brought about, when
even the resulting whole does not present a selective value?--then, of
course, we impose a still more rigid test.

Well, notwithstanding the difficulty of proving such a negative as the
absence of natural selection where adaptive development is concerned, I
believe that there are cases which conform to both these tests
simultaneously; and, moreover, that they are to be found in most
abundance where the theory of use-inheritance would most expect them to
occur--namely, in the province of reflex action. For the very essence of
this theory is the doctrine, that constantly associated use of the same
parts for the performance of the same action will progressively organize
those parts into a reflex mechanism--no matter how high a degree of
co-adaptation may thus be reached on the one hand, or how low a degree
of utilitarian value on the other.

Having now stated the general or abstract principles which I regard as
constituting a defence of the Lamarckian factors, so far as this admits
of being raised on grounds of physiology, we will now consider a few
concrete cases by way of illustration. It is needless to multiply such
cases for the mere purpose of illustration. For, on reading those here
given, every physiologist will at once perceive that they might be added
to indefinitely. The point to observe is, the relation in which these
samples of reflex action stand to the general principles in question;
for there is nothing unusual in the samples themselves. On the contrary,
they are chosen because they are fairly typical of the phenomena of
reflex action in general.

In our own organization there is a reflex mechanism which ensures the
prompt withdrawal of the legs from any source of irritation supplied to
the feet. For instance, even after a man has broken his spine in such a
manner as totally to interrupt the functional continuity of his spinal
cord and brain, the reflex mechanism in question will continue to
retract his legs when his feet are stimulated by a touch, a burn, &c.
This responsive action is clearly an adaptive action, and, as the man
neither feels the stimulation nor the resulting movement, it is as
clearly a reflex action. The question now is as to the mode of its
origin and development.

I will not here dwell upon the argument from co-adaptation, because this
may be done more effectually in the case of more complicated reflex
actions, but will ask whether we can reasonably hold that this
particular reflex action--comparatively simple though it is--has ever
been of selective value to the human species, or to the ancestors
thereof? Even in its present fully-formed condition it is fairly
questionable whether it is of any adaptive _value_ at all. The movement
performed is no doubt an adaptive _movement_; but is there any occasion
upon which the reflex mechanism concerned therein can ever have been of
adaptive _use_? Until a man's legs have been paralyzed as to their
voluntary motion, he will always promptly withdraw his feet from any
injurious source of irritation by means of his conscious intelligence.
True, the reflex mechanism secures an almost inappreciable saving in the
time of response to a stimulus, as compared with the time required for
response by an act of will; but the difference is so exceedingly small,
that we can hardly suppose the saving of it in this particular case to
be a matter of any adaptive--much less selective--importance. Nor is it
more easy to suppose that the reflex mechanism has been developed by
natural selection for the purpose of replacing voluntary action when the
latter has been destroyed or suspended by grave spinal injury,
paralysis, coma, or even ordinary sleep. In short, even if for the sake
of argument we allow it to be conceivable that any single human being,
ape, or still more distant ancestor, has ever owed its life to the
possession of this mechanism, we may still be certain that not one in a
million can have done so. And, if this is the case with regard to the
mechanism as now fully constructed, still more must it have been the
case with regard to all the previous stages of construction. For here,
without elaborating the point, it would appear that a process of
construction by survival of the fittest alone is incomprehensible.

On the other hand, of course, the theory of use-inheritance furnishes a
fully intelligible--whether or not a true--explanation. For those
nerve-centres in the spinal cord which co-ordinate the muscles required
for retracting the feet are the centres used by the will for this
purpose. And, by hypothesis, the frequent use of them for this purpose
under circumstances of stimulation which render the muscular response
appropriate, will eventually establish an organic connexion between such
response and the kind of stimulation to which it is appropriate--even
though there be no utilitarian reason for its establishment[43]. To
invert a phrase of Aristotle, we do not frequently use this mechanism
because we have it (seeing that in our normal condition there is no
necessity for such use); but, by hypothesis, we have it because we have
frequently used its several elements in appropriate combination.

    [43] It may be said, with regard to this particular reflex, that it
         may perhaps be, so to speak, a mechanical accident, arising
         from the contiguity of the sensory and motor roots in the cord.
         But as this suggestion cannot apply to other reflexes presently
         to be adduced, it need not be considered.

I will adduce but one further example in illustration of these general
principles--passing at once from the foregoing case of comparative
simplicity to one of extreme complexity.

There is a well-known experiment on a brainless frog, which reveals a
beautiful reflex mechanism in the animal, whereby the whole body is
enabled continually to readjust its balance on a book (or any other
plane surface), as this is slowly rotated on a horizontal axis. So long
as the book is lying flat, the frog remains motionless; but as soon as
the book is tilted a little, so that the frog is in danger of slipping
off, all the four feet begin to crawl up the hill; and the steeper the
hill becomes, the faster they crawl. When the book is vertical, the frog
has reached the now horizontal back, and so on. Such being the facts,
the question is--How can the complicated piece of machinery thus implied
have been developed by natural selection? Obviously it cannot have been
so by any of the parts concerned having been originally distributed
among different individuals, and afterwards united in single individuals
by survival (i.e. free intercrossing) of the fittest. In other words,
the case is obviously one of co-adaptation, and not one of the blending
of adaptations. Again, and no less obviously, it is impossible that the
co-adaptation can have been _gradually developed_ by natural selection,
because, in order to have been so, it must by hypothesis have been of
some degree of use in every one of its stages; yet it plainly cannot
have been until it had been fully perfected in all its astonishing
complexity[44].

    [44] Of course it will be observed that the question is not with
         regard to the development of all the nerves and muscles
         concerned in this particular process. It is as to the
         development of the co-ordinating centres, which thus so
         delicately respond to the special stimuli furnished by
         variations of angle to the horizon. And it is as inconceivable
         in this case of reflex action, as it is in almost every other
         case of reflex action, that the highly specialized machinery
         required for performing the adaptive function can ever have had
         its origin in the performance of any other function. Indeed, a
         noticeable peculiarity of reflex mechanisms as a class is the
         highly specialized character of the functions which their
         highly organized structures subserve.

Lastly, not only does it thus appear impossible that during all stages
of its development--or while as yet incapable of performing its
intricate function--this nascent mechanism can have had any adaptive
value; but even as now fully developed, who will venture to maintain
that it presents any selective value? As long as the animal preserves
its brain, it will likewise preserve its balance, by the exercise of its
intelligent volition. And, if the brain were in some way destroyed, the
animal would be unable to breed, or even to feed; so that natural
selection can never have had any _opportunity_, so to speak, of
developing this reflex mechanism in brainless frogs. On the other hand,
as we have just seen, we cannot perceive how there can ever have been
any _raison d'être_ for its development in normal frogs--even if its
development were conceivably possible by means of this agency. But if
practice makes perfect in the race, as it does in the individual, we can
immediately perceive that the constant habit of correctly adjusting its
balance may have gradually developed, in the batrachian organization,
this non-necessary reflex[45].

    [45] We meet with a closely analogous reflex mechanism in brainless
         vertebrata of other kinds; but these do not furnish such good
         test cases, because the possibility of natural selection cannot
         be so efficiently attenuated. The perching of brainless birds,
         for instance, at once refers us to the roosting of sleeping
         birds, where the reflex mechanism concerned is clearly of high
         adaptive value. Therefore such a case is not available as a
         test, although the probability is that birds have inherited
         their balancing mechanisms from their sauropsidian ancestors,
         where it would have been of no such adaptive importance.

And, of course, this example--like that of withdrawing the feet from a
source of stimulation, which a frog will do as well as a man--does not
stand alone. Without going further a-field than this same animal, any
one who reads, from our present point of view, Goltz's work on the
reflex actions of the frog, will find that the great majority of
them--complex and refined though most of them are--cannot conceivably
have ever been of any use to any frog that was in undisturbed possession
of its brain.

Hence, not to occupy space with a reiteration of facts all more or less
of the same general kind, and therefore all presenting identical
difficulties to ultra-Darwinian theory, I shall proceed to give two
others which appear to me of particular interest in the present
connexion, because they furnish illustrations of reflex actions in a
state of only partial development, and are therefore at the present
moment demonstrably useless to the animal which displays them.

Many of our domesticated dogs, when we gently scratch their sides and
certain other parts of the body, will themselves perform scratching
movements with the hind leg of the same side as that upon which the
irritation is being supplied. According to Goltz[46], this action is a
true reflex; for he found that it is performed equally well in a dog
which has been deprived of its cerebral hemispheres, and therefore of
its normal volition. Again, according to Haycraft[47], this reflex is
congenital, or not acquired during the life-time of each individual dog.
Now, although the action of scratching is doubtless adaptive, it appears
to me incredible that it could ever have become organized into a
congenital reflex by natural selection. For, in order that it should,
the scratching away fleas would require to have been a function of
selective value. Yet, even if the irritation caused by fleas were
supposed to be so far fatal in the struggle for existence, it is certain
that they would always be scratched away by the conscious intelligence
of each individual dog; and, therefore, that no advantage could be
gained by organizing the action into a reflex. On the other hand, if
acquired characters are ever in any degree transmitted, it is easy to
understand how so frequently repeated an action should have become, in
numberless generations of dogs, congenitally automatic.

    [46] _Pflüger's Archiv_, Bd. xx. s. 23 (1879).

    [47] _Brain_, part xlviii, pp. 516-19 (1889).--There is still better
         proof of this in the case of certain rodents. For instance,
         observing that rats and mice are under the necessity of very
         frequently scratching themselves with their hind-feet, I tried
         the experiment of removing the latter from newly-born
         individuals--i.e. before the animals were able to co-ordinate
         their movements, and therefore before they had ever even
         attempted to scratch themselves. Notwithstanding that they were
         thus destitute of individual experience with regard to the
         benefit of scratching, they began their scratching movements
         with their stumps as soon as they were capable of executing
         co-ordinated movements, and afterwards continued to do so till
         the end of their lives with as much vigour and frequency as
         unmutilated animals. Although the stumps could not reach the
         seats of irritation which were bent towards them, they used to
         move rapidly in the air for a time sufficient to have given the
         itching part a good scratch, had the feet been present--after
         which the animals would resume their sundry other avocations
         with apparent satisfaction. These facts showed the hereditary
         response to irritation by parasites to be so strong, that even
         a whole life-time's experience of its futility made no
         difference in the frequency or the vigour thereof.

So much for the general principle of selective value as applied to this
particular case. And similarly, of course, we might here repeat the
application of all the other general principles, which have just been
applied in the two preceding cases. But it is only one of these other
general principles which I desire in the present case specially to
consider, for the purpose of considering more closely than hitherto the
difficulty which this principle presents to ultra-Darwinian theory.

The difficulty to which I allude is that of understanding how all the
stages in the _development_ of a reflex action can have been due to
natural selection, seeing that, before the reflex mechanism has been
sufficiently elaborated to perform its function, it cannot have
presented any degree of utility. Now the particular force of the present
example, the action of scratching--as also of the one to
follow--consists in the fact that it is a case where a reflex action is
not yet completely organized. It appears to be only in course of
construction, so that it is neither invariably present, nor, when it is
present, is it ever fully adapted to the performance of its function.

That it is not invariably present (when the brain is so) may be proved
by trying the simple experiment on a number of puppies--and also of
full-grown dogs. Again, that even when it is present it is far from
being fully adapted to the performance of its function, may be proved by
observing that only in rare instances does the scratching leg succeed in
scratching the place which is being irritated. The movements are made
more or less at random, and as often as not the foot fails to touch the
body at any place at all. Hence, although we have a "prophecy" of a
reflex action well designed for the discharge of a particular function,
at present the machinery is not sufficiently perfected for the adequate
discharge of that function. In this important respect it differs from
the otherwise closely analogous reflex action of the frog, whereby the
foot of the hind leg is enabled to localize with precision a seat of
irritation on the side of the body. But this beautiful mechanism in the
frog cannot have sprung into existence ready formed at any historical
moment in the past history of the phyla. It must have been the subject
of a more or less prolonged evolution, in some stage of which it must
presumably have resembled the now nascent scratching reflex of the dog,
in making merely abortive attempts at localizing the seat of
irritation--supposing, of course, that some physiologist had been there
to try the experiment by first removing the brain. Now, even if one
could imagine it to be, either in the frog or in the dog, a matter of
selective importance that so exceedingly refined a mechanism should have
been developed for the sole purpose of inhibiting the bites of
parasites--which in every normal animal would certainly be discharged by
an _intentional_ performance of the movements in question,--even if, in
order to save an hypothesis at all costs, we make so violent a
supposition as this, still we should do so in vain. For it would still
remain undeniably certain that the reflex mechanism is _not_ of any
selective value. Even now the mechanism in the dog is not sufficiently
precise to subserve the only function which occasionally and abortively
it attempts to perform. Thus it has all the appearance of being but an
imitating shadow of certain neuro-muscular adjustments, which have been
habitually performed in the canine phyla by a volitional response to
cutaneous irritation. Were it necessary, this argument might be
strengthened by observing that the reflex action is positively
_improved_ by removal of the brain.

The second example of a nascent reflex in dogs which I have to mention
is as follows.

Goltz found that his brainless dogs, when wetted with water, would shake
themselves as dry as possible, in just the same way as normal dogs will
do under similar circumstances. This, of course, proves that the shaking
movements may be performed by a reflex mechanism, which can have no
other function to perform in the organization of a dog, and which,
besides being of a highly elaborate character, will respond only to a
very special kind of stimulation. Now, here also I find that the
mechanism is congenital, or not acquired by individual experience. For
the puppies on which I experimented were kept indoors from the time of
their birth--so as never to have had any experience of being wetted by
rain, &c.--till they were old enough to run about with a full power of
co-ordinating their general movements. If these young animals were
suddenly plunged into water, the shock proved too great: they would
merely lie and shiver. But if their feet alone were wetted, by being
dipped in a basin of water, the puppies would soon afterwards shake
their heads in the peculiar manner which is required for shaking water
off the ears, and which in adult dogs constitutes the first phase of a
general shaking of the whole body.

Here, then, we seem to have good evidence of all the same facts which
were presented in the case of the scratching reflex. In the first
place, co-adaptation is present in a very high degree, because this
shaking reflex in the dog, unlike the skin-twitching reflex in the
horse, does not involve only a single muscle, or even a single group of
muscles; it involves more or less the co-ordinated activity of many
voluntary muscles all over the body. Such, at any rate, is the case when
the action is performed by the intelligent volition of an adult dog; and
if a brainless dog, or a young puppy, does not perform it so extensively
or so vigorously, this only goes to prove that the reflex has not yet
been sufficiently developed to serve as a substitute for intelligent
volition--i.e. that it is _useless_, or a mere organic shadow of the
really adaptive substance. Again, even if this nascent reflex had been
so far developed as to have been capable of superseding voluntary
action, still we may fairly doubt whether it could have proved of
selective value. For it is questionable whether the immediate riddance
of water after a wetting is a matter of life and death to dogs in a
state of nature. Moreover, even if it were, every individual dog would
always have got rid of the irritation, and so of the danger, by means of
a _voluntary_ shake--with the double result that natural selection has
never had any opportunity of gradually building up a special reflex
mechanism for the purpose of securing a shake, and that the canine race
have not had to wait for any such unnecessary process. Lastly, such a
process, besides being unnecessary, must surely have been, under any
circumstances, impossible. For even if we were to suppose--again for the
sake of saving an hypothesis at any cost--that the presence of a
fully-formed shaking reflex is of selective value in the struggle for
existence, it is perfectly certain that all the stages through which the
construction of so elaborate a mechanism must have passed could not have
been, under any circumstances, of any such value.

But, it is needless to repeat, according to the hypothesis of
use-inheritance, there is no necessity to suppose that these incipient
reflex mechanisms _are_ of any value. If function produces structure in
the race as it does in the individual, the voluntary and frequently
repeated actions of scratching and shaking may very well have led to an
organic integration of the neuro-muscular mechanisms concerned. Their
various parts having been always co-ordinated for the performance of
these actions by the intelligence of innumerable dogs in the past, their
co-adapted activity in their now automatic responses to appropriate
stimuli presents no difficulty. And the consideration that neither in
their prospectively more fully developed condition, nor, _a fortiori_,
in their present and all previous stages of evolution, can these reflex
mechanisms be regarded as presenting any selective--or even so much as
any adaptive--value, is neither more nor less than the theory of
use-inheritance would expect.

Thus, with regard to the phenomena of reflex action in general, all the
facts are such as this theory requires, while many of the facts are such
as the theory of natural selection alone cannot conceivably explain.
Indeed, it is scarcely too much to say, that most of the facts are such
as directly contradict the latter theory in its application to them.
But, be this as it may, at present there are only two hypotheses in the
field whereby to account for the facts of adaptive evolution. One of
these hypotheses is universally accepted, and the only question is
whether we are to regard it as _alone_ sufficient to explain _all_ the
facts. The other hypothesis having been questioned, we can test its
validity only by finding cases which it is fully capable of explaining,
and which do not admit of being explained by its companion hypothesis. I
have endeavoured to show that we have a large class of such cases in the
domain of reflex action, and shall next endeavour to show that there is
another large class in the domain of instinct.

       *       *       *       *       *

If instinct be, as Professor Hering, Mr. Samuel Butler, and others have
argued, "hereditary habit"--i. e. if it comprises an element of
transmitted experience--we at once find a complete explanation of many
cases of the display of instinct which otherwise remain inexplicable.
For although a large number--or even, as I believe, a large majority--of
instincts are explicable by the theory of natural selection alone, or by
supposing that they were gradually developed by the survival of
fortuitous variations in the way of advantageous psychological
peculiarities, this only applies to comparatively simple instincts, such
as that of a protectively coloured animal exhibiting a preference for
the surroundings which it resembles, or even adopting attitudes in
imitation of objects which occur in such surroundings. But in all cases
where instincts become complex and refined, we seem almost compelled to
accept Darwin's view that their origin is to be sought in consciously
intelligent adjustments on the part of ancestors.

Thus, to give only one example, a species of Sphex preys upon
caterpillars, which it stings in their nerve-centres for the purpose of
paralyzing, without killing them. The victims, when thus rendered
motionless, are then buried with the eggs of the Sphex, in order to
serve as food for her larvae which subsequently develop from these eggs.
Now, in order thus to paralyze a caterpillar, the Sphex has to sting it
successively in nine minute and particular points along the ventral
surface of the animal--and this the Sphex unerringly does, to the
exclusion of all other points of the caterpillar's anatomy. Well, such
being the facts--according to M. Fabre, who appears to have observed
them carefully--it is conceivable enough, as Darwin supposed[48], that
the ancestors of the Sphex, being like many other hymenopterous insects
highly intelligent, should have observed that on stinging caterpillars
in these particular spots a greater amount of effect was produced than
could be produced by stinging them anywhere else; and, therefore, that
they habitually stung the caterpillars in these places only, till, in
course of time, this originally intelligent habit became by heredity
instinctive. But now, on the other hand, if we exclude the possibility
of this explanation, it appears to me incredible that such an instinct
should ever have been evolved at all; for it appears to me incredible
that natural selection, unaided by originally intelligent action, could
ever have developed such an instinct out of merely fortuitous
variations--there being, by hypothesis, nothing to _determine_
variations of an insect's mind in the direction of stinging caterpillars
only in these nine intensely localized spots[49].

    [48] For details of his explanation of this particular case, for
         which I particularly inquired, see _Mental Evolution in
         Animals_, pp. 301-2.

    [49] Note B.

Again, there are not a few instincts which appear to be wholly useless
to their possessors, and others again which appear to be even
deleterious. The dusting over of their excrement by certain
freely-roaming carnivora; the choice by certain herbivora of particular
places on which to void their urine, or in which to die; the howling of
wolves at the moon; purring of cats, &c., under pleasurable emotion; and
sundry other hereditary actions of the same apparently unmeaning kind,
all admit of being readily accounted for as useless habits originally
acquired in various ways, and afterwards perpetuated by heredity,
because not sufficiently deleterious to have been stamped out by natural
selection[50]. But it does not seem possible to explain them by survival
of the fittest in the struggle for existence.

    [50] For fuller treatment see _Mental Evolution in Animals_, pp.
         274-285, 378-379, 381-383.

Finally, in the case of our own species, it is self-evident that the
aesthetic, moral, and religious instincts admit of a natural and easy
explanation on the hypothesis of use-inheritance, while such is by no
means the case if that hypothesis is rejected. Our emotions of the
ludicrous, of the beautiful, and of the sublime, appear to be of the
nature of hereditary instincts; and be this as it may, it would further
appear that, whatever else they may be, they are certainly not of a
life-preserving character. And although this cannot be said of the
moral sense when the theory of natural selection is extended from the
individual to the tribe, still, when we remember the extraordinary
complexity and refinement to which they have attained in civilized man,
we may well doubt whether they can have been due to natural selection
alone. But space forbids discussion of this large and important question
on the present occasion. Suffice it therefore to say, that I doubt not
Weismann himself would be the first to allow that his theory of heredity
encounters greater difficulties in the domain of ethics than in any
other--unless, indeed, it be that of religion[51].

    [51] For an excellent essay on the deleterious character of early
         forms of religion from a biological point of view, see the Hon.
         Lady Welby, _An Apparent Paradox in Mental Evolution_ (Journ.
         Anthrop. Inst. May 1891).

       *       *       *       *       *

I have now given a brief sketch of the indirect evidence in favour of
the so-called Lamarckian factors, in so far as this appears fairly
deducible from the facts of reflex action and of instinct. It will now
be my endeavour to present as briefly what has to be said against this
evidence.

As previously observed, the facts of reflex action have not been
hitherto adduced in the present connexion. This has led me to occupy
considerably more space in the treatment of them than those of instinct.
On this account, also, there is here nothing to quote, or to consider,
_per contra_. On the other hand, however, Weismann has himself dealt
with the phenomena of instinct in animals, though not, I think, in
man--if we except his brilliant essay on music. Therefore let us now
begin this division of our subject by briefly stating, and considering,
what he has said upon the subject.

The answer of Weismann to difficulties which arise against the
ultra-Darwinian theory in the domain of instinct, is as follows:--

     "The necessity for extreme caution in appealing to the supposed
     hereditary effects of use, is well shown in the case of those
     numerous instincts which only come into play once in a life-time,
     and which do not therefore admit of improvement by practice. The
     queen-bee takes her nuptial flight only once, and yet how many and
     complex are the instincts and the reflex mechanisms which come into
     play on that occasion. Again, in many insects the deposition of
     eggs occurs but once in a life-time, and yet such insects always
     fulfil the necessary conditions with unfailing accuracy[52]."

    [52] _Essays_, i. p. 93.

But in this rejoinder the possibility is forgotten, that although such
actions are _now_ performed only once in the individual life-time,
_originally_--i.e. when the instincts were being developed in a remote
ancestry--they may have been performed on many frequent and successive
occasions during the individual life-time. In all the cases quoted by
Weismann, instincts of the kind in question bear independent evidence of
high antiquity, by occurring in whole genera (or even families), by
being associated with peculiar and often highly evolved structures
required for their performance, and so on. Consequently, in these cases
ample time has been allowed for subsequent changes of habit, and of
seasonal alterations with respect to propagation--both these things
being of frequent and facile occurrence among animals of all kinds, even
within periods which fall under actual observation. Nevertheless, I do
not question that there are instinctive activities which, as far as we
are able to see, can never have been performed more than once in each
individual life-time[53]. The fact, however, only goes to show what is
fully admitted--that some instincts (and even highly complex instincts)
have apparently been developed by natural selection alone. Which, of
course, is not equivalent to showing that all instincts must have been
developed by natural selection alone. The issue is not to be debated on
general grounds like this, but on those of particular cases. Even if it
were satisfactorily proved that the instincts of a queen-bee have been
developed by natural selection, it would not thereby be proved that such
has been the case with the instincts of a Sphex wasp. One can very well
understand how the nuptial flight of the former, with all its associated
actions, may have been brought about by natural selection alone; but
this does not help us to understand how the peculiar instincts of the
latter can have been thus caused.

    [53] See _Mental Evolution in Animals_, pp. 377-8.

Strong evidence in favour of Weismann's views does, however, at first
sight seem to be furnished by social hymenoptera in other respects. For
not only does the queen present highly specialized and altogether
remarkable instincts; but the neuters present totally different and even
still more remarkable instincts--which, moreover, are often divided into
two or more classes, corresponding with the different "castes." Yet the
neuters, being barren females, never have an opportunity of bequeathing
their instincts to progeny. Thus it appears necessary to suppose that
the instincts of all the different castes of neuters are latent in the
queen and drones, together with the other instincts which are patent in
both. Lastly, it seems necessary to suppose that all this wonderful
organization of complex and segregated instincts must have been built up
by natural selection acting exclusively on the queens and drones--seeing
that these exercise their own instincts only once in a life-time, while,
as just observed, the neuters cannot possibly bequeath their individual
experience to progeny. Obviously, however, natural selection must here
be supposed to be operating at an immense disadvantage; for it must have
built up the often diverse and always complex instincts of neuters, not
directly, but indirectly through the queens and drones, which never
manifest any of these instincts themselves.

Now Darwin fully acknowledged the difficulty of attributing these
results to the unaided influence of natural selection; but the fact of
neuter insects being unable to propagate seemed to him to leave no
alternative. And so it seems to Weismann, who accordingly quotes these
instincts in support of his views. And so it seemed to me, until my work
on _Animal Intelligence_ was translated into French, and an able Preface
was supplied to that translation by M. Perrier. In this Preface it is
argued that we are not necessarily obliged to exclude the possibility of
Lamarckian principles having operated in the original formation of these
instincts. On the contrary, if such principles ever operate at all,
Perrier shows that here we have a case where it is virtually certain
that they must have operated. For although neuter insects are now unable
to propagate, their organization indicates--if it does not actually
prove--that they are descended from working insects which were able to
propagate. Thus, in all probability, what we now call a "hive" was
originally a society of sexually mature insects, all presenting the same
instincts, both as to propagation and to co-operation. When these
instincts, thus common to all individuals composing the hive, had been
highly perfected, it became of advantage in the struggle for existence
(between different hives or communities) that the functions of
reproduction should devolve more upon some individuals, while those of
co-operation should devolve more upon others. Consequently, this
division of labour began, and gradually became complete, as we now find
it in bees and ants. Perrier sustains the hypothesis thus briefly
sketched by pointing to certain species of social hymenoptera where we
may actually observe different stages of the process--from cases where
all the females of the hive are at the same time workers and breeders,
up to the cases where the severance between these functions has become
complete. Therefore, it seems to me, it is no longer necessary to
suppose that in these latter cases all the instincts of the (now) barren
females can only have been due to the unaided influence of natural
selection.

Nevertheless, although I think that Perrier has made good his position
thus far, that his hypothesis fails to account for some of the instincts
which are manifested by neuter insects, such as those which, so far as I
can see, must necessarily be supposed to have originated after the
breeding and working functions had become separated--seeing that they
appear to have exclusive reference to this peculiar state of matters.
Possibly, however, Perrier might be able to meet each of these
particular instincts, by showing how they could have arisen out of
simpler beginnings, prior to the separation of the two functions in
question. There is no space to consider such possibilities in detail;
but, until this shall have been done, I do not think we are entitled to
conclude that the phenomena of instinct as presented by neuter insects
are demonstrably incompatible with the doctrines of Lamarck--or, that
these phenomena are available as a logical proof of the unassisted
agency of natural selection in the case of instincts in general[54].

    [54] [See H. Spencer, _The Inadequacy of Natural Selection, A
         Rejoinder to Professor Weismann_, Contemp. Rev. 1893; and
         _Weismannism once more_, Ibid. Oct. 1894; Weismann, _The
         All-sufficiency of Natural Selection_, Ibid. 1893; and _The
         Effect of External Influences upon Development_, "Romanes
         Lecture" 1894: also _Neuter Insects and Lamarckism_, W. Platt
         Ball, Natural Science, Feb. 1894, and _Neuter Insects and
         Darwinism_, J. T. Cunningham, Ibid. April 1894. C. Ll. M.]


(B.)
_Inherited Effects of Use and of Disuse._

There is no doubt that Darwin everywhere attaches great weight to this
line of evidence. Nevertheless, in my opinion, there is equally little
doubt that, taken by itself, it is of immeasurably less weight than
Darwin supposed. Indeed, I quite agree with Weismann that the whole of
this line of evidence is practically worthless; and for the following
reasons.

The evidence on which Darwin relied to prove the inherited effects of
use and disuse was derived from his careful measurements of the increase
or decrease which certain bones of our domesticated animals have
undergone, as compared with the corresponding bones of ancestral stocks
in a state of nature. He chose domesticated animals for these
investigations, because, while yielding unquestionable cases of
increased or diminished use of certain organs over a large number of
sequent generations, the results were not complicated by the possible
interference of natural selection on the one hand, or by that of the
economy of nutrition on the other. For "with highly-fed domesticated
animals there seems to be no economy of growth, or any tendency to the
elimination of superfluous details[55];" seeing that, among other
considerations pointing in the same direction, "structures which are
rudimentary in the parent species, sometimes become partially
re-developed in our domesticated productions[56]."

    [55] _Variation of Plants and Animals_, vol. ii. p. 289.

    [56] _Ibid._ p. 346.

The method of Darwin's researches in this connexion was as follows.
Taking, for example, the case of ducks, he carefully weighed and
measured the wing-bones and leg-bones of wild and tame ducks; and he
found that the wing-bones were smaller, while the leg-bones were larger,
in the tame than in the wild specimens. These facts he attributed to
many generations of tame ducks using their wings less, and their legs
more, than was the case with their wild ancestry. Similarly he compared
the leg-bones of wild rabbits with those of tame ones, and so forth--in
all cases finding that where domestication had led to increased use of a
part, that part was larger than in the wild parent stock; while the
reverse was the case with parts less used. Now, although at first sight
these facts certainly do seem to yield good evidence of the inherited
effects of use and disuse, they are really open to the following very
weighty objections.

First of all, there is no means of knowing how far the observed effects
may have been due to increased or diminished use during only the
individual life-time of each domesticated animal. Again, and this is a
more important point, in all Darwin's investigations the increase or
decrease of a part was estimated, not by directly comparing, say the
wing-bones of a domesticated duck with the wing-bones of a wild duck,
but by comparing the _ratio_ between the wing and leg bones of a tame
duck with the _ratio_ between the wing and leg bones of a wild duck.
Consequently, if there be any reason to doubt the supposition that a
really inherited decrease in the size of a part thus estimated is due to
the inherited effects of disuse, such a doubt will also extend to the
evidence of increased size being due to the inherited effects of use.
Now there is the gravest possible doubt lying against the supposition
that any really inherited decrease in the size of a part is due to the
inherited effects of disuse. For it may be--and, at any rate to some
extent, must be--due to another principle, which it is strange that
Darwin should have overlooked. This is the principle which Weismann has
called Panmixia, and which cannot be better expressed than in his own
words:--

     "A goose or a duck must possess strong powers of flight in the
     natural state, but such powers are no longer necessary for
     obtaining food when it is brought into the poultry-yard; so that a
     rigid selection of individuals with well-developed wings at once
     ceases among its descendants. Hence, in the course of generations,
     a deterioration of the organs of flight must necessarily
     ensue[57]."

    [57] _Essays_, i. p. 90.

Or, to state the case in another way: if any structure which was
originally built up by natural selection on account of its use, ceases
any longer to be of so much use, in whatever degree it ceases to be of
use, in that degree will the premium before set upon it by natural
selection be withdrawn. And the consequence of this withdrawal of
selection as regards that particular part will be to allow the part to
degenerate in successive generations. Such is the principle which
Weismann calls Panmixia, because, by the withdrawal of selection from
any particular part, promiscuous breeding ensues with regard to that
part. And it is easy to see that this principle must be one of very
great importance in nature; because it must necessarily come into
operation in all cases where any structure or any instinct has, through
any change in the environment or in the habits of a species, ceased to
be useful. It is likewise easy to see that its effect must be the same
as that which was attributed by Darwin to the inherited effect of
disuse; and, therefore, that the evidence on which he relied in proof of
the inherited effects both of use and of disuse is vitiated by the fact
that the idea of Panmixia did not occur to him.

Here, however, it may be said that the idea first occurred to me[58]
just after the publication of the last edition of the _Origin of
Species_. I called the principle the Cessation of Selection--which I
still think a better, because a more descriptive, term than Panmixia;
and at that time it appeared to me, as it now appears to Weismann,
entirely to supersede the necessity of supposing that the effect of
disuse is ever inherited in any degree at all. Thus it raised the whole
question as to the admissibility of Lamarckian principles in general; or
the question on which we are now engaged touching the possible
inheritance of acquired, as distinguished from congenital, characters.
But on discussing the matter with Mr. Darwin, he satisfied me that the
larger question was not to be so easily closed. That is to say, although
he fully accepted the principle of the Cessation of Selection, and as
fully acknowledged its obvious importance, he convinced me that there
was independent evidence for the transmission of acquired characters,
sufficient in amount to leave the general structure of his previous
theory unaffected by what he nevertheless recognized as a factor which
must necessarily be added. All this I now mention in order to show that
the issue which Weismann has raised since Darwin's death was expressly
contemplated during the later years of Darwin's life. For if the idea of
Panmixia--in the absence of which Weismann's entire system would be
impossible--had never been present to Darwin's mind, we should have been
left in uncertainty how he would have regarded this subsequent revolt
against what are generally called the Lamarckian principles[59].

    [58] _Nature_, vol. ix. pp. 361-2, 440-1; and vol. x. p. 164.

    [59] Appendix I.

Moreover, in this connexion we must take particular notice that the
year after I had published these articles on the Cessation of Selection,
and discussed with Mr. Darwin the bearing of this principle on the
question of the transmission of acquired characters, Mr. Galton followed
with his highly important essay on Heredity. For in this essay Mr.
Galton fully adopted the principle of the Cessation of Selection, and
was in consequence the first publicly to challenge the Lamarckian
principles--pointing out that, if it were thus possible to deny the
transmission of acquired characters _in toto_, "we should be relieved
from all further trouble"; but that, if such characters are transmitted
"in however faint a degree, a complete theory of heredity must account
for them." Thus the question which, in its revived condition, is now
attracting so much attention, was propounded in all its parts some
fifteen or sixteen years ago; and no additional facts or new
considerations of any great importance bearing upon the subject have
been adduced since that time. In other words, about a year after my own
conversations with Mr. Darwin, the whole matter was still more
effectively brought before his notice by his own cousin. And the result
was that he still retained his belief in the Lamarckian factors of
organic evolution, even more strongly than it was retained either by Mr.
Galton or myself[60].

    [60] For a fuller statement of Mr. Galton's theory of Heredity, and
         its relation to Weismann's, see _An Examination of
         Weismannism_.

We have now considered the line of evidence on which Darwin chiefly
relied in proof of the transmissibility of acquired characters; and it
must be allowed that this line of evidence is practically worthless.
What he regarded as the inherited effects of use and of disuse may be
entirely due to the cessation of selection in the case of our
domesticated animals, combined with an active _reversal_ of selection in
the case of natural species. And in accordance with this view is the
fact that the degeneration of disused parts proceeds much further in the
case of wild species than it does in that of domesticated varieties. For
although it may be said that in the case of wild species more time has
been allowed for a greater accumulation of the inherited effects of
disuse than can have been the case with domesticated varieties, the
alternative explanation is at least as probable--that in the case of
wild species the merely negative, or passive, influence of the
_cessation_ of selection has been continuously and powerfully assisted
by the positive, or active, influence of the _reversal_ of selection,
through economy of growth and the general advantage to be derived from
the abolition of useless parts[61].

    [61] For a fuller explanation of the important difference between
         the mere cessation and the actual reversal of selection, see
         Appendix I.

The absence of any good evidence of this direct kind in favour of
use-inheritance will be rendered strikingly apparent to any one who
reads a learned and interesting work by Professor Semper[62]. His object
was to show the large part which he believed to have been played by
external conditions of life in directly modifying organic types--or, in
other words, of proving that side of Lamarckianism which refers to the
immediate action of the environment, whether with or without the
co-operation of use-inheritance and natural selection. Although Semper
gathered together a great array of facts, the more carefully one reads
his book the more apparent does it become that no single one of the
facts is in itself conclusive evidence of the transmission to progeny of
characters which are acquired through use-inheritance or through direct
action of the environment. Every one of the facts is susceptible of
explanation on the hypothesis that the principle of natural selection
has been the only principle concerned. This, however, it must be
observed, is by no means equivalent to proving that characters thus
acquired are not transmitted. As already pointed out, it is
impracticable with species in a state of nature to dissociate the
distinctively Darwinian from the possibly Lamarckian factors; so that
even if the latter are largely operative, we can only hope for direct
evidence of the fact from direct experiments on varieties in a state of
domestication. To this branch of our subject, therefore, we will now
proceed.

    [62] _Animal Life_, International Scientific Series, vol. xxxi.




CHAPTER IV.

CHARACTERS AS HEREDITARY AND ACQUIRED
(_continued_).


(C.)
_Experimental Evidence in favour of the Inheritance of Acquired
Characters._


Notwithstanding the fact already noticed, that no experiments have
hitherto been published with reference to the question of the
transmission of acquired characters[63], there are several researches
which, with other objects in view, have incidentally yielded seemingly
good evidence of such transmission. The best-known of these
researches--and therefore the one with which I shall begin--is that of
Brown-Séquard touching the effects of certain injuries of the nervous
system in guinea-pigs.

    [63] The experiments of Galton and Weismann upon this subject are
         nugatory, as will be shown later on. But since the above was
         written an important research has been published by Mr.
         Cunningham, of the Marine Biological Association. For a full
         account I must refer the reader to his forthcoming paper in the
         _Philosophical Transactions_. The following is his own
         statement of the principal results:--

         "A case which I have myself recently investigated
         experimentally seems to me to support very strongly the theory
         of the inheritance of acquired characters, I have shown that in
         normal flat-fishes, if the lower side be artificially exposed
         to light for a long time, pigmentation is developed on that
         side; but when the exposure is commenced while the specimens
         are still in process of metamorphosis, when pigment-cells are
         still present on the lower side, the action of light does not
         prevent the disappearance of these pigment-cells. They
         disappear as in individuals living under normal conditions, but
         after prolonged exposure pigment-cells reappear. The first fact
         proves that the disappearance of the pigment-cells from the
         lower side in the metamorphosis is an hereditary character, and
         not a change produced in each individual by the withdrawal of
         the lower side from the action of light. On the other hand, the
         experiments show that the absence of pigment-cells from the
         lower side throughout life is due to the fact that light does
         not act upon that side, for, when it is allowed to act,
         pigment-cells appear. It seems to me the only reasonable
         conclusion from these facts is, that the disappearance of
         pigment-cells was originally due to the absence of light, and
         that this change has now become hereditary. The pigment-cells
         produced by the action of light on the lower side are in all
         respects similar to those normally present on the upper side of
         the fish. If the disappearance of the pigment-cells were due
         entirely to a variation of the germ-plasm, no external
         influence could cause them to reappear, and, on the other hand,
         if there were no hereditary tendency, the colouration of the
         lower side of the flat-fish when exposed would be rapid and
         complete."--_Natural Science_, Oct. 1893.

During a period of thirty years Brown-Séquard bred many thousands of
guinea-pigs as material for his various researches; and in those whose
parents had not been operated upon in the ways to be immediately
mentioned, he never saw any of the peculiarities which are about to be
described. Therefore the hypothesis of coincidence, at all events, must
be excluded. The following is his own summary of the results with which
we are concerned:--

     1st. Appearance of epilepsy in animals born of parents which had
     been rendered epileptic by an injury to the spinal cord.

     2nd. Appearance of epilepsy also in animals born of parents which
     had been rendered epileptic by section of the sciatic nerve.

     3rd. A change in the shape of the ear in animals born of parents in
     which such a change was the effect of a division of the cervical
     sympathetic nerve.

     4th. Partial closure of the eyelids in animals born of parents in
     which that state of the eyelids had been caused either by section
     of the cervical sympathetic nerve, or the removal of the superior
     cervical ganglion.

     5th. Exophthalmia in animals born of parents in which an injury to
     the restiform body had produced that protrusion of the eyeball.
     This interesting fact I have witnessed a good many times, and seen
     the transmission of the morbid state of the eye continue through
     four generations. In these animals, modified by heredity, the two
     eyes generally protruded, although in the parents usually only one
     showed exophthalmia, the lesion having been made in most cases only
     on one of the corpora restiformia.

     6th. Haematoma and dry gangrene of the ears in animals born of
     parents in which these ear-alterations had been caused by an injury
     to the restiform body near the nib of the calamus.

     7th. Absence of two toes out of the three of the hind leg, and
     sometimes of the three, in animals whose parents had eaten up their
     hind-leg toes which had become anaesthetic from a section of the
     sciatic nerve alone, or of that nerve and also of the crural.
     Sometimes, instead of complete absence of the toes, only a part of
     one or two or three was missing in the young, although in the
     parent not only the toes but the whole foot were absent (partly
     eaten off, partly destroyed by inflammation, ulceration, or
     gangrene.)

     8th. Appearance of various morbid states of the skin and hair of
     the neck and face in animals born of parents having had similar
     alterations in the same parts, as effects of an injury to the
     sciatic nerve.

These results[64] have been independently vouched for by two of
Brown-Séquard's former assistants--Dr. Dupuy, and the late Professor
Westphal. Moreover, his results with regard to epilepsy have been
corroborated also by Obersteiner[65]. I may observe, in passing, that
this labour of testing Brown-Séquard's statements is one which, in my
opinion, ought rather to have been undertaken, if not by Weismann
himself, at all events by some of his followers. Both he and they are
incessant in their demand for evidence of the transmission of acquired
characters; yet they have virtually ignored the foregoing very
remarkable statements. However, be this as it may, all that we have now
to do is to consider what the school of Weismann has had to say with
regard to these experiments on the grounds of general reasoning which
they have thus far been satisfied to occupy.

    [64] For Professor Weismann's statement of and discussion of these
         results see _Essays_, vol. i. p. 313.

    [65] _Oesterreichische medicinische Jahrbücher_, 1875, 179.

In view of Obersteiner's corroboration of Brown-Séquard's results
touching the artificial production and subsequent transmission of
epilepsy, Weismann accepts the facts, but, in order to save his theory
of heredity, he argues that the transmission may be due to a traumatic
introduction of "some unknown microbe" which causes the epilepsy in the
parent, and, by invading the ova or spermatozoa as the case may be, also
produces epilepsy in the offspring. Here, of course, there would be
transmission of epilepsy, but it would not be, technically speaking, an
hereditary transmission. The case would resemble that of syphilis, where
the sexual elements remain unaffected as to their congenital endowments,
although they have been made the vehicles for conveying an organic
poison to the next generation.

Now it would seem that this suggestion is not, on the face of it, a
probable one. For "some unknown microbe" it indeed must be, which is
always on hand to enter a guinea-pig when certain operations are being
performed on certain parts of the nervous system, but yet will never
enter when operations of any kind are being effected elsewhere.
Moreover, Westphal has produced the epilepsy _without any incision_, by
striking the heads of the animals with a hammer[66]. This latter fact,
it appears to me, entirely abolishes the intrinsically improbable
suggestion touching an unknown--and strangely eclectic--microbe.
However, it is but fair to state what Weismann himself has made of this
fact. The following is what he says:--

    [66] _Loc. cit._

     "It is obvious that the presence of microbes can have nothing to do
     with such an attack, but the shock alone must have caused
     morphological and functional changes in the centre of the pons and
     medulla oblongata, identical with those produced by microbes in the
     other cases.... Various stimuli might cause the nervous centres
     concerned to develop the convulsive attack which, together with its
     after-effects, we call epilepsy. In Westphal's case, such a
     stimulus would be given by a powerful mechanical shock (viz. blows
     on the head with a hammer); in Brown-Séquard's experiments, by the
     penetration of microbes[67]."

    [67] _Essays_, vol. i. p. 315.

But from this passage it would seem that Weismann has failed to notice
that in "Westphal's case," as in "Brown-Séquard's experiments," the
epilepsy was _transmitted to progeny_. That epilepsy may be produced in
guinea-pigs by a method which does not involve any cutting (i.e.
possibility of inoculation) would no doubt tend to corroborate the
suggestion of microbes being concerned in its transmission when it is
produced by cutting, _if in the former case there were no such
transmission_. But as there _is_ transmission in _both_ cases, the
facts, so far as I can see, entirely abolish the suggestion. For they
prove that even when epilepsy is produced in the parents under
circumstances which render "it obvious that the presence of microbes can
have nothing to do with such an attack," the epileptiform condition is
notwithstanding transmitted to the progeny. What, then, is gained by
retaining the intrinsically improbable hypothesis of microbes to explain
the fact of transmission "in Brown-Séquard's experiments," when this
very same fact is proved to occur without the possibility of microbes
"in Westphal's case"?

The only other objection with regard to the seeming transmission of
traumatic epilepsy which Weismann has advanced is, that such epilepsy
may be produced by two or three very different operations--viz. division
of the sciatic nerves (one or both), an injury to the spinal cord, and a
stroke on the head. Does not this show, it is asked, that the epileptic
condition of guinea-pigs is due to a generally unstable condition of the
whole nervous system and is not associated with any particular part
thereof? Well, supposing that such is the case, what would it amount to?
I cannot see that it would in any way affect the only question in
debate--viz. What is the significance of the fact that epilepsy is
_transmitted_? Even if it be but "a tendency," "a disposition," or "a
diathesis" that is transmitted, it is none the less a case of
transmission, in fact quite as much so as if the pathological state were
dependent on the impaired condition of any particular nerve-centre. For,
it must be observed, there can be no question that it is always produced
by an operation of _some_ kind. If it were ever to originate in
guinea-pigs spontaneously, there might be some room for supposing that
its transmission is due to a congenital tendency running through the
whole species--although even then it would remain unaccountable, on the
ultra-Darwinian view, why this tendency should be congenitally
_increased_ by means of an operation. But epilepsy does not originate
spontaneously in guinea-pigs; and therefore the criticism in question
appears to me irrelevant.

Again, it may be worth while to remark that Brown-Séquard's experiments
do not disprove the possibility of its being some one nerve-centre which
is concerned in all cases of traumatic epilepsy. And this possibility
becomes, I think, a probability in view of Luciani's recent experiments
on the dog. These show that the epileptic condition can be produced in
this animal by injury to the cortical substance of the hemispheres, and
is then transmitted to progeny[68]. These experiments, therefore, are of
great interest--first, as showing that traumatic and transmissible
epilepsy is not confined to guinea-pigs; and next, as indicating that
the pathological state in question is associated with the highest
nerve-centres, which may therefore well be affected by injury to the
lower centres, or even by section of a large nerve trunk.

    [68] _Les fonctions du Cerveau_, p. 102.

So much, then, with regard to the case of transmitted epilepsy. But now
it must be noted that, even if Weismann's suggestion touching microbes
were fully adequate to meet this case, it would still leave unaffected
those of transmitted protrusion of the eye, drooping of the eyelid,
gangrene of the ear, absence of toes, &c. In all these cases the facts,
as stated by Brown-Séquard, are plainly unamenable to any explanation
which would suppose them due to microbes, or even to any general
neurotic condition induced by the operation. They are much too definite,
peculiar, and localized. Doubtless it is on this account that the school
of Weismann has not seriously attempted to deal with them, but merely
recommends their repetition by other physiologists[69]. Certain
criticisms, however, have been urged by Weismann against the
_interpretation_ of Brown-Séquard's facts as evidence in favour of the
transmission of acquired characters. It does not appear to me that these
criticisms present much weight; but it is only fair that we should here
briefly consider them[70].

    [69] _Essays_, vol. i. p. 82.

    [70] As Weismann gives an excellent abstract of all the alleged
         facts up to date (_Essays_, vol. i. pp. 319-324), it is
         needless for me to supply another, further than that which I
         have already made from Brown-Séquard.

First, with regard to Brown-Séquard's results other than the production
of transmitted epilepsy, Weismann allows that the hypothesis of microbes
can scarcely apply. In order to meet these results, therefore, he
furnishes another suggestion--viz. that where the nervous system has
sustained "a great shock," the animals are very likely to bear "weak
descendants, and such as are readily affected by disease." Then, in
answer to the obvious consideration, "that this does not explain why the
offspring should suffer from the same disease" as that which has been
produced in the parents, he adds--"But this does not appear to have been
by any means invariably the case. For 'Brown-Séquard himself says, the
changes in the eye of the offspring were of a very variable nature, and
were only occasionally exactly similar to those observed in the
parents.'"

Now, this does not appear to me a good commentary. In the first place,
it does not apply to the other cases (such as the ears and the toes),
where the changes in the offspring, when they occurred at all, _were_
exactly similar to those observed in the parents, save that some of them
occasionally occurred on the _opposite_ side, and frequently also on
_both_ sides of the offspring. These subordinate facts, however, will
not be regarded by any physiologist as making against the more ready
interpretation of the results as due to heredity. For a physiologist
well knows that homologous parts are apt to exhibit correlated
variability--and this especially where variations of a congenital kind
are concerned, and also where there is any reason to suppose that the
nervous system is involved. Moreover, even in the case of the eye, it
was always protrusion that was caused in the parent and transmitted to
the offspring as a result of injuring the restiform bodies of the
former; while it was always partial closure of the eyelids that was
caused and transmitted by section of the sympathetic nerve, or removal
of the cervical ganglia. Therefore, if we call such effects "diseases,"
surely it _was_ "the same disease" which in each case appeared in the
parents and reappeared in their offspring. Again, the "diseases" were so
peculiar, definite, and localized, that I cannot see how they can be
reasonably ascribed to a general nervous "shock." Why, for instance, if
this were the case, should a protruding eye never result from removal
of the cervical ganglia, a drooping eyelid from a puncture of the
restiform body, a toeless foot from either or both of these operations,
and so on? In view of such considerations I cannot deem these
suggestions touching "microbes" and "diseases" as worthy of the
distinguished biologist from whom they emanate.

Secondly, Weismann asks--How can we suppose these results to be
instances of the transmission of acquired characters, when from
Brown-Séquard's own statement of them it appears that the mutilation
itself was not inherited, but only its effects? Neither in the case of
the sciatic nerve, the sympathetic nerve, the cervical ganglion, nor the
restiform bodies, was there ever any trace of transmitted injury in the
corresponding parts of the offspring; so that, if the "diseases" from
which they suffered be regarded as hereditary, we have to suppose that a
consequence was in each case transmitted without the transmission of its
cause, which is absurd. But I do not think that this criticism can be
deemed of much weight by a physiologist as distinguished from a
naturalist. For nothing is more certain to a student of physiology, in
any of its branches, than that negative evidence, if yielded by the
microscope alone, is most precarious. Therefore it does not need a
_visible_ change in the nervous system to be present, in order that the
part affected should be functionally weak or incapable: pathology can
show numberless cases of nerve-disorder the "structural" causes of which
neither the scalpel nor the microscope can detect. So that, if any
peculiar form of nerve-disorder is transmitted to progeny, and if it be
certain that it has been caused by injury to some particular part of
the nervous system, I cannot see that there is any reason to doubt the
transmission of a nervous lesion merely on the ground that it is not
visibly discernible. Of course there may be other grounds for doubting
it; but I am satisfied that this ground is untenable. Besides, it must
be remembered, as regards the particular cases in question, that no one
has thus far investigated the histology of the matter by the greatly
improved methods which are now at our disposal.

       *       *       *       *       *

I have now considered all the criticisms which have been advanced
against what may be called the Lamarckian interpretation of
Brown-Séquard's results; and I think it will be seen that they present
very little force--even if it can be seen that they present any force at
all. But it must be remembered that this is a different thing from
saying that the Lamarckian interpretation is the true one. The facts
alleged are, without question, highly peculiar; and, on this account
alone, Brown-Séquard's interpretation of them ought to be deemed
provisional. Hence, although as yet they have not encountered any valid
criticism from the side of ultra-Darwinian theory, I do not agree with
Darwin that, on the supposition of their truth as facts, they furnish
positive proof of the transmission of acquired characters. Rather do I
agree with Weismann that further investigation is needed in order to
establish such an important conclusion on the basis of so unusual a
class of facts. This further investigation, therefore, I have
undertaken, and will now state the results.

Although this work was begun over twenty years ago, and then yielded
negative results, it was only within the last decade that I resumed it
more systematically, and under the tutelage of Brown-Séquard himself.
During the last two years, however, the experiments have been so much
interrupted by illness that even now the research is far from complete.
Therefore I will here confine myself to a tabular statement of the
results as far as they have hitherto gone, on the understanding that, in
so far as they are negative or doubtful, I am not yet prepared to
announce them as final.

We may take Brown-Séquard's propositions in his own order, as already
given on page 104.

     1st. Appearance of epilepsy in animals born of parents which had
     been rendered epileptic by an injury to the spinal cord.

     2nd. Appearance of epilepsy also in animals born of parents which
     had been rendered epileptic by section of the sciatic nerve.

I did not repeat these experiments with a view to producing epilepsy,
because, as above stated, they had been already and sufficiently
corroborated in this respect. But I repeated many times the experiments
of dividing the sciatic nerve for the purpose of testing the statements
made later on in paragraphs 7 and 8, and observed that it almost always
had the effect of producing epilepsy in the animal thus operated
upon--and this of a peculiar kind, the chief characteristics of which
may here be summarized. The epileptiform habit does not supervene until
some considerable time after the operation; it is then transitory,
lasting only for some weeks or months. While the habit endures the fits
never occur spontaneously, but only as a result of irritating a small
area of skin behind the ear on the same side of the body as that on
which the sciatic nerve had been divided. Effectual irritation may be
either mechanical (such as gentle pinching), electrical, or, though less
certainly, thermal. The area of skin in question, soon after the
epileptiform habit supervenes, and during all the time that it lasts,
swarms with lice of the kind which infest guinea-pigs--i.e. the lice
congregate in this area, on account, I think, of the animal being there
insensitive, and therefore not disturbing its parasites in that
particular spot; otherwise it would presumably throw itself into fits by
scratching that spot. On removing the skin from the area in question, no
kind or degree of irritation supplied to the subjacent tissue has any
effect in producing a fit. A fit never lasts for more than a very few
minutes, during which the animal is unconscious and convulsed, though
not with any great violence. The epileptiform habit is but rarely
transmitted to progeny. Most of these observations are in accordance
with those previously made by Brown-Séquard, and also by others who have
repeated his experiments under this heading. I can have no doubt that
the injury of the sciatic nerve or spinal cord produces a change in some
of the cerebral centres, and that it is this change--whatever it is and
in whatever part of the brain it takes place--which causes the
remarkable phenomena in question.

     3rd. A change in the shape of the ear in animals born of parents in
     which such a change was the effect of a division of the cervical
     sympathetic nerve.

     4th. Partial closure of the eyelids in animals born of parents in
     which that state of the eyelids had been caused either by section
     of the cervical sympathetic nerve, or the removal of the superior
     cervical ganglion.

I have not succeeded in corroborating these results. It must be added,
however, that up to the time of going to press my experiments on this,
the easiest branch of the research, have been too few fairly to prove a
negative.

     5th. Exophthalmia in animals born of parents in which an injury to
     the restiform body had produced that protrusion of the eyeball....
     In these animals, modified by heredity, the two eyes generally
     protruded, although in the parents usually only one showed
     exophthalmia, the lesion having been made in most cases only on one
     of the corpora restiformia.

I have fully corroborated the statement that injury to a particular spot
of the restiform body is quickly followed by a marked protrusion of the
eyeball on the same side. I have also had many cases in which some of
the progeny of parents thus affected have shown considerable protrusion
of the eyeballs on both sides, and this seemingly abnormal protrusion
has been occasionally transmitted to the next generation. Nevertheless,
I am far from satisfied that this latter fact is anything more than an
accidental coincidence. For I have never seen the so-called exophthalmia
of progeny exhibited in so high a degree as it occurs in the parents as
an immediate result of the operation, while, on examining any large
stock of normal guinea-pigs, there is found a considerable amount of
individual variation in regard to prominence of eyeballs. Therefore,
while not denying that the obviously abnormal amount of protrusion due
to the operation may be inherited in lesser degrees, and thus may be the
cause of the unusual degree of prominence which is sometimes seen in the
eyeballs of progeny born of exophthalmic parents, I am unable to affirm
so important a conclusion on the basis supplied by these experiments.

     6th. Haematoma and dry gangrene of the ears in animals born of
     parents in which these ear-alterations had been caused by an injury
     to the restiform body.

As regards the animals operated upon (i. e. the parents), I find that
the haematoma and dry gangrene may supervene either several weeks after
the operation, or at any subsequent time up to many months. When it does
supervene it usually affects the upper parts of both ears, and may then
eat its way down until, in extreme cases, it has entirely consumed
two-thirds of the tissue of both ears. As regards the progeny of animals
thus affected, in some cases, but by no means in all, a similarly morbid
state of the ears may arise apparently at any time in the life-history
of the individual. But I have observed that in cases where two or more
individuals _of the same litter_ develop this diseased condition, they
usually do so at about the same time--even though this be many months
after birth, and therefore after the animals are fully grown. But in
progeny the morbid process never goes so far as in the parents which
have been operated upon, and it almost always affects the _middle_
thirds of the ears. In order to illustrate these points, reproductions
of two of my photographs are appended. They represent the consequences
of the operation on a male and a female guinea-pig. Among the progeny of
both these animals there were several in which a portion of each ear was
consumed by apparently the same process, where, of course, there had
been no operation.

[Illustration: FIG. 1.--Reproduction of photographs from life of a male
and female guinea-pig, whose left restiform bodies had been injured by a
scalpel six months previously. The loss of tissue in both ears was due
to haematoma and dry gangrene, which, however, had ceased when the
photograph was taken.]

It should be observed that not only is a different _part_ of the ear
affected in the progeny, but also a very much less _quantity_ thereof.
Naturally, therefore, the hypothesis of heredity seems less probable
than that of mere coincidence on the one hand, or of transmitted
microbes on the other. But I hope to have fairly excluded both these
alternative explanations. For, as regards merely accidental coincidence,
I have never seen this very peculiar morbid process in the ears, or in
any other parts, of guinea-pigs which have neither themselves had their
restiform bodies injured, nor been born of parents thus mutilated. As
regards the hypothesis of microbes, I have tried to inoculate the
corresponding parts of the ears of normal guinea-pigs, by first
scarifying those parts and then rubbing them with the diseased surfaces
of the ears of mutilated guinea-pigs; but have not been able in this way
to communicate the disease.

It will be seen that the above results in large measure corroborate the
statements of Brown-Séquard; and it is only fair to add that he told me
they are the results which he had himself obtained most frequently, but
that he had also met with many cases where the diseased condition of the
ears in parents affected the same parts in their progeny, and also
occurred in more equal degrees. Lastly, I should like to remark, with
regard to these experiments on restiform bodies, and for the benefit of
any one else who may hereafter repeat them, that it will be necessary
for him to obtain precise information touching the _modus operandi_. For
it is only one very localized spot in each restiform body which has to
be injured in order to produce any of the results in question. I myself
lost two years of work on account of not knowing this exact spot before
going to Paris for the purpose of seeing Brown-Séquard himself perform
the operation. I had in the preceding year seen one of his assistants do
so, but this gentleman had a much more careless method, and one which in
my hands yielded uniformly negative results. The exact spot in question
in the restiform body is as far forwards as it is possible to reach, and
as far down in depth as is compatible with not producing rotatory
movements.

     7th. Absence of two toes out of the three of the hind leg, and
     sometimes of the three, in animals whose parents had eaten up their
     hind-leg toes which had become anaesthetic from a section of the
     sciatic nerve alone, or of that nerve and also of the crural.
     Sometimes, instead of complete absence of the toes, only a part of
     one or two or three was missing in the young, although in the
     parent not only the toes but the whole foot were absent.

As I found that the results here described were usually given by
division of the sciatic nerve alone--or, more correctly, by excision of
a considerable portion of the nerve, in order to prevent regeneration--I
did not also divide the crural. But, although I have bred numerous
litters from parents thus injured, there has been no case of any
inherited deficiency of toes. My experiments in this connexion were
carried on through a series of six successive generations, so as to
produce, if possible, a cumulative effect. Nevertheless, no effect of
any kind was produced. On the other hand, Brown-Séquard informed me that
he had observed this inherited absence of toes only in about one or two
per cent. of cases. Hence it is possible enough, that my experiments
have not been sufficiently numerous to furnish a case. It may be added
that there is here no measurable possibility of accidental coincidence
(seeing that normal guinea-pigs do not seem ever to produce young with
any deficiency of toes), while the only possibility of mal-observation
consists in some error with regard to the isolation (or the tabulation)
of parents and progeny. Such an error, however, may easily arise. For
gangrene of the toes does not set in till some considerable time after
division of the sciatic nerve. Hence, if the wound be healed before the
gangrene begins, and if any mistake has been made with regard to the
isolation (or tabulation) of the animal, it becomes possible that the
latter should be recorded as an uninjured, instead of an injured,
individual. On this account one would like to be assured that
Brown-Séquard took the precaution of examining the state of the sciatic
nerve in those comparatively few specimens which he alleges to have
displayed such exceedingly definite proof of the inheritance of a
mutilation. For it is needless to remark, after what has been said in
the preceding chapter on the analogous case of epilepsy, that the proof
would not be regarded by any physiologist as displaced by the fact that
there is no observable deficiency in the sciatic nerve of the toeless
young.

     8th. Appearance of various morbid states of the skin and hair of
     the neck and face in animals born of parents having had similar
     alterations in the same parts, as effects of an injury to the
     sciatic nerve.

I have not paid any attention to this paragraph, because the facts which
it alleges did not seem of a sufficiently definite character to serve as
a guide to further experiment.

On the whole, then, as regards Brown-Séquard's experiments, it will be
seen that I have not been able to furnish any approach to a full
corroboration. But I must repeat that my own experiments have not as yet
been sufficiently numerous to justify me in repudiating those of his
statements which I have not been able to verify.

The only other experimental results, where animals are concerned, which
seemed to tell on the side of Lamarckianism, are those of Mr.
Cunningham, already alluded to. But, as the research is still in
progress, the school of Weismann may fairly say that it would be
premature to discuss its theoretical bearings.

       *       *       *       *       *

Passing now from experiments on animals to experiments on plants, I must
again ask it to be borne in mind, that here also no researches have been
published, which have had for their object the testing of the question
on which we are engaged. As in the case of animals, therefore, so in
that of plants, we are dependent for any experimental results bearing
upon the subject to such as have been gained incidentally during the
course of investigations in quite other directions.

Allusion has already been made, in my previous essay, to De Vries'
observations on the chromatophores of algae passing from the ovum of the
mother to the daughter organism; and we have seen that even Weismann
admits, "It appears possible that a transmission of somatogenetic
variation has here occurred[71]." It will now be my object to show that
such variations appear to be sometimes transmitted in the case of
higher plants, and this under circumstances which carry much less
equivocal evidence of the inheritance of acquired characters, than can
be rendered by the much more simple organization of an alga.

    [71] _Examination of Weismannism_, p. 83.

I have previously mentioned Hoffmann's experiments on transplantation,
the result of which was to show that variations, directly induced by
changed conditions of life, were reproduced by seed[72]. Weismann,
however, as we have seen, questions the _somatogenetic_ origin of these
variations--attributing the facts to a _blastogenetic_ change produced
in the plants by a direct action of the changed conditions upon the
germ-plasm itself[73]. And he points out that whether he is right or
wrong in this interpretation can only be settled by ascertaining whether
the observable somatic changes occur in the generation which is first
exposed to the changed conditions of life. If they do occur in the first
generation, they are somatogenetic changes, which afterwards react on
the substance of heredity, so as to transmit the acquired peculiarities
to progeny. But if they do not occur till the second (or any later)
generation, they are presumably blastogenetic. Unfortunately Hoffmann
does not appear to have attended to this point with sufficient care, but
there are other experiments of the same kind where the point has been
specially observed.

    [72] _Examination of Wiesmannism_, p. 93.

    [73] _Ibid._ p. 153.

For instance, M. L. A. Carrière[74] gathered seed from the wild radish
(_Raphanus Raphanistrum_) in France, and sowed one lot in the light dry
soil near the Museum of Natural History in Paris, while another lot was
sown by him at the same time in heavy soil elsewhere. His object was to
ascertain whether he could produce a good cultivated radish by
methodical selection; and this he did; in a wonderfully rapid manner,
during the course of a very few generations. But the point for us is,
that _from the first_ the plants grown in the light soil of Paris
presented sundry marked differences from those grown in the heavy soil
of the country; and that these points of difference had nothing to do
with the variations on which his artificial selection was brought to
bear. For while his artificial selection was directed to increasing the
_size_ of the "root," the differences in question had reference to its
_form_ and _colour_. In Paris an elongated form prevailed, which
presented either a white or a rose colour: in the country the form was
more rounded, and the colour violet, dark brown, or "almost black." Now,
as these differences were strongly apparent in the first generation, and
were not afterwards made the subject of selection, both in origin and
development they must have been due to "climatic" influences acting on
the somatic tissues. And although the author does not appear to have
tested their hereditary characters by afterwards sowing the seed from
the Paris variety in the country, or _vice versa_, we may fairly
conclude that these changes must have been hereditary--1st, from the
fact of their intensification in the course of the five sequent
generations over which the experiment extended, and, 2nd, from the very
analogous results which were similarly obtained in the following case
with another genus, where both the somatogenetic and the hereditary
characters of the change were carefully and specially observed. This
case is as follows.

    [74] _Origine des Plantes Domestiques, démontrée par la culture du
         Radis Sauvage_ (Paris, 1869).

The late Professor James Buckman, F.R.S., saved some seed from wild
parsnips (_P. sativa_) in the summer of 1847, and sowed under changed
conditions of life in the spring of 1848. The plants grown from these
wild seeds were for the most part like wild plants; but some of them had
"already (i.e. in the autumn of 1848) the light green and smooth aspect
devoid of hairs which is peculiar to the cultivated plant; and among the
latter there were a few with longer leaves and broader divisions of
leaf-lobes than the rest--the leaves, too, all growing systematically
round one central bud. The roots of the plant when taken up were
observed to be for the most part more fleshy than those of wild
examples[75]."

    [75] _Journl. Agric. Soc._ 1848.

Professor Buckman then proceeds to describe how he selected the best
samples for cultivation in succeeding generations, till eventually the
variety which he called "The Student" was produced, and which Messrs.
Sutton still regard as the best variety in their catalogue. That is to
say, it has come true to seed for the last forty years; and although
such great excellence and stability are doubtless in chief part due to
the subsequent process of selection by Professor Buckman in the years
1848-1850, this does not affect the point with which we are here
concerned--namely, that the somatogenetic changes of the plants in the
first generation were transmitted by seed to the second generation, and
thus furnished Professor Buckman with the material for his subsequent
process of selection. And the changes in question were not merely of a
very definite character, but also of what may be termed a very _local_
character--affecting only particular tissues of the soma, and therefore
expressive of a high degree of _representation_ on the part of the
subsequently developed seed, by which they were faithfully reproduced in
the next generation.

Here is another case. M. Lesage examined the tissues of a large number
of plants growing both near to, and remote from, the sea. He suspected
that the characteristic fleshiness, &c. of seaside plants was due to the
influence of sea-salt; and proved that such was the case by causing the
characters to occur in inland plants as a result of watering them with
salt-water. Then he adds:--

     "J'ai réussi surtout pour le _Lepidium sativum_ cultivé en 1888;
     j'ai obtenu pour la même plante des résultats plus nets encore dans
     la culture de 1889, entreprise en semant les graines récoltées avec
     soin des pots de l'année précédente et traitées exactement de la
     même façon[76]."

    [76] _Rev. Gén. de Bot._ tom. ii. p. 64.

Here, it will be observed, there was no selection; and therefore the
increased hereditary effect in the second generation must apparently be
ascribed to a continuance of influence exercised by somatic tissues on
germinal elements; for at the time when the changes were produced no
seed had been formed. In other words, the accumulated change, like the
initial change, would seem to have been exclusively of somatogenetic
origin; and yet it so influenced the qualities of the seed (as this was
afterwards formed), that the augmented changes were transmitted to the
next generation, part for part, as the lesser changes had occurred in
the preceding generation. "This experiment, therefore, like Professor
Buckman's, shows that the alteration of the tissues was carried on in
the second generation from the point gained in the first. In both cases
no germ-plasm (in the germ-cells) existed at the time during which the
alterations arose, as they were confined to the vegetative system; and
in the case of the parsnips and carrots, being biennials no germ-cells
are produced till the second year has arrived[77]."

    [77] I am indebted to the Rev. G. Henslow for the references to
         these cases. This and the passages which follow are quoted from
         his letters to me.

Once more, Professor Bailey remarks:--

     "Squashes often show remarkable differences when grown upon
     different soils; and these differences can sometimes be perpetuated
     for a time by seeds. The writer has produced, from the same parent,
     squashes so dissimilar, through the simple agency of a change of
     soil in one season, that they might readily be taken for distinct
     varieties. Peas are known to vary in the same manner. The seeds of
     a row of peas of the same kind, last year gave the writer marked
     variations due to differences of soil.... Pea-growers characterize
     soils as 'good' and 'viney.' Upon the latter sort the plants run to
     vine at the expense of the fruit, and their offspring for two or
     three generations have the same tendency[78]."

    [78] _Gardener's Chronicle_, May 31, 1890, p. 677.

I think these several cases are enough to show that, while the
Weismannian assumption as to the seeming transmission of somatogenetic
characters being restricted to the lowest kinds of plants is purely
gratuitous, there is no small amount of evidence to the contrary--or
evidence which seems to prove that a similar transmission occurs
likewise in the higher plants. And no doubt many additional cases might
be advanced by any one who is well read in the literature of economic
botany.

It appears to me that the only answer to such cases would be furnished
by supposing that the hereditary changes are due to an alteration of the
residual "germ-plasm" in the wild seed, when this is first exposed to
the changed conditions of life, due to its growth in a strange kind of
soil--e.g. while germinating in an unusual kind of earth for producing
the first generation. But this would be going a long way to save an
hypothesis. In case, however, it should now be suggested, I may remark
that it would be negatived by the following facts.[79]

    [79] Since the above was written Professor Weismann has advanced, in
         _The Germ-plasm_, a suggestion very similar to this. It is
         sufficient here to remark, that nearly all the facts and
         considerations which ensue in the present chapter are
         applicable to his suggestion, the essence of which is
         anticipated in the above paragraph.

In the first place, an endless number of cases might be quoted where
somatogenetic changes thus produced by changed conditions of life are
not hereditary. Therefore, in all these cases it is certainly not the
"germ-plasm" that is affected. In other words, there can be no question
that somatogenetic changes of the kinds above mentioned do very readily
admit of being produced in the first generation by changes of soil,
altitude, &c. And that somatogenetic changes thus produced should not
always--or even generally--prove themselves to be hereditary from the
first moment of their occurrence, is no more than any theory of
heredity would expect. Indeed, looking to the known potency of
reversion, the wonder is that in any case such changes should become
hereditary in a single generation. On the other hand, there is no reason
to imagine that the hypothetical germ-plasm--howsoever _unstable_ we may
suppose it to be--can admit of being directly affected by a change of
soil in a single generation. For, on this view, it must presumably be
chiefly affected during the short time that the seed is germinating; and
during that time the changed conditions can scarcely be conceived as
having any points of attack, so to speak, upon the residual germ-plasm.
There are no roots on which the change of _soil_ can make itself
perceptible, nor any stem and leaves on which the change of _atmosphere_
can operate. Yet the changed condition's may produce hereditary
modifications in any parts of the plant, which are not only precisely
analogous to non-hereditary changes similarly produced in the somatic
tissues of innumerable other plants, but are always of precisely the
same kind in the same lot of plants that are affected. When all the
radishes grown from wild seed in Paris, for instance, varied in the
direction of rotundity and dark colour, while those grown in the country
presented the opposite characters, we can well understand the facts as
due to an entire season's action upon the whole of the growing plant,
with the result that all the changes produced in each set of plants were
similar--just as in the cases where similarly "climatic" modifications
are not hereditary, and therefore unquestionably due to changed
conditions acting on roots, stems, leaves, or flowers, as the case may
be. On the other hand, it is not thus intelligible that during the
short time of germination the changed conditions should effect a
re-shuffling (or any other modification) of the "germ-plasm" in the
seeds--and this in such a manner that the effect on the residual
germ-plasm reserved for future generations is precisely similar to that
produced on the somatic tissues of the developing embryo.

In the second place, as we have seen, in some of the foregoing cases the
changes were produced months--and even years--before the seeds of the
first germination were formed. Therefore the hereditary effect, if
subsequent to the period of embryonic germination, must have been
produced on germ-plasm as this occurs diffused through the somatic
tissues. But, if so, we shall have to suppose that such germ-plasm is
afterwards gathered in the seeds when these are subsequently formed.
This supposition, however, would be radically opposed to Weismann's
theory of heredity: nor do I know of any other theory with which it
would be reconcilable, save such as entertain the possibility of the
Lamarckian factors.

Lastly, in the third place, I deem the following considerations of the
highest importance:--

     "As other instances in which peculiar structures are now hereditary
     may be mentioned aquatic plants and those producing subterraneous
     stems. Whether they be dicotyledons or monocotyledons, there is a
     fundamental agreement in the anatomy of the roots and stem of
     aquatic plants, and, in many cases, of the leaves as well. Such has
     hitherto been attributed to the aquatic habit. The inference or
     deduction was, of course, based upon innumerable coincidences; the
     water being supposed to be the direct cause of the degenerate
     structures, which are hereditary and characteristic of such plants
     in the wild state. M. Costantin has, however, verified this
     deduction, by making terrestrial and aerial stems to grow
     underground and in water: the structures _at once_ began to assume
     the subterranean or aquatic type, as the case might be; and,
     conversely, aquatic plants made to grow upon land _at once_ began
     to assume the terrestrial type of structure, while analogous
     results followed changes from a subterranean to an aerial position,
     and _vice versa_."

This is also quoted from the Rev. Prof. Henslow's letters to me, and the
important point in it is, that the great changes in question are proved
to be of a purely "somatogenetic" kind; for they occurred "at once" _in
the ready-grown plant_, when the organs concerned were exposed to the
change from aquatic to terrestrial life, or _vice versa_--and also from
a subterranean to an aerial position, or _vice versa_. Consequently,
even the abstract possibility of the changed conditions of life having
operated on the _seed_ is here excluded. Yet the changes are of
precisely the same kind as are now _hereditary_ in the wild species. It
thus appears undeniable that all these remarkable and uniform changes
must originally have been somatogenetic changes; yet they have now
become blastogenetic. This much, I say, seems undeniable; and therefore
it goes a long way to prove that the non-blastogenetic character of the
changes has been due to their originally somatogenetic character. For,
if not, how did natural selection ever get an opportunity of making any
of them blastogenetic, when every individual plant has always presented
them as already given somatogenetically? This last consideration appears
in no small measure to justify the opinion of Mr. Henslow, who
concludes--"These experiments prove, not only that the influence of the
environment is _at once_ felt by the organ; but that it is indubitably
the _cause_ of the now specific and hereditary traits peculiar to
normally aquatic, subterranean, and aerial stems, or roots[80]."

    [80] It also serves to show that Weismann's newer doctrine of
         similar "determinants" occurring both in the germ and in the
         somatic tissues is a doctrine which cannot be applied to rebut
         this evidence of the transmission of acquired characters in
         plants. Therefore even its hypothetical validity as applied by
         him to explain the seasonal variation of butterflies is
         rendered in a high degree dubious.

He continues to furnish other instances in the same line of proof--such
as the distinctive "habits" of insectivorous, parasitic, and climbing
plants; the difference in structure between the upper and under sides of
horizontal leaves, &c. "For here, as in all organs, we discover by
experiment how easily the anatomy of plants can be affected by their
environment; and that, as long as the latter is constant, so are the
characters of the plants constant and hereditary."

     [The following letter, contributed by Dr. Hill to _Nature_, vol. I.
     p. 617, may here be quoted. C. Ll. M.

     "It may be of interest to your readers to know that two guinea-pigs
     were born at Oxford a day or two before the death Dr. Romanes, both
     of which exhibited a well-marked droop of the left upper eyelid.
     These guinea-pigs were the offspring of a male and a female
     guinea-pig in both of which I had produced for Dr. Romanes, some
     months earlier, a droop of the left upper eyelid by division of the
     left cervical sympathetic nerve. This result is a corroboration of
     the series of Brown-Séquard's experiments on the inheritance of
     acquired characteristics. A very large series of such experiments
     are of course needed to eliminate all sources of error, but this I
     unfortunately cannot carry out at present, owing to the need of a
     special farm in the country, for the proper care and breeding of
     the animals.--LEONARD HILL.

     "Physiological Laboratory, Univ. Coll. London, Oct. 18, 1894."]




CHAPTER V.

CHARACTERS AS HEREDITARY AND ACQUIRED
(_continued_).


(A. and B.)


_Direct and Indirect Evidence in favour of the Non-inheritance of
Acquired Characters_[81].

    [81] [_See_ note appended to Preface. C. LI. M.]

The strongest argument in favour of "continuity" is that based upon the
immense difference between congenital and acquired characters in respect
of heritability. For that there is a great difference in this respect is
a matter of undeniable fact. And it is obvious that this difference, the
importance of which must be allowed its full weight, is just what we
should expect on the theory of the continuity of the germ-plasm, as
opposed to that of pangenesis. Indeed it may be said that the difference
in question, while it constitutes important _evidence_ in favour of the
former theory, is a _difficulty_ in the way of the latter. But here two
or three considerations must be borne in mind.

In the first place, this fact has long been one which has met with wide
recognition and now constitutes the main ground on which the theory of
continuity stands. That is to say, it was the previous knowledge of
this contrast between congenital and acquired characters which led to
the formulation of a theory of continuity by Mr. Galton, and to its
subsequent development by Prof Weismann.

But, in the second place, there is a wide difference between the
certainty of this fact and that of the theory based upon it. The certain
fact is, that a great distinction in respect of heritability is
observable between congenital and acquired characters. The theory, as
formulated by Weismann, is that the distinction is not only great but
absolute, or, in other words, that in no case and in no degree can any
acquired character be ever inherited. This hypothesis, it will be
observed, goes far beyond the observed fact, for it is obviously
possible that, notwithstanding this great difference in regard to
heritability between congenital and acquired characters, the latter may
nevertheless, sometimes and in some degree, be inherited, however much
difficulty we may experience in observing these lesser phenomena in
presence of the greater. The Weismannian hypothesis of _absolute_
continuity is one thing, while the observed fact of at least a _high
relative degree_ of continuity is quite another thing. And it is
necessary to be emphatic on this point, since some of the reviewers of
my _Examination of Weismannism_ confound these two things. Being
apparently under the impression that it was reserved for Weismann to
perceive the fact of there being a great difference between the
heritability of congenital and acquired characters, they deem it
inconsistent in me to acknowledge this fact while at the same time
questioning the hypothetical basis of his fundamental postulate touching
the absolute continuity of germ-plasm. It is one merit of Galton's
theory, as against Weismann's, that it does not dogmatically exclude the
possible interruption of continuity on some occasions and in some
degree. Herein, indeed, would seem to lie the central core of the whole
question in dispute. For it is certain and has long been known that
individually acquired characters are at all events much less heritable
than are long-inherited or congenital ones. But Lamarckian theory
supposes that congenital characters were in some cases originally
acquired, and that what are now blastogenetic characters were in some
cases at first somatogenetic and have become blastogenetic only in
virtue of sufficiently long inheritance. Since Darwin's time, however,
evolutionists (even of the so-called Lamarckian type) have supposed that
natural selection greatly assists this process of determining which
somatogenetic characters shall become congenital or blastogenetic. Hence
all schools of evolutionists are, and have long been, agreed in
regarding the continuity principle as true in the main. No evolutionist
would at any time have propounded the view that one generation depends
for _all_ its characters on those acquired by its _immediate_ ancestors,
for this would merely be to unsay the theory of Evolution itself, as
well as to deny the patent facts of heredity as shown, for example, in
atavism. At most only some fraction of a _per cent._ could be supposed
to do so. But Weismann's contention is that this principle is not only
true in the main, but _absolutely_ true; so that natural selection
becomes all in all or not at all. Unless Weismannism be regarded as
this doctrine of absolutism it permits no basis for his attempted theory
of evolution.

And, whatever may be said to the contrary by the more enthusiastic
followers of Prof. Weismann, I must insist that there is the widest
possible difference between the truly scientific question of fact which
is assumed by Weismann as answered (the base-line of the diagram on p.
43), and the elaborate structure of deductive reasoning which he has
reared on this assumption (the Y-like structure). Even if the assumption
should ever admit of inductive proof, the almost bewildering edifice of
deductive reasoning which he has built upon it would still appear to me
to present extremely little value of a scientific kind. Interesting
though it may be as a monument of ingenious speculation hitherto unique
in the history of science, the mere flimsiness of its material must
always prevent its far-reaching conclusions from being worthy of serious
attention from a biological point of view. But having already attempted
to show fully in my _Examination_ this great distinction between the
scientific importance of the question which lies at the base of
"Weismannism," and that of the system which he has constructed on his
assumed answer thereto, I need not now say anything further with regard
to it.

Again, on the present occasion and in this connexion I should like to
dissipate a misunderstanding into which some of the reviewers of the
work just mentioned have fallen. They appear to have concluded that
because I have criticized unfavourably a considerable number of
Weismann's theories, I have shown myself hostile to his entire system.
Such, however, is by no means the case; and the misunderstanding can
only be accounted for by supposing that the strongly partisan spirit
which these critics display on the side of neo-Darwinism has rendered
them incapable of appreciating any attempt at impartial--or even so much
as independent--criticism. At all events, it is a matter of fact that
throughout the work in question I have been particularly careful to
avoid this misunderstanding as to my own position. Over and over again
it is there stated that, far from having any objection to the principle
of "Continuity" as represented in the base-line of the above diagram, I
have been convinced of its truth ever since reading Mr. Galton's _Theory
of Heredity_ in 1875. All the "hard words" which I have written against
Weismann's system of theories have reference to those parts of it which
go to constitute the Y-like structure of the diagram.

It is, however, desirable to recur to another point, and one which I
hope will be borne in mind throughout the following discussion. It has
already been stated, a few pages back, that the doctrine of continuity
admits of being held in two very different significations. It may be
held as absolute, or as relative. In the former case we have the
Weismannian doctrine of germ-plasm: the substance of heredity is taken
to be a substance _per se_, which has always occupied a separate
"sphere" of its own, without any contact with that of somatoplasm
further than is required for its lodgement and nutrition; hence it can
never have been in any degree modified as to its hereditary qualities by
use-inheritance or any other kind of somatogenetic change; it has been
_absolutely_ continuous "since the first origin of life." On the other
hand, the doctrine of continuity may be held in the widely different
sense in which it has been presented by Galton's theory of Stirp. Here
the doctrine is, that while for the most part the phenomena of heredity
are due to the continuity of the substance of heredity through
numberless generations, this substance ("Stirp") is nevertheless not
absolutely continuous, but may admit, in small though cumulative
degrees, of modification by use-inheritance and other factors of the
Lamarckian kind. Now this all-important distinction between these two
theories of continuity has been fully explained and thoroughly discussed
in my _Examination_; therefore I will not here repeat myself further
than to make the following remarks.

The Weismannian doctrine of continuity as absolute (base-line of the
diagram) is necessary for the vast edifice of theories which he has
raised upon it (the Y), first as to the minute nature and exact
composition of the substance of heredity itself ("Germ-plasm"), next as
to the precise mechanism of its action in producing the visible
phenomena of heredity, variation, and all allied phenomena, and, lastly,
the elaborate and ever-changing theory of organic evolution which is
either founded on or interwoven with this vast system of hypothetic
speculation. Galton's doctrine of continuity, on the other hand, is a
"Theory of Heredity," and a theory of heredity alone. It does not meddle
with any other matters whatsoever, and rigidly avoids all speculation
further than is necessary for the bare statement and inductive support
of the doctrine in question. Hence, it would appear that this, the only
important respect wherein the doctrine of continuity as held by Galton
differs from the doctrine as held by Weismann, arisen from the necessity
under which the latter finds himself of postulating _absolute_
continuity as a logical basis for his deductive theory of the precise
mechanism of heredity on the one hand, and of his similarly deductive
theory of evolution on the other. So far as the doctrine of continuity
is itself concerned (i.e. the question of the inheritance of acquired
characters), there is certainly no more inductive reason for supposing
the continuity absolute "since the first origin of life," than there is
for supposing it to be more or less susceptible of interruption by the
Lamarckian factors. In other words, but for the sake of constructing a
speculative foundation for the support of his further theories as to
"the architecture of germ-plasm" and the factors of organic evolution,
there is no reason why Weismann should maintain the absolute separation
of the "sphere" of germ-plasm from that of somatoplasm. On the contrary,
he has no reason for concluding against even a considerable and a
frequent amount of cutting, or overlapping, on the part of these two
spheres.

But although this seems to me sufficiently obvious, as I have shown at
greater length in the _Examination of Weismannism_, it must not be
understood that I hold that there is room for any large amount of such
overlapping. On the contrary, it appears to me as certain as anything
can well be that the amount of such overlapping from one generation to
another, if it ever occur at all, must be exceedingly small, so that,
if we have regard to only a few sequent generations, the effects of
use-inheritance, and Lamarckian factors are, at all events as a rule,
demonstrably imperceptible. But this fact does not constitute any
evidence--as Weismann and his followers seem to suppose--against a
possibly important influence being exercised by the Lamarckian factors,
in the way of gradual increments through a long series of generations.
It has long been well known that acquired characters are at best far
less fully and far less certainly inherited than are congenital ones.
And this fact is of itself sufficient to prove the doctrine of
continuity to the extent that even the Lamarckian is rationally bound to
concede. But the fact yields no proof--scarcely indeed so much as a
presumption--in favour of the doctrine of continuity as absolute. For it
is sufficiently obvious that the adaptive work of heredity could not be
carried on at all if there had to be a discontinuity in the substance of
heredity at every generation, or even after any very large number of
generations.

Little more need be said concerning the arguments which fall under the
headings A and B. The Indirect evidence is considered in Appendix I of
the _Examination of Weismannism_; while the Direct evidence is
considered in the text of that work in treating of Professor Weismann's
researches on the _Hydromedusae_ (pp. 71-76).

The facts of karyokinesis are generally claimed by the school of
Weismann as making exclusively in favour of continuity as absolute. But
this is a partisan view to take. In any impartial survey it should be
seen that while the facts are fairly interpretable on Weismann's theory,
they are by no means proof thereof. For any other theory of Heredity
must suppose the material of heredity to be of a kind more or less
specialized, and the mechanism of heredity extremely precise and well
ordered. And this is all that the facts of karyokinesis prove. Granting
that they prove continuity, they cannot be held to prove that continuity
to be absolute. In other words, the facts are by no means incompatible
with even a large amount of commerce between germ-plasm and
somato-plasm, or a frequent transmission of acquired characters.

Again, Weismann's theory, that the somatic and the germ-plasm
determinants may be similarly and simultaneously modified by external
conditions may be extended much further than he has used it himself, so
as to exclude, or at any rate invalidate, _all_ evidence in favour of
Lamarckianism, other than the inheritance of the effects of use and
disuse. All evidence from apparently inherited effects produced by
change of external conditions is thus virtually put out of court,
leaving only evidence from the apparently inherited effects of
functionally produced modifications. And this line of evidence is
invalidated by Panmixia. Hence there remain only the arguments from
selective value and co-adaptation. Weismann meets these by adducing the
case of neuter insects, which have been already considered at sufficient
length.


(C.)
_Experimental Evidence as to the Non-inheritance of Acquired
Characters._


Let us now proceed to the experimental evidence which has been adduced
on the side of Weismannism.

Taking this evidence in order of date, we have first to mention that on
which the school of Weismann has hitherto been satisfied almost
exclusively to rely. This is the line of negative evidence, or the
seeming absence of any experimental demonstration of the inheritance of
acquired characters. This kind of evidence, however, presents much less
cogency than is usually supposed. And it has been shown in the last
chapter that the amount of experimental evidence in favour of the
transmission of acquired characters is more considerable than the school
of Weismann seems to be aware--especially in the vegetable kingdom. I do
not think that this negative line of evidence presents much weight; and,
to show that I am not biassed in forming this judgement, I may here
state that few have more reason than myself for appreciating the weight
of such evidence. For, as already stated, when first led to doubt the
Lamarckian factors, now more than twenty years ago, I undertook a
research upon the whole question--only a part of which was devoted to
testing the particular case of Brown-Séquard's statements, with the
result recorded in the preceding chapter. As this research yielded
negative results in all its divisions--and, not only in the matter of
Brown-Séquard's statements--I have not hitherto published a word upon
the subject. But it now seems worth while to do so, and for the
following reasons.

First, as just observed, a brief account of my old experiences in this
field will serve to show what good reason I have for feeling the weight
of such negative evidence in favour of Continuity as arises from failure
to produce any good experimental evidence to the contrary. In the second
place, now that the question has become one of world-wide interest, it
would seem that even negative results deserve to be published for
whatever they may be worth on the side of Neo-Darwinism. Lastly, in the
third place, although the research yielded negative results in my hands,
it is perhaps not undesirable to state the nature of it, if only to
furnish suggestions to other physiologists, in whose hands the
experiments--especially in these days of antiseptics--may lead to a
different termination. Altogether I made thousands of experiments in
graft-hydridization (comprising bines, bulbs of various kinds, buds, and
tubers); but with uniformly negative results. With animals I tried a
number of experiments in grafting characteristic congenital tissues from
one variety on another--such as the combs of Spanish cocks upon the
heads of Hamburgs; also, in mice and rats, the grafting together of
different varieties; and, in rabbits and bitches, the transplantation of
ovaries of newly-born individuals belonging to different well-marked
breeds. This latter experiment seems to be one which, if successfully
performed (so that the transplanted ovaries would form their attachment
in a young bitch puppy and subsequently yield progeny to a dog of the
same breed as herself) would furnish a crucial test as to the
inheritance or non-inheritance of acquired characters. Therefore I
devoted to it a large share of my attention, and tried the experiment in
several different ways. But I was never able to get the foreign
ovary--or even any portion thereof--to graft. Eventually the passing of
the Vivisection Act caused me to abandon the whole research as far as
animals were concerned--a research, indeed, of which I had become
heartily tired, since in no one instance did I obtain any adhesion.
During the last few years, however, I have returned to these experiments
under a licence, and with antiseptic precautions, but with a similar
want of success. Perhaps this prolonged and uniformly fruitless
experience may now have the effect of saving the time of other
physiologists, by warning them off the roads where there seems to be no
thoroughfare. On the other hand, it may possibly lead some one else to
try some variation in the method, or in the material, which has not
occurred to me. In particular, I am not without hope that the
transplantation of ovaries in very young animals may eventually prove to
be physiologically possible; and, if so, that the whole issue as between
the rival theories of heredity will be settled by the result of a single
experiment. Possibly some of the invertebrata will be found to furnish
the suitable material, although I have been unable to think of any of
these which present sufficiently well-marked varieties for the purpose.
But, pending the successful accomplishment of this particular experiment
in the grafting of any animal tissue, I think it would be clearly
unjustifiable to conclude against the Lamarckian factors on the ground
of any other experiments yielding negative results in but one generation
or even in a large number of sequent generations.

For instance, the latter consideration applies to the negative results
of Mr. Francis Galton's celebrated _Experiments in Pangenesis_.[82].
These consisted in transfusing the blood of one variety of rabbit into
the veins of both sexes of another, and then allowing the latter to
breed together: in no case was there any appearance in the progeny of
characters distinctive of the variety from which the transfused blood
was derived. But, as Mr. Galton himself subsequently allowed, this
negative result constitutes no disproof of pangenesis, seeing that only
a portion of the parents' blood was replaced; that this portion, even if
charged with "gemmules," would contain but a very small number of these
hypothetical bodies, compared with those contained in all the tissues of
the parents; and that even this small proportional number would
presumably be soon overwhelmed by those contained in blood newly-made by
the parents. Nevertheless the experiment was unquestionably worth
trying, on the chance of its yielding a positive result; for, in this
event, the question at issue would have been closed. Accordingly I
repeated these experiments (with the kind help of Professor Schäfer),
but with slight differences in the method, designed to give pangenesis a
better chance, so to speak.

    [82] _Proc. R. S. 1871._

Thus I chose wild rabbits to supply the blood, and Himalayan to receive
it--the former being the ancestral type (and therefore giving reversion
an opportunity of coming into play), while the latter, although a
product of domestication, is a remarkably constant variety, and one
which differs very much in size and colour from the parent species.
Again, instead of a single transfusion, there were several transfusions
performed at different times. Moreover, we did not merely allow the
blood of one rabbit to flow into the veins of the other (whereby little
more than half the blood could be substituted); but sacrificed three
wild rabbits for refilling the vascular system of each tame one on each
occasion. Even as thus improved, however, the experiment yielded only
negative results, which, therefore, we never published.

Subsequently I found that all this labour, both on Mr. Galton's part and
our own, was simply thrown away--not because it yielded only negative
results, but because it did not serve as a crucial experiment at all.
The material chosen was unserviceable for the purpose, inasmuch as
rabbits, even when crossed in the ordinary way, never throw intermediate
characters. Needless to say, had I been aware of this fact before, I
should never have repeated Mr. Galton's experiments--nor, indeed, would
he have originally performed them had he been aware of it. So all this
work goes for nothing. The research must begin all over again with some
other animals, the varieties of which when crossed do throw intermediate
characters.

Therefore I have this year made arrangements for again repeating the
experiments in question--only, instead of rabbits, using well-marked
varieties of dogs. A renewed attack of illness, however, has
necessitated the surrender of this research to other hands, with a
consequent delay in its commencement.

My ignorance of the unfortunate peculiarity displayed by rabbits in not
throwing intermediate characters has led to a further waste of time in
another line of experiment. On finding that mammalian ovaries did not
admit of being grafted, it seemed to me that the next best thing to try
would be the transplantation of fertilized ova from one variety to
another, for the purpose of ascertaining whether, if a parturition
should take place under such circumstances, gestation by the uterine
mother would affect the characters of the ovum derived from the ovarian
mother--she, of course, having been fertilized by a male of her own
variety. Of course it was necessary that both the mothers should be in
season at about the same time, and therefore I again chose rabbits,
seeing that in the breeding season they are virtually in a chronic state
of "heat." I selected Himalayans and Belgian hares, because they are
well-marked varieties, breed true, and in respect of colour are very
different from one another. It so happened that while I was at work upon
this experiment, it was also being tried, unknown to me, by Messrs.
Heape and Buckley who, curiously enough, employed exactly the same
material. They were the first to obtain a successful result. Two
fertilized ova of the Angora breed having been introduced into the
fallopian tube of a Belgian hare, developed there in due course, and
gave rise to two Angora rabbits in no way modified by their Belgian hare
gestation[83].

    [83] _Proc. R. S. 1890_, vol. xlviii. p. 457. It should be stated
         that the authors do not here concern themselves with any theory
         of heredity.

But, interesting and suggestive as this experiment is in other
connexions, it is clearly without significance in the present one, for
the reason already stated. It will have to be tried on well-marked
varieties of other species of animals, which are known to throw
intermediate characters. Even, however, if it should then yield a
similarly negative result, the fact would not tell against the
inheritance of acquired characters; seeing that an ovum by the time it
is ripe is a finished product, and therefore not to be expected, on any
theory of heredity, to be influenced as to its hereditary potentialities
by the mere process of gestation. On the other hand, if it should prove
that it does admit of being thus affected, so that against all
reasonable expectation the young animal presents any of the hereditary
characters of its uterine mother, the fact would terminate the question
of the transmission of acquired characters--and this quite as
effectually as would a similarly positive result in the case of progeny
from an ingrafted ovary of a different variety. In point of fact, the
only difference between the two cases would be, that in the former it
_might_ prove possible to close the question on the side of
Lamarckianism, in the latter it would _certainly_ close the question,
either on this side or on the opposite as the event would determine.

The only additional fact that has hitherto been published by the school
of Weismann is the result of Weismann's own experiment in cutting off
the tails of mice through successive generations. But this experiment
does not bear upon any question that is in debate; for no one who is
acquainted with the literature of the subject would have expected any
positive result to follow from such a line of inquiry. As shown further
back in the text, Darwin had carefully considered the case of
mutilations, and explained that their non-transmissibility constitutes
no valid objection to his theory of pangenesis. Furthermore, it may now
be added, he expressly alluded in this connexion to the cutting off of
tails, as practised by horse-breeders and dog-fanciers, "through a
number of generations, without any inherited effect." He also alluded to
the still better evidence which is furnished by the practice of
circumcision. Therefore it is difficult to understand the object of
Weismann's experiment. Yet, other than the result of this experiment, no
new fact bearing on the question at issue has been even so much as
alleged.




CHAPTER VI.

CHARACTERS AS HEREDITARY AND ACQUIRED
(_conclusion_[84]).

    [84] _See_ note appended to Preface. C. Ll. M.

In the foregoing chapters I have endeavoured to be, before all things,
impartial; and if it seems that I have been arguing chiefly in favour of
the Lamarckian principles, this has been because the only way of
examining the question is to consider what has to be said on the
affirmative side, and then to see what the negative side can say in
reply. Before we are entitled to discard the Lamarckian factors _in
toto_, we must be able to destroy all evidence of their action. This,
indeed, is what the ultra-Darwinians profess to have done. But is not
their profession premature? Is it not evident that they have not
sufficiently considered certain general facts of nature, or certain
particular results of experiment, which at all events appear
inexplicable by the theory of natural selection alone? In any case the
present discussion has been devoted mainly to indicating such general
facts and particular results. If I have fallen into errors, either of
statement or of reasoning, it is for the ultra-Darwinians to correct
them; but it may be well to remark beforehand, that any criticism of a
merely general kind touching the comparative paucity of the facts thus
adduced in favour of Lamarckian doctrine, will not stand as a valid
criticism. For, as we have seen in the opening part of the discussion,
even if use-inheritance and direct action of the environment have been
of high importance as factors of organic evolution, it must be in almost
all cases impossible to dissociate their influence from that of natural
selection--at any rate where plants and animals in a state of nature are
concerned. On the other hand, experiments expressly devised to test the
question have not hitherto been carried out. Besides, the facts and
arguments here adduced are but _comparatively_ few. For, unless it can
be shown that what has been said of reflex action, instinct, so-called
"self-adaptation" in plants, &c., is wrong in principle, the facts which
tell in favour of Lamarckian theory are _absolutely_ very numerous. Only
when considered in relation to cases where we are unable to exclude the
conceivable possibility of natural selection having been at work, can it
be said that the facts in question are not numerous.

Comparatively few, then, though the facts may be of which I have given
some examples, in my opinion they are amply sufficient for the purpose
in hand. This purpose is to show that the question which we are now
considering is very far from being a closed question; and, therefore,
that the school of Weismann is much too precipitate in alleging that
there is neither any necessity for, nor evidence of, the so-called
Lamarckian factors[85]. And this opinion, whatever it may be worth, is
at all events both deliberate and impartial. As one of the first to
doubt the transmission of acquired characters, and as one who has spent
many years in experimental inquiries upon the subject, any bias that I
may have is assuredly against the Lamarckian principles--seeing that
nearly all my experiments have yielded negative results. It was Darwin
himself who checked this bias. But if the ultra-Darwinians of the last
ten years had succeeded in showing that Darwin was mistaken, I should be
extremely glad to fall into line with them. As already shown, however,
they have in no way affected this question as it was left by Galton in
1875. And if it be supposed a matter of but little importance whether we
agree with Galton in largely diminishing the comparative potency of the
Lamarckian principles, or whether we agree with Weismann in abolishing
them together, it cannot be too often repeated that such is an entirely
erroneous view. No matter how faintly or how fitfully acquired
characters may be transmitted, in so far as they are likewise adaptive
characters, their transmission (and therefore their development) must be
cumulative. Hence, the only effect of attenuating our estimate of their
_intensity_, is that of increasing our estimate of their
_duration_--i.e. of the time over which they have to operate in order to
produce important results. And, even so, it is to be remembered that
the importance of such results is not to be estimated by the magnitude
of modification. Far more is it to be estimated by the character of
modification as adaptive. For if functionally produced changes, and
changes produced in adaptive response to the environment, are ever
transmitted in a cumulative manner, a time must sooner or later arrive
when they will reach a selective value in the struggle for
existence--when, of course, they will be rapidly augmented by natural
selection. Thus, if in any degree operative at all, the great function
of these principles must be that of supplying to natural selection those
incipient stages of adaptive modifications in all cases where, but for
their agency, there would have been nothing of the kind to select.
Themselves in no way dependent on adaptive modifications having already
attained a selective value, these Lamarckian principles are (under the
Darwinian theory) direct causes of determinate variation in adaptive
lines; and variation in those lines being cumulative, the result is that
natural selection is in large part presented with the raw material of
its manufacture--special material of the particular kinds required, as
distinguished from promiscuous material of all kinds. And the more
complex the manufacture the more important will be the work of this
subordinate factory. We can well imagine how the shell of a nut, for
instance, or even the protective colouring of an insect, may have been
gradually built up by natural selection alone. But just in proportion as
structures or organs are not merely thus of passive _use_ (where, of
course, the Lamarckian principles cannot obtain), but require to be
actively _used_, in that proportion does it become difficult to
understand the _incipient_ construction of them by natural selection
alone. Therefore, in many such cases, if the incipient construction is
not to be explained by the Lamarckian principles, it is difficult to see
how it is to be explained at all.

    [85] E.g. "The supposed transmission of this artificially produced
         disease (epilepsy) is the only definite instance which has been
         brought forward in support of the transmission of acquired
         characters."--_Essays_, p. 328.

Furthermore, since the question as to the transmission of acquired
characters stands now exactly as it did after the publication of Mr.
Galton's _Theory of Heredity_ twenty years ago, it would seem that our
judgement with regard to it should remain exactly what it was then.
Although we must "out-Darwin Darwin" to the extent of holding that he
assigned too large a measure of intensity to the Lamarckian factors, no
sufficient reason has been shown for denying the existence of these
factors _in toto_; while, on the other hand, there are certain general
considerations, and certain particular facts, which appear to render it
probable that they have played a highly important part in the process of
organic evolution as a whole. At the same time, and in the present state
of our information, this judgement must be deemed provisional, or liable
eventually to be overturned by experimental proof of the non-inheritance
of acquired characters. But, even if this should ever be finally
accomplished, the question would still remain whether the principle of
natural selection alone is capable of explaining all the facts of
adaptation; and, for my own part, I should then be disposed to believe
that there must be some other, though hitherto undiscovered, principle
at work, which co-operates with natural selection, by playing the
subordinate role which was assigned by Darwin to the principles of
Lamarck.

Finally, let it be noted that no part of the foregoing argument is to be
regarded as directed against the _principle_ of what Professor Weismann
calls "continuity." On the contrary, it appears to be self-evident that
this principle must be accepted in some degree or another by every one,
whether Darwinians, Neo-Darwinians, Lamarckians, Neo-Lamarckians, or
even the advocates of special creation. Yet, to hear or to read some of
the followers of Weismann, one can only conclude that, prior to his
publications on the subject, they had never thought about it at all.
These naturalists appear to suppose that until then the belief of
Darwinians was, that there could be no hereditary "continuity" between
any one organic type and another (such, for instance, as between Ape and
Man), but that the whole structure of any given generation must be due
to "gemmules" or "somato-plasm," derived exclusively from the preceding
generation. Nothing can show more ignorance, or more thoughtlessness,
with regard to the whole subject. The very basis of the general theory
of evolution is that there must always have been a continuity in the
material substance of heredity since the time when the process of
evolution began; and it was not reserved for our generation, or even for
our century, to perceive the special nature of this material substance
in the case of sexual organisms. No, the real and the sole question,
where Weismann's theory of heredity is concerned, is simply this--Are we
to hold that this material substance has been _absolutely_ continuous
"since the first origin of sexual propagation," always occupying a
separate "sphere" of its own, at all events to the extent of never
having been modified by the body substance in which it resides
(Lamarckian factors); _or_, are we to hold that this "germ-plasm,"
"stirp," or "formative-material," has been but _relatively_ continuous,
so as to admit of some amount of commerce with body-substance, and
therefore to admit of acquired characters, when sufficiently long
continued as such, eventually becoming congenital? If this question be
answered in the latter sense, of course the further question arises as
to the _degree_ of such commerce, or the _time_ during which acquired
characters must continue to be acquired in successive generations before
they can sufficiently impress themselves on the substance of heredity to
become congenital. But this is a subordinate question, and one which, in
the present state of our information, it seems to me almost useless to
speculate upon. My own opinion has always been the same as that of Mr.
Galton; and my belief is that eventually both Weismann and his followers
will gravitate into it. It was in order to precipitate this result as
far as possible that I wrote the _Examination_. If it ever should be
accomplished, Professor Weismann's elaborate theory of evolution will
have had its bases removed.




SECTION II

_UTILITY_




CHAPTER VII.

CHARACTERS AS ADAPTIVE AND SPECIFIC.


One of the great changes which has been wrought in biological science by
the Darwinian theory of natural selection, consists in its having
furnished an intelligible explanation of the phenomena of _adaptation_.
Indeed, in my opinion, this is the most important function which this
theory has had to perform; and although we still find systematic
zoologists and systematic botanists who hold that the chief merit of
Darwin's work consists in its having furnished an explanation of the
origin of _species_, a very little consideration is enough to show that
such an idea is but a survival, or a vestige, of an archaic system of
thought. So long as species were regarded as due to separate acts of
creation, any theory which could explain their production by a process
of natural evolution became of such commanding importance in this
respect, that we cannot wonder if in those days the principal function
of Darwin's work was held to be what the title of that work--_The Origin
of Species by means of Natural Selection_--itself serves to convey. And,
indeed, in those days this actually was the principal function of
Darwin's work, seeing that in those days the _fact_ of evolution
itself, as distinguished from its _method_, had to be proved; and that
the whole proof had to stand or fall with the evidence which could be
adduced touching the mutability of species. Therefore, without question,
Darwin was right in placing this issue as to the stability or
instability of species in the forefront of his generalizations, and
hence in constituting it the title of his epoch-making book. But
nowadays, when the fact of evolution has been sufficiently established,
one would suppose it self-evident that the theory of natural selection
should be recognized as covering a very much larger field than that of
explaining the origin of _species_--that it should be recognized as
embracing the whole area of organic nature in respect of _adaptations_,
whether these happen to be distinctive of species only, or of genera,
families, orders, classes, and sub-kingdoms. For it follows from the
general fact of evolution that species are merely arbitrary divisions,
which present no deeper significance from a philosophical point of view
than is presented by well-marked varieties, out of which they are in all
cases believed to have arisen, and from which it is often a matter of
mere individual taste whether they shall be separated by receiving the
baptism of a specific name. Yet, although naturalists are now
unanimously agreed that what they classify as species are nothing
more than pronounced--and in some greater or less degree
permanent--varieties, so forcible is the influence of traditional modes
of thought, that many zoologists and botanists still continue to regard
the origin of species as a matter of more importance than the origin of
adaptations. Consequently, they continue to represent the theory of
natural selection as concerned, primarily, with explaining the origin of
species, and denounce as a "heretic" any one who regards the theory as
primarily a theory of the origin and cumulative development of
adaptations--whether structural or instinctive, and whether the
adaptations are severally characteristic of species only or of any of
the higher taxonomic divisions. Indeed, these naturalists appear to deem
it in some way a disparagement of the theory to state that it is,
primarily, a theory of adaptations, and only becomes secondarily a
theory of species in those comparatively insignificant cases where the
adaptations happen to be distinctive of the lowest order of taxonomic
division--a view of the matter which may fitly be compared to that of an
astronomer who should define the nebular hypothesis as a theory of the
origin of Saturn's rings. It is indeed a theory of the origin of
Saturn's rings; but only because it is a theory of the origin of the
entire solar system, of which Saturn's rings form a part. Similarly, the
theory of natural selection is a theory of the entire system of organic
nature in respect of adaptations, whether these happen to be distinctive
of particular species only, or are common to any number of species.

Now the outcry which has been raised over this definition of the theory
of natural selection is a curious proof of the opposition which may be
furnished by habitual modes of thought to an exceedingly plain matter of
definition. For, I submit, that no one can deny any of the following
propositions; nor can it be denied that from these propositions the
foregoing definition of the theory in question follows by way of
necessity. The propositions are, first, that natural selection is taken
to be the agency which is mainly, if not exclusively, concerned in the
evolution of adaptive characters: secondly, that these characters, when
evolved, are in some cases peculiar to single species only, while in
other cases, and in process of time, they become the common property of
many species: thirdly, that in cases where they are peculiar to single
species only, they constitute at all events one of the reasons (or even,
as the ultra-Darwinians believe, the only reason) why the particular
species presenting them have come to be species at all. Now, these being
the propositions on which we are all agreed, it obviously follows, of
logical necessity, that the theory in question is primarily one which
explains the existence of adaptive characters wherever these occur; and,
therefore, whether they happen to be restricted to single species, or
are common to a whole group of species. Of course in cases where they
are restricted to single species, the theory which explains the origin
of these particular adaptations becomes also a theory which explains the
origin of these particular species; seeing that, as we are all agreed,
it is in virtue of such particular adaptations that such particular
species exist. Yet even in these cases the theory is, primarily, a
theory of the adaptations in virtue of which the particular species
exists; for, _ex hypothesi_, it is the adaptations which condition the
species, not the species the adaptations. But, as just observed,
adaptations may be the common property of whole groups of species; and
thus the theory of natural selection becomes a theory of the origin of
genera, of families, of orders, and of classes, quite as much as it is a
theory of the origin of species. In other words, it is everywhere a
theory of adaptations; and it is only where the adaptations happen to be
restricted to single species that the theory therefore and incidentally
becomes also a theory of the particular species which presents them.
Hence it is by no means the same proposition to affirm that the theory
of natural selection is a theory of the origin of species, and that it
is a theory of the origin of adaptations, as some of my critics have
represented it to be; for these two things are by no means conterminous.
And in as far as the two propositions differ, it is perfectly obvious
that the latter is the true one.

Possibly, however, it may be said--Assuredly natural selection is a
theory of the origin (i.e. cumulative development) of adaptations; and,
no less assuredly, although species owe their origin to such
adaptations, there is now no common measure between these two things,
seeing that in numberless cases the same adaptations are the common
property of numberless species. But, allowing all this, we must still
remember that in their _first beginnings_ all these adaptations must
have been distinctive of, or peculiar to, some one particular species,
which afterwards gave rise to a whole genus, family, order, or class of
species, all of which inherited the particular adaptations derived from
this common ancestor, while progressively gaining additional adaptive
characters severally distinctive of their subsequently diverging lines
of descent. So that really all adaptive characters must originally have
been specific characters; and therefore there is no real distinction to
draw between natural selection as a theory of species and as a theory of
adaptations.

Well, if this objection were to be advanced, the answer would be
obvious. Although it is true that every adaptive character which is now
common to a group of species must originally have been distinctive of a
single parent species, it by no means follows that in its first
beginning as a specific character it appeared in the fully developed
form which it now presents as a generic, family, ordinal, or yet higher
character. On the contrary, it is perfectly certain that in the great
majority of instances such cannot possibly have been the case; and the
larger the group of species over which any particular adaptive character
now extends, the more evidently do we perceive that this character must
itself have been the product of a gradual evolution by natural selection
through an innumerable succession of species in branching lines. The
wing of a bird, for example, is an adaptive structure which cannot
possibly have ever appeared suddenly as a merely specific character: it
must have been slowly elaborated through an incalculable number of
successive species, as these branched into genera, families, and orders
of the existing class. So it is with other class distinctions of an
adaptive kind; and so, in progressively lessening degrees, is it with
adaptive characters of an ordinal, a family, or a generic value. That is
to say, in _all_ cases where an adaptive structure is common to any
considerable group of species, we meet with clear evidence that the
structure has been the product of evolution through the ancestry of
those species; and this evidence becomes increasingly cogent the higher
the taxonomic value of the structure. Indeed, it may be laid down as a
general rule, that the greater the _degree_ of adaptation the greater is
its _diffusion_--both as regards the number of species which present it
now, and the number of extinct species through which it has been handed
down, in an ever ramifying extension and in an ever improving form.
Species, therefore, may be likened to leaves: successive and transient
crops are necessary for the gradual building up of adaptations, which,
like the woody and permanent branches, grow continuously in importance
and efficiency through all the tree of life. Now, in my view, it is the
great office of natural selection to see to the growth of these
permanent branches; and although natural selection has likewise had an
enormously large share in the origination of each successive crop of
leaves--nay, let it be granted to the ultra-Darwinians for the sake of
argument, an exclusive prerogative in this respect--still, in my view,
this is really the least important part of its work. Not as an
explanation of those merely permanent varieties which we call species,
but as an explanation of the adaptive machinery of organic nature, which
has led to the construction both of the animal and vegetable kingdoms in
all their divisions do I regard the Darwinian theory as one of the
greatest generalizations in the history of science.

       *       *       *       *       *

I have dwelt thus at some length upon a mere matter of definition
because, as we shall now find, although it is but a matter of
definition, it is fraught with consequences of no small importance to
the general theory of descent. Starting from an erroneous definition of
the theory of natural selection as primarily a theory of the origin of
species, both friends and foes of the theory have concluded that the
principle of utility must by hypothesis be of universal occurrence so
far as species are concerned; whereas, if once these naturalists were to
perceive that their definition of the theory is erroneous, they would
likewise perceive that their conclusion cannot follow deductively from
the theory itself. If such a conclusion is to be established at all, it
can only be by other and independent evidence of the inductive kind--to
wit, by actual observation.

Hence we see the importance of starting with an accurate definition of
the theory before proceeding to examine the doctrine of utility as of
universal application to species--a doctrine which, as just stated, has
been habitually and expressly deduced from the theory. This doctrine
occurs in two forms; or, more correctly, there are with reference to
this subject two distinct doctrines, which partly coincide and partly
exclude one another. First, it is held by some naturalists that all
species must necessarily owe their origin to natural selection. And
secondly, it is held by other naturalists, that not only all species,
but likewise all specific characters must necessarily do the same. Let
us consider these two doctrines separately.

The first, and less extensive doctrine, rests on the deduction that
every species must owe its differentiation as a species to the evolution
of at least one adaptive character, which is peculiar to that species.
Although, when thus originated, a species may come to present any
number of other peculiar characters of a non-adaptive kind, these merely
indifferent peculiarities are supposed to hang, as it were, on the peg
supplied by the one adaptive peculiarity; it is the latter which
conditions the species, and so furnishes an opportunity for any number
of the former to supervene. But without the evolution of at least one
adaptive character there could have been no distinct species, and
therefore no merely adventitious characters as belonging to that
species. I will call this the Huxleyan doctrine, because Professor
Huxley is its most express and most authoritative supporter.

The second and more extensive doctrine I will call, for the same reason,
the Wallacean doctrine. This is, as already stated, that it follows
deductively from the theory of natural selection, that not only all
species, but even all the distinctive characters of every species, must
necessarily be due to natural selection; and, therefore, can never be
other than themselves useful, or, at the least, correlated with some
other distinctive characters which are so.

Here, however, I should like to remark parenthetically, that in choosing
Professor Huxley and Mr. Wallace as severally representative of the
doctrines in question, I earnestly desire to avoid any appearance of
discourtesy towards such high authorities.

I am persuaded--as I shall hereafter seek to show Darwin was
persuaded--that the doctrine of utility as universal where species are
concerned, is, in both the above forms, unsound. But it is less
detrimental in its Huxleyan than in its Wallacean form, because it does
not carry the erroneous deduction to so extreme a point. Therefore let
us first consider the doctrine in its more restricted form, and then
proceed, at considerably greater length, to deal with it in its more
extended form.

       *       *       *       *       *

The doctrine that all _species_ must necessarily be due to natural
selection, and therefore must severally present at least one adaptive
character, appears to me doubly erroneous.

In the first place, it is drawn from what I have just shown to be a
false premiss; and, in the second place, the conclusion does not follow
even from this premiss. That the premiss--or definition of the theory as
primarily a theory of the origin of species--is false, I need not wait
again to argue. That the conclusion does not follow even from this
erroneous premiss, a very few words will suffice to prove. For, even if
it were true that natural selection is primarily a theory of the origin
of species, it would not follow that it must therefore be a theory of
the origin of _all_ species. This would only follow if it were first
shown that the theory is not merely _a_ theory of the origin of species,
but _the_ theory of the origin of species--i.e. that there can be no
further theory upon this subject, or any cause other than natural
selection which is capable of transforming any single specific type.

Needless to say, this cannot be shown by way of deduction from the
theory of natural selection itself--which, nevertheless, is the only way
whereby it is alleged that the doctrine is arrived at[86].

    [86] For a full treatment of Professor Huxley's views upon this
         subject, see Appendix II.

       *       *       *       *       *

From the doctrine of utility as advocated by Professor Huxley, we may
now pass on to consider it in the much more comprehensive form advocated
by Mr. Wallace. Of course it is obvious that if the doctrine is
erroneous in its Huxleyan form, much more must it be so in its
Wallacean; and, therefore, that having shown its erroneousness in its
less extended application, there is little need to consider it further
in its more extended form. Looking, however, to its importance in this
more extended application, I think we ought to examine it independently
as thus presented by Mr. Wallace and his school. Let us therefore
consider, on its own merits, the following statement:--It follows
directly from the theory of natural selection that not only all species,
but likewise all specific characters, must be due to natural selection,
and, therefore, must all be of use to the species which present them, or
else correlated with other characters which are so.

It seems worth while to observe, _in limine_, that this doctrine is
contradicted by that of Professor Huxley. For supposing natural
selection to be the only principle concerned in the origin of all
species, it by no means follows that it is the sole agency concerned in
the origin of all specific characters. It is enough for the former
proposition if only some of the characters distinctive of any given
species--nay, as he very properly expresses it, if only one such
character--has been due to natural selection; for it is clear that, as
he adds, "any number of indifferent [specific] characters" may thus have
been furnished with an opportunity, so to speak, of being produced by
causes other than natural selection. Hence, as previously remarked, the
Huxleyan doctrine, although coinciding with the Wallacean up to the
point of maintaining utility as the only principle which can be
concerned in the origin of species, designedly excludes the Wallacean
doctrine where this proceeds to extend any similar deduction to the case
of specific characters[87].

    [87] Professor Huxley's views upon this matter are quoted _in
         extenso_ in Appendix II.

In the next place, and with special reference to the Wallacean doctrine,
it is of importance to observe that, up to a certain point there is
complete agreement between Darwinists of all schools. We all accept
natural selection as a true cause of the origin of species (though we
may not all subscribe to the Huxleyan deduction that it is necessarily a
cause of the origin of _all_ species). Moreover, we agree that specific
characters are often what is called rudimentary or vestigial; and, once
more, that our inability to detect the use of any given structure or
instinct is no proof that such a structure or instinct is actually
useless, seeing that it may very probably possess some function hitherto
undetected, or possibly undetectable. Lastly, we all agree that a
structure which is of use may incidentally entail the existence of some
other structure which is not of use; for, in virtue of the so-called
principle of correlation, the useless structure may be an indirect
consequence of natural selection, since its development may be due to
that of the useful structure, with the growth of which the useless one
is correlated.

Nevertheless, while fully conceding all these facts and principles to
the Wallacean party, those who think with Professor Huxley--and still
more, of course, those few naturalists who think as I do--are unable
to perceive that they constitute any grounds for holding the doctrine
that all specific _characters_ are, or formerly have been, directly or
indirectly due to natural selection. My own reasons for dissenting from
this Wallacean doctrine are as follows.

       *       *       *       *       *

From what has just been said, it will be apparent that the question in
debate is not merely a question of fact which can be settled by a direct
appeal to observation. If this were the case, systematic naturalists
could soon settle the question by their detailed knowledge of the
structures which are severally distinctive of any given group of
species. But so far is this from being the case, that systematic
naturalists are really no better qualified to adjudicate upon the matter
than are naturalists who have not devoted so much of their time to
purely diagnostic work. The question is one of general principles, and
as such cannot be settled by appeals to special cases. For example,
suppose that the rest of this chapter were devoted to a mere enumeration
of cases where it appears impossible to suggest the utility of certain
specific characters, although such cases could be adduced by the
thousand, how should I be met at the end of it all? Not by any one
attempting to suggest the utility, past or present, of the characters
named; but by being told that they must all present some _hidden_ use,
must be _vestigial_, or else must be due to _correlation_. By appealing
to one or other of these assumptions, our opponents are always able to
escape the necessity of justifying their doctrine in the presence of
otherwise inexplicable facts. No matter how many seemingly "indifferent
characters" we may thus accumulate, Mr. Wallace and his followers will
always throw upon us the impossible burden of proving the negative, that
these apparently useless characters do _not_ present some hidden or
former use, are _not_ due to correlation, and therefore have _not_ been
produced by natural selection. It is in vain to retort that the burden
of proof really lies the other way, or on the side of those who affirm
that there is utility where no man can see it, or that there is
correlation where no one can detect it. Thus, so far as any appeal to
particular facts is concerned, it does not appear that there is any
_modus vivendi_. Our opinions upon the question are really determined by
the views which we severally take on matters of general principle. The
issue, though it has a biological bearing, is a logical issue, not a
biological one: it turns exclusively on those questions of definition
and deduction with which we have just been dealing.

But although it thus follows that we cannot determine in fact what
proportion of apparently useless characters are or are not really
useful, we may very easily determine in fact what proportion of specific
characters _fail to present any observable evidences of utility_. Yet,
even upon this question of observable fact, it is surprising to note the
divergent statements which have of late years been made by competent
writers; statements in fact so divergent that they can only be explained
by some want of sufficient thought on the part of those naturalists who
are antecedently persuaded that all specific characters must be either
directly or indirectly due to natural selection. Hence they fail to give
to apparently useless specific characters the attention which, apart
from any such antecedent persuasion, they deserve. For example, a few
years ago I incidentally stated in a paper before the Linnaean Society,
that "a large proportional number of specific characters" are of a
trivial and apparently unmeaning kind, to which no function admits of
being assigned, and also stated that Darwin himself had expressly given
utterance to the same opinion. When these statements were made, I did
not anticipate that they would be challenged by anybody, except perhaps,
by Mr. Wallace. And, in order now to show that my innocence at that time
was not due to ignorance of contemporary thought on such matters, a
sentence may here be quoted from a paper which was read at the meeting
of the British Association of the same year, by a highly competent
systematic naturalist, Mr. Henry Seebohm, and soon afterwards
extensively republished. Criticizing adversely my then recently
published paper, he said:--

     "I fully admit the truth of this statement; and I presume that few
     naturalists would be prepared to deny that 'distinctions of
     specific value frequently have reference to structures which are
     without any utilitarian significance[88].'"

    [88] _Geographical Distribution of the Family Charadriidae_, p. 19.

But since that time the course of Darwinian speculation has been greatly
influenced by the writings of Weismann, who, among other respects in
which he out-darwins Darwin, maintains the doctrine of utility as
universal. In consequence of the influence which these writings have
exercised, I have been more recently and extensively accused of "heresy"
to Darwinian principles, for having stated that "a large proportional
number of specific characters" do not admit of being proved useful, or
correlated with other characters that are useful. Now, observe, we have
here a simple question of fact. We are not at present concerned with the
question how far the argument from ignorance may be held to apply in
mitigation of such cases; but we are concerned only with the question of
fact, as to what proportional number of cases actually occur where we
are _unable to suggest_ the use of specific characters, or the useful
characters with which these apparently useless ones are correlated. I
maintain, as a matter of fact, that the cases in question embrace "a
large proportional number of specific characters." On the other hand, I
am accused of betraying ignorance of species, and of the work of
"species-makers," in advancing this statement; and have been told by Mr.
Wallace, and others of his school, that there is absolutely no evidence
to be derived from nature in support of my views. Well, in the first
place, if this be the case, it is somewhat remarkable that a large body
of competent naturalists, such as Bronn, Broca, Nägeli, Kerner, Sachs,
De Vries, Focke, Henslow, Haeckel, Kölliker, Eimer, Giard, Pascoe,
Mivart, Seebohm, Lloyd Morgan, Dixon, Beddard, Geddes Gulick, and also,
as we shall presently see, Darwin himself, should have fallen into the
same error. And it is further remarkable that the more a man devotes
himself to systematic work in any particular department--whether as an
ornithologist, a conchologist, an entomologist, and so forth--the less
is he disposed to accept the dogma of specific characters as universally
adaptive characters. But, in the second place, and quitting
considerations of mere authority, I appeal to the facts of nature
themselves; and will now proceed, as briefly as possible, to indicate
the result of such an appeal.

For the following reasons, that birds and mammals seem to furnish the
best field for testing the question by direct observation. First, these
classes present many genera which have been more carefully worked out
than is usually the case with genera of invertebrates, or even of
cold-blooded vertebrates. Secondly, they comprise many genera each
including a large number of species, whose habits and conditions of life
are better known than is the case with species belonging to large genera
of other classes. Thirdly, as birds and mammals represent the highest
products of evolution in respect of organization, a more severe test is
imposed than could be imposed elsewhere, when the question is as to the
utility of specific characters; for if these highest products of
organization fail to reveal, in a large proportional number of cases,
the utility of their specific characters, much more is this likely to be
the case among organic beings which stand lower in the scale of
organization, and therefore, _ex hypothesi_, are less elaborate products
of natural selection. Fourthly, and lastly, birds and mammals are the
classes which Mr. Wallace has expressly chosen to constitute his ground
of argument with regard to the issue on which we are now engaged.

It would take far too long to show, even in epitome, the results of this
inquiry. Therefore I will only state the general upshot. Choosing genera
of birds and mammals which contain a large number of species whose
diagnostic characters have been worked out with most completeness, I
restricted the inquiry to specific distinctions of colour, not only for
the sake of having a uniform basis for comparisons, but still more
because it seemed that the argument from our ignorance of possibly
unknown uses could be more successfully met in the case of slight
differences of colour or of shading, than in that of any differences of
structure or of form. Finally, after tabulating all the differences of
colour which are given as diagnostic of each species in a genus, and
placing in one column those which may conceivably be useful, while
placing in another column those of which it appeared inconceivable that
any use could be suggested, I added up the figures in the two columns,
and thus obtained a grand total of all the specific characters of the
genus in respect of colours, separated into the two classes of
conceivably useful and apparently useless. Now, in all cases the
apparently useless characters largely preponderated over the conceivably
useful ones; and therefore I abundantly satisfied myself regarding the
accuracy of my previous statement, that a large proportional number--if
not an actual majority--of specific characters belong to the latter
category.

The following is a brief abstract of these results.

With respect to Birds, a large number of cases were collected wherein
the characters of allied species differ from one another in such minute
respects of colour or shading, that it seemed unreasonable to suppose
them due to any selective value to the birds in question. It is
needless--even if it were practicable on the present occasion--to
adduce this evidence in detail, since an exceedingly good sample of it
may be found in a small book which is specially devoted to considering
the question in its relation to birds. I allude to an essay by Mr.
Charles Dixon, entitled _Evolution without Natural Selection_ (1885). In
this work Mr. Dixon embodies the results of five years' "careful working
at the geographical distribution and variations of plumage of
Palaearctic birds and their allies in various other parts of the world";
and shows, by a large accumulation of facts, not only that there is no
utility to be suggested in reference to the minute or trivial
differences of colouration which he describes; but also that these
differences are usually correlated with isolation on the one hand, or
with slight differences of climate on the other. Now it will be shown
later on that both these agents can be proved, by independent evidence,
capable of inducing changes of specific type without reference to
utility: therefore the correlation which Mr. Dixon unquestionably
establishes between apparently useless (because utterly trivial)
specific distinctions on the one hand, and isolation or climatic change
on the other, constitutes additional evidence to show that the
uselessness is not only apparent, but real. Moreover I have collected a
number of cases where such minute differences of colour between allied
species of birds happen to affect parts of the plumage which are
_concealed_--as for instance, the breast and abdomen of creepers. In
such cases it seems impossible to suggest how natural selection can have
operated, seeing that the parts affected are not exposed to the view
either of enemies or of prey.

Analogous illustrations to any amount may be drawn from Mammals. For
instance, I have worked through the Marsupials with the aid of Mr.
Oldfield Thomas' diagnostic description of their numerous species. Now,
let us take any one of the genera, such as the kangaroos. This comprises
23 species living on an island continent of high antiquity, and not
exposed to the depredations of any existing carnivorous enemies; so that
there is here no present need to vary colour for purposes of protection.
Moreover, in all cases the diagnostic distinctions of colour are so
exceedingly trivial, that even if large carnivora were recently abundant
in Australia, no one could reasonably suggest that the differences in
question would then have been protective. On an average, each of the 23
species presents rather more than 20 peculiarities of shading, which are
quoted as specifically diagnostic. Altogether there are 474 of these
peculiarities distributed pretty evenly among the 23 species; and in no
case can I conceive that utility can be suggested.

       *       *       *       *       *

Hitherto we have been considering the question of fact, as to whether "a
large proportional number of specific characters" do or do not admit of
having their utility demonstrated, or even so much as plausibly
suggested. In the result, I can only conclude that this question of fact
is really not an open one, seeing that it admits of an abundantly
conclusive answer by any naturalist who will take the trouble to work
through the species of any considerable number of genera in the way
above indicated. But although the question of fact is thus really
closed, there remains a more ultimate question as to its theoretical
interpretation. For, as already pointed out, no matter how great an
accumulation of such facts may be collected, our opponents are always
able to brush them aside by their _a priori_ appeal to the argument from
ignorance. In effect they say--We do not care for any number of
thousands of such facts; it makes no difference to us what "proportional
number" of specific characters fail to show evidence of utility; you are
merely beating the air by adducing them, for we are already persuaded,
on antecedent grounds, that _all_ specific characters _must_ be either
themselves useful, or correlated with others that are, whether or not we
can perceive the utility, or suggest the correlation.

To this question of theoretical interpretation, therefore, we must next
address ourselves. And here, first of all, I should like to point out
how sturdy must be the antecedent conviction of our opponents, if they
are to maintain it in the face of such facts as have just been adduced.
It must be remembered that this antecedent conviction is of a most
uncompromising kind. By its own premisses it is committed to the
doctrine that _all_ specific characters, without a single exception,
_must_ be either useful, vestigial, or correlated. Well, if such be the
case, is it not somewhat astonishing that out of 474 differences of
colour which are distinctive of the 23 species of the genus Macropus, no
single one appears capable of having any utility demonstrated, or indeed
so much as suggested? For even the recent theory that slight differences
of colour, which cannot be conceived as serving any other purpose, may
enable the sexes of the same species quickly to recognize each other, is
not here available. The species of the genus Macropus are more
conspicuously distinguished by differences of size and form than by
these minute differences of colour; and therefore no such use can be
attributed to the latter. And, as previously stated, even within the
order Marsupialia the genus Macropus is not at all exceptional in this
respect; so that by including other genera of the order it would be easy
to gather such apparently indifferent specific characters by the
hundred, without any one of them presenting evidence--or even
suggestion--of utility. How robust therefore is the faith of an _a
priori_ conviction which can stand against such facts as these! What,
then, are the _a priori_ grounds on which it stands? Mr. Wallace, the
great leader of this school of thought, says:--

     "It is a necessary deduction from the theory of natural selection,
     that none of the definite facts of organic nature, no special
     organ, no characteristic form or marking, no peculiarities of
     instinct or of habit, no relations between species or between
     groups of species, can exist, but which must now be, or once have
     been, _useful_ to the individuals or the races which possess
     them[89]."

    [89] _Contributions to the Theory of Natural Selection_, p. 47
         (1870); republished in 1892.

Here, then, we have in brief compass the whole essence of our opponents'
argument. It is confessedly an argument _a priori_, a deduction from the
theory of natural selection, a supposed consequence of that theory which
is alleged to be so necessary that to dispute the consequence is
tantamount to denying the theory from which it is derived. In short, as
before stated, it is a question of theory, not a question of fact: our
difference of opinion is logical, not biological: it depends on our
interpretation of principles, not on our observation of species. It will
therefore be my endeavour to show that the reasoning in question is
fallacious: that it is _not_ a necessary deduction from the theory of
natural selection that no characteristic form or marking, no
peculiarities of instinct or of habit, can exist, but which must now be,
or once have been, useful, or correlated with some other peculiarity
that is useful.

"The tuft of hair on the breast of a wild turkey-cock _cannot be of any
use_, and it is doubtful whether it can be ornamental in the eyes of the
female bird;--indeed, had the tuft appeared under domestication, it
would have been called a monstrosity[90]."

    [90] _Origin of Species_, p. 70: italics mine.

As a matter of common sense, unprejudiced by dogma, this appears to be a
perfectly sound judgement; but if Wallace had asked Darwin to prove such
a negative, Darwin could only have replied that it was for Wallace to
prove the affirmative--and thus the issue would have been thrown back
upon a discussion of general principles. Then Wallace would have
said--"The assertion of inutility in the case of any organ or
peculiarity which is not a rudiment or a correlation _is not, and can
never be_, the statement of a fact, but _merely an expression of our
ignorance of its purpose or origin_[91]." Darwin, however, would have
replied:--"Our ignorance of the laws of variation is profound"; and
while, on this account, we ought "to be extremely cautious in
_pretending to decide what structures are now, or have formerly been, of
use to each species_," in point of fact "there can be little doubt that
the tendency to vary in the same manner has _often_ been so strong, that
_all_ individuals of the same _species_ have been similarly modified
_without the aid of any form of selection_[92]."

    [91] _Darwinism_, p. 137: italics mine.

    [92] _Origin of Species_, p. 72: Mr. Wallace himself quotes this
         passage (_Darwinism_, p. 141); but says with regard to it "the
         important word 'all' is probably an oversight." In the Appendix
         (II), on Darwin's views touching the doctrine of utility I
         adduce a number of precisely equivalent passages, derived from
         all his different works on evolution, and _every one of them_
         presenting "the important word 'all.'"

It will be my endeavour in the following discussion to show that Darwin
would have had an immeasurable advantage in this imaginary debate.

To begin with, Wallace's deductive argument is a clear case of circular
reasoning. We set out by inferring that natural selection is a cause
from numberless cases of observed utility as an effect: yet, when "in a
large proportional number" of cases we fail to perceive any imaginable
utility, it is argued that nevertheless utility must be there, since
otherwise natural selection could not have been the cause.

Be it observed, in any given case we may properly anticipate utility as
_probable_, even where it is not perceived; because there are already so
enormous a number of cases where it is perceived, that, if the principle
of natural selection be accepted at all, we must conclude with Darwin
that it is "the _main_ means of modification." Therefore, in particular
cases of unperceived utility we may take this antecedent probability as
a guide in our biological researches--as has been done with such
brilliant success both by Darwin and Wallace, as well as by many of
their followers. But this is a very different thing from laying down the
universal maxim, that in _all_ cases utility _must_ be present, whether
or not we shall ever be able to detect it[93]. For this universal maxim
amounts to an assumption that natural selection has been the
"_exclusive_ means of modification." That it has been "the main means of
modification" is proved by the generality of the observed facts of
adaptation. That it has been "the exclusive means of modification," with
the result that these facts are universal, cannot be thus proved by
observation. Why, then, is it alleged? Confessedly it is alleged by way
of deduction from the theory of natural selection itself. Or, as above
stated, after having deduced the theory from the facts, it is sought to
deduce the facts from the theory.

    [93] See Introductory Chapter, p. 20.

Thus far I have been endeavouring to show that the universality of
adaptation cannot be inferred from its generality, or from the theory of
natural selection itself. But, of course, the case would be quite
different if there were any independent evidence--or rather, let us say,
any logical argument--to show that natural selection is "the exclusive
means of modification." For in this event it would no longer involve
circular reasoning to maintain that all specific characters are likewise
adaptive characters. It might indeed appear antecedently improbable that
no other principle than natural selection can possibly have been
concerned in the differentiation of those relatively permanent varieties
which we call species--that in all the realm of organic nature, and in
all the complexities of living processes, there is no room for any
other influence in the production of change, even of the most trivial
and apparently unmeaning kind. But if there were any good evidence or
logical argument to the contrary, this antecedent presumption would have
to give way; and the certainty that all specific characters are likewise
adaptive characters would be determined by the cogency of such evidence
or argument as could be adduced. In short, we are not entitled to
conclude--and still less does it follow "as a necessary deduction from
the theory of natural selection"--that all the details of specific
differentiation must in every case be either useful, vestigial, or
correlated, _unless it has been previously shown, by independent
evidence, or accurate reasoning, that there is no room for any other
principle of specific change_.

This, apparently, is the central core of the question. Therefore I will
now proceed to consider such arguments as have been adduced to prove
that, other than natural selection, there _can_ have been no "means of
modification." And, after having exhibited the worthlessness of these
arguments, I will devote the next chapter to showing that, as a matter
of observable fact, there _are_ a considerable number of other
principles, which can be proved to be capable of producing such minute
differences of form and colour as "in a large proportional number" of
cases constitute diagnostic distinctions between species and species.

First, then, for the reasons _a priori_--and they are confessedly _a
priori_--which have been adduced to prove that natural selection has
been what in Darwin's opinion it has not been,--"the _exclusive_ means
of modification." Disregarding the Lamarckian factors--which, even if
valid, have but little relation to the present question, seeing that
they are concerned, almost exclusively, with the evolution of _adaptive_
characters--it is alleged that natural selection must occupy the whole
field, because no other principle of change can be allowed to operate in
the presence of natural selection. Now, I fully agree that this
statement may hold as regards any principle of change which is
deleterious; but clearly it does not hold as regards any principle which
is merely neutral. If any one were to allege that specific characters
are frequently detrimental to the species presenting them, he would no
doubt lay himself open to the retort that natural selection could not
allow such characters to persist; or, which amounts to the same thing,
that it _does_ "necessarily follow from the theory of natural selection"
that specific characters can never be in any large number, or in any
large measure, _harmful_ to the species presenting them. But where
the statement is that specific characters are frequently
_indifferent_--again to use Professor Huxley's term--the retort loses
all its relevancy. No reason has ever been shown why natural selection
should interfere with merely indifferent characters, supposing such to
have been produced by any of the agencies which we shall presently have
to consider. Therefore this argument--or rather assertion--goes for
nothing.

The only other argument I have met with on this side of the question is
one that has recently been adduced by Mr. Wallace. He says:--

     "One very weighty objection to the theory that _specific_
     characters can ever be wholly useless appears to have been
     overlooked by those who have maintained the frequency of such
     characters, and that is, their almost necessary instability[94]."

    [94] _Darwinism_, p. 138.

This argument he proceeds to elaborate at considerable length, but fails
to perceive what appears to me the obvious answer. Provided that the
cause of the useless character is constant, there is no difficulty in
understanding why the character is stable. Utility is not the only
principle that can lead to stability: any other principle must do the
same, provided that it acts for a sufficient length of time, and with a
sufficient degree of uniformity, on all the individuals of a species.
This is a consideration the cogency of which was clearly recognized by
Darwin, as the following quotations will show. Speaking of unadaptive
characters, he says they may arise as merely

     "fluctuating variations, which sooner or later become _constant_
     through the nature of the organism and of surrounding conditions,
     _but not through natural selection_[95]."

    [95] _Origin of Species_, p. 176: italics mine, as also in the
         following.

Elsewhere we read:--

     "Each of the endless variations which we see in the plumage of our
     fowls must have had some efficient cause; and if the _same_ cause
     were to act _uniformly_ during a long series of generations on
     _many_ individuals, _all_ probably would be modified in the same
     manner."

As special illustrations of this fact I may quote the following cases
from Darwin's works.

     "Dr. Bachman states that he has seen turkeys raised from the eggs
     of wild species, lose their metallic tints, and become spotted in
     the third generation. Mr. Yarrell many years ago informed me that
     the wild ducks bred in St James' Park lost their true plumage
     after a few generations. An excellent observer (Mr. Hewitt) ...
     found that he could not breed wild ducks true for more than five or
     six generations, as they proved so much less beautiful. The white
     collar round the neck of the mallard became broader and more
     irregular, and white feathers appeared in the duckling's wings
     &c.[96]"

    [96] _Var._ vol. ii. p. 250.

Now, such cases--to which numberless others might be added--prove that
even the subtle and inconspicuous causes incidental to domestication are
capable of inducing changes of specific character quite as great, and
quite as "stable," as any that in a state of nature are taken to
constitute specific distinctions. Yet there can here be no suggestion of
utility, inasmuch as the change takes place in the course of a few
generations, and therefore without leaving time for natural selection to
come into play--even if it ever could come into play among the sundry
domesticated birds in question.

But the facts of domestication also make for the same conclusion in
another way--namely, by proving that when time enough _has_ been allowed
for the production of useless changes of greater magnitude, such changes
are not infrequently produced. And the value of this line of evidence is
that, great as are the changes, it is impossible that either natural or
artificial selection can have been concerned in their production. It
will be sufficient to give two examples--both with regard to structure.

The first I will render in the words whereby it has already been stated
in my own paper on _Physiological Selection_, because I should like to
take this opportunity of answering Mr. Wallace's objection to it.

     "Elsewhere (_Origin of Species_, p. 158) Mr. Darwin points out that
     modifications which appear to present obvious utility are often
     found on further examination to be really useless. This latter
     consideration, therefore, may be said to act as a foil to the one
     against which I am arguing, namely, that modifications which appear
     to be useless may nevertheless be useful. But here is a still more
     suggestive consideration, also derived from Mr. Darwin's writings.
     Among our domesticated productions changes of structure--or even
     structures wholly new--not unfrequently arise, which are in every
     way analogous to the apparently useless distinctions between wild
     species. Take, for example, the following most instructive case:--

     [Illustration: Fig. 2.--Old Irish Pig, showing jaw-appendages
     (after Richardson).]

     "'Another curious anomaly is offered by the appendages described by
     M. Eudes-Deslongchamps as often characterizing the Normandy pigs.
     These appendages are always attached to the same spot, to the
     corners of the jaws; they are cylindrical, about three inches in
     length, covered with bristles, and with a pencil of bristles rising
     out of a sinus on one side; they have a cartilaginous centre with
     two small longitudinal muscles; they occur either symmetrically on
     both sides of the face, or on one side alone. Richardson figures
     them on the gaunt old Irish Greyhound pig; and Nathusius states
     that they occasionally appear in all the long-eared races, but are
     not strictly inherited, for they occur or fail in the animals of
     the same litter. As no wild pigs are known to have analogous
     appendages, we have at present no reason to suppose that their
     appearance is due to reversion; and if this be so, we are forced to
     admit that a somewhat complex, though apparently useless, structure
     may be suddenly developed without the aid of selection[97].'"

    [97] _Variation_, &c. vol. i. pp. 78-79.

To this case Mr. Wallace objects:--

     "But it is expressly stated that they are not constant; they appear
     'frequently' or 'occasionally,' they are 'not strictly inherited,
     for they occur or fail in animals of the same litter'; and they are
     not always symmetrical, sometimes appearing on one side of the face
     alone. Now, whatever may be the cause or explanation of these
     anomalous appendages, they cannot be classed with 'specific
     characters,' the most essential features of which are, that they
     _are_ symmetrical, that they _are_ inherited, and that they _are_
     constant[98]."

    [98] _Darwinism_, pp. 139-40.

But, to begin with, I have not classed these appendages with "specific
characters," nor maintained that Normandy pigs ought to be regarded as
specifically distinct on account of them. What I said was:--

     "Now, if any such structure as this occurred in a wild species, and
     if any one were to ask what is the use of it, those who rely on the
     argument from ignorance would have a much stronger case than they
     usually have; for they might point to the cartilage supplied with
     muscles, and supporting a curious arrangement of bristles, as much
     too specialized a structure to be wholly meaningless. Yet we happen
     to know that this particular structure is wholly meaningless[99]."

    [99] Mr. Wallace deems the concluding words "rather confident." I
         was not, however, before aware that he extended his _a priori_
         views on utility to domesticated varieties which are bred for
         the slaughter-house. If he now means to indicate that these
         appendages are possibly due to natural selection, he is surely
         going very far to save his _a priori_ dogma; and in the case
         next adduced will have to go further still.

In the next place, is it either fair or reasonable to expect that a
varietal character of presumably very recent origin should be as
strongly inherited--and therefore as constant both in occurrence and
symmetry--as a true specific character, say, of a thousand times its
age? Even characters of so-called "constant varieties" in a state of
nature are usually less constant than specific characters; while, again,
as Darwin says, "it is notorious that specific characters are more
variable than generic,"--the reason in both cases being, as he proceeds
to show, that the less constant characters are characters of more recent
origin, and therefore less firmly fixed by heredity[100]. Hence I do not
understand how Mr. Wallace can conclude, as he does, "that, admitting
that this peculiar appendage is wholly useless and meaningless, the fact
would be rather an argument against specific characters being also
meaningless, because the latter never have the characteristics [i.e.
inconstancy of occurrence, form, and transmission] which this particular
variation possesses[101]." Mr. Wallace can scarcely suppose that when
specific characters first arise, they present the three-fold kind of
constancy to which he here alludes. But, if not, can it be denied that
these peculiar appendages appear to be passing through a phase of
development which all "specific characters" must have passed through,
before they have had time enough to be firmly fixed by heredity[102]?

    [100] _Origin of Species_, pp. 122-3.

    [101] _Darwinism_, p. 140.

    [102] In the next paragraph Mr. Wallace says that the appendages in
          question "are apparently of the same nature as the 'sports'
          that arise in our domesticated productions, but which, as Mr.
          Darwin says, without the aid of selection would soon
          disappear." But I cannot find that Mr. Darwin has made any
          such statement: what he does say is, that whether or not a
          useless peculiarity will soon disappear without the aid of
          selection depends upon the nature of the causes which produce
          it. If these causes are of a merely transitory nature, the
          peculiarity will also be transitory; but if the causes be
          constant, so will be the result. Again, the point to be
          noticed about this "sport" is, that, unlike what is usually
          understood by a "sport," it affects a whole race or breed, is
          transmitted by sexual propagation, and has already attained so
          definite a size and structure, that it can only be reasonably
          accounted for by supposing the continued operation of _some
          constant_ cause. This cause can scarcely be correlation of
          growth, since closely similar appendages are often seen in so
          different an animal as a goat. Here, also, they run in breeds
          or strains, are strongly inherited, and more "constant," as
          well as more "symmetrical" than they are in pigs. This, at all
          events, is the account I have received of them from
          goat-breeders in Switzerland.

If, however, even this should be denied, what will be said of the second
case, that of the niata cattle?

     "I saw two herds on the northern bank of the Plata.... The forehead
     is very short and broad, with the nasal end of the skull, together
     with the whole plane of the upper molar-teeth, curved upwards. The
     lower jaw projects beyond the upper, and has a corresponding upward
     curvature.... The skull which I presented to the College of
     Surgeons has been thus described by Professor Owen. 'It is
     remarkable from the stunted development of the nasals,
     premaxillaries, and fore part of the lower jaw, which is unusually
     curved upwards to come into contact with the premaxillaries. The
     nasal bones are about one-third the ordinary length, but retain
     almost their normal breadth. The triangular vacuity is left between
     them and the frontal and lachrymal, which latter bone articulates
     with the premaxillary, and thus excludes the maxillary from any
     junction with the nasal.' So that even the connexion of some of
     the bones is changed. Other differences might be added: thus the
     plane of the condyles is somewhat modified, and the terminal edge
     of the premaxillaries forms an arch. In fact, on comparison with
     the skull of a common ox, scarcely a single bone presents the same
     exact shape, and the whole skull has a wonderfully different
     appearance[103]."

    [103] Darwin, _Variation_, &c., vol. i. pp. 92-4.

[Illustration: Fig. 3.--Drawn from nature. R. Coll. Surg. Mus.]

As I cannot find that this remarkable skull has been figured before, I
have had the accompanying woodcut made in order to compare it with the
skull of a Charsley Forest ox; and a glance is sufficient to show what
"a wonderfully different appearance" it presents.

       *       *       *       *       *

Now the important points in the present connexion with regard to this
peculiar race of cattle are the following.

Their origin is not known; but it must have been subsequent to the year
1552, when cattle were first introduced to America from Europe, and it
is known that such cattle have been in existence for at least a century.
The breed is very true, and a niata bull and cow invariably produce
niata calves. A niata bull crossed with a common cow, and the reverse
cross, yield offspring having an intermediate character, but with the
niata peculiarities highly conspicuous[104].

    [104] _Ibid._ p. 94.

Here, then, we have unquestionable evidence of a whole congeries of very
distinctive characters, so unlike anything that occurs in any other
cattle, that, had they been found in a state of nature, they would have
been regarded as a distinct species. And the highly peculiar characters
which they present conform to all "the most essential features of
specific characters," as these are stated by Mr. Wallace in his
objection to the case of the pig's appendages. That is to say, "they
_are_ symmetrical, they _are_ inherited, and they _are_ constant." In
point of fact, they are _always_ "constant," both as to occurrence and
symmetry, while they are so completely "inherited" that not only does "a
niata bull and cow _invariably_ produce niata calves"; but even when
crossed with other cattle the result is a _hybrid_, "with the niata
character _strongly_ displayed."

Hence, if we were to follow Mr. Wallace's criteria of specific
characters, which show that the pig's appendages "cannot be classed with
specific characters" (or with anything of the nature of specific
characters), it would follow that the niata peculiarities _can_ be so
classed. This, therefore, is a case where he will find all the reasons
which in other cases he takes to justify him in falling back upon the
argument from ignorance. The cattle are half wild, he may urge; and so
the three-fold constancy of their peculiar characters may very well be
due, either directly or indirectly, to natural selection--i.e. they may
either be of some hidden use themselves, or correlated with some other
modifications that are of use: it is, he may say, as in such cases he
often does say, for us to disprove both these possibilities.

Well, here we have one of those rare cases where historical information,
or other accidents, admit of our discharging this burden of proving a
negative. Darwin's further description shows that this customary refuge
in the argument from ignorance is most effectually closed. For--

     "When the pasture is tolerably long, these cattle feed as well as
     common cattle with their tongue and palate; but during the great
     droughts, when so many animals perish on the Pampas, the niata
     breed lies under a great disadvantage, and would, if not attended
     to, become extinct; for the common cattle, like horses, are able to
     keep alive by browsing with their lips on the twigs of trees and on
     reeds; this the niatas cannot so well do, as their lips do not
     join, and hence they are found to perish before the common cattle.
     This strikes me as a good illustration of how little we are able to
     judge from the ordinary habits of an animal, on what circumstances,
     occurring only at long intervals of time, its rarity or extinction
     may depend. It shows us, also, how natural selection would have
     determined the rejection of the niata modification, had it arisen
     in a state of nature[105]."

    [105] Darwin, _Variation_, &c. vol. i. p. 94.

Hence, it is plainly _impossible_ to attribute this modification to
natural selection, either as acting directly on the modified parts
themselves, or indirectly through correlation of growth. And as the
modification is of specific magnitude on the one hand, while it presents
all "the most essential features of specific characters" on the other, I
do not see any means whereby Mr. Wallace can meet it on his _a priori_
principles. It would be useless to answer that these characters,
although conforming to all his tests of specific characters, differ in
respect of being deleterious, and would therefore lead to extermination
were the animals in a wholly wild state; because, considered as an
argument, this would involve the assumption that, apart from natural
selection, only deleterious characters can arise under nature--i. e.
that merely "indifferent" characters can never do so, which would be
absurd. Indeed, I have chosen this case of the niata cattle expressly
because their strongly marked peculiarities _are_ deleterious, and
therefore exclude Mr. Wallace's appeal to the argument from ignorance of
a possible utility. But if even these pronounced and deleterious
peculiarities can arise and be perpetuated with such constancy and
fidelity, much more is this likely to be the case with less pronounced
and merely neutral peculiarities.

It may, however, be further objected that these cattle are not
improbably the result of _artificial_ selection. It may be suggested
that the semi-monstrous breed originated in a single congenital
variation, or "sport," which was isolated and multiplied as a curiosity
by the early settlers. But even if such be the explanation of this
particular case, the fact would not weaken our illustration. On the
contrary, it would strengthen our general argument, by showing an
additional means whereby indifferent specific characters can arise and
become fixed in a state of nature. As it seems to me extremely probable
that the niata cattle did originate in a congenital monstrosity, which
was then isolated and multiplied by human agency (as is known to have
been the case with the "ancon sheep"), I will explain why this tends to
strengthen our general argument.

It is certain that if these animals were ever subject to artificial
isolation for the purpose of establishing their breed, the process must
have ceased a long time ago, seeing that there is no memory or tradition
of its occurrence. Now this proves that, however the breed may have
originated, it has been able to maintain its many and highly peculiar
characters for a number of generations without the help of selection,
either natural or artificial. This is the first point to be clear upon.
Be its origin what it may, we know that this breed has proved capable of
perpetuating itself with uniform "constancy" for a number of generations
after the artificial selection has ceased--supposing such a process ever
to have occurred. And this certain fact that artificial selection, even
if it was originally needed to establish the type, has not been needed
to perpetuate the type, is a full answer to the supposed objection. For,
in view of this fact, it is immaterial what the origin of the niata
breed may have been. In the present connexion, the importance of this
breed consists in its proving the subsequent "stability" of an almost
monstrous form, continued through a long series of generations by the
force of heredity alone, without the aid of any form of selection.

The next point is, that not only is a seeming objection to the
illustration thus removed, but that, if we do entertain the question of
origin, and if we do suppose the origin of these cattle to have been in
a congenital "sport," afterwards multiplied by artificial isolation, we
actually strengthen our general argument by increasing the importance of
this particular illustration. For the illustration then becomes
available to show how indifferent specific characters may sometimes
originate in merely individual sports, which, if not immediately
extinguished by free intercrossing, will perpetuate themselves by the
unaided force of heredity. But this is a point to which we shall recur
in the ensuing chapter.

In conclusion, it is worth while to remark, with regard to Mr. Wallace's
argument from constancy, that, as a matter of fact, utility does not
seem to present any greater power in securing "stability of characters"
than any other cause of like constancy. Thus, for instance, whatever the
causes may have been which have produced and perpetuated the niata breed
of cattle, they have certainly produced a wonderful "stability" of a
great modification in a wonderfully short time. And the same has to be
said of the ducks in St. James' Park, as well as sundry other cases. On
the other hand, when, as in the case of numberless natural species,
modification has been undoubtedly produced by natural selection,
although the modification must have had a very much longer time in which
to have been fixed by heredity, it is often far from being
stable--notwithstanding that Mr. Wallace regards stability as a
criterion of specific characters. Indeed--and this is more suggestive
still--there even seems to be a kind of _inverse_ proportion between the
utility and the stability of a specific character. The explanation
appears to be (_Origin of Species_, pp. 120-2), that the more a specific
character has been forced on by natural selection on account of its
utility, the less time will it have had to become well fixed by heredity
before attaining a full development. Moreover, as Darwin adds, in cases
where the modification has not only been thus "comparatively recent,"
but also "extraordinarily great," the probability is that the parts so
modified must have been very variable in the first instance, and so are
all the more difficult to render constant by heredity. Thus we see that
utility is no better--even if it be so good--a cause of stability in
specific characters, as are the unknown causes of stability in many
varietal characters[106].

    [106] Should it be objected that useless characters, according to my
          own view of the Cessation of Selection, ought to disappear,
          and therefore cannot be constant, the answer is evident. For,
          by hypothesis, it is only those useless characters which were
          at one time useful that disappear under this principle.
          Selection cannot cease unless it was previously present--i.e.
          save in cases where the now useless character was originally
          due to selection. Hence, in all cases where it was due to any
          other cause, the useless character will persist at least as
          long as its originating cause continues to operate. And even
          after the latter (whatever it may be) has ceased to operate,
          the useless character will but slowly degenerate, until the
          eventual failure of heredity causes it to disappear _in
          toto_--long before which time it may very well have become a
          genetic, or some higher, character.




CHAPTER VIII.

CHARACTERS AS ADAPTIVE AND SPECIFIC
(_continued_).


Let us now proceed to indicate some of the causes, other than natural
selection, which may be regarded as adequate to induce such changes in
organic types as are taken by systematists to constitute diagnostic
distinctions between species and species. We will first consider causes
external to organisms, and will then go on to consider those which occur
within the organisms themselves: following, in fact, the classification
which Darwin has himself laid down. For he constantly speaks of such
causes as arising on the one hand, from "changed conditions of life"
and, on the other hand, from "the nature of the organism"--that is, from
internal processes leading to "variations which seem to us in our
ignorance to arise spontaneously."

In neither case will it be practicable to give more than a brief
_résumé_ of all that might be said on these interesting topics.


I. _Climate._

There is an overwhelming mass of evidence to prove that the assemblage
of external conditions of life conveniently summarized in the word
Climate, exercise a potent, an uniform, and a permanent influence on
specific characters.

With regard to plants, Darwin adduces a number of facts to show the
effects of climate on wheat, cabbages, and other vegetables. Here, for
example, is what he says with regard to maize imported from America to
Germany:--

     "During the first year the plants were twelve feet high, and a few
     seeds were perfected; the lower seeds in the ear kept true to their
     proper form, but the upper seeds became slightly changed. In the
     second generation the plants were from nine to ten feet high, and
     ripened their seed better; the depression on the outer side of the
     seed had almost disappeared, and the original beautiful white
     colour had become duskier. Some of the seeds had even become
     yellow, and in their now rounded form they approached the common
     European maize. In the third generation nearly all resemblance to
     the original and very distinct American parent-form was lost[107]."

    [107] _Variation_, &c. vol. i. p. 340.

As these "highly remarkable" changes were effected in but three
generations, it is obvious that they cannot have been dependent on
selection of any kind. The same remark applies to trees. Thus,--

     "Mr. Meehan has compared twenty-nine kinds of American trees with
     their nearest European allies, all grown in close proximity and
     under as nearly as possible the same conditions. In the American
     species he finds, with the rarest exceptions, that the leaves fall
     earlier in the season, and assume before their fall a brighter
     tint; that they are less deeply toothed or serrated; that the buds
     are smaller; that the trees are more diffuse in growth and have
     fewer branchlets; and, lastly, that the seeds are smaller--all in
     comparison with the corresponding European species. Now,
     considering that these corresponding trees belong to several
     distinct orders, and that they are adapted to widely different
     stations, it can hardly be supposed that their differences are of
     any special service to them in the New and Old worlds; and, if so,
     such differences cannot have been gained through natural selection,
     and must be attributed to the long continued action of a different
     climate[108]."

    [108] _Variation_, &c. vol. ii. p. 271.

These cases, however, I quote mainly in order to show Darwin's opinion
upon the matter, with reference to the absence of natural selection.
For, where the vegetable kingdom is concerned, the fact of climatic
variation is so general, and in its relation to diagnostic work so
important, that it constitutes one of the chief difficulties against
which species-makers have to contend. And the more carefully the subject
is examined the greater does the difficulty become. But, as to this and
other general facts, it will be best to allow a recognized authority to
speak; and therefore I will give a few extracts from Kerner's work on
_Gute und schlechte Arten_.

He begins by showing that geographical (or it may be topographical)
varieties of species are often so divergent, that without a knowledge of
intermediate forms there could be no question as to their being good
species. As a result of his own researches on the subject, he can
scarcely find language strong enough to express his estimate of the
extent and the generality of this source of error. In different parts of
Europe, or even in different parts of the Alps, he has found these
climatic varieties in such multitudes and in such high degrees both of
constancy and divergence, that, after detailing his results, he
finishes his essay with the following remarkable conclusions:--

     "Die Wissenchaft geht aber ihren Entwicklungsgang im grossen Ganzen
     gerade so, wie die Erkenntniss bei jedem einzelnen Naturforscher.
     Fast jeder Botaniker muss seinen Entwicklungsgang durchmachen und
     gelangt endlich mehr oder weniger nahe zu demselben Ziele. Die
     Ungleichheit besteht nur darin, dass der eine langsamer, der andere
     aber rascher bei dem Ziele ankommt. Anfänglich müht sich jeder ab,
     die Formen in hergebrachter Weise zu gliedern und die 'guten Arten'
     herauszulesen. Mit der Erweiterung des Gesichtskreises und mit der
     Vermehrung der Anschauungen aber schwindet auch immer mehr der
     Boden unter den Füssen, die bisher für unverrückbar gehaltenen
     Grenzen der gut geglaubten Arten stellen sich als eine der Natur
     angelegte Zwangsjacke heraus, die Uebcrzeugung, dass die Grenzen,
     welche wir ziehen, eben nur künstliche sind, gewinnt immer mehr und
     mehr die Oberhand, und wer nicht gerade zu den hartgesottenen
     Eigensinnigen gehört, und wer die Wahrheit höher stellt als das
     starre Festhalten an seinen früheren Ansichten, geht schliesslich
     bewusst oder unbewusst in das Lager derjenigen über, in welchem
     auch ich mir ein bescheidenes Plätzchen aufgesucht habe."

By these "hard-boiled" botanists he means those who entertain the
traditional notion of a species as an assemblage of definite
characters, always and everywhere associated together. This notion
(Artsbeständigkeit) must be entirely abandoned. Summarizing Kerner's
facts for their general results we find that his extensive
investigations have proved that in his numberless kinds of European
plants the following relations frequently obtain. Supposing that there
are two or more allied species, A and B, then A' and B' may be taken to
represent their respective types as found in some particular area. It
does not signify whether A' and B' are geographically remote from, or
close to, A and B; the point is that, whether in respect of temperature,
altitude, moisture, character of soil, &c., there is some difference in
the conditions of life experienced by the plants growing at the
different places. Now, in numberless plants it is found that the typical
or constant peculiarities of A' differ more from those of A than they do
from those of B; while, conversely, the characters of A' may bear more
resemblance to those of B' than they do to those of A--on account of
such characters being due to the same external causes in both cases. The
consequence is that A' might more correctly be classified with B', or
_vice versa_. Another consequence is that whether A and B, or A' and B',
be recorded as the "good species" usually depends upon which has
happened to have been first described.

Such a mere abstract of Kerner's general results, however, can give no
adequate idea of their cogency: for this arises from the number of
species in which specific characters are thus found to change, and even
to _interchange_, with different conditions of life. Thus he gives an
amusing parable of an ardent young botanist, Simplicius, who starts on a
tour in the Tyrol with the works of the most authoritative systematists
to assist him in his study of the flora. The result is that Simplicius
becomes so hopelessly bewildered in his attempts at squaring their
diagnostic descriptions with the facts of nature, that he can only
exclaim in despair--"Sonderbare Flora, diese tirolische, in welcher so
viele characteristische Pflanzen nur schlechte Arten, oder gar noch
schlechter als schlechte Arten, sind." Now, in giving illustrations of
this young man's troubles, Kerner fills five or six pages with little
else than rows of specific names.

Upon the whole, Kerner concludes that the more the subject is studied,
the more convinced must the student become that all distinction between
species as "good" and "bad" vanishes. In other words, the more that our
knowledge of species and of their diagnostic characters increases, the
more do we find that "bad species" multiply at the expense of "good
species"; so that eventually we must relinquish the idea of "good
species" altogether. Or, conversely stated, we must agree to regard as
equally "good species" any and every assemblage of individuals which
present the same peculiarities: provided that these peculiarities do not
rise to a generic value, they equally deserve to be regarded as
"specific characters," no matter how trivial, or how local, they may be.
In fact, he goes so far as to say that when, as a result of experiments
in transplantation from one set of physical conditions to another,
seedlings are found to present any considerable and constant change in
their specific characters, these seedlings are no less entitled to be
regarded as a "good species" than are the plants from which they have
been derived. Probably few systematists will consent to go quite so far
as this; but the fact that Kerner has been led deliberately to propound
such a statement as a result of his wide observations and experiments is
about as good evidence as possible on the points with which we are here
concerned. For even Simplicius would hardly be quite so simple as to
suppose that each one of all the characters which he observes in his
"remarkable flora," so largely composed of "bad or even worse than bad
species," is of utilitarian significance.

Be it noted, however, that I am not now expressing my own opinion. There
are weighty reasons against thus identifying climatic variations with
good species--reasons which will be dealt with in the next chapter.
Kerner does not seem to appreciate the weight of these reasons, and
therefore I do not call him as a witness to the subject as a whole; but
only to that part of it which has to do with the great and general
importance of climatic variability in relation to diagnostic work. And
thus far his testimony is fully corroborated by every other botanist who
has ever attended to the subject. Therefore it does not seem worth while
to quote further authorities in substantiation of this point, such as
Gärtner, De Candolle, Nägeli, Peter, Jordan, &c. For nowadays no one
will dispute the high generality and the frequently great extent of
climatic variation where the vegetable kingdom is concerned. Indeed, it
may fairly be doubted whether there is any one species of plant, whose
distribution exposes it to any considerable differences in its external
conditions of life, which does not present more or less considerable
differences as to its characters in different parts of its range. The
principal causes of such climatic variation appear to be the chemical,
and, still more, the mechanical nature of soil; temperature; intensity
and diurnal duration of light in spring and summer; moisture; presence
of certain salts in the air and soil of marine plants, or of plants
growing near mineral springs; and sundry other circumstances of a more
or less unknown character.

Before closing these remarks on climatic variation in the vegetable
kingdom, prominent attention must be directed to a fact of broad
generality and, in relation to our present subject, of considerable
importance. This is that the same external causes very frequently
produce the same effects in the way of specific change throughout large
numbers of _unrelated_ species--i.e. species belonging to different
genera, families, and orders. Moreover, throughout all these unrelated
species, we can frequently trace a uniform correlation between the
degrees of change and the degrees to which they have been subjected to
the causes in question.

As examples, all botanists who have attended to the subject are struck
by the similarity of variation presented by different species growing on
the same soils, altitudes, latitudes, longitudes, and so forth. Plants
growing on chalky soils, when compared with those growing on richer
soils, are often more thickly covered with down, which is usually of a
white or grey colour. Their leaves are frequently of a bluish-green
tint, more deeply cut, and less veined, while their flowers tend to be
larger and of a lighter tint. There are similarly constant differences
in other respects in varieties growing on sundry other kinds of soils.
Sea-salt has the general effect, on many different kinds of plants, of
producing moist fleshy leaves, and red tints. Experiments in
transplantation have shown that these changes may be induced
artificially; so there can be no doubt as to its being this that and the
other set of external conditions which produces them in nature. Again,
dampness causes leaves to become smoother, greener, less cut, and the
flowers to become darker; while dryness tends to produce opposite
effects. I need not go on to specify the particular results on all kinds
of plants of altitude, latitude, longitude, and so forth. For we are
concerned only with the fact that these two correlations may be regarded
as general laws appertaining to the vegetable kingdom--namely, (A) that
the same external causes produce similar varietal effects in numerous
unallied species of plants; and, (B) that the more these species are
exposed to such causes the greater is the amount of varietal effect
produced--so that, for instance, on travelling from latitude to
latitude, longitude to longitude, altitude to altitude, &c., we may see
greater and greater degrees of such definite and more or less common
varietal changes affecting the unallied species in question. Now these
general laws are of importance for us, because they prove unequivocally
that it is the direct action of external conditions of life which
produce climatic variations of specific types. And, taken in connexion
with the results of experiments in transplantation (which in a single
generation may yield variations similar to those found in nature under
similar circumstances), these general laws still further indicate that
climatic variations are "indifferent" variations. In other words, we
find that changes of specific characters are of widespread occurrence in
the vegetable kingdom, that they are constantly and even proportionally
related to definite external circumstances, but yet that, in as far as
they are climatic, they cannot be attributed to the agency of natural
selection[109].

    [109] Since the above paragraphs have been in type, the Rev. G.
          Henslow has published his Linnaean Society papers which are
          mentioned in the introductory chapter, and which deal in more
          detail with this subject, especially as regards the facies of
          desert floras.

Turning next to animals, it may first be observed that climatic
conditions do not appear to exercise an influence either so general or
so considerable as in the case of plants. Nevertheless, although these
influences are relatively more effective in the vegetable kingdom than
they are in the animal, absolutely considered they are of high
generality and great importance even in the latter. But as this fact is
so well recognized by all zoologists, it will be needless to give more
than a very few illustrations. Indeed, throughout this discussion on
climatic influences my aim is merely to give the general reader some
idea of their importance in regard to systematic natural history; and,
therefore, such particular cases as are mentioned are selected only as
samples of whole groups of cases more or less similar.

With regard to animals, then, we may best begin by noticing that, just
as in the case of plants, there is good evidence of the same external
causes producing the same effects in multitudes of species belonging to
different genera, families, orders, and even classes. Moreover, we are
not without similarly good evidence of _degrees_ of specific change
taking place in correlation with _degrees_ of climatic change, so that
we may frequently trace a gradual progress of the former as we advance,
say, from one part of a large continent to another. Instances of these
correlations are not indeed so numerous in the animal kingdom as they
are in the vegetable. Nevertheless they are amply sufficient for our
present purposes.

For example, Mr. Allen has studied in detail changes of size and colour
among birds and mammals on the American continent; and he finds a
wonderfully close sliding scale of both, corresponding stage by stage
with gradual changes of climate. Very reasonably he attributes this to
the direct influence of climatic conditions, without reference to
natural selection--as does also Mr. Gould with reference to similar
facts which he has observed among the birds of Australia. Against this
view Mr. Wallace urges, "that the effects are due to the greater or less
need of protection." But it is difficult to believe that such can be the
case where so innumerable a multitude of widely different species are
concerned--presenting so many diverse habits, as well as so many
distinct habitats. Moreover, the explanation seems incompatible with the
_graduated_ nature of the change, and also with the fact that not only
colouration but size, is implicated.

We meet with analogous facts in butterflies. Thus _Lycaena agestis_ not
only presents seasonal variations, (A) and (B); but while (A) and (B)
are respectively the winter and summer forms in Germany, (B) and (C) are
the corresponding forms in Italy. Therefore, (B) is in Germany the
summer form, and in Italy the winter form--the German winter form (A)
being absent in Italy, while the Italian summer form (C) is absent in
Germany. Probably these facts are due to differences of temperature in
the two countries, for experiments have shown that when pupae of sundry
species of moths and butterflies are exposed to different degrees of
temperature, the most wonderful changes of colour may result in the
insects which emerge. The remarkable experiments of Dorfmeister and
Weismann in relation to this subject are well known. More recently Mr.
Merrifield has added to their facts, and concludes that the action of
cold upon the pupae--and also, apparently, upon the larvae--has a
tendency to produce dark hues in the perfect insect[110].

    [110] _Trans. Entom. Soc._ 1889, part i. p. 79 _et seq._

But, passing now from such facts of climatic variations over wide areas
to similar facts within small areas, in an important _Memoir on the Cave
Fauna of North America_, published a few years ago by the American
Academy of Sciences, it is stated:--

     "As regards change of colour, we do not recall an exception to the
     general rule that all cave animals are either colourless or nearly
     white, or, as in the case of Arachnida and Insects, much paler than
     their out-of-door relatives."

Now, when we remember that these cave faunas comprise representatives of
nearly all classes of the animal kingdom, it becomes difficult, if not
impossible, to imagine that so universal a discharge of colouring can be
due to natural selection. It must be admitted that the only way in which
natural selection could act in this case would be indirectly through the
principle of correlation. There being no light in the caves, it can be
of no advantage to the animals concerned that they should lose their
colour for the sake of protection, or for any other reason of a
similarly direct kind. Therefore, if the loss of colour is to be
ascribed to natural selection, this can only be done by supposing that
natural selection has here acted indirectly through the principle of
correlation. There is evidence to show that elsewhere modification or
loss of colour is in some cases brought about by natural selection, on
account of the original colour being correlated with certain
physiological characters (such as liability to particular diseases,
&c.); so that when natural selection operates directly upon these
physiological characters, it thereby also operates indirectly upon the
correlated colours. But to suppose that this can be the explanation of
the uniform diminution of colour in all inhabitants of dark caves would
be manifestly absurd. If there were only one class of animals in these
caves, such as Insects, it might be possible to surmise that their
change of colour is due to natural selection acting directly upon their
physiological constitutions, and so indirectly upon their colours. But
it would be absurd to suppose that such can be the explanation of the
facts, when these extend in so similar a manner over so many scores of
species belonging to such different types of animal life.

With more plausibility it might be held that the universal discharge of
colour in these cave-faunas is due, not to the presence, but to the
absence of selection--i. e. to the cessation of selection, or panmixia.
But against this--at all events as a full or general explanation--lie
the following facts. First, in the case of Proteus--which has often been
kept for the purposes of exhibition &c., in tanks--the skin becomes dark
when the animal is removed from the cave and kept in the light.
Secondly, deep-sea faunas, though as much exposed as the cave-faunas, to
the condition of darkness, are not by any means invariably colourless.
On the contrary, they frequently present brilliant colouration. Thus it
is evident that if panmixia be suggested in explanation of the
discharge of colouring in cave-faunas, the continuance of colour in
deep-sea faunas appears to show the explanation insufficient. Thirdly,
according to my view of the action of panmixia as previously explained,
no _total_ discharge of colouration is likely to be caused by such
action alone. At most the bleaching as a result of the mere withdrawal
of selection would proceed only to some comparatively small extent.
Fourthly, Mr. Packard in the elaborate _Memoir on Cave Fauna_, already
alluded to, states that in some of the cases the phenomena of bleaching
appear to have been induced within very recent times--if not, indeed,
within the limits of a single generation. Should the evidence in support
of this opinion prove trustworthy, of course in itself it disposes of
any suggestion either of the presence or the absence of natural
selection as concerned in the process.

Nevertheless, I myself think it inevitable that to some extent the
cessation of selection must have helped in discharging the colour of
cave faunas; although for the reasons now given it appears to me that
the main causes of change must have been of that direct order which we
understand by the term climatic.

As regards dogs, the Rev. E. Everest found it impossible to breed Scotch
setters in India true to their type. Even in the second generation no
single young dog resembled its parents either in form or shape. "Their
nostrils were more contracted, their noses more pointed, their size
inferior, and their limbs more slender[111]." Similarly on the coast of
New Guinea, Bosman says that imported breeds of dogs "alter strangely;
their ears grow long and stiff like those of foxes, to which colour they
also incline ... and in three or four broods their barking turns into a
howl[112]."

    [111] _Variation_, &c. vol. i. p. 40.

    [112] _Variation_, &c. vol. i. p. 40.

Darwin gives numerous facts showing the effects of climate on horses,
cattle, and sheep, in altering, more or less considerably, the
characters of their ancestral stocks. He also gives the following
remarkable case with regard to the rabbit. Early in the fifteenth
century a common rabbit and her young ones were turned out on the island
of Porto Santo, near Madeira. The feral progeny now differ in many
respects from their parent stock. They are only about one-third of the
weight, present many differences in the relative sizes of different
parts, and have greatly changed in colour. In particular, the black on
the upper surface of the tail and tips of the ears, which is so constant
in all other wild rabbits of the world as to be given in most works as a
specific character, has entirely disappeared. Again, "the throat and
certain parts of the under surface, instead of being pure white, are
generally grey or leaden colour," while the upper surface of the whole
body is redder than in the common rabbit. Now, what answer have our
opponents to make to such a case as this? Presumably they will answer
that the case simply proves the action of natural selection during the
best part of 400 years on an isolated section of a species. Although we
cannot say of what use all these changes have been to the rabbits
presenting them, nevertheless we _must_ believe that they have been
produced by natural selection, and therefore _must_ present some hidden
use to the isolated colony of rabbits thus peculiarly situated. Four
centuries is long enough to admit of natural selection effecting all
these changes in the case of so rapidly breeding an animal as the
rabbit, and therefore it is needless to look further for any explanation
of the facts. Such, I say, is presumably the answer that would be given
by the upholders of natural selection as the only possible cause of
specific change. But now, in this particular case it so happens that the
answer admits of being conclusively negatived, by showing that the great
assumption on which it reposes is demonstrably false. For Darwin
examined two living specimens of these rabbits which had recently been
sent from Porto Santo to the Zoological Gardens, and found them coloured
as just described. Four years afterwards the dead body of one of them
was sent to him, and then he found that the following changes had taken
place. "The ears were plainly edged, and the upper surface of the tail
was covered with blackish-grey fur, and the whole body was much less
red; so that under the English climate this individual rabbit has
recovered the proper colour of its fur in rather less than four years!"

Mr. Darwin adds:--

     "If the history of these Porto Santo rabbits had not been known,
     most naturalists, on observing their much reduced size, their
     colour, reddish above and grey beneath, their tails and ears not
     tipped with black, would have ranked them as a distinct species.
     They would have been strongly confirmed in this view by seeing them
     alive in the Zoological Gardens, and hearing that they refused to
     couple with other rabbits. Yet this rabbit, which there can be
     little doubt would thus have been ranked as a distinct species, as
     certainly originated since the year 1420[113]."

    [113] _Variation_, &c. vol. i. p. 120.

Moreover, it certainly originated as a direct result of climatic
influences, independent of natural selection; seeing that, as soon as
individual members of this apparently new species were restored to their
original climate, they recovered their original colouration.

As previously remarked, it is, from the nature of the case, an
exceedingly difficult thing to prove in any given instance that natural
selection has not been the cause of specific change, and so finally to
disprove the assumption that it must have been. Here, however, on
account of historical information, we have a crucial test of the
validity of this assumption, just as we had in the case of the niata
cattle; and, just as in their case, the result is definitely and
conclusively to overturn the assumption. If these changes in the Porto
Santo rabbits had been due to the gradual influence of natural selection
guided by inscrutable utility, it is simply impossible that the same
individual animals, in the course of their own individual life-times,
should revert to the specific characters of their ancestral stock on
being returned to the conditions of their ancestral climate. Therefore,
unless any naturalist is prepared to contradict Darwin's statement that
the changes in question amount to changes of specific magnitude, he can
find no escape from the conclusion that distinctions of specific
importance may be brought about by changes of habitat alone, without
reference to utility, and therefore independently of natural selection.


II. _Food._

Although, as yet, little is definitely known on the subject, there can
be no doubt that in the case of many animals differences of food induce
differences of colour within the life-time of individuals, and therefore
independently of natural selection.

Thus, sundry definite varieties of the butterfly _Euprepia caja_ can be
reared according to the different nourishment which is supplied to the
caterpillar; and other butterflies are also known on whose colouring and
markings the food of the caterpillar has great influence[114].

    [114] See especially, Koch, _Die Raupen und Schmetterling der
          Wetterau_, and _Die Schmetterling des Südwestlichen
          Deutschlands_, whose very remarkable results of numerous and
          varied experiments are epitomized by Eimer, _Organic
          Evolution_, Eng. Trans. pp. 147-153; also Poulton, _Trans.
          Entom. Soc._ 1893.

Again, I may mention the remarkable case communicated to Darwin by
Moritz Wagner, of a species of _Saturnia_, some pupae of which were
transported from Texas to Switzerland in 1870. The moths which emerged
in the following year were like the normal type in Texas. Their young
were supplied with leaves of _Juglans regia_, instead of their natural
food, _J. nigra_; and the moths into which these caterpillars changed
were so different from their parents, both in form and colour, "that
they were reckoned by entomologists as a distinct species[115]."

    [115] Mivart, _On Truth_, p. 378.

With regard to mollusks, M. Costa tells us that English oysters, when
turned down in the Mediterranean, "_rapidly_ became like the true
Mediterranean oyster, altered their manner of growth, and formed
prominent diverging rays." This is most probably due to some change of
food. So likewise may be the even more remarkable case of _Helix
nemoralis_, which was introduced from Europe to Virginia a few years
ago. Under the new conditions it varied to such an extent that up to
last year no less than 125 varieties had been discovered. Of these 67,
or more than half, are new--that is, unknown in the native continent of
the species[116].

    [116] Cockerell, _Nature_, vol. xli. p. 393.

In the case of Birds, the Brazilian parrot _Chrysotis festiva_ changes
the green in its feathers to red or yellow, if fed on the fat of certain
fishes; and the Indian Lori has its splendid colouring preserved by a
peculiar kind of food (Wallace). The Bullfinch is well known to turn
black when fed on hemp seeds, and the Canary to become red when fed on
cayenne pepper (Darwin). Starting from these facts, Dr. Sauermann has
recently investigated the subject experimentally; and finds that not
only finches, but likewise other birds, such as fowls, and pigeons, are
subject to similar variations of colour when fed on cayenne pepper; but
in all cases the effect is produced only if the pepper is given to the
young birds before their first moult. Moreover, he finds that a moist
atmosphere facilitates the change of colour, and that the ruddy hue is
discharged under the influence either of sunlight or of cold. Lastly, he
has observed that sundry other materials such as glycerine and aniline
dyes, produce the same results; so there can be no doubt that organic
compounds probably occur in nature which are capable of directly
affecting the colours of plumage when eaten by birds. Therefore the
presence of such materials in the food-stuffs of birds occupying
different areas may very well in many cases determine differences of
colouration, which are constant or stable so long as the conditions of
their production are maintained.


III. _Sexual Selection._

Passing on now to causes of specific change which are internal, or
comprised within the organisms themselves, we may first consider the
case of Sexual Selection.

Mr. Wallace rejects the theory of sexual selection _in toto_, and
therefore nothing that can be said under this head would be held by him
to be relevant. Many naturalists, however, believe that Darwin was right
in the large generalization which he published under this title; and in
so far as any one holds that sexual selection is a true cause of
specific modification, he is obliged to believe that innumerable
specific characters--especially in birds and mammals--have been produced
without reference to utility (other, of course, than utility for sexual
purposes), and therefore without reference to natural selection. This is
so obvious that I need not pause to dilate upon it. One remark, however,
may be useful. Mr. Wallace is able to make a much more effective use of
his argument from "necessary instability" when he brings it against the
Darwinian doctrine of sexual selection, than he does when he brings it
against the equally Darwinian doctrine of specific characters in general
not being all necessarily due to natural selection. In the latter case,
it will be remembered, he is easily met by showing that the causes of
specific change other than natural selection, such as food, climate,
&c., may be quite as general, persistent, and uniform, as natural
selection itself; and therefore in this connexion Mr. Wallace's argument
falls to the ground. But the argument is much more formidable as he
brings it to bear against the theory of sexual selection. Here he asks,
What is there to guarantee the uniformity and the constancy of feminine
taste with regard to small matters of embellishment through thousands of
generations, and among animals living on extensive areas? And, as we
have seen in Part 1, it is not easy to supply an answer. Therefore this
argument from the "necessary instability of character" is of
immeasurably greater force as thus applied against Darwin's doctrine of
sexual selection, than it is when brought against his doctrine that all
specific characters need not necessarily be due to natural selection.
Therefore, also, if any one feels disposed to attach the smallest degree
of value to this argument in the latter case, consistency will require
him to allow that in the former case it is simply overwhelming, or in
itself destructive of the whole theory of sexual selection. And,
conversely, if his belief in the theory of sexual selection can survive
collision with this objection from instability, he ought not to feel any
tremor of contact when the objection is brought to bear against his
scepticism regarding the alleged utility of all specific characters. For
assuredly no specific character which is apparent to our eyes can be
supposed to be so refined and complex (and therefore so presumably
inconstant and unstable), as are those minute changes of cerebral
structure on which a psychological preference for all the refined
shadings and many pigments of a complicated pattern must be held
ultimately to depend. For this reason, then, as well as for those
previously adduced, if any one agrees with Darwin in holding to the
theory of sexual selection notwithstanding this objection from the
necessary instability of unuseful embellishments, _a fortiori_ he ought
to disregard the objection altogether in its relation to useless
specific characters of other kinds.

But quite apart from this consideration, which Mr. Wallace and his
followers may very properly say does not apply to them, let us see what
they themselves have made of the facts of secondary sexual
characters--which, of course, are for the most part specific
characters--in relation to the doctrine of utility.

Mr. Wallace himself, in his last work, quotes approvingly a letter which
he received in 1869 from the Rev. O Pickard-Cambridge, as follows:--

     "I myself doubt that particular application of the Darwinian theory
     which attributes male peculiarities of form, structure, colour, and
     ornament to female appetency or predilection. There is, it seems to
     me, undoubtedly something in the male organization of a special and
     sexual nature, which, of its own vital force, develops the
     remarkable male peculiarities so commonly seen, _and of no
     imaginable use to that sex_. In as far as these peculiarities show
     a great vital power, they point out to us the finest and strongest
     individuals of the sex, and show us which of them would most
     certainly appropriate to themselves the best and greatest number of
     females, and leave behind them the strongest and greatest number of
     progeny. And here would come in, as it appears to me, the proper
     application of Darwin's theory of Natural Selection; _for the
     possessors of greatest vital power being those most frequently
     produced and reproduced, the external signs of it would go on
     developing in an ever increasing exaggeration_, only to be checked
     where it became really detrimental in some respect or other to the
     individual[117]."

    [117] _Darwinism_, pp.[typo: period missing in scan] 296-7: italics
          mine.

Here then the idea is, as more fully expressed by Mr. Wallace in the
context, that all the innumerable, frequently considerable, and
generally elaborate "peculiarities of form, structure, colour, and
ornament," which Darwin attributed to sexual selection, are really due
to "the laws of growth." Diverse, definite, and constant though these
specific peculiarities be, they are all but the accidental or
adventitious accompaniments of "vigour," or "vital power," due to
natural selection. Now, without waiting to dispute this view, which has
already been dealt with in the chapter on Sexual Selection in Part I, it
necessarily follows that "a large proportional number of specific
characters," which, while presenting "no imaginable use," are very much
less remarkable, less considerable, less elaborate, &c., must likewise
be due to this "correlation with vital power." But if the principle of
correlation is to be extended in this vague and general manner, it
appears to me that the difference between Mr. Wallace and myself, with
respect to the principle of utility, is abolished. For of course no one
will dispute that the prime condition to the occurrence of "specific
characters," whether useful or useless, is the existence of some form
which has been denominated a "species" to present them; and this is
merely another way of saying that such characters cannot arise except in
correlation with a general fitness due to natural selection. Or, to put
the case in Mr. Wallace's own words--"This development [of useless
specific characters] will necessarily proceed by the agency of natural
selection [as a necessary condition] _and the general laws which
determine the production of colour and of ornamental appendages_." The
case, therefore, is just the same as if one were to say, for example,
that all the ailments of animals and plants proceed from correlation
with life (as a necessary condition), "and the general laws which
determine the production" of ill-health, or of specific disease. In
short, the word "correlation" is here used in a totally different sense
from that in which it is used by Darwin, and in which it is elsewhere
used by Wallace for the purpose of sustaining his doctrine of specific
characters as necessarily useful. To say that a useless character A is
correlated with a useful one B, is a very different thing from saying
that A is "correlated with vital power," or with the general conditions
to the existence of the species to which it belongs. So far as the
present discussion is concerned, no exception need be taken to the
latter statement. For it simply surrenders the doctrine against which I
am contending.


IV. _Isolation._

It is the opinion of many naturalists who are well entitled to have an
opinion upon the subject, that, in the words of Mr. Dixon, "Isolation
can preserve a non-beneficial as effectually as natural selection can
preserve a beneficial variation[118]." The ground on which this doctrine
rests is thus clearly set forth by Mr. Gulick:--"The fundamental cause
of this seems to lie in the fact that no two portions of a species
possess exactly the same average characters; and, therefore, that the
initial differences are for ever reacting on the environment and on each
other in such a way as to ensure increasing divergence in each
generation, as long as the individuals of the two groups are kept from
intergenerating[119]." In other words, as soon as a portion of a species
is separated from the rest of that species, so that breeding between the
two portions is no longer possible, the general average of characters in
the separated portion not being in all respects precisely the same as it
is in the other portion, the result of in-breeding among all individuals
of the separated portion will eventually be different from that which
obtains in the other portion; so that, after a number of generations,
the separated portion may become a distinct species from the effect of
isolation alone. Even without the aid of isolation, any original
difference of average characters may become, as it were, magnified in
successive generations, provided that the divergence is not harmful to
the individuals presenting it, and that it occurs in a sufficient
proportional number of individuals not to be immediately swamped by
intercrossing. For, as Mr. Murphy has pointed out, in accordance with
Delbœuf's law, "if, in any species, a number of individuals, bearing a
ratio not infinitely small to the entire number of births, are in every
generation born with a particular variation which is neither beneficial
nor injurious, and if it be not counteracted by reversion, then the
proportion of the new variety to the original form will increase till it
approaches indefinitely near to equality[120]." Now even Mr. Wallace
himself allows that this must be the case; and thinks that in these
considerations we may find an explanation of the existence of certain
definite varieties, such as the melanic form of the jaguar, the brindled
or ring-eyed guillemot, &c. But, on the other hand, he thinks that such
varieties must always be unstable, and continually produced in varying
proportions from the parent forms. We need not, however, wait to dispute
this arbitrary assumption, because we can see that it fails, even as an
assumption, in all cases where the superadded influence of isolation is
concerned. Here there is nothing to intercept the original tendency to
divergent evolution, which arises directly out of the initially
different average of qualities presented by the isolated section of the
species, as compared with the rest of that species[121].

    [118] _Nature_, vol. xxxiii. p. 100.

    [119] _Divergent Evolution through Cumulative Segregation_, Linn.
          Journ. Zoology, vol. xx. p. 215.

    [120] _Habit and Intelligence_, p. 241.

    [121] Allusion may here again be made to the case of the niata
          cattle. For here is a case where a very extreme variety is
          certainly not unstable, nor produced in varying proportions
          from the parent form. Moreover, as we have seen in the
          preceding chapter, this almost monstrous variety most probably
          originated as an individual sport--being afterwards maintained
          and multiplied for a time by artificial selection. Now,
          whether or not this was the case, we can very well see that it
          may have been. Hence it will serve to illustrate another
          possibility touching the origin and maintenance of useless
          specific characters. For what is to prevent an individual
          congenital variation of any kind (provided it be not harmful)
          from perpetuating itself as a "varietal," and eventually,
          should offspring become sufficiently numerous, a "specific
          character"? There is nothing to prevent this, save panmixia,
          or the presence of free intercrossing. But, as we shall see in
          the next division of this treatise, there are in nature many
          forms of isolation. Hence, as often as a small number of
          individuals may have experienced isolation in any of its
          forms, opportunity for perpetuation will have been given to
          any congenital variations which may happen to arise. Should
          any of these be pronounced variations, it would afterwards be
          ranked as a specific character. I do not myself think that
          this is the way in which indifferent specific characters
          _usually_ originate. On the contrary, I believe that their
          origin is most frequently due to the influence of isolation on
          the average characters of the whole population, as briefly
          stated in the text. But here it seems worth while to notice
          this possibility of their occasionally arising as merely
          individual variations, afterwards perpetuated by any of the
          numerous isolating conditions which occur in nature. For, if
          this can be the case with a varietal form so extreme as to
          border on the monstrous, much more can it be so with such
          minute differences as frequently go to constitute specific
          distinctions. It is the business of species-makers to search
          out such distinctions, no matter how trivial, and to record
          them as "specific characters." Consequently, wherever in
          nature a congenital variation happens to arise, and to be
          perpetuated by the force of heredity alone under any of the
          numerous forms of isolation which occur in nature, there will
          be a case analogous to that of the niata cattle.

As we shall have to consider the important principle of isolation more
fully on a subsequent occasion, I need not deal with it in the present
connexion, further than to remark that in this principle we have what
appears to me a full and adequate condition to the rise and continuance
of specific characters which need not necessarily be adaptive
characters. And, when we come to consider the facts of isolation more
closely, we shall find superabundant evidence of this having actually
been the case.


V. _Laws of Growth._

Under this general term Darwin included the operation of all unknown
causes internal to organisms leading to modifications of form or
structure--such modifications, therefore, appearing to arise, as he says
"spontaneously," or without reference to utility. That he attributed no
small importance to the operation of these principles is evident from
the last edition of the _Origin of Species_. But as these "laws of
growth" refer to causes confessedly unknown, I will not occupy space by
discussing this division of our subject--further than to observe that,
as we shall subsequently see, many of the facts which fall under it are
so irreconcilably adverse to the Wallacean doctrine of specific
characters as universally adaptive, that in the face of them Mr. Wallace
himself appears at times to abandon his doctrine _in toto_.




CHAPTER IX.

CHARACTERS AS ADAPTIVE AND SPECIFIC
(_continued_).


It must have appeared strange that hitherto I should have failed to
distinguish between "true species" and merely "climatic varieties." But
it will conduce to clearness of discussion if we consider our subject
point by point. Therefore, having now given a fair statement of the
facts of climatic variation, I propose to deal with their theoretical
implications--especially as regards the distinction which naturalists
are in the habit of drawing between them and so-called true species.

First of all, then, what is this distinction? Take, for example, the
case of the Porto Santo rabbits. To almost every naturalist who reads
what has been said touching these animals, it will have appeared that
the connexion in which they are adduced is wholly irrelevant to the
question in debate. For, it will be said that the very fact of the
seemingly specific differentiation of these animals having proved to be
illusory when some of them were restored to their ancestral conditions,
is proof that their peculiar characters are not specific characters; but
only what Mr. Wallace would term "individual characters," or variations
that are not _inherited_. And the same remark applies to all the other
cases which have been adduced to show the generality and extent of
climatic variation, both in other animals and also in plants. Why, then,
it will be asked, commit the absurdity of adducing such cases in the
present discussion? Is it not self-evident that however general, or
however considerable, such merely individual, or non-heritable,
variations may be, they cannot possibly have ever had anything to do
with the origin of _species_? Therefore, is it not simply preposterous
to so much as mention them in relation to the question touching the
utility of specific characters?

Well, whether or not it is absurd and preposterous to consider climatic
variations in connexion with the origin of species, will depend, and
depend exclusively, on what it is that we are to understand by a
species. Hitherto I have assumed, for the sake of argument, that we all
know what is meant by a species. But the time has now come for showing
that such is far from being the case. And as it would be clearly absurd
and preposterous to conclude anything with regard to specific characters
before agreeing upon what we mean by a character as specific, I will
begin by giving all the logically possible definitions of a species.

1. _A group of individuals descended by way of natural generation from
an originally and specially created type._

This definition may be taken as virtually obsolete.

2. _A group of individuals which, while fully fertile_ inter se, _are
sterile with all other individuals--or, at any rate, do not generate
fully fertile hybrids._

This purely physiological definition is not nowadays entertained by any
naturalist. Even though the physiological distinction be allowed to
count for something in otherwise doubtful cases, no systematist would
constitute a species on such grounds alone. Therefore we need not
concern ourselves with this definition, further than to observe that it
is often taken as more or less supplementary to each of the following
definitions.

3. _A group of individuals which, however many characters they share
with other individuals, agree in presenting one or more characters of a
peculiar kind, with some certain degree of distinctness._

In this we have the definition which is practically followed by all
naturalists at the present time. But, as we shall presently see more
fully, it is an extremely lax definition. For it is impossible to
determine, by any fixed and general rule, what degree of distinctness on
the part of peculiar characters is to be taken as a uniform standard of
specific separation. So long as naturalists believed in special
creation, they could feel that by following this definition (3) they
were at any rate doing their best to tabulate very real distinctions in
nature--viz. between types as originally produced by a supernatural
cause, and as subsequently more or less modified (i.e. within the limits
imposed by the test of cross-fertility) by natural causes. But
evolutionists are unable to hold any belief in such real distinctions,
being confessedly aware that all distinctions between species and
varieties are purely artificial. So to speak, they well know that it is
they themselves who create species, by determining round what degrees of
differentiation their diagnostic boundaries shall be drawn. And, seeing
that these degrees of differentiation so frequently shade into one
another by indistinguishable stages (or, rather, that they _always_ do
so, unless intermediate varieties have perished), modern naturalists are
well awake to the impossibility of securing any approach to a uniform
standard of specific distinction. On this account many of them feel a
pressing need for some firmer definition of a species than this
one--which, in point of fact, scarcely deserves to be regarded as a
definition at all, seeing that it does not formulate any definite
criterion of specific distinctness, but leaves every man to follow his
own standards of discrimination. Now, as far as I can see, there are
only two definitions of a species which will yield to evolutionists the
steady and uniform criterion required. These two definitions are as
follows.

4. _A group of individuals which, however many characters they share
with other individuals, agree in presenting one or more characters of a
peculiar and hereditary kind, with some certain degree of distinctness._

It will be observed that this definition is exactly the same as the last
one, save in the addition of the words "and hereditary." But, it is
needless to say, the addition of these words is of the highest
importance, inasmuch as it supplies exactly that objective and rigid
criterion of specific distinctness which the preceding definition lacks.
It immediately gets rid of the otherwise hopeless wrangling over species
as "good" and "bad," or "true" and "climatic," of which (as we have
seen) Kerner's essay is such a remarkable outcome. Therefore
evolutionists have more and more grown to lay stress on the hereditary
character of such peculiarities as they select for diagnostic features
of specific distinctness. Indeed it is not too much to say that, at the
present time, evolutionists in general recognize this character as,
theoretically, indispensable to the constitution of a species. But it is
likewise not too much to say that, practically, no one of our systematic
naturalists has hitherto concerned himself with this matter. At all
events, I do not know of any who has ever taken the trouble to ascertain
by experiment, with regard to any of the species which he has
constituted, whether the peculiar characters on which his diagnoses have
been founded are, or are not, hereditary. Doubtless the labour of
constituting (or, still more, of _re_-constituting) species on such a
basis of experimental inquiry would be insuperable; while, even if it
could be accomplished, would prove undesirable, on account of the chaos
it would produce in our specific nomenclature. But, all the same, we
must remember that this nomenclature as we now have it--and, therefore,
the partitioning of species as we have now made them--has no reference
to the criterion of heredity. Our system of distinguishing between
species and varieties is not based upon the definition which we are now
considering, but upon that which we last considered--frequently coupled,
to some undefinable extent, with No. 2.

5. There is, however, yet another and closer definition, which may be
suggested by the ultra-Darwinian school, who maintain the doctrine of
natural selection as the only possible cause of the origin of species,
namely:--

_A group of individuals which, however many characters they share with
other individuals, agree in presenting one or more characters of a
peculiar, hereditary, and adaptive kind, with some certain degree of
distinctness._

Of course this definition rests upon the dogma of utility as a necessary
attribute of characters _quâ_ specific--i.e. the dogma against which the
whole of the present discussion is directed. Therefore all I need say
with reference to it is, that at any rate it cannot be adduced in any
argument where the validity of its basal dogma is in question. For it
would be a mere begging of this question to argue that every species
must present at least one peculiar and adaptive character, because,
according to definition, unless an organic type does present at least
one such character, it is not a specific type. Moreover, and quite apart
from this, it is to be hoped that naturalists as a body will never
consent to base their diagnostic work on what at best must always be a
highly speculative extension of the Darwinian theory. While, lastly, if
they were to do so with any sort of consistency, the precise adaptation
which each peculiar character subserves, and which because of this
adaptation is constituted a character of specific distinction, would
have to be determined by actual observation. For no criterion of
specific distinction could be more vague and mischievous than this one,
if it were to be applied on grounds of mere inference that such and such
a character, because seemingly constant, must "necessarily" be either
useful, vestigial, or correlated.

Such then, as far as I can see, are all the definitions of a species
that are logically possible[122]. Which of them is chosen by those who
maintain the necessary usefulness of all specific characters? Observe,
it is for those who maintain this doctrine to choose their definition:
it is not for me to do so. My contention is, that the term does not
admit of any definition sufficiently close and constant to serve as a
basis for the doctrine in question--and this for the simple reason that
species-makers have never agreed among themselves upon any criterion of
specific distinction. My opponents, on the other hand, are clearly bound
to take an opposite view, because, unless they suppose that there is
some such definition of a species, they would be self-convicted of the
absurdity of maintaining a great generalization on a confessedly
untenable basis. For example, a few years ago I was allowed to raise a
debate in the Biological Section of the British Association on the
question to which the present chapters are devoted. But the debate ended
as I had anticipated that it must end. No one of the naturalists present
could give even the vaguest definition of what was meant by a
species--or, consequently, of a character as specific. On this account
the debate ended in as complete a destruction as was possible of the
doctrine that all the distinctive characters of every species must
necessarily be useful, vestigial, or correlated. For it became
unquestionable that the same generalization admitted of being made, with
the same degree of effect, touching all the distinctive characters of
every "snark."

    [122] It is almost needless to say that by a definition as "logical"
          is meant one which, while including all the differentiae of
          the thing defined, excludes any qualities which that thing may
          share in common with any other thing. But by definitions as
          "logically possible" I mean the number of separate definitions
          which admit of being correctly given of the same thing from
          different points of view. Thus, for instance, in the present
          case, since the above has been in type the late M.
          Quatrefages' posthumous work on _Darwin et ses Précurseurs
          Français_ has been published, and gives a long list of
          definitions of the term "species" which from time to time have
          been enunciated by as many naturalists of the highest standing
          as such (pp. 186-187). But while none of these twenty or more
          definitions is logical in the sense just defined, they all
          present one or other of the differentiae given by those in the
          text.

Probably, however, it will be thought unfair to have thus sprung a
difficult question of definition in oral debate. Therefore I allude to
this fiasco at the British Association, merely for the purpose of
emphasizing the necessity of agreeing upon some definition of a species,
before we can conclude anything with regard to the generalization of
specific characters as necessarily due to natural selection. But when a
naturalist has had full time to consider this fundamental matter of
definition, and to decide on what his own shall be, he cannot complain
of unfairness on the part of any one else who holds him to what he thus
says he means by a species. Now Mr. Wallace, in his last work, has given
a matured statement of what it is that he means by a species. This,
therefore, I will take as the avowed basis of his doctrine touching the
necessary origin and maintenance of all specific characters by natural
selection. His definition is as follows:--

     "An assemblage of individuals which have become somewhat modified
     in structure, form, and constitution, _so as to adapt them to
     slightly different conditions of life_; which can be differentiated
     from allied assemblages; which reproduce their like; which usually
     breed together; and, perhaps, when crossed with their near allies,
     always produce offspring which are more or less sterile _inter
     se_[123]."

    [123] Darwinism, p. 167.

From this definition the portion which I have italicized must be omitted
in the present discussion, for the reasons already given while
considering definition No. 5. What remains is a combination of Nos. 2
and 4. According to Mr. Wallace, therefore, our criterion of a species
is to be the heredity of peculiar characters, combined, perhaps, with a
more or less exclusive fertility of the component individuals _inter
se_. This is the basis on which his generalization of the utility of
specific characters as necessary and universal is reared. Here, then, we
have something definite to go upon, at all events as far as Mr. Wallace
is concerned. Let us see how far such a basis of definition is competent
to sustain his generalization.

First of all it must be remarked that, as species have actually been
constituted by systematists, the test of exclusive fertility does not
apply. For my own part I think this is to be regretted, because I
believe that such is the only natural--and therefore the only
firm--basis on which specific distinctions can be reared. But, as
previously observed, this is not the view which has been taken by our
species-makers. At most they regard the physiological criterion as but
lending some additional weight to their judgement upon morphological
features, in cases where it is doubtful whether the latter alone are of
sufficient distinctness to justify a recognition of specific value. Or,
conversely, if the morphological features are clearly sufficient to
justify such a recognition, yet if it happens to be known that there is
full fertility between the form presenting them and other forms which do
not, then the latter fact will usually prevent naturalists from
constituting the well differentiated form a species on grounds of its
morphological features alone--as, for instance, in the case of our
domesticated varieties. In short, the physiological criterion has not
been employed with sufficient closeness to admit of its being now
comprised within any practical definition of the term "species"--if by
this term we are to understand, not what any one may think species
_ought to be_, but what species actually _are_, as they have been
constituted for us by their makers.

From all this it follows that the definition of the term "species" on
which Mr. Wallace relies for his deduction with respect to specific
characters, is the definition No. 4. In other words, omitting his
_petitio principii_ and his allusion to the test of fertility, the great
criterion in his view is the criterion of Heredity. And in this all
other evolutionists, of whatever school, will doubtless agree with him.
They will recognize that it is really the distinguishing test between
"climatic varieties" and "true species," so that however widely or
however constantly the former may diverge from one another in regard to
their peculiar characters, they are not to be classed among the latter
unless their peculiar characters are likewise hereditary characters.

Now, if we are all agreed so far, the only question that remains is
whether or not this criterion of Heredity is capable of supplying a
basis for the generalization, that all characters which have been ranked
as of specific value must necessarily be regarded as presenting also an
adaptive, or life-serving, value? I will now endeavour to show that
there are certain very good reasons for answering this question in the
negative.


(A.)

In the first place, even if the modifications induced by the direct
action of a changed environment are not hereditary, who is to know that
they are not? Assuredly not the botanist or zoologist who in a
particular area finds what he is fully entitled to regard as a
well-marked specific type. Only by experiments in transposition could it
be proved that the modifications have been produced by local conditions;
and although the researches of many experimentalists have shown how
considerable and how constant such modifications may be, where is the
systematic botanist who would ever think of transplanting an apparently
new species from one distant area to another before he concludes that it
is a new species? Or where is the systematic zoologist who would take
the trouble to transport what appears to be an obviously endemic species
of animal from one country to another before venturing to give it a new
specific name? No doubt, both in the case of plants and animals, it is
tacitly assumed that constant differences, if sufficient in amount to be
regarded as specific differences are hereditary; but there is not one
case in a hundred where the validity of this assumption has ever been
tested by experiments in transposition. Therefore naturalists are apt to
regard it as remarkable when the few experiments which have been made in
this direction are found to negative their assumption--for example,
that a diagnostic character in species of the genus _Hieratium_ is found
by transplantation not to be hereditary, or that the several named
species of British trout are similarly proved to be all "local
varieties" of one another. But, in point of fact, there ought to be
nothing to surprise us in such results--unless, indeed, it is the
unwarrantable nature of the assumption that any given differences of
size, form, colour, &c., which naturalists may have regarded as of
specific value, are, on this account, hereditary. Indeed, so surprising
is this assumption in the face of what we know touching both the extent
and the constancy of climatic variation, that it seems to me such a
naturalist as Kerner, who never considers the criterion of heredity at
all, is less assailable than those who profess to constitute this their
chief criterion of specific distinction. For it is certain that whatever
their professions may have nowadays become, systematic naturalists have
never been in the habit of really following this criterion. In theory
they have of late years attached more and more weight to definition No.
4; but in practice they have always adopted definition No. 3. The
consequence is, that in literally numberless cases (particularly in the
vegetable kingdom) "specific characters" are assumed to be hereditary
characters merely because systematic naturalists have bestowed a
specific name on the form which presents them. Nor is this all. For,
conversely, even when it is known that constant morphological characters
are unquestionably hereditary characters, if they happen to present but
small degrees of divergence from those of allied forms, then the form
which presents them is not ranked as a species, but as a constant
variety. In other words, when definitions 3 and 4 are found to clash, it
is not 4, but 3, that is followed. In short, even up to the present
time, systematic naturalists play fast and loose with the criterion of
Heredity to such an extent, that, as above observed, it has been
rendered wellnigh worthless in fact, whatever may be thought of it in
theory.

Now, unless all this can be denied, what is the use of representing that
a species is distinguished from a variety--"climatic" or otherwise--by
the fact that its constituent individuals "reproduce their like"? We are
not here engaged on any abstract question of what might have been the
best principles of specific distinction for naturalists to have adopted.
We are engaged on the practical question of the principles which they
actually have adopted. And of these principles the reproduction of like
by like, under all circumstances of environment, has been virtually
ignored.


(B.)

In the second place, supposing that the criterion of Heredity had been
as universally and as rigidly employed by our systematists in their work
of constructing species as it has been but occasionally and loosely
employed, could it be said that even then a basis would have been
furnished for the doctrine that all specific characters must necessarily
be useful characters? Obviously not, and for the following reasons.

It is admitted that climatic characters are not necessarily--or even
generally--useful characters. Consequently, if there be any reason for
believing that climatic characters may become in time hereditary
characters, the doctrine in question would collapse, even supposing that
all specific types were to be re-constituted on a basis of experimental
inquiry, for the purpose of ascertaining which of them conform to the
test of Heredity. Now there are very good reasons for believing that
climatic characters not unfrequently do become hereditary characters;
and it was mainly in view of those reasons that I deemed it worth while
to devote so much space in the preceding chapter to the facts of
climatic variation. I will now state the reasons in question under two
different lines of argument.

We are not as yet entitled to conclude definitely against the possible
inheritance of acquired characters. Consequently, we are not as yet
entitled to assume that climatic characters--i. e. characters acquired
by converse with a new environment, continued, say, since the last
glacial period--can never have become congenital characters. But, if
they ever have become congenital characters, they will have become, at
all events as a general rule, congenital characters that are useless;
for it is conceded that, _quâ_ climatic characters, they have not been
due to natural selection.

Doubtless the followers of Weismann will repudiate this line of
argument, if not as entirely worthless, at all events as too
questionable to be of much practical worth. But even to the followers of
Weismann it may be pointed out, that the Wallacean doctrine of the
origin of all specific characters by means of natural selection was
propounded many years before either Galton or Weismann had questioned
the transmission of acquired characters. However. I allow that this line
of argument has now become--for the time being at all events--a dubious
line, and will therefore at once pass on to the second line, which is
not open to doubt from any quarter.

Whether or not we accept Weismann's views, it will here be convenient to
employ his terminology, since this will serve to convey the somewhat
important distinctions which it is now my object to express.

In the foregoing paragraphs, under heading (A), we have seen that there
must be "literally numberless forms" which have been ranked as true
species, whose diagnostic characters are nevertheless not congenital. In
the case of plants especially, we know that there must be large numbers
of named species which do not conform to the criterion of Heredity,
although we do not know which species they are. For present purposes,
however, it is enough for us to know that there are many such named
species, where some change of environment has acted directly and
similarly on all the individual "somas" exposed to it, without affecting
their "germ-plasms," or the material bases of their hereditary
qualities. For named species of this kind we may employ the term
_somatogenetic species_.

But now, if there are any cases where a change of environment does act
on the germ-plasms exposed to it, the result would be what we may call
_blastogenetic species_--i.e. species which conform to the criterion of
Heredity, and would therefore be ranked by all naturalists as "true
species." It would not signify in such a case whether the changed
conditions of life first affected the soma, and then, through changed
nutrition, the germ-plasm; or whether from the first it directly
affected the germ-plasm itself. For in either case the result would be a
"species," which would continue to reproduce its peculiar features by
heredity.

Now, the supposition that changed conditions of life may thus affect the
congenital endowments of germ-plasm is not a gratuitous one. The sundry
facts already given in previous chapters are enough to show that the
origin of a blastogenetic species by the direct action on germ-plasm of
changed conditions of life is, at all events, a possibility. And a
little further thought is enough to show that this possibility becomes a
probability--if not a virtual certainty. Even Weismann--notwithstanding
his desire to maintain, as far as he possibly can, the "stability" of
germ-plasm--is obliged to allow that external conditions acting on the
organism may in some cases modify the hereditary qualities of its
germ-plasm, and so, as he says, "determine the phyletic development of
its descendants." Again, we have seen that he is compelled to interpret
the results of his own experiments on the climatic varieties of certain
butterflies by saying, "I cannot explain the facts otherwise than by
supposing the passive acquisition of characters produced by direct
influences of climate"; by which he means that in this case the
influence of climate acts directly on the hereditary qualities of
germ-plasm. Lastly, and more generally, he says:--

     "But although I hold it improbable that individual variability can
     depend on a direct action of external influences upon the
     germ-cells and their contained germ-plasm, because--as follows from
     sundry facts--the molecular structure of the germ-plasm must be
     very difficult to change, yet it is by no means to be implied that
     this structure may not possibly be altered by influences of the
     same kind continuing for a very long time. Thus it seems to me the
     possibility is not to be rejected, that influences continued for a
     long time, that is, for generations, such as temperature, kind of
     nourishment, &c., which may affect the germ-cells as well as any
     other part of the organism, may produce a change in the
     constitution of the germ-plasm. But such influences would not then
     produce individual variation, but would necessarily modify in the
     same way all the individuals of a species living in a certain
     district. It is possible, though it cannot be proved, that many
     climatic varieties have arisen in this manner."

So far, then, we have testimony to this point, as it were, from a
reluctant witness. But if we have no theory involving the "stability of
germ-plasm" to maintain, we can scarcely fail to see how susceptible the
germ-plasm is likely to prove to changed conditions of life. For we know
how eminently susceptible it is in this respect when gauged by the
practical test of fertility; and as this is but an expression of its
extraordinarily complex character, it would indeed be surprising if it
were to enjoy any immunity against modification by changed conditions of
life. We have seen in the foregoing chapter how frequently and how
considerably somatogenetic changes are thus caused, so as to produce
"somatogenetic species"--or, where we happen to know that the changes
are not hereditary, "climatic varieties." But the constitution of
germ-plasm is much more complex than that of any of the structures which
are developed therefrom. Consequently, the only wonder is that hitherto
experimentalists have not been more successful in producing
"blastogenetic species" by artificial changes of environment. Or, as Ray
Lankester has well stated this consideration, "It is not difficult to
suggest possible ways in which the changed conditions, shown to be
important by Darwin, could act through the parental body upon the
nuclear matter of the egg-cell and sperm-cell, with its immensely
complex and therefore unstable constitution.... The wonder is, not that
[blastogenetic] variation occurs, but that it is not excessive and
monstrous in every product of fertilization[124]."

    [124] _Nature_, Dec. 12, 1889, p. 129.

If to this it should be objected that, as a matter of fact,
experimentalists have not been nearly so successful in producing
congenital modifications of type by changed conditions of life as they
have been in thus producing merely somatic modifications; or if it
should be further objected that we have no evidence at all in nature of
a "blastogenetic species" having been formed by means of climatic
influences alone,--if these objections were to be raised, they would
admit of the following answer.

With regard to experiments, so few have thus far been made upon the
subject, that objections founded on their negative results do not carry
much weight--especially when we remember that these results have not
been uniformly negative, but sometimes positive, as shown in Chapter VI.
With regard to plants and animals in a state of nature, the objection is
wholly futile, for the simple reason that in as many cases as changed
conditions of life may have caused an hereditary change of specific
type, there is now no means of obtaining "evidence" upon the subject.
But we are not on this account entitled to conclude against the
probability of such changes of specific type having been more or less
frequently thus produced. And still less can we be on this account
entitled to conclude against the _possibility_ of such a change having
ever occurred in any single instance. Yet this is what must be concluded
by any one who maintains that the origin of all species--and, _a
fortiori_, of all specific characters--must _necessarily_ have been due
to natural selection.

Now, if all this be admitted--and I do not see how it can be reasonably
questioned--consider how important its bearing becomes on the issue
before us. If germ-plasm (using this term for whatever it is that
constitutes the material basis of heredity) is ever capable of having
its congenital endowments altered by the direct action of external
conditions, the resulting change of hereditary characters, whatever else
it may be, need not be an adaptive change. Indeed, according to
Weismann's theory of germ-plasm, the chances must be infinitely against
the change being an adaptive one. On the theory of pangenesis--that is
to say, on the so-called Lamarckian principles--there would be much more
reason for entertaining the possibly adaptive character of hereditary
change due to the direct action of the environment. Therefore we arrive
at this curious result. The more that we are disposed to accept
Weismann's theory of heredity, and with it the corollary that natural
selection is the sole cause of adaptive modification in species the less
are we entitled to assume that all specific characters must necessarily
be adaptive. Seeing that in nature there are presumably many cases like
those of Hoffmann's plants, Weismann's butterflies, &c., where the
hereditary qualities of germ-plasm have (on his hypothesis) been
modified by changed conditions of life, we are bound to believe that, in
all cases where such changes do not happen to be actively deleterious,
they will persist. And inasmuch as characters which are only of
"specific" value must be the characters most easily--and therefore most
frequently--induced by any slight changes in the constitution of
germ-plasm, while, for the same reason (namely, that of their trivial
nature) they are least likely to prove injurious, it follows that the
less we believe in the functionally-produced adaptations of Lamarck, the
more ought we to resist the assumption that all specific characters must
necessarily be adaptive characters.

       *       *       *       *       *

Upon the whole, then, and with regard to the direct action of external
conditions, I conclude--not only from general considerations, but also
from special facts or instances quite sufficient for the purpose--that
these must certainly give rise to immense numbers of somatogenetic
species on the one hand, and probably to considerable numbers of
blastogenetic species on the other; that in neither case is there any
reason for supposing the distinctively "specific characters" to be other
than "neutral" or "indifferent"; while there are the best of reasons for
concluding the contrary. So that, under this division of our subject
alone (B), there appears to be ample justification for the statement
that "a large proportional number of specific characters" are in
reality, as they are in appearance, destitute of significance from a
utilitarian point of view.


(C.)

Thus far in the present chapter we have been dealing exclusively with
the case of "climatic variation," or change of specific type due to
changes in the external conditions of life. But it will be remembered
that, in the preceding chapter, allusion was likewise made to changes of
specific type due to internal causes, or to what Darwin has called "the
nature of the organism." Under this division of our subject I mentioned
especially Sexual Selection, which is supposed to arise in the aesthetic
taste of animals themselves; Isolation, which is supposed to originate
new types by allowing the average characters of an isolated section of
an old type to develop a new history of varietal change, as we shall see
more fully in the ensuing part of this treatise; and the Laws of Growth,
which is a general term for the operation of unknown causes of change
incidental to the living processes of organisms which present the
change.

Now, under none of these divisions of our subject can there be any
question touching the criterion of Heredity. For if new species--or even
single specific characters of new species--are ever produced by any of
these causes, they must certainly all "reproduce their like." Therefore
the only question which can here obtain is as to whether or not such
causes ever do originate new species, or even so much as new specific
characters. Mr. Wallace, though not always consistently, answers this
question in the negative; but the great majority of naturalists follow
Darwin by answering it in the affirmative. And this is enough to show
the only point which we need at present concern ourselves with
showing--viz. that the question is, at the least, an open one. For as
long as this question is an open one among believers in the theory of
natural selection, it must clearly be an unwarrantable deduction from
that theory, that all species, and _a fortiori_ all specific characters,
are necessarily due to natural selection. The deduction cannot be
legitimately drawn until the possibility of any other cause of specific
modification has been excluded. But the bare fact of the question as
just stated being still and at the least an open question, is enough to
prove that this possibility has not been excluded. Therefore the
deduction must be, again on this ground alone (C), unwarrantable.

       *       *       *       *       *

Such are my several reasons--and it is to be observed that they are all
_independent_ reasons--for concluding that it makes no practical
difference to the present discussion whether or not we entertain
Heredity as a criterion of specific distinction. Seeing that our
species-makers have paid so little regard to this criterion, it is
neither absurd nor preposterous to have adduced, in the preceding
chapter, the facts of climatic variation. On the contrary, as the
definition of "species" which has been practically followed by our
species-makers in No. 3, and not No. 4, these facts form part and parcel
of our subject. It is perfectly certain that, in the vegetable kingdom
at all events, "a large proportional number" of specifically diagnostic
characters would be proved by experiment to be "somatogenetic"; while
there are numerous constant characters classed as varietal, although it
is well known that they are "blastogenetic." Moreover, we can scarcely
doubt that many specific characters which are also hereditary characters
owe their existence, not to natural selection, but to the direct action
of external causes on the hereditary structure of "germ-plasm"; while,
even apart from this consideration, there are at least three distinct
and highly general principles of specific change, which are accepted by
the great majority of Darwinists, and the only common peculiarity of
which is that they produce hereditary changes of specific types without
any reference to the principle of utility.




CHAPTER X.

CHARACTERS AS ADAPTIVE AND SPECIFIC
(_concluded_).


Our subject is not yet exhausted. For it remains to observe the
consequences which arise from the dogma of utility as the only _raison
d'être_ of species, or of specific characters, when this dogma is
applied in practice by its own promoters.

       *       *       *       *       *

Any definition of "species"--excepting Nos. 1, 2, and 5, which may here
be disregarded--must needs contain some such phrase as the one with
which Nos. 3 and 4 conclude. This is, that peculiar characters, in order
to be recognized as of specific value, must present neither more nor
less than "some certain degree of distinctness." If they present more
than this degree of distinctness, the form, or forms, in question must
be ranked as generic; while if they present less than this degree of
distinctness, they must be regarded as varietal--and this even if they
are known to be mutually sterile. What, then, is this certain degree of
distinctness? What are its upper and lower limits? This question is one
that cannot be answered. From the very nature of the case it is
impossible to find a uniform standard of distinction whereby to draw
our boundary lines between varieties and species on the one hand, or
between species and genera on the other. One or two quotations will be
sufficient to satisfy the general reader upon this point.

Mr. Wallace himself alludes to "the great difficulty that is felt by
botanists in determining the limits of species in many large genera,"
and gives as examples well-known instances where systematic botanists of
the highest eminence differ hopelessly in their respective estimates of
"specific characters." Thus:--

     "Mr. Baker includes under a single species, Rosa canina, no less
     than twenty-eight named varieties distinguished by more or less
     constant characters, and often confined to special localities, and
     to these are referred about seventy of the species of British and
     continental botanists. Of the genus Rubus or bramble, five British
     species are given in Bentham's _Handbook of British Flora_, while
     in the fifth edition of Babington's _Manual of British Botany_,
     published about the same time, no less than forty-five species are
     described. Of willows (Salix) the same two works enumerate fifteen
     and thirty-one species respectively. The hawkweeds (Hieracium) are
     equally puzzling, for while Mr. Bentham admits only seven British
     species, Professor Babington describes no less than seventy-two,
     besides several named varieties[125]."

    [125] _Darwinism_, p. 77.

Mr. Wallace goes on to quote further instances, such as that of Draba
verna, which Jordan has found to present, in the south of France alone,
no less than fifty-two permanent varieties, which all "come true from
seed, and thus present all the characteristics of a true species"; so
that, "as the plant is very common almost all over Europe, and ranges
from North America to the Himalayas, the number of similar forms over
this wide area would probably have to be reckoned by hundreds, if not by
thousands[126]."

    [126] _Darwinism_, p. 77.

One or two further quotations may be given to the same general effect,
selected from the writings of specialists in their several departments.

     "There is nothing that divides systematists more than what
     constitutes a genus. Species that resemble each other more than
     other species, is perhaps the best definition that can be given.
     This is obviously an uncertain test, much depending on individual
     judgement and experience; but that, in the evolution of forms, such
     difficulties should arise in the limitation of genera and species
     was inevitable. What is a generic character in one may be only a
     specific character in another. As an illustration of the uncertain
     importance of characters, I may mention the weevil genus
     _Centrinus_ in which the leading characters in the classification
     of the family to which it belongs are so mixed that systematists
     have been content to keep the species together in a group that
     cannot be defined.... No advantage or disadvantage is attached,
     apparently, to any of the characters. There are about 200 species,
     all American.

     The venation of the wings of insects is another example of
     modifications without serving any special purpose. There is no vein
     in certain Thripidae, and only a rudiment or a single vein in
     Chalcididae. There are thousands of variations more or less marked,
     some of the same type with comparatively trivial variation, others
     presenting distinct types, even in the same family, such genera,
     for example, as _Polyneura_, _Tettigetra_, _Huechys_, &c. in the
     Cicadidae.

     Individual differences have often been regarded as distinctive of
     species; varieties also are very deceptive, and races come very
     near to species. A South-American beetle, _Arescus histrio_, has
     varieties of yellow, red, and black, or these colours variously
     intermixed, and, what is very unusual, longitudinal stripes in some
     and transverse bars in others, and all taken in the same locality.
     Mr. A. G. Butler, of the British Museum, is of opinion that 'what
     is generally understood by the term species (that is to say, a
     well-defined, distinct, and constant type, having no near allies)
     is non-existent in the Lepidoptera, and that the nearest approach
     to it in this order is a constant, though but slightly differing,
     rare or local form--that genera, in fact, consist wholly of a
     gradational series of such forms (Ann. Mag. Nat. Hist. 5, xix.
     103)[127].'"

    [127] Pascoe, _The Darwinian Theory of the Origin of Species_, 1891,
          pp. 31-33, and 46.

So much as regards entomology, and still living forms. In illustration
of the same principles in connexion with palaeontological series, I may
quote Würtenberger, who says:--

     "With respect to these fossil forms [i.e. multitudinous forms of
     fossil Ammonites], it is quite immaterial whether a very short or a
     somewhat longer part of any branch be dignified with a separate
     name, and regarded as a species. The prickly Ammonites, classed
     under the designation of Armata, are so intimately connected that
     it becomes impossible to separate the accepted species sharply from
     one another. The same remark applies to the group of which the
     manifold forms are distinguished by their ribbed shells, and are
     called Planulata[128]."

    [128] _Neuer Beitrag zum geologischen Beweis der Darwinischen
          Theorie_, 1873.

I had here supplied a number of similar quotations from writers in
various other departments of systematic work, but afterwards struck them
out as superfluous. For it is not to be anticipated that any competent
naturalist will nowadays dispute that the terms "variety," "species,"
and "genus" stand for merely conventional divisions, and that whether a
given form shall be ranked under one or the other of them is often no
more than a matter of individual taste. From the nature of the case
there can be no objective, and therefore no common, standards of
delimitation. This is true even as regards any one given department of
systematic work; but when we compare the standards of delimitation which
prevail in one department with those which prevail in another, it
becomes evident that there is not so much as any attempt at agreeing
upon a common measure of specific distinction.

But what, it may well be asked, is the use of thus insisting upon
well-known facts, which nobody will dispute? Well, in the first place,
we have already seen, in the last chapter, that it is incumbent on those
who maintain that all species, or even all specific characters, must be
due to natural selection, to tell us what they mean by a species, or by
characters as specific. If I am told to believe that the definite
quality A is a necessary attribute of B, and yet that B is "not a
distinct entity," but an undefinable abstraction, I can only marvel that
any one should expect me to be so simple. But, without recurring to this
point, the use of insisting on the facts above stated is, in the second
place, that otherwise I cannot suppose any general reader could believe
them in view of what is to follow. For he cannot but feel that the cost
of believing them is to render inexplicable the mental processes of
those naturalists who, in the face of such facts, have deduced the
following conclusions.

The school of naturalists against which I am contending maintains, as a
generalization deduced from the theory of natural selection, that all
species, or even all specific characters, must necessarily owe their
origin to the principle of utility. Yet this same school does not
maintain any such generalization, either with regard to varietal
characters on the one hand, or to generic characters on the other. On
the contrary, Professor Huxley, Mr. Wallace, and all other naturalists
who agree with them in refusing to entertain so much as the abstract
possibility of any cause other than natural selection having been
productive of species, fully accept the fact of other causes having been
largely concerned in the production of varieties, genera, families, and
all higher groups, or of the characters severally distinctive of each.
Indeed, Mr. Wallace does not question what appears to me the extravagant
estimate of Professor Cope, that the non-adaptive characters distinctive
of those higher groups are fully equal, in point of numbers, to the
adaptive. But, surely, if the theory of evolution by natural selection
is, as we all agree, a true theory of the origin of species, it must
likewise be a true theory of the origin of genera; and if it be supposed
essential to the integrity of the theory in its former aspect that all
specific characters should be held to be useful, I fail to see how, in
regard to its latter aspect, we are so readily to surrender the
necessary usefulness of all generic characters. And exactly the same
remark applies to the case of constant "varieties," where again the
doctrine of utility as universal is not maintained. Yet, according to
the general theory of evolution, constant varieties are what Darwin
termed "incipient species," while species are what may be termed
"incipient genera." Therefore, if the doctrine of utility as universal
be conceded to fail in the case of varieties on the one hand and of
genera on the other, where is the consistency in maintaining that it
must "necessarily" hold as regards the intermediate division, species?
Truly the shade of Darwin may exclaim, "Save me from my friends." And
truly against logic of this description a follower of Darwin must find
it difficult to argue. If one's opponents were believers in special
creation, and therefore stood upon some definite ground while
maintaining this difference between species and all other taxonomic
divisions, there would at least be some issue to argue about. But when
on the one hand it is conceded that species are merely arbitrary
divisions, which differ in no respect as to the process of their
evolution from either varieties or genera, while on the other hand it is
affirmed that there is thus so great a difference in the result, all we
can say is that our opponents are entangling themselves in the meshes of
a sheer contradiction.

Or, otherwise stated, specific characters differ from varietal
characters in being, as a rule, more pronounced and more constant: on
this account advocates of utility as universal apply the doctrine to
species, while they do not feel the "necessity" of applying it to
varieties. But now, generic and all higher characters are even more
constant and more pronounced than specific characters--not to say, in
many cases, more generally diffused over a larger number of organisms
usually occupying larger areas. Therefore, _a fortiori_, if for the
reasons above stated evolutionists regard it as a necessary deduction
from the theory of natural selection that all specific characters must
be useful, much more ought it to be a necessary deduction from this
theory that all generic, and still more all higher, characters must be
useful. But, as we have seen, this is not maintained by our opponents.
On the contrary, they draw the sharpest distinction between specific and
all other characters in this respect, freely conceding that both those
below and those above them need not--and very often do not--present any
utilitarian significance.

Although it appears to me that this doctrine is self-contradictory, and
on this ground alone might be summarily dismissed, as it is now held in
one or other of its forms by many naturalists, I will give it a more
detailed consideration in both its parts--namely, first with respect to
the distinction between varieties and species, and next with respect to
the distinction between species and genera.

       *       *       *       *       *

Until it can be shown that species are something more than merely
arbitrary divisions, due to the disappearance of intermediate varietal
links; that in some way or another they _are_ "definite entities," which
admit of being delineated by the application of some uniform or general
principles of definition; that, in short, species have only then been
classified as such when it has been shown that the origin of each has
been due to the operation of causes which have not been concerned in the
production of varieties;--until these things are shown, it clearly
remains a gratuitous dogma to maintain that forms which have been called
species differ from forms which have been called varieties in the
important respect, that they (let alone each of all their distinctive
characters) must necessarily have been due to the principle of utility.
Yet, as we have seen, even Mr. Wallace allows that a species is "not a
distinct entity," but "an assemblage of individuals which have become
somewhat modified in structure, form, and constitution"; while estimates
of the kinds and degrees of modification which are to be taken as of
specific value are conceded to be undefinable, fluctuating, and in not a
few cases almost ludicrously divergent.

Perhaps one cannot more forcibly present the rational value of this
position than by noting the following consequences of it. Mr. Gulick
writes me that while studying the land-shells of the Sandwich Islands,
and finding there a rich profusion of unique varieties, in cases where
the intermediate varieties were rare he could himself have created a
number of species by simply throwing these intermediate varieties into
his fire. Now it follows from the dogma which we are considering, that,
by so doing, not only would he have created new species, but at the same
time he would have proved them due to natural selection, and endowed the
diagnostic characters of each with a "necessarily" adaptive meaning,
which previously it was not necessary that they should present. Before
his destruction of these intermediate varieties, he need have felt
himself under no obligation to assume that any given character at either
end of the series was of utilitarian significance: but, after his
destruction of the intermediate forms, he could no longer entertain any
question upon the matter, under pain of being denounced as a Darwinian
heretic.

Now the application is self-evident. It is a general fact, which admits
of no denial, that the more our knowledge of any flora or fauna
increases, the greater is the number of intermediate forms which are
brought to light, either as still existing or as having once existed.
Consequently, the more that such knowledge increases, the more does our
catalogue of "species" diminish. As Kerner says, "bad species" are
always multiplying at the expense of "good species"; or, as Oscar
Schmidt (following Häckel) similarly remarks, if we could know as much
about the latter as we do about the former, "all species, without any
exception, would become what species-makers understand by 'bad
species'[129]." Hence we see that, just as Mr. Gulick could have created
good species by secretly destroying his intermediate varieties, so has
Nature produced her "good species" for the delectation of systematists.
And just as Mr. Gulick, by first hiding and afterwards revealing his
intermediate forms, could have made the self-same characters in the
first instance necessarily useful, but ever afterwards presumably
useless, so has Nature caused the utility of diagnostic characters to
vary with our knowledge of her intermediate forms. It belongs to the
essence of our theory of descent, that in _all_ cases these intermediate
forms must either be now existing or have once existed; and, therefore,
that the work of species-makers consists in nothing more than marking
out the _lacunae_ in our knowledge of them. Yet we are bound to believe
that wherever these _lacunae_ in our knowledge occur, there occurs also
the objective necessity of causation as utilitarian--a necessity,
however, which vanishes so soon as our advancing information supplies
the intermediate forms in question. It may indeed appear strange that
the utility or non-utility of organic structures should thus depend on
the accidents of human knowledge; but this is the Darwinian faith, and
he who doubts the dogma is to be anathema.

    [129] _The Doctrine of Descent and Darwinism_, Eng. Trans. p. 102.

Turning next to the similar distinction which it is sought to draw
between species and genera, here it will probably be urged, as I
understand it to be urged by Mr. Wallace, that generic characters (and
still more characters of families, orders, &c.) refer back to so remote
a state of things that utility may have been present at their birth
which has disappeared in their maturity. In other words, it is held that
all generic characters were originally specific characters; that as such
they were all originally of use; but that, after having been rendered
stable by heredity, many of them may have ceased to be of service to the
descendants of those species in which they originated, and whose
extinction has now made it impossible to divine what that service may
have been.

Now, in the first place; this is not the interpretation adopted by
Darwin. For instance, he expressly contrasts such cases with those of
vestigial or "rudimentary" structures, pointing out that they differ
from vestigial structures in respect of their permanence. One quotation
will be sufficient to establish the present point.

     "A structure which has been developed through long-continued
     selection, when it ceases to be of service to a species, generally
     becomes variable, as we see with rudimentary organs, for it will no
     longer be regulated by this same power of selection. But when, from
     the nature of the organism and of the conditions, modifications
     have been induced which are unimportant for the welfare of the
     species, they may be, and apparently often have been, transmitted
     in nearly the same state to numerous, otherwise modified,
     descendants[130]."

    [130] _Origin of Species_, p. 175.

Here, and in the context, we have a sufficiently clear statement of
Darwin's view--first, that unadaptive characters may arise in _species_
as "fluctuating variations, which sooner or later become _constant_
through the nature of the organism and of surrounding conditions, as
well as through the intercrossing of distinct individuals, but _not_
through natural selection"[131]; second, that such unadaptive characters
may then be transmitted in this their stable condition to
species-progeny, so as to become distinctive of genera, families, &c.;
third, that, on account of such characters not being afterwards liable
to diverse adaptive modifications in different branches of the
species-progeny, they are of more value as indicating lines of pedigree
than are characters which from the first have been useful; and, lastly,
they are therefore now empirically recognized by systematists as of most
value in guiding the work of classification. To me it appears that this
view is not only perfectly rational in itself, but likewise fully
compatible with the theory of natural selection--which, as I have
previously shown, is _primarily_ a theory of adaptive characters, and
therefore not necessarily a theory of _all_ specific characters. But to
those who think otherwise, it must appear--and does appear--that there
is something wrong about such a view of the case--that it was not
consistent in the author of the _Origin of Species_ thus to refer
non-adaptive generic characters to a parentage of non-adaptive specific
characters. Nevertheless, as a matter of fact, Darwin was perfectly
consistent in putting forth this view, because, unlike Wallace, he was
not under the sway of any antecedent dogma erroneously deduced from the
theory of natural selection.

    [131] _Ibid._ p. 176: italics mine.

Next without reference to Darwin's authority, let us see for ourselves
where the inconsistency really lies. To allow that generic characters
may be useless, while denying that specific characters can ever be so
(unless correlated with others that are useful), involves an appeal to
the argument from ignorance touching the ancestral habits,
life-conditions, &c., of a parent species now extinct. Well, even upon
this assumption of utility as obsolete, there remains to be explained
the "stability" of useless characters now distinctive of genera,
families, orders, and the rest. We know that specific characters which
have owed their origin to utility and have afterwards ceased to present
utility, degenerate, become variable, inconstant, "rudimentary," and
finally disappear. Why, then, should these things not happen with regard
to useless generic distinctions? Still more, why should they not happen
with regard to family, ordinal, and class distinctions? On the lines
against which I am arguing it would appear impossible that any answer to
this question can be suggested. For what explanation can be given of the
contrast thus presented between the obsolescence of specific characters
where previous utility is demonstrable, and the permanence of higher
characters whose previous utility is assumed? As we have already seen,
Mr. Wallace himself employs this consideration of permanence and
constancy against the view that any cause other than natural selection
can have been concerned in the origin and maintenance of _specific_
characters. But he does not seem to see that the consideration cuts two
ways--and much more forcibly against his views than in favour of them.
For while, as already shown in the chapter before last, it is
sufficiently easy to dispose of the consideration as Wallace uses it (by
simply pointing out with Darwin that any causes other than natural
selection which may have been concerned in the genesis of _specific_
characters, must, if equally uniform in their operation, equally give
rise to permanence and constancy in their results); on the other hand,
it becomes impossible to explain the stability of useless _generic_
characters, if, as Wallace's use of the argument requires, natural
selection is the only possible cause of stability. The argument is one
that cannot be played with fast and loose. Either utility is the sole
condition to the stability of _any_ diagnostic character (in which case
it is not open to Mr. Wallace to assume that all _generic_ or higher
characters which are now useless have owed their origin to a past
utility); or else utility is not the sole condition to stability (in
which case his use of the present argument in relation to _specific_
characters collapses). We have seen, indeed, in the chapter before last,
that his use of the argument collapses anyhow, or quite irrespective of
his inconsistent attitude towards generic characters, with which we were
not then concerned. But the point now is that, as a mere matter of
logic, the argument from stability as Wallace applies it to the case of
specific characters, is incompatible with his argument that useless
generic characters may originally have been useful specific characters.
It can scarcely be questioned that the transmutation of a species into a
genus must, as a rule, have allowed time enough for a newly
acquired--i.e. peculiar specific-character--to show some signs of
undergoing degeneration, if, as supposed, the original cause of its
development and maintenance was withdrawn when the parent species began
to ramify into its species-progeny. Yet, as Darwin says, "it is
notorious that specific characters are more variable than generic[132]."
So that, upon the whole, I do not see how on grounds of general
reasoning it is logically possible to maintain Mr. Wallace's distinction
between specific and generic characters in respect of necessary utility.

    [132] _Origin of Species_, p. 122.

But now, and lastly, we shall reach the same conclusion if, discarding
all consideration of general principles and formal reasoning, we fasten
attention upon certain particular cases, or concrete facts. Thus, to
select only two illustrations within the limits of genera, it is a
diagnostic feature of the genus _Equus_ that small warty callosities
occur on the legs. It is impossible to suggest any useful function that
is now discharged by these callosities in any of the existing species of
the genus. If it be assumed that they must have been of some use to the
species from which the genus originally sprang, the assumption, it seems
to me, can only be saved by further assuming that in existing species of
the genus these callosities are in a vestigial condition--i. e. that in
the original or parent species they performed some function which is
now obsolete. But against these assumptions there lies the following
fact. The callosities in question are not similarly distributed through
all existing species of the genus. The horse has them upon all his four
legs, while other species have them only upon two. Therefore, if all
specific characters are necessarily due to natural selection, it is
manifest that these callosities are _not_ now vestigial: on the
contrary, they _must_ still be--or, at best, have recently been--of so
much importance to all existing species of the genus, that not only is
it a matter of selection-value to all these species that they should
possess these callosities; but it is even a matter of selection-value to
a horse that he should possess four of them, while it is equally a
matter of selection-value to the ass that he should possess only two.
Here, it seems to me, we have once more the doctrine of the necessary
utility of specific characters reduced to an absurdity; while at the
same time we display the incoherency of the distinction between specific
characters and generic characters in respect of this doctrine. For the
distinction in such a case amounts to saying that a generic character,
if evenly distributed among all the species, need not be an adaptive
character; whereas, if any one of the species presents it in a slightly
different form, the character must be, on this account, necessarily
adaptive. In other words, the uniformity with which a generic character
occurs among the species of the genus is taken to remove that character
from the necessarily useful class, while the absence of such uniformity
is taken as proof that the character must be placed within the
necessarily useful class. Which is surely no less a _reductio ad
absurdum_ with regard to the generic character than the one just
presented with regard to its variants as specific characters. And, of
course, this twofold absurdity is presented in all cases where a generic
character is unequally distributed among the constituent species of a
genus.

[Illustration: Fig. 4.--Lower Teeth of Orang (after Tomes).]

But here is an illustration of another class of cases. Mr. Tomes has
shown that the molar teeth of the Orang present an extraordinary and
altogether superfluous amount of attachment in their sockets--the fangs
being not only exceedingly long, and therefore deeply buried in the
jaw-bone, but also curving round one another, so as still further to
strengthen the whole[133]. In the allied genera of anthropoid apes there
is no such abnormal amount of attachment. Now, the question is, of what
conceivable use can it _ever_ have been, either to the existing genus,
or to its parent species, that such an abnormal amount of attachment
should obtain? It certainly is not required to prevent dislocation of
the teeth, seeing that in all allied genera, and even in man himself,
the amount of attachment is already so great that teeth will break
before they can be drawn by anything short of a dentist's forceps.
Therefore I conclude that this peculiarity in the dentition of the genus
must have arisen in its parent species by way of what Darwin calls a
"fluctuating variation," without utilitarian significance. And I adduce
it in the present connexion because the peculiarity is one which is
equally unamenable to a utilitarian explanation, whether it happens to
occur as a generic or a specific character.

    [133] _A Manual of Dental Anatomy_, p. 455.

Numberless similar cases might be quoted; but probably enough has now
been said to prove the inconsistency of the distinction which our
opponents draw between specific and all higher characters in respect of
utility. In point of fact, a very little thought is enough to show that
no such distinction admits of being drawn; and, therefore, that any one
who maintains the doctrine of utility as universal in the case of
specific characters, must in consistency hold to the same doctrine in
the case of generic and all higher characters. And the fact that our
opponents are unable to do this becomes a virtual confession on their
part of the futility of the generalization which they have
propounded[134].

    [134] It may be observed that this distinction was not propounded by
          Mr. Wallace--nor, so far as I am aware, by anybody else--until
          he joined issue with me on the subject of specific characters.
          Whether he has always held this important distinction between
          specific and generic characters, I know not; but, as
          originally enunciated, his doctrine of utility as universal
          was subject to no such limitation: it was stated
          unconditionally, as applying to all taxonomic divisions
          indifferently. The words have already been quoted on page 180;
          and, if the reader will turn to them, he may further observe
          that, prior to our discussion, Mr. Wallace made no allowance
          for the principle of correlation, which, as we have seen,
          furnishes so convenient a loop-hole of escape in cases where
          even the argument from our ignorance of possible utility
          appears absurd. In his latest work, however, he is much less
          sweeping in his statements. He limits his doctrine to the case
          of "specific characters" alone, and even with regard to them
          makes unlimited drafts upon the principle of correlation.

On what then do Mr. Wallace and his followers rely for their great
distinction between specific and all other characters in respect of
utility? This is the final and fundamental question which I must leave
these naturalists themselves to answer; for my whole contention is, that
it is unanswerable. But although I am satisfied that they have nothing
on which to base their generalization, it seems worth while to conclude
by showing yet one further point. And this is, that these naturalists
themselves, as soon as they quit merely abstract assertions and come to
deal with actual facts, contradict their own generalization. It is worth
while to show this by means of a few quotations, that we may perceive
how impossible it is for them to sustain their generalization in the
domain of fact.

As it is desirable to be brief, I will confine myself to quoting from
Mr. Wallace.

     "Colour may be looked upon as a necessary result of the highly
     complex chemical constitution of animal tissues and fluids. The
     blood, the bile, the bones, the fat, and other tissues have
     characteristic, and often brilliant colours, which we cannot
     suppose to have been determined for any special purpose as colours,
     since they are usually concealed. The external organs and
     integuments, would, by the same general laws, naturally give rise
     to a greater variety of colour[135]."

    [135] _Darwinism_, p. 297.

Surely comment is needless. Have the colour of external organs and
integuments nothing to do with the determining of specific distinctions
by systematists? Or, may we not rather ask, are there any other
"characters" which have had more to do with their delineation of animal
species? Therefore, if "the external organs and integuments naturally
give rise to a greater variety of colours," for non-utilitarian reasons,
than is the case with internal organs and tissues; while even the latter
present, for similarly non-utilitarian reasons, such variety and
intensity of colours as they do; must it not follow that, on the ground
of the "Laws of Growth" alone, Mr. Wallace has conceded the entire case
as regards "a large proportional number of specific characters" being
non-adaptive--"spontaneous" in their occurrence, and "meaningless" in
their persistence?

Once more:--

     "The enormously lengthened plumes of the bird of paradise and of
     the peacock, can, however, have no such use [i.e. for purposes of
     defence], but must be rather injurious than beneficial in the
     birds' ordinary life. The fact that they have been developed to so
     great an extent in a few species is an indication of such perfect
     adaptation to the conditions of existence, such complete success in
     the battle for life, that there is, in the adult male at all
     events, a surplus of strength, vitality, and growth-power, which is
     able to expend itself in this way without injury. That such is the
     case is shown by the great abundance of most of the species which
     possess these wonderful superfluities of plumage.... Why, in allied
     species, the development of accessory plumes has taken different
     forms, we are unable to say, except that it may be due to that
     individual variability which has served as a starting-point for so
     much of what seems to us strange in form, or fantastic in colour,
     both in the animal and vegetable world[136]."

    [136] _Darwinism_, pp. 292-3.

Here, again, one need only ask, How can such statements be reconciled
with the great dogma, "which is indeed a necessary deduction from the
theory of Natural Selection, namely, that none of the definite facts of
organic nature, no special organ, no characteristic form or marking can
exist, but which must now be, or once have been, _useful_"? Can it be
said that the plumes of a bird of paradise present "no characteristic
form," or the tail of a peacock "no characteristic marking"? Can it be
held that all the "fantastic colours," which Darwin attributes to sexual
selection, and all the "strange forms" in the vegetable world which
present no conceivable reference to adaptation, are to be ascribed to
"individual variability" without reference to utility, while at the same
time it is held, "as a necessary deduction from the theory of Natural
Selection," that _all_ specific characters must be "_useful_"? Or must
we not conclude that we have here a contradiction as direct as a
contradiction can well be[137]?

    [137] Since the above was written both Mr. Gulick and Professor
          Lloyd Morgan have independently noticed the contradiction.

Nor is it any more possible to reconcile these contradictory statements
by an indefinite extension of the term "correlation," than we found it
to be in the cases previously quoted. It might indeed be logically
possible, howsoever biologically absurd, to attribute the tail of a
peacock--with all its elaboration of structure and pattern of colour,
with all the drain that its large size and weight makes upon the vital
resources of the bird, with all the increased danger to which it exposes
the bird by rendering it more conspicuous, more easy of capture, &c.--to
correlation with some useful character peculiar to peacocks. But to say
that it is due to correlation with general "vitality," is merely to
discharge the doctrine of correlation of any assignable meaning.
Vitality, or "perfect adaptation to the conditions of existence," is
obviously a prime condition to the occurrence of a peacock's tail, as it
is to the occurrence of a peacock itself; but this is quite a different
thing from saying that the specific characters which are presented by a
peacock's tail, although useless in themselves, are correlated with some
other and useful specific characters of the same bird--as we saw in a
previous chapter with reference to secondary sexual characters in
general. Therefore, when Mr. Wallace comes to the obvious question why
it is that even in "allied species," which must be in equally "perfect
adaptation to the conditions of existence," there are no such "wonderful
superfluities of plumage," he falls back--as he previously fell back--on
whatever unknown _causes_ it may have been which produced the peacock's
tail, when the primary _condition_ to their operation has been furnished
by "complete success in the battle for life."

I have quoted the above passages, not so much for the sake of exposing
fundamental inconsistencies on the part of an adversary, as for the sake
of observing that they constitute a much truer exposition of "Darwinism"
than do the contradictory views expressed in some other parts of the
work bearing that title. For even if characters of so much size and
elaboration as the tail of a peacock, the plumes of a bird of paradise
&c., are admitted to be due to non-utilitarian causes, much more must
innumerable other characters of incomparably less size and elaboration
be mere "superfluities." Without being actually deleterious, "a large
proportional number of specific characters," whose utility is not
apparent, must _a fortiori_ have been due to "individual variation," to
"general laws which determine the production" of such characters--or, in
short, to some causes other than natural selection. And this, I say, is
a doctrine much more in harmony with "Darwinism" than is the
contradictory doctrine which I am endeavouring to resist.

But once again, and still more generally, after saying of "the delicate
tints of spring foliage, and the intense hues of autumn," that "as
colours they are unadaptive, and appear to have no more relation to the
well-being of plants themselves than do the colours of gems and
minerals," Mr. Wallace proceeds thus:--

     "We may also include in the same category those algae and fungi
     which have bright colours--the red snow of the Arctic regions, the
     red, green, or purple seaweeds, the brilliant scarlet, yellow,
     white or black agarics, and other fungi. All these colours are
     probably the direct results of chemical composition or molecular
     structure, and being thus normal products of the vegetable
     organism, need no special explanation from our present point of
     view; and the same remark will apply to the varied tints of the
     bark of trunks, branches and twigs, which are often of various
     shades of brown and green, or even vivid reds and yellows[138]."

    [138] _Darwinism_, p. 302.

Here, as Mr. Gulick has already observed, "Mr. Wallace seems to admit
that instead of useless specific characters being unknown, they are so
common and so easily explained by 'the chemical constitution of the
organism' that they claim no special attention[139]." And whatever
answer Mr. Wallace may make to this criticism, I do not see how he is to
meet the point at present before us--namely, that, upon his own showing,
there are in nature numberless instances of "characters which are
useless without being hurtful," and which nevertheless present absolute
"constancy." If, in order to explain the contradiction, he should fall
back upon the principle of correlation, the case would not be in any way
improved. For, here again, if the term correlation were extended so as
to include "the chemical constitution or the molecular structure of the
organism," it would thereby be extended so as to discharge all Darwinian
significance from the term.

    [139] _American Journal of Science_, Vol. XL. art. I. on _The
          Inconsistencies of Utilitarianism as the Exclusive Theory of
          Organic Evolution_.


_Summary._

I will conclude this discussion of the Utility question by
recapitulating the main points in an order somewhat different from that
in which they have been presented in the foregoing chapters. Such a
variation may render their mutual connexions more apparent. But it is
only to the main points that allusion will here be made, and, in order
the better to show their independent character, I will separately number
them.

       *       *       *       *       *

1. The doctrine of utility as universal, whether with respect to species
only or likewise with respect to specific characters, is confessedly an
_a priori_ doctrine, deduced by way of general reasoning from the theory
of natural selection.

2. Being thus founded exclusively on grounds of deduction, the doctrine
cannot be combated by any appeal to facts. For this question is not one
of fact: it is a question of reasoning. The treatment of our subject
matter is logical: not biological.

3. The doctrine is both universal and absolute. According to one form of
it _all_ species, and according to another form of it _all_ specific
characters, must _necessarily_ be due to the principle of utility.

4. The doctrine in both its forms is deduced from a definition of the
theory of natural selection as a theory, and the sole theory, of the
origin of _species_; but, as Professor Huxley has already shown, it does
not really follow, even from this definition, that all specific
_characters_ must be "necessarily useful." Hence the two forms of the
doctrine, although coincident with regard to species, are at variance
with one another in respect of specific characters. Thus far, of course,
I agree with Professor Huxley; but if I have been successful in showing
that the above definition of the theory of natural selection is
logically fallacious, it follows that the doctrine in both its forms is
radically erroneous. The theory of natural selection is not, accurately
speaking, a theory of the origin of species: it is a theory of the
origin and cumulative development of adaptations, to whatever order of
taxonomic division these may happen to belong. Thus the premisses of the
deduction which we are considering collapse: the principle of utility is
shown not to have any other or further reference to species, or to
specific characters, than it has to fixed varieties, genera, families,
&c., or to the characters severally distinctive of each.

5. But, quitting all such antecedent considerations, we next proceeded
to examine the doctrine _a posteriori_, taking the arguments which have
been advanced in favour of the doctrine, other than those which rest
upon the fallacious definition. These arguments, as presented by Mr.
Wallace, are two in number.

First, it is represented that natural selection must occupy the whole
field, because no other principle of change can be allowed to operate in
the presence of natural selection. Now I fully agree that this statement
holds as regards any principle of change which is deleterious, but I
cannot agree that it does so as regards any such principle which is
merely neutral. No reason has ever been shown why natural selection
should interfere with "indifferent" characters--to adopt Professor
Huxley's term--supposing such to have been produced by any of the
agencies which we shall presently have to name. Therefore this
argument--or rather assertion--goes for nothing.

Mr. Wallace's second argument is, that utility is the only principle
which can endow specific characters with their characteristic stability.
But this again is mere assertion. Moreover, it is assertion opposed
alike to common sense and to observable fact. It is opposed to common
sense, because it is obvious that any other principle would equally
confer stability on characters due to it, provided that its action is
constant, as Darwin expressly held. Again, this argument is opposed to
fact, because we know of thousands of cases where peculiar characters
are stable, which, nevertheless, cannot possibly be due to natural
selection. Of such are the Porto Santo rabbits, the niata cattle, the
ducks in St. James' Park, turkeys, dogs, horses, &c., and, in the case
of plants, wheat, cabbage, maize, &c., as well as all the hosts of
climatic varieties, both of animals and plants, in a state of nature.
Indeed, on taking a wide survey of the facts, we do not find that the
principle of utility is any better able to confer stability of character
than are many other principles, both known and unknown. Nay, it is
positively less able to do so than are some of these other principles.
Darwin gives two very probable reasons for this fact; but I need not
quote them a second time. It is enough to have seen that this argument
from stability or constancy is no less worthless than the previous one.
Yet these are the only two arguments of a corroborative kind which Mr.
Wallace adduces whereby to sustain his "necessary deduction."

6. At this point, therefore, it may well seem that we need not have
troubled ourselves any further with a generalization which does not
appear to have anything to support it. And to this view of the case I
should myself agree, were it not that many naturalists now entertain the
doctrine as an essential article of their Darwinian creed. Hence, I
proceeded to adduce considerations _per contra_.

Seeing that the doctrine in question can only rest on the assumption
that there is no cause other than natural selection which is capable of
originating any single species--if not even so much as any single
specific character--I began by examining this assumption. It was shown
first that, on merely antecedent grounds, the assumption is "infinitely
precarious." There is absolutely no justification for the statement that
in all the varied and complex processes of organic nature natural
selection is the only possible cause of specific change. But, apart
altogether from this _a priori_ refutation of the dogma, our analysis
went on to show that, in point of actual fact, there are not a few
well-known causes of high generality, which, while having no connexion
with the principle of utility, are demonstrably capable of originating
species and specific characters--if by "species" and "specific
characters" we are to understand organic types which are ranked as
species, and characters which are described as diagnostic of species.
Such causes I grouped under five different headings, viz. Climate, Food,
Sexual Selection, Isolation, and Laws of Growth. Sexual Selection and
Isolation are, indeed, repudiated by Mr. Wallace; but, in common I
believe with all biologists, he accepts the other three groups of causes
as fully adequate to produce such kinds and degrees of modification as
are taken to constitute specific distinction. And this is amply
sufficient for our present purposes. Besides, under the head of Sexual
Selection, it does not signify in the present connexion whether or not
we accept Darwin's theory on this subject. For, in any case, the facts
of secondary sexual characters are indisputable: these characters are,
for the most part, specific characters: and they cannot be explained by
the principle of utility. Even Mr. Wallace does not attempt to do so;
and the explanation which he does give is clearly incompatible with his
doctrine touching the necessarily life-serving value of all specific
characters. Lastly, the same has to be said of the Laws of Growth. For
we have just seen that on the grounds of this principle likewise Mr.
Wallace abandons the doctrine in question. As regards Isolation, much
more remains to be said in the ensuing portion of this work, while, as
regards Climatic Variation, there are literally innumerable cases where
changes of specific type are known to have been caused by this means.

7. To the latter class of cases, however, it will be objected that these
changes of specific type, although no doubt sufficiently "stable" so
long as the changed conditions remain constant, are found by experiment
not to be hereditary; and this clearly makes all the difference between
a true specific change and a merely fictitious appearance of it.

Well, in the first place, this objection can have reference only to the
first two of the five principles above stated. It can have no reference
to the last three, because of these heredity constitutes the very
foundation. This consideration ought to be borne in mind throughout. But
now, in the second place, even as regards changes produced by climate
and food, the reply is nugatory. And this for three reasons, as follows.

(_a_) No one is thus far entitled to conclude against the possible
transmission of acquired characters; and, so long as there is even so
much as a possibility of climatic (or any other admittedly
non-utilitarian) variations becoming in this way hereditary, the reply
before us merely begs the question.

(_b_) Even supposing, for the sake of argument, that acquired characters
can never in any case become congenital, there remains the strong
probability--sanctioned as such even by Weismann--that changed
conditions of life may not unfrequently act upon the material of
heredity itself, thus giving rise to specific changes which are from
the first congenital, though not utilitarian. Indeed, there are not a
few facts (Hoffmann's plants, Weismann's butterflies, &c.), which can
only be explained either in this way, or as above (_a_). And in the
present connexion it is immaterial which of these alternative
explanations we choose to adopt, seeing that they equally refute our
opponents' objection. And not only do these considerations--(_a_) and
(_b_)--refute this particular objection; they overturn on new and
independent grounds the whole of our opponents' generalization. For the
generalization is, that the principle of utility, acting through natural
selection, is "necessarily" the sole principle which can be concerned in
hereditary changes of specific type. But here we perceive both a
possibility (_a_) and a probability (_b_), if not indeed a certainty,
that quite other principles have been largely concerned in the
production of such changes.

(_c_) Altogether apart from these considerations, there remains a much
more important one. For the objection that fixed--or "stable"--climatic
varieties differ from true species in not being subject to heredity,
raises the question--What are we to understand by a "species"? This
question, which was thus far purposely left in abeyance, had now to be
dealt with seriously. For it would clearly be irrational in our
opponents to make this highly important generalization with regard to
species and specific characters, unless they are prepared to tell us
what they mean by species, and therefore by characters as specific. In
as far as there is any ambiguity on this point it makes entirely for
our side in the debate, because even any small degree of uncertainty
with regard to it would render the generalization in question
proportionally unsound. Yet it is notorious that no word in existence is
more vague, or more impossible to define, than the word "species." The
very same men who at one time pronounce their great generalization with
regard to species, at another time asseverate that "a species is not a
definite entity," but a merely abstract term, serving to denote this
that and the other organic type, which this that and the other
systematist regards as deserving such a title. Moreover it is
acknowledged that systematists differ among themselves to a wide extent
as to the kinds and degrees of peculiarity which entitle a given form to
a specific rank. Even in the same department of systematic work much
depends on merely individual taste, while in different departments
widely different standards of delimination are in vogue. Hence, our
_reductio ad absurdum_ consists in this--that whether a given form is to
be regarded as necessarily due to natural selection, and whether all its
distinctive characters are to be regarded as necessarily utilitarian
characters, will often depend on whether it has been described by
naturalist A or by naturalist B. There is no one criterion--there is not
even any one set of criteria--agreed upon by naturalists for the
construction of specific types. In particular, as regards the principle
of heredity, it is not known of one named species in twenty--probably
not in a hundred--whether its diagnostic characters are hereditary
characters; while, on the other hand, even in cases where experiment has
proved "constant varieties" to be hereditary--and even also
cross-sterile with allied varieties--it is only some three or four
living botanists who for these reasons advocate the elevation of such
varieties to the rank of species. In short, as we are not engaged on any
abstract question touching the principles on which species ought to have
been constituted by their makers, but upon the actual manner in which
they have been, the criterion of heredity must needs be disregarded in
the present discussion, as it has been in the work of systematists. And
the result of this is, that any objection to our introducing the facts
of climatic variation in the present discussion is excluded. In
particular, so far as any question of heredity is concerned, all these
facts are as assuredly as they are cogently relevant. It is perfectly
certain that there is "a large proportional number" of named
species--particularly of plants--which further investigation would
resolve into climatic varieties. With the advance of knowledge, "bad
species" are always increasing at the expense of "good species," so that
we are now justified in concluding with Kerner, Häckel, and other
naturalists best qualified to speak on this subject, that if we could
know as much about the past history and present relations of the
remaining good species as we do about the bad, all the former, without
exception, would become resolved into the latter. In point of fact, and
apart altogether from the inductive experience on which this conclusion
is based, the conclusion follows "as a necessary deduction" from the
general theory of descent. For this theory essentially consists in
supposing either the past or the present existence of intermediate
varietal forms in all cases, with the consequence that "good species"
serve merely to mark _lacunae_ in our knowledge of what is everywhere a
finely graduated process of transmutation. Hence, if we place this
unquestionably "necessary deduction" from the general theory of descent
side by side with the alleged "necessary deduction" from the theory of
natural selection, we cannot avoid the following absurdity--Whether or
not a given form is to be regarded as necessarily due to natural
selection, and all its characters necessarily utilitarian, is to be
determined, and determined solely, by the mere accident of our having
found, or not having found, either in a living or in a fossil state, its
varietal ancestry.

8. But this leads us to consider the final and crowning incongruities
which have been dealt with in the present chapter. For here we have
seen, not only that our opponents thus draw a hard and fast line between
"varieties" and "species" in regard to "necessary origin" and "necessary
utility," but that they further draw a similar line between "species"
and "genera" in the same respects. Yet, in accordance with the general
theory of evolution, it is plainly as impossible to draw any such line
in the one case as it is to do so in the other. Just as fixed varieties
are what Darwin called "incipient species," so are species incipient
genera, genera incipient families, and so on. Evolutionists must believe
that the process of evolution is everywhere the same. Nevertheless,
while admitting all this, the school of Huxley contradicts itself by
alleging some unintelligible exception in the case of "species," while
the school of Wallace presses this exception so as to embrace "specific
characters." Indeed Mr. Wallace, while maintaining that all specific
characters must necessarily be useful, maintains at the same time that
any number of varietal characters on the one hand, and a good half of
generic characters on the other, are probably useless. Thus he
contradicts his argument from the "constancy of specific characters"
(seeing that generic characters are still more constant), as later on we
saw that he contradicts his deductive generalization touching their
necessary utility, by giving a non-utilitarian explanation of whole
multitudes of specific characters. I need not, however, again go over
the ground so recently traversed; but will conclude by once more
recurring to the only explanation which I have been able to devise of
the otherwise inexplicable fact, that in regard to this subject so many
naturalists still continue to entangle themselves in the meshes of
absurdity and contradiction.

       *       *       *       *       *

The only conceivable explanation is, that these naturalists have not yet
wholly divested themselves of the special creation theory. Although
professing to have discarded the belief that "species" are "definite
entities," differing in kind from "varieties" on the one hand and from
"genera" on the other, these writers are still imbued with a vague
survival of that belief. They well know it to belong to the very essence
of their new theory that "species" are but "pronounced varieties," or,
should we prefer it, "incipient genera"; but still they cannot
altogether escape the pre-Darwinian conception of species as organic
units, whose single mode of origin need not extend to other taxonomic
groups, and whose characters therefore present some exceptional
significance to the scientific naturalist. So to speak, such divinity
doth still hedge a species, that even in the very act of declaring it
but an idol of their own creation, these naturalists bow before their
fetish as something that is unique--differing alike in its origin and in
its characters from the varieties beneath and the genera above. The
consequence is that they have endeavoured to reconcile these
incompatible ideas by substituting the principle of natural selection
for that of super-natural creation, where the particular case of
"species" is concerned. In this way, it vaguely seems to them, they are
able to save the doctrine of some one mode of origin as appertaining to
species, which need not "necessarily" appertain to any other taxonomic
division. All other such divisions they regard, with their pre-Darwinian
forefathers, as merely artificial constructions; but, likewise with
these forefathers, they look upon species as natural divisions, proved
to be such by a single and necessary mode of origin. Hence, Mr. Wallace
expressly defines a species with reference to this single and necessary
mode of origin (_see_ above, p. 235), although he must be well aware
that there is no better, or more frequent, proof of it in the case of
species, than there is in that of somewhat less pronounced types on the
one hand (fixed varieties), or of more pronounced types on the other
(genera, families, &c.). Hence, also, the theory of natural selection is
defined as _par excellence_ a theory of the origin of species; it is
taken as applying to the particular case of the origin of species in a
peculiarly stringent manner, or in a manner which does not apply to the
origin of any other groups. And I believe that an important accessory
reason of the continuance of this view for more than thirty years after
the publication of the _Origin of Species by means of Natural
Selection_, is to be found in the title of that work. "Natural
Selection" has thus become verbally associated with "Origin of Species,"
till it is thoughtlessly felt that, in some way or another, natural
selection must have a peculiar reference to those artificially
delineated forms which stand anywhere between a fixed variety and a
so-called genus. This verbal association has no doubt had the effect of
still further preserving the traditional halo of mystery which clings to
the idea of a "species." Hence it comes that the title which Darwin
chose--and, looking to the circumstances of the time, wisely chose--for
his great work, has subsequently had the effect of fostering the very
idea which it was the object of that work to dissipate, namely, that
species are peculiar entities, which differ more or less in origin or
kind from all other taxonomic groups. The full title of this work
is--_The Origin of Species by means of Natural Selection: or the
Preservation of Favoured Races in the Struggle for Life_. Now, supposing
that instead of this its author had chosen some such title as the
following:--_The Origin of Organic Types by means of Adaptive Evolution:
or Survival of the Fittest Forms in the Struggle for Life_. Of course
this would have been a bad substitute from various points of view; but
could any objection have been urged against it from our present point of
view? I do not see that there could. Yet, if such had been the title, I
have little doubt that we should never have heard of those great
generalizations with regard to species and specific characters, the
futility of which it has been the object of these chapters to expose.

       *       *       *       *       *

In conclusion, it only remains to reiterate that in thus combating what
appears to me plainly erroneous deductions from the theory of natural
selection, I am in no wise combating that theory itself. On the
contrary, I hope that I am rendering it no unimportant service by
endeavouring to relieve it of a parasitic growth--an accretion of false
logic. Regarding as I do the theory of natural selection as, primarily,
a theory of the origin (or cumulative development) of adaptations, I see
in merely non-adaptive characters--be they "specific" or other--a
comparatively insignificant class of phenomena, which may be due to a
great variety of incidental causes, without any further reference to the
master-principle of natural selection than that in the presence of this
principle none of these non-adaptive characters can be actively
deleterious. But that there may be "any number of indifferent
characters" it is no part of the theory of natural selection to deny;
and all attempts to foist upon it _a priori_ "deductions" opposed alike
to the facts of nature and to the logic of the case, can only act to the
detriment of the great generalization which was expressly guarded from
such fallacies by the ever-careful judgement of Darwin.




APPENDICES AND NOTES




APPENDIX I.

ON PANMIXIA.


There are several points of considerable theoretical importance
connected with Panmixia, which were omitted from the text, in order to
avoid distracting attention from the main issue which is there under
consideration. These side issues may now be appropriately presented in
the form in which they were published in _Nature_, March 13, 1890[140].
After stating, in almost the same words, what has already been said in
Chapter X, this paper proceeds, with the exception of a few verbal
alterations, as follows.

    [140] Vol. xli. p. 438.

     "There is, however, one respect in which Professor Weismann's
     statement of the principle of panmixia differs from that which was
     considered by Mr. Darwin; and it is this difference of
     statement--which amounts to an important difference of theory--that
     I now wish to discuss.

     "The difference in question is, that while Professor Weismann
     believes the cessation of selection to be capable of inducing
     degeneration down to the almost complete disappearance of a
     rudimentary organ, I have argued that, _unless assisted by some
     other principle_, it can at most only reduce the degenerating organ
     to considerably above one-half its original size--or probably not
     through so much as one-quarter. The ground of this argument (which
     is given in detail in the _Nature_ articles of 1873-1874) is, that
     panmixia depends for its action upon fortuitous variations round an
     ever-diminishing average--the average thus diminishing because it
     is no longer _sustained_ by natural selection. But although no
     longer sustained by _natural selection_, it does continue to be
     sustained by _heredity_; and therefore, as long as the force of
     heredity persists unimpaired, fortuitous variations alone--or
     variation which is no longer controlled by natural
     selection--cannot reduce the dwindling organ to so much as one-half
     of its original size; indeed, as above foreshadowed, the balance
     between the positive force of heredity and the negative effects of
     promiscuous variability will most likely be arrived at above the
     middle line thus indicated. Only if for any reason the force of
     heredity begins to fail can the average round which the cessation
     of selection works become a progressively diminishing average. In
     other words, so long as the original force of heredity as regards
     the useless organ remains unimpaired, the mere withdrawal of
     selection cannot reduce the organ much below the level of
     efficiency above which it was previously _maintained_ by the
     _presence_ of selection. If we take this level to be 80 or 90 per
     cent. of the original size, cessation of selection will reduce the
     organ through the 10 or 20 per cent., and there leave it
     fluctuating about this average, unless for any reason the force of
     heredity begins to fail--in which case, of course, the average will
     progressively fall in proportion to the progressive weakening of
     this force.

     "Now, according to my views, the force of heredity under such
     circumstances is always bound to fail, and this for two reasons. In
     the first place, it must usually happen that when an organ becomes
     useless, natural selection as regards that organ will not only
     _cease_, but become _reversed_. For the organ is now absorbing
     nutriment, causing weight, occupying space, and so on, _uselessly_.
     Hence, even if it be not also a source of actual danger, 'economy
     of growth' will determine a reversal of selection against an organ
     which is now not merely useless, but deleterious. And this
     degenerating influence of the reversal of selection will throughout
     be assisted by the cessation of selection, which will now be always
     acting round a continuously sinking average. Nevertheless, a point
     of balance will eventually be reached in this case, just as it was
     in the previous case where the cessation of selection was supposed
     to be working alone. For, where the reversal of selection has
     reduced the diminishing organ to so minute a size that its presence
     is no longer a source of detriment to the organism, the cessation
     of selection will carry the reduction a small degree further; and
     then the organ will remain as a 'rudiment.' And so it will remain
     permanently, unless there be some further reason why the still
     remaining force of heredity should be abolished. This further (or
     second) reason I found in the consideration that, however enduring
     we may suppose the force of heredity to be, we cannot suppose that
     it is actually everlasting; and, therefore, that we may reasonably
     attribute the eventual disappearance of rudimentary organs to the
     eventual failure of heredity itself. In support of this view there
     is the fact that rudimentary organs, although very persistent, are
     not everlasting. That they should be very persistent is what we
     should expect, if the hold which heredity has upon them is great in
     proportion to the time during which they were originally useful,
     and thus firmly stamped upon the organization by natural selection
     causing them to be strongly inherited in the first instance. For
     example, we might expect that it would be more difficult finally to
     eradicate the rudiment of a wing than the rudiment of a feather;
     and accordingly we find it a general rule that long-enduring
     rudiments are rudiments of organs distinctive of the higher
     taxonomic divisions--i.e. of organs which were longest in building
     up, and therefore longest sustained in a state of working
     efficiency.

     "Thus, upon the whole, my view of the facts of degeneration remains
     the same as it was when first published in these columns seventeen
     years ago, and may be summarized as follows.

     "The cessation of selection when working alone (as it probably does
     during the first centuries of its action upon structures or colours
     which do not entail any danger to, or perceptible drain upon, the
     nutritive resources of the organism) cannot cause degeneration
     below, probably, some 10 to 20 per cent. But if from the first the
     cessation of selection has been assisted by the _reversal_ of
     selection (on account of the degenerating structure having
     originally been of a size sufficient to entail a perceptible drain
     on the nutritive resources of the organism, having now become a
     source of danger, and so forth), the two principles acting together
     will continue to reduce the ever-diminishing structure down to the
     point at which its presence is no longer a perceptible disadvantage
     to the species. When that point is reached, the reversal of
     selection will terminate, and the cessation of selection will not
     then be able of itself to reduce the organ through more than at
     most a very few further percentages of its original size. But,
     after this point has been reached, the now total absence of
     selection, either for or against the organ, will sooner or later
     entail this further and most important consequence, a failure of
     heredity as regards the organ. So long as the organ was of use, its
     efficiency was constantly _maintained_ by the _presence_ of
     selection--which is merely another way of saying that selection was
     constantly maintaining the force of heredity as regards that organ.
     But as soon as the organ ceased to be of use, selection ceased to
     maintain the force of heredity; and thus, sooner or later, that
     force began to waver or fade. Now it is this wavering or fading of
     the force of heredity, thus originally due to the cessation of
     selection, that in turn co-operates with the still continued
     cessation of selection in reducing the structure below the level
     where its reduction was left by the actual reversal of selection.
     So that from that level downwards the cessation of selection, and
     the consequent failing of heredity, act and react in their common
     work of causing obsolescence. In the case of newly added
     characters, the force of heredity will be less than in that of more
     anciently added characters; and thus we can understand the long
     endurance of 'vestiges' characteristic of the higher taxonomic
     divisions, as compared with those characteristic of the lower. But
     in all cases, if time enough be allowed under the cessation of
     selection, the force of heredity will eventually fall to zero, when
     the hitherto obsolescent structure will finally become obsolete. In
     cases of newly added and comparatively trivial characters, with
     regard to which reversal of selection is not likely to take place
     (e.g. slight differences of colour between allied species),
     cessation of selection is likely to be very soon assisted by a
     failure in the force of heredity; seeing that such newly added
     characters will not be so strongly inherited as are the more
     ancient characters distinctive of higher taxonomic groups.

     "Let us now turn to Weismann's view of degeneration. First of all,
     he has omitted to perceive that 'panmixia' alone (if unassisted
     either by reversed selection or an inherent diminishing of the
     force of heredity) cannot reduce a functionless organ to the
     condition of a _rudiment_. Therefore he everywhere represents
     panmixia (or the mere _cessation_ of selection) as of itself
     sufficient to cause degeneration, say from 100 to 5, instead of
     from 100 to 90 or 80, which, for the reasons above given, appeared
     (and still appears) to me about the most that this principle can
     accomplish, so long as the original force of heredity continues
     unimpaired. No doubt we have here what must be regarded as a mere
     oversight on the part of Professor Weismann; but the oversight is
     rendered remarkable by the fact that he _does_ invoke the aid of
     reversed selection _in order to explain the final disappearance of
     a rudiment_. Yet it is self-evident that the reversal of selection
     must be much more active during the initial than during the final
     stages of degeneration, seeing that, _ex hypothesi_, the greater
     the degree of reduction which has been attained the less must be
     the detriment arising from any useless expenditure of nutrition,
     &c.

     "And this leads me to a second oversight in Professor Weismann's
     statement, which is of more importance than the first. For the
     place at which he does invoke the assistance of reversed selection
     is exactly the place at which reversed selection must necessarily
     have ceased to act. This place, as already explained, is where an
     obsolescent organ has become rudimentary, or, as above supposed,
     reduced to 5 per cent. of its original size; and the reason why he
     invokes the aid of reversed selection at this place is in order to
     save his doctrine of 'the stability of germ-plasm.' That the force
     of heredity should finally become exhausted if no longer
     _maintained_ by the _presence_ of selection, is what Darwin's
     theory of perishable gemmules would lead us to expect, while such a
     fact would be fatal to Weismann's theory of an imperishable
     germ-plasm. Therefore he seeks to explain the eventual failure of
     heredity (which is certainly a fact) by supposing that after the
     point at which the cessation of selection alone can no longer act
     (and which his first oversight has placed some 80 per cent. too
     low), the reversal of selection will begin to act directly against
     the force of heredity as regards the diminishing organ, until such
     direct action of reversed selection will have removed the organ
     altogether. Or, in his own words, 'The complete disappearance of a
     rudimentary organ can only take place by the operation of natural
     selection; this principle will lead to its diminution, inasmuch as
     the disappearing structure takes the place and the nutriment of
     other useful and important organs.' That is to say, the
     rudimentary organ finally disappears, not because the force of
     heredity is finally exhausted, but because natural selection has
     begun to utilize this force against the continuance of the
     organ--always picking out those congenital variations of the organ
     which are of smallest size, and thus, by its now _reversed_ action,
     _reversing_ the force of heredity as regards the organ.

     "Now the oversight here is in not perceiving that the smaller the
     disappearing structure becomes, the less hold must 'this principle'
     of reversed selection retain upon it. As above observed, during the
     earlier stages of reduction (or while co-operating with the
     cessation of selection) the reversal of selection will be at its
     _maximum_ of efficiency; and, as the process of diminution
     continues, a point must eventually be reached at which the reversal
     of selection can no longer act. Take the original mass of a now
     obsolescent organ in relation to that of the entire organism of
     which it then formed a part to be represented by the ratio 1:100.
     For the sake of argument we may assume that the mass of the
     organism has throughout remained constant, and that by 'mass' in
     both cases is meant capacity for absorbing nutriment, causing
     weight, occupying space, and so forth. Now, we may further assume
     that when the mass of the organ stood to that of its organism in
     the ratio of 1:100, natural selection was strongly reversed with
     respect to the organ. But when this ratio fell to 1:1000, the
     activity of such reversal must have become enormously diminished,
     even if it still continued to exercise any influence at all. For we
     must remember, on the one hand, that the reversal of selection can
     only act as long as the presence of a diminishing organ continues
     to be so injurious that variations in its size are matters of life
     and death in the struggle for existence; and, on the other hand,
     that natural selection in the case of the diminishing organ does
     not have reference to the presence and the absence of the organ,
     but only to such variations in its mass as any given generation may
     supply. Now, the process of reduction does not end even at 1:1000.
     It goes on to 1:10,000, and eventually 1:∞. Consequently, however
     great our faith in natural selection may be, a point must
     eventually come for all of us at which we can no longer believe
     that the reduction of an obsolescent organ is due to reversed
     selection. And I cannot doubt that if Professor Weismann had
     sufficiently considered the matter, he would not have committed
     himself to the statement that 'the complete disappearance of a
     rudimentary organ can only take place by the operation of natural
     selection.'

     "According to my view, the complete disappearance of a rudimentary
     organ can only take place by the _cessation_ of natural selection,
     which permits the eventual exhaustion of heredity, when heredity is
     thus simply left to itself. During all the earlier stages of
     reduction, the cessation of selection was assisted in its work by
     the reversal of selection; but when the rudiment became too small
     for such assistance any longer to be supplied, the rudiment
     persisted in that greatly reduced condition until the force of
     heredity with regard to it was eventually worn out. This appears to
     me, as it appeared in 1873, the only reasonable conclusion that can
     be drawn from the facts. And it is because this conclusion is fatal
     to Professor Weismann's doctrine of the permanent 'stability' of
     germ-plasm, while quite in accordance with all theories which
     belong to the family of pangenesis, that I deem the facts of
     degeneration of great importance as tests between these rival
     interpretations of the facts of heredity. It is on this account
     that I have occupied so much space with the foregoing discussion;
     and I shall be glad to ascertain whether any of the followers of
     Professor Weismann are able to controvert these views.

                                                "GEORGE J. ROMANES."

     "P.S.--Since the above article was sent in, Professor Weismann has
     published in these columns (February 6) his reply to a criticism by
     Professor Vines (October 24, 1889). In this reply he appears to
     have considerably modified his views on the theory of degeneration;
     for while in his Essays he says (as in the passage above quoted)
     that 'the complete disappearance of a rudimentary organ can only
     take place by the operation of natural selection'--i.e. only by the
     _reversal_ of selection,--in his reply to Professor Vines he says,
     'I believe that I have proved that organs no longer in use become
     rudimentary, and must finally disappear, solely by 'panmixia'; not
     through the direct action of disuse, but because natural selection
     no longer sustains their standard structure'--i.e. solely by the
     _cessation_ of selection. Obviously, there is here a flat
     contradiction. If Professor Weismann now believes that a
     rudimentary organ 'must finally disappear _solely_' through the
     _withdrawal_ of selection, he has abandoned his previous belief
     that 'the complete disappearance of a rudimentary organ can _only_
     take place by the _operation_ of selection.' And this change of
     belief on his part is a matter of the highest importance to his
     system of theories as a whole, since it betokens a surrender of his
     doctrine of the 'stability' of germ-plasm--or of the virtually
     everlasting persistence of the force of heredity, and the
     consequent necessity for a reversal of this force itself (by
     natural selection placing its premium on _minus_ instead of on
     _plus_ variations), in order that a rudimentary organ should
     finally disappear. In other words, it now seems he no longer
     believes that the force of heredity in one direction (that of
     sustaining a rudimentary organ) can only be abolished by the active
     influence of natural selection determining this force in the
     opposite direction (that of removing a rudimentary organ). It seems
     he now believes that the force of heredity, if merely left to
     itself by the withdrawal of natural selection altogether, will
     sooner or later become exhausted through the mere lapse of time.
     This, of course, is my own theory of the matter as originally
     published in these columns; but I do not see how it is to be
     reconciled with Professor Weismann's doctrine of so high a degree
     of stability on the part of germ-plasm, that we must look to the
     Protozoa and the Protophyta for the original source of congenital
     variations as now exhibited by the Metazoa and Metaphyta.
     Nevertheless, and so far as the philosophy of degeneration is
     concerned, I shall be very glad if (as it now appears) Professor
     Weismann's more recent contemplation has brought his principle of
     panmixia into exact coincidence with that of my cessation of
     selection."

Before passing on it may here be noted that, to any one who believes in
the inheritance of acquired characters, there is open yet another
hypothetical cause of degeneration, and one to which the final
disappearance of vestigial organs may be attributed. Roux has shown in
his work on _The Struggle for Existence between Parts of an Organism_
that the principle of selection must operate in every constituent
tissue, and as between every constituent cell of which an organism is
composed. Now, if an organ falls into disuse, its constituent cells
become worsted in their struggles with other cells in the organism.
Hence, degeneration of the disused organ may progressively increase,
quite independently of any struggle for existence on the part of the
organism as a whole. Consequently, degeneration may proceed without any
reference to the principle of "economized nutrition"; and, if it does
so, and if the effects of its doing so are transmitted from generation
to generation, the disused organ will finally disappear by means of
Roux's principle.

The long communication above quoted led to a still longer correspondence
in the pages of _Nature_. For Professor Ray Lankester wrote[141] to
impugn the doctrine of panmixia, or cessation of selection, _in toto_,
arguing with much insistence that "cessation of selection must be
supplemented by economy of growth in order to produce the results
attributed to panmixia." In other words, he denied that panmixia alone
can cause degeneration in any degree at all; at most, he said, it can be
but "a condition," or "a state," which occurs when an organ or part
ceases to be useful, and therefore falls under the degenerating
influence of active causes, such as economy of nutrition. Or, in yet
other words, he refused to recognize that any degenerative process can
be due to natural selection as merely withdrawn: only when, besides
being _withdrawn_, natural selection is _reversed_, did he regard a
degenerative process as possible. As a result of the correspondence,
however, he eventually[142] agreed that, if the "birth-mean" of an
organ, in respect either of size or complexity of structure, be lower
than the "selection-mean" while the organ is useful (a fact which he
does not dispute); then, if the organ ceases to be useful, it will
degenerate by the withdrawal of selection alone. Which, of course, is
merely a re-statement of the doctrine of panmixia, or cessation of
selection, in somewhat varied terminology--provided that the birth-mean
be taken over a number of generations, or not only over a few following
the selection-mean of the structure while still in its highest state of
efficiency. For the sake of brevity I will hereafter speak of these "few
following" generations by the term of "first generations."

    [141] _Nature_, vol. xli. p. 486.

    [142] _Ibid._ vol. xlii. p. 52.

It remains to consider the views of Professor Lloyd Morgan upon the
subject. In my opinion he is the shrewdest, as well as the most logical
critic that we have in the field of Darwinian speculation; therefore, if
possible, I should like to arrive at a full agreement with him upon this
matter. His latest utterance with regard to it is as follows:--

     "To account for the diminution of organs or structures no longer of
     use, apart from any inherited effects of disuse, Mr. Romanes has
     invoked the Cessation of Selection; and Mr. Francis Galton has, in
     another connexion, summarized the effects of this cessation of
     selection in the convenient phrase 'Regression to Mediocrity.' This
     is the Panmixia of Professor Weismann and his followers; but the
     phrase regression to mediocrity through the cessation of selection
     appears to me preferable. It is clear that so long as any organ or
     structure is subject to natural selection through elimination, it
     is, if not actually undergoing improvement, kept at a high standard
     of efficiency through the elimination of all those individuals in
     which the organ in question falls below the required standard. But
     if, from change in the environment or any other cause, the
     character in question ceases to be subject to selection,
     elimination no longer takes place, and the high standard will no
     longer be maintained. There will be reversion to mediocrity. The
     probable amount of this reversion is at present a matter under
     discussion[143]."

    [143] _Presidential Address to the Bristol Naturalists' Society_,
          1891.

So far, then, Professor Lloyd Morgan is in complete agreement with
previous writers upon the subject. He does not doubt that the cessation
of selection must always be a cause of degeneration: the only question
is as to the _potency_ of this cause, or the _amount_ of degeneration
which it is capable of effecting.

Taking, first, the case of bulk or size of an organ, as distinguished
from its organization or complexity, we have seen that Weismann
represents the cessation of selection--even if working quite alone, or
without any assistance from the reversal of selection--to be capable of
reducing a fully developed organ to the state of a rudiment, or even, if
we take his most recent view, of abolishing the organ _in toto_.

Professor Lloyd Morgan, on the other hand, does not think that the
cessation of selection alone can cause reduction further than the level
of "mediocrity" in the first generations--or, which is much the same
thing, further than the difference between the "birth-mean" and the
"selection-mean" of the first generations. This amount of reduction he
puts at 5 per cent., as "a very liberal estimate."

Here, then, we have three estimates of the amount of degeneration which
can be produced by panmixia alone, where mere size or bulk of an organ
is concerned--say, 3 to 5 per cent., 10 to 20 per cent., and 95 per
cent. to 0. At first sight, these differences appear simply ludicrous;
but on seeking for the reasons of them, we find that they are due to
different views touching the manner in which panmixia operates. The
oversights which have led to Weismann's extremely high estimate have
already been stated. The reason of the difference between the extremely
low estimate of Professor Lloyd Morgan, as compared with my own
intermediate one, is, that he supposes the power of panmixia to become
exhausted as soon as the level of mediocrity of the first generations
has become the general level in succeeding generations. In my view,
however, the level of mediocrity is itself a sinking level in
successive generations, with the result that there is no reason why the
reducing power of panmixia should ever become exhausted, save that the
more reduction it effects the greater is the force of heredity which
remains to be overcome, as previously explained. Thus the only question
between Professor Lloyd Morgan and myself is--Does the level of
mediocrity fall in successive generations under the cessation of
selection, or does it remain permanently where it used to be under the
presence of selection? Does the "birth-mean" remain constant throughout
any number of generations, notwithstanding that the sustaining influence
of selection has been withdrawn; or does it progressively sink as a
consequence of such withdrawal?

In order to answer this question we had better begin by considering now
the case of organization of structure, as distinguished from mere size
of structure. Take any case where a complex organ--such as a compound
eye--has been slowly elaborated by natural selection, and is it not
self-evident that, when natural selection is withdrawn, the complex
structure will deteriorate? In other words, the level of mediocrity, say
in the hundred thousandth generation after the sustaining influence of
natural selection has been withdrawn, will not be so high as it was in
the first generations. For, by hypothesis, there is now no longer any
elimination of unfavourable variations, which may therefore perpetuate
themselves as regards any of the parts of this highly complex mechanism;
so that it is only a matter of time when the mechanism must become
disintegrated. I can scarcely suppose that any one who considers the
subject will question this statement, and therefore I will not say
anything that might be said in the way of substantiating it. But, if the
statement be assented to, it follows that there is no need to look for
any cause of deterioration, further than the withdrawal of selection--or
cessation of the principle which (as we are supposing) had hitherto
been the sole means of maintaining efficient harmony among all the
independently variable parts of the highly complex structure.

Now, I hold that the same thing is true, though in a lesser degree, as
regards degeneration of size. That there is no difference _in kind_
between the two cases, Professor Lloyd Morgan implicitly allows; for
what he says is--

     "In any long-established character, such as wing-power in birds,
     brain-development, the eyes of crustacea, &c., no shortcomer in
     these respects would have been permitted by natural selection to
     transmit his shortcomings for hundreds of generations. All tendency
     to such shortcomings would, one would suppose, have been bred out
     of the race. If after this long process of selection there still
     remains a strong tendency to deterioration, this tendency demands
     an explanation[144]."

    [144] _Presidential Address to the Bristol Naturalists' Society_,
          1891.

Here, then, deterioration as to size of structure (wings of birds), and
deterioration as to complexity of structure (brain and eyes) are
expressly put upon the same footing. Therefore, if in the latter case
the "tendency to deterioration" does not "demand an explanation," beyond
the fact that the hitherto maintaining influence has been withdrawn,
neither is any such further explanation demanded in the former case.
Which is exactly my own view of the matter. It is also Mr. Galton's
view. For although, in the passage formerly quoted, Professor Lloyd
Morgan appears to think that by the phrase "Regression to Mediocrity"
Mr. Galton means to indicate that panmixia can cause degeneration only
as far as the mediocrity level of the first generations, this, in point
of fact, is not what Galton means, nor is it what he says. The phrase in
question occurs "in another connexion," and, indeed, in a different
publication. But where he expressly alludes to the cessation of
selection, this is what he says. The italics are mine.

     "A special cause may be assigned for the effects of use in causing
     hereditary _atrophy_ of disused parts. It has already been shown
     that all exceptionally developed organs tend to deteriorate:
     consequently, those that are not _protected_ by selection will
     _dwindle_. The level of muscular efficiency in the wing of a
     strongly flying bird [curiously enough, the same case that is
     chosen by Professor Lloyd Morgan to illustrate his opposite view],
     is like the level of water in the leaky vessel of a Danaid, only
     secured to the race by _constant effort_, so to speak. _Let the
     effort be relaxed ever so little, and the level immediately
     falls[145]._"

    [145] _A Theory of Heredity_, Journal of Anthropological Institute,
          1875. Vol. v. p. 345.

I take it, then, that the burden of proof lies with Professor Lloyd
Morgan to show why the withdrawal of selection is _not_ sufficient to
account for degeneration any further than the mediocrity-level in the
former presence of selection. Why does "the strong tendency[146] to
deterioration demand an explanation," further than the fact that when
all variations below the average in every generation are allowed to
survive, they must gradually lower the average itself through a series
of generations? To answer that any such tendency "would have been bred
out of the race" by the previous action of selection, is to suppose that
the function of selection is at an end when once it has built up a
structure to the highest point of working efficiency,--that the presence
of selection is no longer required to _maintain_ the structure at that
point. But it is enough to ask in reply--Why, under the cessation of
selection, does _complexity_ of structure degenerate so much more
rapidly than _size_ of structure? Why is it, for instance, that "the
eyes of crustacea" in dark caves have entirely disappeared, while their
foot-stalks (when originally present) still remain? Can it be maintained
that "for hundreds of generations" natural selection was more intent on
developing the foot-stalks than the eyes which were mounted upon
them--so that while the latter were left by selection with "a strong
tendency to deterioration," the former have had this tendency "bred out
in the race"[147]?

    [146] No one has supposed that the tendency need be "strong": it has
          only to be persistent.

    [147] Of course it must be observed that degeneration of complexity
          involves also degeneration of size, so that a more correct
          statement of the case would be--Why, under the cessation of
          selection, does an organ of extreme complexity degenerate much
          more rapidly than one of much less complexity? For example,
          under domestication the brains of rabbits and ducks appear to
          have been reduced in some cases by as much as 50 per cent.
          (Darwin, and Sir J. Crichton Browne.) But if it is possible to
          attribute this effect--or part of it--to an artificial
          selection of stupid animals, I give in the text an example
          occurring under nature. Many other cases, however, might be
          given to show the general rule, that under cessation of
          selection complexity of structure degenerates more
          rapidly--and also more thoroughly--than size of it. This, of
          course, is what Mr. Galton and I should expect, seeing that
          the more complex a structure the greater are the number of
          points for deterioration to invade when the structure is no
          longer "protected by selection." (On the other hand, of
          course, this fact is opposed to the view that degeneration of
          useless structures below the "birth-mean" of the first
          generations, is exclusively due to the reversal of selection;
          for economy of growth, deleterious effect of weight, and so
          forth, ought to affect size of structure _much more_ than
          complexity of it.) But I choose the above case, partly because
          Professor Lloyd Morgan has himself alluded to "the eyes of
          crustacea," and partly because Professor Ray Lankester has
          maintained that the loss of these eyes in dark caves is due to
          the reversal of selection, as distinguished from the cessation
          of it. In view of the above parenthesis it will be seen that
          the point is not of much importance in the present connexion;
          but it appears to me that cessation of selection must here
          have had at least the larger share in the process of atrophy.
          For while the economy of nutrition ought to have removed the
          relatively large _foot-stalks_ as rapidly as the _eyes_, I
          cannot see that there is any advantage, other than the economy
          of nutrition, to be gained by the rapid loss of hard-coated
          _eyes_, even though they have ceased to be of use.

To sum up. There is now no question in any quarter touching the fact
that panmixia, or the cessation of selection, is a true cause of
degeneration. The only question is as to the amount of degeneration
which it is able to effect when not assisted by the reversal of
selection, or any other cause of degeneration. Moreover, even with
regard to this question of amount, there is no doubt on any side that
panmixia alone causes degeneration _more rapidly_ where it has to do
with complexity of organization, than it does where it is concerned with
a mere reduction of mass.

The question as to the amount of degeneration that is caused by the
cessation of selection alone is without any practical importance where
species in a state of nature are concerned, because here the cessation
of selection is probably always associated more or less with the
reversal of it; and it is as impossible as it is immaterial to determine
the relative shares which these two co-operating principles take in
bringing about the observed results. But where organisms in a state of
domestication are concerned, the importance of the question before us is
very great. For if the cessation of selection alone is capable of
reducing an organ through 10 or 12 per cent. of its original size,
nearly all the direct evidence on which Darwin relied in favour of
use-inheritance is destroyed. On the other hand, if reduction through 5
per cent. be deemed a "very liberal estimate" of what this principle can
accomplish, the whole body of Darwin's direct evidence remains as he
left it. I have now given my reasons for rejecting this lower estimate
on the one band, and what seems to me the extravagant estimate of
Weismann on the other. But my own intermediate estimate is enough to
destroy the apparent proof of use-inheritance that was given by Darwin.
Therefore it remains for those who deny Lamarckian principles, either to
accept some such estimate, or else to acknowledge the incompatibility of
any lower one with the opinion that there is no evidence in favour of
these principles.




APPENDIX II.

ON CHARACTERS AS ADAPTIVE AND SPECIFIC.


It is the object of this Appendix to state, more fully than in the text,
the opinions with regard to this subject which have been published by
the two highest authorities on the theory of natural selection--Darwin
and Professor Huxley. I will take first the opinion of Professor Huxley,
quoted _in extenso_, and then consider it somewhat more carefully than
seemed necessary in the text.

As far as I am aware, the only occasion on which Professor Huxley has
alluded to the subject in question, is in his obituary notice of Darwin
in the _Proceedings of the Royal Society_, Vol. XLIV, No. 269, p. xviii.
The allusion is to my paper on _Physiological Selection_, in the
_Journal of the Linnæan Society_, Zool. Vol. XIX, pp. 337-411. But it
will be observed that the criticism has no reference to the theory which
it is the object of that paper to set forth. It refers only to my
definition of the theory of natural selection as primarily a theory of
the origin, or cumulative development, of adaptations. This criticism,
together with my answer thereto at the time, is conveyed in the
following words.

     "Every variety which is selected into a species is favoured and
     preserved in consequence of being, in some one or more respects,
     better adapted to its surroundings than its rivals. In other words,
     every species which exists, exists in virtue of adaptation, and
     whatever accounts for that adaptation accounts for the existence of
     the species. To say that Darwin has put forward a theory of the
     adaptation of species, but not of their origin, is therefore to
     misunderstand the first principles of the theory. For, as has been
     pointed out, it is a necessary consequence of the theory of
     selection that every species must have some one or more structural
     or functional peculiarities, in virtue of the advantage conferred
     by which it has fought through the crowd of its competitors, and
     achieved a certain duration. In this sense, it is true that every
     species has been 'originated' by selection."

     Now, in the first place, I have nowhere said that "Darwin has put
     forward a theory of the adaptation of species, but not of their
     origin." I said, and continue to say, that he has put forward a
     theory of _adaptations in general_, and that where such adaptations
     appertain to species only (i.e. are peculiar to particular
     species), the theory becomes "_also_ a theory of the origin of the
     species which present them." The only possible misunderstanding,
     therefore, which can here be alleged against me is, that I fail to
     perceive it as a "necessary consequence of the theory of selection
     that _every_ species _must_ have some one or more structural or
     functional _peculiarities_" of an adaptive or utilitarian kind.
     Now, if this is a misunderstanding, I must confess to not having
     had it removed by Mr. Huxley's exposition.

     The whole criticism is tersely conveyed in the form of two sequent
     propositions--namely, "Every species which exists, exists in virtue
     of adaptation; and whatever accounts for that adaptation accounts
     for the existence of the species." My answer is likewise two-fold.
     First, I do not accept the premiss; and next, even if I did, I can
     show that the resulting conclusion would not overturn my
     definition. Let us consider these two points separately, beginning
     with the latter, as the one which may be most briefly disposed of.

     I. Provisionally conceding that "every species which exists, exists
     in virtue of adaptation," I maintain that my definition of the
     theory of natural selection still holds good. For even on the basis
     of this concession, or on the ground of this assumption, the theory
     of natural selection is not shown to be "_primarily_" a theory of
     the origin of species. It follows, indeed, from the assumption--is,
     in fact, part and parcel of the assumption--that all species have
     been originated by natural selection; but why? _Only because
     natural selection has originated those particular adaptive features
     in virtue of which (by the hypothesis) species exist as species._
     It is only in virtue of having created these features that natural
     selection has created the species presenting them--just as it has
     created genera, families, orders, &c., in virtue of _other_
     adaptive features extending through progressively wider areas of
     taxonomic division. Everywhere and equally this principle has been
     "primarily" engaged in the evolution of adaptations, and if one
     result of its work has been that of enabling the systematist to
     trace lines of genetic descent under his divisions of species,
     genera, and the rest, such a result is but "secondary" or
     "incidental."

     In short, it is "_primarily_" a theory of adaptations _wherever
     these occur_, and only becomes "_also_" or "_incidentally_" a
     theory of species in cases where adaptations happen to be
     restricted in their occurrence to organic types of a certain order
     of taxonomic division.

     II. Hitherto, for the sake of argument, I have conceded that, in
     the words of my critic, "it is a necessary consequence of the
     theory of selection that every species must have some one or more
     structural or functional peculiarities" of an adaptive kind. But
     now I will endeavour to show that this statement does not "follow
     as a necessary consequence" from "the theory of selection."

     Most obviously "it follows" from the theory of selection that
     "every variety which is selected into a species is favoured and
     preserved in consequence of being, in some one or more respects,
     better adapted to its surroundings than its rivals." This, in fact,
     is no more than a re-statement of the theory itself. But it does
     _not_ follow that "every species which exists, exists in virtue of
     adaptation" _peculiar to that species_; i.e. that every species
     which exists, exists _in virtue of having been "selected_." This
     may or may not be true as a matter of fact: as a matter of logic,
     the inference is not deducible from the selection theory. Every
     variety which is "_selected into_" a species must, indeed, present
     some such peculiar advantage; but this is by no means equivalent to
     saying, "in other words," that every variety which _becomes_ a
     species must do so. For the latter statement imports a completely
     new assumption--namely, that every variety which _becomes_ a
     species must do so because it has been "_selected into_" a species.
     In short, what we are here told is, that if we believe the
     selection principle to have given origin to some species, we must
     further believe, "as a necessary consequence," that it has given
     origin to all species.

The above reply, which is here quoted _verbatim_ from _Nature_, Vol. 38,
p. 616-18, proceeded to show that it does not belong to "the first
principles of the theory of natural selection" to deny that no other
cause than natural selection can possibly be concerned in the origin of
species; and facts were given to prove that such unquestionably has been
the case as regards the origin of "local" or "permanent" _varieties_.
Yet such varieties are what Darwin correctly terms "incipient" species,
or species in process of taking _origin_. Therefore, if Professor
Huxley's criticism is to stand at all, we must accept it "as a necessary
consequence of the theory of selection," that every such _variety_
"which exists, exists in virtue of adaptation"--a statement which is
_proved_ to be untrue by the particular cases forthwith cited. But as
this point has been dealt with much more fully in the text of the
present treatise, I shall sum up the main points in a few words.

The criticism is all embodied in two propositions--namely, (_a_) that
the theory of natural selection carries with it, as a "necessary
consequence," the doctrine that survival of the fittest has been the
cause of the origin of _all_ species; and (_b_) that therefore it
amounts to one and the same thing whether we define the theory as a
theory of species or as a theory of adaptations. Now, as a mere matter
of logical statement, it appears to me that both these propositions are
unsound. As regards the first, if we hold with Darwin that other causes
have co-operated with natural selection in the origination of some (i.
e. many) species, it is clearly no part of the theory of natural
selection to assume that none of these causes can ever have acted
independently. In point of fact, as we have seen in the foregoing
chapters, such has probably and frequently been the case under the
influences of isolation, climate, food, sexual selection, and laws of
growth; but I may here adduce some further remarks with regard to yet
another possible cause. If the Lamarckian principles are valid at all,
no reason can be shown why in some cases they may not have been
competent _of themselves_ to induce morphological changes of type by
successive increments, until a transmutation of species is effected by
their action alone--as, indeed, Weismann believes to have been the case
with all the species of Protozoa[148]. That such actually has often been
the case also with numberless species of Metozoa, is the belief of the
neo-Lamarckians; and whether they are right or wrong in holding this
belief, it is equally certain that, _as a matter of logical reasoning_,
they are not compelled by it to profess any _disbelief_ in the agency of
natural selection. They may be mistaken as to the facts, as Darwin in a
lesser degree may have been similarly mistaken; but just as Darwin has
nowhere committed himself to the statement that _all_ species must
_necessarily_ have been originated by natural selection, so these
neo-Lamarckians are perfectly logical in holding that _some_ species may
have been wholly caused by the inheritance of acquired characters, as
_other_ species may have been wholly caused by the natural selection of
congenital characters. In short, unless we begin by assuming (with
Wallace and against Darwin) that there _can be no other cause_ of the
origin of species than that which is furnished by natural selection, we
have no basis for Professor Huxley's statement "that every species has
been originated by selection"; while, if we do set out with this
assumption, we end in a mere tautology. What ought to be done is to
prove the validity of this assumption; but, as Professor Huxley makes
no attempt to do this, his criticism amounts to mere begging of the
question.

    [148] Since the above was written Professor Weismann has transferred
          this doctrine from the Protozoa to their ancestors.

And now, as regards the second point (_b_), even if we grant the
assumption that natural selection is the only possible cause of the
origin of species--or, which is the same thing, that every species has
been originated by natural selection,--is it likewise the same thing
whether we define the theory of natural selection as a theory of species
or as a theory of adaptations? Professor Huxley's criticism endeavours
to show that it is; but a little consideration is enough to show that it
is not. What does follow from the assumption is, that, _so far as
specific characters are concerned_, it is one and the same thing to say
that the theory is a theory of species, and to say that it is a theory
of adaptations. But specific characters are not conterminous with
adaptive characters; for innumerable adaptive characters are not
distinctive of species, but of genera, families, orders, classes, and
sub-kingdoms. Therefore, if it is believed (as, of course, Professor
Huxley believes) that the theory in question explains the evolution of
all adaptive characters, obviously it is not one and the same thing to
define it indifferently as a theory of species or as a theory of
adaptations.

Now, all this is not merely a matter of logic chopping. On the contrary,
the question whether we are to accept or to reject the deduction that
all species must necessarily have owed their origin to natural
selection, is a question of no small importance to the general theory of
evolution. And our answer to this question must be determined by that
which we give to the ulterior question--Is the theory of natural
selection to be defined as a theory of species, or as a theory of
adaptations?

       *       *       *       *       *

We now pass on to our consideration of Darwin's opinion touching the
question, as stated by himself,--"The doctrine of utility, how far
true?" As I cannot ascertain that Darwin has anywhere expressed an
opinion as to whether natural selection has been necessarily concerned
in the origin of all _species_, the issue here is as to whether he held
this with regard to all _specific characters_. It will be remembered
that while opposing this doctrine as erroneous both in logic and in
fact, I have represented that it is not a doctrine which Darwin
sanctioned; but, on the contrary, that it is one which he expressly
failed to sanction, by recognizing the frequent inutility of specific
characters. Mr. Wallace, on the other hand, alleges that Darwin did
believe in the universal--as distinguished from the general--utility of
such characters. And he adds that he has "looked in vain in Mr. Darwin's
works" for any justification of my statements to the contrary[149].
Therefore I will endeavour to show that Mr. Wallace's search has not
been a very careful one.

    [149] _Darwinism_, p. 131. He says:--"I have looked in vain in Mr.
          Darwin's works for any such acknowledgement" (i.e. "that a
          large proportion of specific distinctions must be conceded
          useless to the species presenting them").

We must remember, however, that it was not until the appearance of my
paper on _Physiological Selection_, four years after Darwin's death,
that the question now in debate was raised. Consequently, he never had
occasion to deal expressly with this particular question--viz. whether
"the doctrine of utility" has any _peculiar_ reference to _specific_
characters--as he surely would have done had he entertained the
important distinction between specific and all other characters which
Mr. Wallace now alleges that he did entertain. But, be this as it may,
we cannot expect to find in Darwin's writings any express allusion to a
question which had not been raised until 1886. The most we can expect to
find are scattered sentences which prove that the distinction in
question was never so much as present to his mind,--i. e. never occurred
to him as even a possible distinction.

I will first take the passages which Mr. Wallace himself supplies from
among those which I had previously indicated.

     "But when, from the nature of the organism and of the conditions,
     modifications have been induced which are unimportant for the
     welfare of the _species_, they may be, and apparently often have
     been, transmitted in nearly the same state to numerous, otherwise
     modified, descendants[150]."

    [150] _Origin of Species_, p. 175. Italics mine.

On this passage Mr. Wallace remarks that the last five words "clearly
show that such characters are usually not 'specific,' in the sense that
they are such as distinguish species from one another, but are found in
numerous allied species." But I cannot see that the passage shows
anything of the sort. What to my mind it does show is, (_a_) that Mr.
Darwin repudiated Mr. Wallace's doctrine touching the _necessary_
utility of _all_ specific characters: (_b_) that he takes for granted
the contrary doctrine touching the inutility of _some_ specific
characters: (_c_) that without in this place alluding to the
proportional number of useless specific characters, he refers their
origin in some cases to "the nature of the organism" (i.e. "spontaneous
variability" due to internal causes), and in other cases to "the
conditions" (i.e. variability induced by external causes): (_d_) that
when established as a specific character by heredity, such a useless
character was held by him not to tend to become obsolete by the
influence of natural selection or any other cause; but, on the contrary,
to be "transmitted in nearly the same state to numerous, otherwise
modified, descendants"--or progeny of the species in genera, families,
&c.: (_e_) and, therefore, that useless characters which are now
distinctive of genera, families, &c., were held by him frequently, if
not usually, to point to uselessness of origin, when first they arose as
merely specific characters. Even the meaning which Mr. Wallace reads
into this passage must imply every one of these points; and therefore I
do not see that he gains much by apparently seeking to add this further
meaning--viz. that in Darwin's opinion there must have been some
unassignable reason preventing the occurrence of useless specific
characters in cases where species are _not_ destined to become the
parents of genera.

Moreover, any such meaning is out of accordance with the context from
which the passage is taken. For, after a long consideration of the
question of utility, Darwin sums up,--"We thus see that with plants many
morphological changes may be attributed to the laws of growth and the
interaction of parts, _independently of natural selection_." And then he
adds,--"From the fact of the above characters being _unimportant for the
welfare of the species_, any slight variations which occurred in them
_would not have been augmented through natural selection_." Again, still
within the same passage, he says, while alluding to the causes other
than natural selection which lead to changes of specific
characters,--"If the _unknown cause_ were to act almost uniformly for a
length of time, we may infer that the result would be almost uniform;
and in this case _all_ the individuals of the _species_ would be
modified in the same manner." For my own part I do not understand how
Mr. Wallace can have overlooked these various references to _species_,
all of which occur on the very page from which he is quoting. The whole
argument is to show that "many morphological changes may be attributed
to the laws of growth and the inter-action of parts [_plus_ external
conditions of life], independently of natural selection"; that such
non-adaptive changes, when they occur as "specific characters," may, if
the species should afterwards give rise to genera, families, &c., become
distinctive of these higher divisions. But there is nothing here, or in
any other part of Darwin's writings, to countenance the inconsistent
notion which Mr. Wallace appears to entertain,--viz. that species which
present useless characters are more apt to give rise to genera,
families, &c., than are species which do not present such characters.

The next passage which Mr. Wallace quotes, with his comments thereon, is
as follows. The italics are his.

     "'Thus a large yet undefined extension may safely be given to the
     direct and indirect results of natural selection; but I now admit,
     after reading the essay of Nägeli on plants, and the remarks by
     various authors with respect to animals, more especially those
     recently made by Professor Broca, that in the earlier editions of
     my Origin of Species I perhaps attributed too much to the action of
     natural selection, or the survival of the fittest. I have altered
     the fifth edition of the Origin so as to confine my remarks to
     adaptive changes of structure; _but I am convinced, from the light
     gained during even the last few years, that very many structures
     which now appear to be useless, will hereafter be proved to be
     useful, and will therefore come within the range of natural
     selection_. Nevertheless I did not formerly consider sufficiently
     the existence of structures which, as far as we can at present
     judge, are neither beneficial nor injurious; and this I believe to
     be one of the greatest oversights as yet detected in my work.'

     Now it is to be remarked that neither in these passages nor in any
     of the other less distinct expressions of opinion on this question,
     does Darwin ever admit that "specific characters"--that is, the
     particular characters which serve to distinguish one species from
     another--are ever useless, much less that "a large proportion of
     them" are so, as Mr. Romanes makes him "freely acknowledge." On the
     other hand, in the passage which I have italicised he strongly
     expresses his view that much of what we suppose to be useless is
     due to our ignorance; and as I hold myself that, as regards many of
     the supposed useless characters, this is the true explanation, it
     may be well to give a brief sketch of the progress of knowledge in
     transferring characters from the one category to the other[151]."

    [151] _Darwinism_, p. 132.

It is needless to continue this quotation, because of course no one is
disputing that an enormous number of specific characters whose utility
is unknown are nevertheless useful, and therefore due to natural
selection. In other words, the question is not--Are there not many
useful specific characters whose utility is unknown? but--Does it follow
from the theory of natural selection that all specific characters must
necessarily be useful? Well, it appears to me that without going further
than the above passage, which Mr. Wallace has quoted, we can see clearly
enough what was Darwin's opinion upon the subject. He did not believe
that it followed _deductively_ from his theory that all specific
characters must necessarily be useful; and therefore he regarded it as a
question of _fact_--to be determined by induction as distinguished from
deduction--in what proportional number of cases they are so. Moreover he
gives it as his more matured opinion, that, "as far as we can at present
judge" (i.e. from the present state of observation upon the subject: if,
with Mr. Wallace, his judgement were _a priori_, why this
qualification?), he had not previously sufficiently considered the
existence of non-adaptive characters--and this he ended by believing was
one of the greatest oversights as yet detected in his work. To me it has
always seemed that this passage is one of the greatest exhibitions of
candour, combined with solidity of judgement, that is to be met with
even in the writings of Darwin. There is no talk about any deductive
"necessity"; but a perfect readiness to allow that causes other than
natural selection may have been at work in evoking non-adaptive
characters, so that the fifth edition of the _Origin of Species_ was
altered in order to confine the theory of natural selection to "adaptive
changes"--i.e. to constitute it, as I have said in other words, "a
theory of the origin, or cumulative development, of _adaptations_."

If to this it be said that in the above passage there is no special
mention of _species_, the quibble would admit of a three-fold reply. In
the first place, the quibble in question had never been raised. As
already stated, it is only since the appearance of my own paper on
_Physiological Selection_ that anybody ever thought of drawing a
distinction between species and genera, such that while all specific
characters must be held necessarily useful, no such necessity extends to
generic characters. In the second place, that Darwin must have had
specific characters (as well as generic) in his mind when writing the
above passage, is rendered unquestionable by the fact that many of the
instances of inutility adduced by Nägeli and Broca have reference to
specific characters. Lastly, as shown in the passages previously quoted
from the sixth edition of the _Origin of Species_, Darwin attributed the
origin of useless generic characters to useless specific characters; so
that Mr. Wallace really gains nothing by his remark that specific
characters are not specially mentioned in the present passage.

Once more:--

     "Darwin's latest expression of opinion on this question is
     interesting, since it shows he was inclined to return to his
     earlier view of the general, or universal, utility of specific
     characters[152]."

    [152] _Darwinism_, p. 142.

This "latest expression of opinion," as I shall immediately prove, shows
nothing of the kind--being, in fact, a mere re-statement of the opinion
everywhere and at all times expressed by Darwin, touching the caution
that must be observed in deciding, _with respect to individual cases_,
whether an apparently useless specific character is to be regarded as
really useless. Moreover, at no time and in no place did Darwin
entertain any "view of the general, or universal, utility of specific
characters." But the point now is, that if (as was the case) Darwin
"inclined" to depart more and more from his earlier view of the highly
_general_ utility of specific characters; and if (as was not the case)
he ended by showing an inclination "_to return_" to this earlier view;
what becomes of the whole of Mr. Wallace's contention against which
this Appendix is directed, namely, _that Darwin never entertained any
other view than that of the "general, or universal, utility of specific
characters_"?

The "latest expression of opinion" which Mr. Wallace quotes, occurs in a
letter written to Professor Semper in 1878. It is as follows:--

     "As our knowledge advances, very slight differences, considered by
     systematists as of no importance in structure, are continually
     found to be functionally important; and I have been especially
     struck with this fact in the case of plants, to which my
     observations have of late years been confined. Therefore it seems
     to me rather rash to consider the slight differences between
     representative species, for instance those inhabiting the different
     islands of the same archipelago, as of no functional importance,
     and as not in any way due to natural selection[153]."

    [153] _Life and Letters_, vol. iii. p. 161.

Now, with regard to this passage it is to be observed, as already
remarked, that it refers to the formation of final judgements touching
_particular cases_: there is nothing to show that the writer is
contemplating _general principles_, or advocating on deductive grounds
the dogma that specific characters must be necessarily and universally
adaptive characters. Therefore, what he here says is neither more nor
less than I have said. For I have always held that it would be "rather
rash" to conclude that any given cases of apparent inutility are
certainly cases of real inutility, _merely on the ground that utility is
not perceived_. But this is clearly quite a distinct matter from
resisting the _a priori_ generalization that all cases of apparent
inutility must certainly be cases of real utility. And, I maintain, in
every part of his writings, without any exception, where Darwin alludes
to this matter of general principle, it is in terms which directly
contradict the deduction in question. As the whole of this Appendix has
been directed to proving that such is the case, it will now, I think, be
sufficient to supply but one further quotation, in order to show that
the above "latest expression of opinion," far from indicating that in
his later years Darwin "inclined" to Mr. Wallace's views upon this
matter, is quite compatible with a distinct "expression of opinion" to
the contrary, in a letter written less than six years before his death.

     "In my opinion _the greatest error which I have committed_, has
     been not allowing sufficient weight to the direct action of the
     environment, i.e. food, climate, &c., _independently of natural
     selection_. Modifications thus caused, _which are neither of
     advantage nor disadvantage to the modified organisms_, would be
     especially favoured, as I can now see chiefly through your
     observations, _by isolation in a small area, where only a few
     individuals lived under nearly uniform conditions_[154]."

    [154] _Life and Letters_, vol. iii. p. 158.

I will now proceed to quote further passages from Darwin's works, which
appear to have escaped the notice of Mr. Wallace, inasmuch as they admit
of no doubt regarding the allusions being to _specific_ characters.

     "_We may easily err in attributing importance to characters, and in
     believing that they have been developed through natural selection._
     We must by no means overlook the effects of the definite action of
     changed conditions of life,--of so-called spontaneous variations,
     which seem to depend in a quite subordinate degree on the nature of
     the conditions,--of the tendency to reversion to long-lost
     characters,--of the complex laws of growth, such as of
     correlation[155], compensation, of pressure of one part on another,
     &c., and finally of sexual selection, by which characters of use to
     one sex are often gained and then transmitted more or less
     perfectly to the other sex, though of no use to this sex. But
     structures thus indirectly gained, _although at first of no
     advantage to a species_, may subsequently have been taken advantage
     of by its modified descendants, under new conditions of life and
     newly acquired habits[156]."

    [155] It must be observed that Darwin uses this word, not as Mr.
          Wallace always uses it (viz. as if correlation can only be
          with regard to adaptive characters), but in the wider sense
          that any change in one part of an organism--whether or not it
          happens to be an adaptive change--is apt to induce changes in
          other parts.

    [156] _Origin of Species_, pp. 157-8.

It appeared--and still appears--to me, that where so many causes are
expressly assigned as producing useless _specific_ characters, and that
some of them (such as climatic influences and independent variability)
must be highly general in their action, I was justified in representing
it as Darwin's opinion that "a large proportional number of specific
characters" are useless to the _species_ presenting them, although
afterwards they may sometimes become of use to genera, families, &c.
Moreover, this passage goes on to point out that specific characters
which at first sight appear to be obviously useful, are sometimes found
by fuller knowledge to be really useless--a consideration which is the
exact inverse of the argument from ignorance as used by Mr. Wallace, and
serves still further to show that in Darwin's opinion utility is by no
means an invariable, still less a "necessary," mark of specific
character. The following are some of the instances which he gives.

     "The sutures in the skulls of young mammals have been advanced as a
     beautiful adaptation for aiding parturition, and no doubt they may
     facilitate, or be indispensable for this act; but as sutures occur
     in the skulls of young birds and reptiles, which have only to
     escape from a broken egg, we may infer that this structure has
     _arisen from the laws of growth_, and has been taken advantage of
     in the parturition of the higher animals[157]."

     "The naked skin on the head of a vulture is generally considered as
     a direct adaptation for wallowing in putridity; and so it may be,
     _or it may possibly be due to the direct action of the putrid
     matter_; but we should be very cautious in drawing any such
     inference [i.e. as to utility] when we see the skin on the head of
     the clean-feeding male Turkey is likewise naked[158]."

    [157] _Ibid._

    [158] _Origin of Species_, pp. 157-8.

Similarly, in the _Descent of Man_ it is said:--

     "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[159]."

    [159] _Descent of Man_, p. 615.

As Mr. Wallace does not recognize sexual selection, he incurs the burden
of proving utility (in the life-preserving sense) in all these
"frequently" occurring cases where there are such "strongly pronounced
modifications," and we have already seen in the text his manner of
dealing with this burden. But the point here is, that whether or not we
accept the theory of sexual selection, we must accept it as Darwin's
opinion--first, that in their beginnings, as _specific_ characters,
these sexual modifications were often of a merely "_general nature_" (or
without reference to utility even in the life-embellishing sense), and
only _afterwards_ "have often been taken advantage of and accumulated
through _sexual_ selection": and, secondly, that "we know they have been
acquired in some instances _at the cost not only of inconvenience, but
of exposure to actual dangers_[160]."

    [160] _Ibid._

We may now pass on to some further, and even stronger, expressions of
opinion with regard to the frequent inutility of _specific_ characters.

     "I have made these remarks only to show that, if we are unable to
     account for the characteristic differences of our several domestic
     breeds, which nevertheless are generally admitted to have arisen
     through ordinary generation from one or a few parent stocks, we
     ought not to lay too much stress on our ignorance of the precise
     cause [i.e. whether natural selection or some other cause] of the
     slight analogous differences between true _species_.... I fully
     admit that _many_ structures are now of no use to their possessors,
     and may never have been of any use to their progenitors; but this
     does not prove that they were formed solely for beauty or variety.
     No doubt the definite action of changed conditions, and the various
     causes of modification, lately specified, have all produced an
     effect, _probably a great effect, independently of any advantage
     thus gained_.... It is scarcely possible to decide how much
     allowance ought to be made for such causes of change, as the
     definite action of external conditions, so-called spontaneous
     variations, and the complex laws of growth; but, _with these
     important exceptions_, we may conclude that the structure of every
     living creature either now is, or formerly was, of some direct or
     indirect use to its possessor[161]."

    [161] _Descent of Man_, pp. 159-60.

Here again, if we remember how "important" these "exceptions" are, I
cannot understand any one doubting Darwin's opinion to have been that a
large proportional number of specific characters are useless. For that
it is "species" which he here has mainly in his mind is evident from
what he says when again alluding to the subject in his "Summary of the
Chapter"--namely, "In _many_ other cases [i.e. in cases where natural
selection has not been concerned] modifications are probably the direct
result of the laws of variation or of growth, independently of any good
having been thus gained." Now, not only do these "laws" apply as much to
species as they do to genera; "but," the passage goes on to say, "even
such structures have often, we may feel assured, been subsequently
taken advantage of, and still further modified, for the good of
_species_ under new conditions of life." Obviously, therefore, the
inutility in such cases is taken to have been prior to any utility
subsequently acquired; and genera are not historically prior to the
species in which they originate.

Here is another quotation:--

     "Thus, as I am inclined to believe, morphological differences,
     which we consider as important--such as the arrangement of the
     leaves, the divisions of the flower or of the ovarium, the position
     of the ovules, &c.--_first_ appeared in _many_ cases as
     _fluctuating variations_, which sooner or later became constant
     through the nature of the organism and of the surrounding
     conditions, as well as through the intercrossing of distinct
     individuals, _but not through natural selection_; for as these
     morphological characters do not affect the welfare of the
     _species_, any slight deviations in them could not have been
     governed or accumulated through this latter agency. It is a strange
     result which we thus arrive at, namely, that characters of slight
     vital importance to the _species_, are the most important to the
     systematist; but, as we shall hereafter see when we treat of the
     genetic principle of classification, this is by no means so
     paradoxical as it may at first appear[162]."

    [162] _Descent of Man_, p. 176.

Clearly the view here expressed is that characters which are now
distinctive of higher taxonomic divisions "first appeared" in the parent
species of such divisions; for not only would it be unreasonable to
attribute the rise and preservation of useless characters to
"fluctuating variations" affecting a number of species or genera
similarly and simultaneously; but it would be impossible that, if such
were the case, they could be rendered "constant through the nature of
the organism and of the surrounding conditions, as well as through the
intercrossing of distinct individuals[163]."

    [163] The passage to which these remarks apply is likewise quoted,
          in the same connexion as above, in my paper on _Physiological
          Selection_. In criticising that paper in _Nature_ (vol. xxxix.
          p. 127), Mr. Thiselton Dyer says of my interpretation of this
          passage, "the obvious drift of this does not relate to
          specific differences, but to those which are characteristic of
          family." But in making this remark Mr. Dyer could not have
          read the passage with sufficient care to note the points which
          I have now explained.

Here is another passage to the same general effect. In alluding to the
objection from inutility as advanced by Bronn, Broca, and Nägeli, Mr.
Darwin says:--"There is much force in the above objection"; and, after
again pointing out the important possibility in any particular cases of
hidden or former use, and the action of the laws of growth, he goes on
to say,--"In the third place, we have to allow for the direct and
definite action of changed conditions of life, and for so-called
spontaneous variations, in which the nature of the conditions plays
quite a subordinate part[164]." Elsewhere he says,--"It appears that I
formerly underrated the frequency and value of these latter forms of
variation as leading to permanent modifications of structure
_independently of natural selection_[165]." The "forms of variation" to
which he here alludes are "variations which seem to us in our ignorance
to arise spontaneously"; and it is evident that such variations cannot
well "arise" in two or more species of a genus similarly and
simultaneously, so as independently to lead "to permanent modifications
of structure" in two or more parallel lines. It is further evident that
by "spontaneous variations" Darwin alludes to extreme cases of
spontaneous departure from the general average of specific characters;
and therefore that lesser or more ordinary departures must be of still
greater "frequency."

    [164] _Origin of Species_, p. 171.

    [165] _Ibid._ p. 421.

Again, speaking of the principles of classification, Darwin writes:--

     "We care not how trifling a character may be--let it be the mere
     inflection of the angle of the jaw, the manner in which an
     insect's wing is folded, whether the skin be covered by hair or
     feathers--if it prevail throughout many and different species,
     especially those having very different habits of life, it assumes
     high value [i.e. for purposes of classification]; for we can
     account for its presence in so many forms with such _different
     habits_, only by inheritance from a common parent. We may err in
     this respect in regard to single points of structure, but when
     several characters, let them be ever so trifling, concur throughout
     a large group of beings _having different habits_, we may feel
     almost sure, on the theory of descent, that these characters have
     been inherited from a common ancestor; and we know that such
     aggregated characters have especial value in classification[166]."

    [166] _Origin of Species_, pp. 372-373.

Now it is evident that this argument for the general theory of evolution
would be destroyed, if Wallace's assumption of utility of specific
characters as universal were to be entertained. And the fact of
apparently "trifling" characters occurring throughout a large group of
beings "having different habits" is proof that they are really trifling,
or without utilitarian significance.

It is needless to multiply these quotations, for it appears to me that
the above are amply sufficient to establish the only point with which we
are here concerned, namely, that Darwin's opinion on the subject of
utility in relation to specific characters was substantially identical
with my own. And this is established, not merely by the literal meaning
of the sundry passages here gathered together from different parts of
his writings; but likewise, and perhaps still more, from the tone of
thought which pervades these writings as a whole. It requires no words
of mine to show that the literal meaning of the above quotations is
entirely opposed to Mr. Wallace's view touching the _necessary_ utility
of _all_ specific characters; but upon the other point--or the general
tone of Mr. Darwin's thought regarding such topics--it may be well to
add two remarks.

In the first place, it must be evident that so soon as we cease to be
bound by any _a priori_ deduction as to natural selection being "the
exclusive means of modifications," it ceases to be a matter of much
concern to the theory of natural selection in what proportion other
means of modification have been at work--especially when non-adaptive
modifications are concerned, and where these have reference to merely
"specific characters," or modifications of the most incipient kind,
least generally diffused among organic types, and representing the
incidence of causes of less importance than any others in the process of
organic evolution considered as a whole. Consequently, in the second
place, we find that Darwin nowhere displays any solicitude touching the
proportional number of specific characters that may eventually prove to
be due to causes other than natural selection. He takes a much wider and
deeper view of organic evolution, and, having entirely emancipated
himself from the former conception of species as the organic units, sees
virtually no significance in specific characters, except in so far as
they are also adaptive characters.

Such, at all events, appears to me the obvious interpretation of his
writings when these are carefully read with a view to ascertaining his
ideas upon "Utilitarian doctrine: how far true." And I make these
remarks because it has been laid to my charge, that in quoting such
passages as the above I have been putting "a strained interpretation"
upon Darwin's utterances: "such admissions," it is said, "Mr. Romanes
appears to me to treat as if wrung from a hostile witness[167]." But,
from what has gone before, it ought to be apparent that I take precisely
the opposite view to that here imputed. Far from deeming these and
similar passages as "admissions wrung from a hostile witness," and far
from seeking to put any "strained interpretation" upon them, I believe
that they are but the plain and unequivocal expressions of an opinion
which I have always understood that Darwin held. And if any one has been
led to think otherwise, I throw back this charge of "strained
interpretation," by challenging such a person to adduce a single
quotation from any part of Darwin's works, which can possibly be held to
indicate that he regarded passages like those above quoted as in any way
out of conformity with his theory of natural selection--or as put
forward merely to "admit the possibility of explanations, to which
really, however, he did not attach much importance." To the best of my
judgement it is only some bias in favour of Mr. Wallace's views that can
lead a naturalist to view in this way the clear and consistent
expression of Darwin's.

    [167] Mr. Thiselton Dyer in _Nature_, _loc. cit._

That Mr. Wallace himself should be biassed in this matter might,
perhaps, be expected. After rendering the following very unequivocal
passage from the _Origin of Species_ (p. 72)--"There can be little doubt
that the tendency to vary in the same manner has often been so strong,
_that all individuals of the same species have been similarly modified
without the aid of any form of selection_"--Mr. Wallace says, "But no
proof whatever is offered of this statement, and it is so entirely
opposed to all we know of the facts of variation as given by Darwin
himself, that the important word 'all' is probably an oversight." But,
if Mr. Wallace had read the very next sentence he would have seen that
here the important word "all" could not _possibly_ have been "an
oversight." For the passage continues,--"Or only a third, fifth, or
tenth part of the individuals may have been thus affected, of which fact
several instances could be given. Thus Graba estimates that about
one-fifth of the guillemots in the Faroe Islands consist of a variety so
well marked, that it was formerly ranked as a distinct species under the
name of Uria lacrymans." And even if this passage had not been thus
specially concerned with the question of the _proportion_ in which
"_individuals of the same species have been similarly modified without
the aid of any form of selection_" the oversight with respect to "the
important word 'all'" would still have remained an oversight of a
recurrent character, as the following additional quotations from other
parts of Darwin's writings may perhaps render apparent.

     "There must be some efficient cause for each slight individual
     difference, as well as for more strongly marked variations which
     occasionally arise; and if the unknown cause were to act
     persistently, it is almost certain that _all_ the individuals of
     the _species_ would be similarly modified[168]."

     "The acquisition of a useless part can hardly be said to raise an
     organism in the natural scale.... We are so ignorant of the
     exciting cause of the above specified modifications; but if the
     unknown cause were to act almost uniformly for a length of time, we
     may infer that the result would be almost uniform; and in this case
     _all_ the individuals of the _species_ would be modified in the
     same manner[169]."

    [168] _Origin of Species_, p. 171.

    [169] _Ibid._ p. 175.

Moreover, when dealing even with such comparatively slight changes as
occur between our domesticated varieties--and which, _a fortiori_, are
less likely to become "stable" through the uniform operation of causes
other than selection, seeing that they are not only smaller in amount
than occurs among natural species, but also have had but a comparatively
short time in which to accumulate--Darwin is emphatic in his assertion
of the same principles. For instance, in the twenty-third chapter of the
_Variation of Plants and Animals under Domestication_, he repeatedly
uses the term "definite action of external conditions," and begins the
chapter by explaining his use of the term thus:--

     "By the term definite action, as used in this chapter, I mean an
     action of such a nature that, when many individuals of the same
     variety are exposed during several generations to any change in
     their physical conditions of life, _all_, or _nearly all_, the
     individuals are modified in the same manner. A new _sub-variety_
     would thus be produced _without the aid of selection_[170]."

    [170] _Variation_, &c., vol. ii. p. 260.

As an example of the special instances that he gives, I may quote the
following from the same work:--

     "Each of the endless variations which we see in the plumage of our
     fowls must have had some efficient cause; and if the same cause
     were to act uniformly during a long series of generations on many
     individuals, _all_ probably would be modified in the same manner."

And, as instances of his more general statements in Chapter XXIII, these
may suffice:--

     "The direct action of the conditions of life, whether leading to
     definite or indefinite results, _is a totally distinct
     consideration from the effects of natural selection_.... The direct
     and definite action of changed conditions, in contradistinction to
     the accumulation of indefinite variations, _seems to me so
     important_ that I will give a large additional body of
     miscellaneous facts[171]."

    [171] _Ibid._ vol. ii. p. 261.

Then, after giving these facts, and showing how in the case of species
in a state of nature it is often impossible to decide how much we are to
attribute to natural selection and how much to the definite action of
changed conditions, he begins his general summary of the chapter thus:--

     "There can be no doubt, from the facts given in the early part of
     this chapter, that extremely slight changes in the conditions of
     life sometimes act in a definite manner on our already variable
     domesticated productions [productions, therefore, with regard to
     which uniformity and 'stability' of modification are least likely
     to arise]; and, as the action Of changed conditions in causing
     general or indefinite variability is accumulative, so it may be
     with their definite action. Hence it is possible that _great_ and
     _definite_ modifications of structure may result from altered
     conditions acting during a long series of generations. In some few
     instances a marked effect has been produced quickly on _all_, or
     _nearly all_, the individuals which have been exposed to some
     considerable change of climate, food, or other circumstance[172]."

    [172] _Variation_, &c., vol. ii. p. 280.

Once more, in order to show that he retained these views to the end of
his life, I may quote a passage from the second edition of the _Descent
of Man_, which is the latest expression of his opinion upon these
points:--

     "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_.... Can we believe that the very slight differences in
     tints and markings between, for instance, the female black-grouse
     and red-grouse serve as a protection? Are partridges as they are
     now coloured, better protected than if they had resembled quails?
     Do the slight differences between the females of the common
     pheasant, the Japan and golden pheasants, serve as a protection, or
     might not their plumage 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, I am not convinced[173]."

    [173] _Descent of Man_, pp. 473-4.

Yet "convinced" he certainly must have been on merely _a priori_
grounds, had he countenanced Mr. Wallace's reasoning from the general
theory of natural selection; and the fact that he here fails to be
convinced even by "what Mr. Wallace has observed of the habits of
certain gallinaceous birds," appears to indicate that he had considered
the question of utility with special reference to Mr. Wallace's opinion.
That opinion was then, as now, the avowed result of a theoretical
prepossession; and this prepossession, as the above quotations
sufficiently show, was expressly repudiated by Darwin.

Lastly, this is not the only occasion on which Darwin expressly
repudiates Mr. Wallace's opinion on the point in question. For it is
notorious that these co-authors of the theory of natural selection have
expressed divergent opinions concerning the origin by natural selection
of the most general of all specific characters--cross-sterility.
Although allowing that cross-sterility between allied species may be of
adaptive value in "keeping incipient species from blending," Darwin
persistently refused to be influenced by Wallace's belief that it is due
to natural selection; i.e. the belief on which alone can be founded the
"necessary deduction" with which we have been throughout concerned.




NOTE A TO PAGE 57.


I think it is desirable here to adduce one or two concrete illustrations
of these abstract principles, in order to show how, as a matter of fact,
the structure of Weismann's theory is such as to preclude the
possibility of its assumptions being disproved--and this even supposing
that the theory is false.

At first sight nothing could seem more conclusive on the side of
Darwinian or Lamarckian principles than are the facts of hereditary
disease, in cases where the disease has unquestionably been acquired by
the parents. Take, for example, the case of gout. Here there is no
suspicion of any microbe being concerned, nor is there any question
about the fact of the disease being one which is frequently acquired by
certain habits of life. Now, suppose the case of a man who in middle age
acquires the gout by these habits of life--such as insufficient
exercise, over-sufficient food, and free indulgence in wine. His son
inherits the gouty diathesis, and even though the boy may have the fear
of gout before his eyes, and consequently avoid over-eating and
alcoholic drinking, &c., the disease may overtake him also. Well, the
natural explanation of all this is, that the sins of the fathers descend
upon the children; that gout acquired may become in the next generation
gout transmitted. But, on the other hand, the school of Weismann will
maintain that the reason why the parent contracted the gout was because
he had a congenital, or "blastogenetic," tendency towards that
disease--a tendency which may, indeed, have been intensified by his
habits of life, but which, in so far as thus intensified, was not
transmitted to his offspring. All that was so transmitted was the
congenital tendency; and all that is proved by such cases as those above
supposed, where the offspring of gouty parents become gouty
notwithstanding their abstemious habits, is that in such offspring the
congenital tendency is even more pronounced than it was in their
parents, and therefore did not require so much inducement in the way of
unguarded living to bring it out. Now, here again, without waiting to
consider the relative probabilities of these two opposing explanations,
it is enough for the purposes of the illustration to remark that it is
obviously impossible to disprove either by means of the other, or by any
class of facts to which they may severally appeal.

I will give only one further example to show the elusiveness of
Weismann's theory, and the consequent impossibility of finding any cases
in nature which will satisfy the conditions of proof which the theory
imposes. In one of his papers Weismann says that if there be any truth
in the Lamarckian doctrine of the transmission of acquired characters,
it ought to follow that the human infant should speak by instinct. For,
ever since man became human he has presumably been a talking animal: at
any rate it is certain that he has been so for an innumerable number of
generations. Therefore, by this time the faculty of language ought to
have been so deeply impressed upon the psychology of the species, that
there ought to be no need to teach the young child its use of language;
and the fact that there is such need is taken by Weismann to constitute
good evidence in proof of the non-transmissibility of individually
acquired characters. Or, to quote his own words, "it has never yet been
found that a child could read of itself, although its parents had
throughout their whole lives practised this art. Not even are our
children able to talk of their own accord; yet not only have their
parents, but, more than that, an infinitely long line of ancestors have
never ceased to drill their brains and to perfect their organs of
speech.... From this alone we may be disposed to doubt whether acquired
capabilities in the true sense can ever be transmitted." Well, in answer
to this particular case, we have first of all to remark that the
construction of even the simplest language is, psychologically
considered, a matter of such enormous complexity, that there is no real
analogy between it and the phenomena of instinct: therefore the fact
that Lamarckian principles cannot be applied to the case of language is
no evidence that they do not hold good as regards instinct. Secondly,
not only the construction, but still more the use of language is quite
out of analogy with all the phenomena of instinct; for, in order to use,
or speak, a language, the mind must already be that of a thinking agent;
and therefore to expect that language should be instinctive is
tantamount to expecting that the thought of which it is the vehicle
should be instinctive--i.e. that human parents should transmit the whole
organization of their own intellectual experiences to their unborn
children. Thirdly, even neglecting these considerations, we have to
remember that language has been itself the product of an immensely long
course of evolution; so that even if it were reasonable to expect that a
child should speak by instinct without instruction, it would be
necessary further to expect that the child should begin by speaking in
some score or two of unknown tongues before it arrived at the one which
alone its parents could understand. Probably these considerations are
enough to show how absurd is the suggestion that Darwinians ought to
expect children to speak by instinct. But, now, although it is for these
reasons preposterous under any theory of evolution to expect that
children should be able to use a fully developed language without
instruction, it is by no means so preposterous to expect that, if all
languages present any one simple set of features in common, these
features might by this time have grown to be instinctive; for these
simple features, being common to all languages, must have been
constantly and forcibly impressed upon the structure of human psychology
throughout an innumerable number of sequent generations. Now, there is
only one set of features common to all languages; and this comprises the
combinations of vowel and consonantal sounds, which go to constitute
what we know as articulate syllables. And, is it not the case that these
particular features, thus common to all languages, as a matter of fact
actually _are_ instinctive? Long before a young child is able to
understand the meanings of any words, it begins to babble articulate
syllables; and I do not know that a more striking fact can be adduced at
the present stage of the Weismann controversy than is this fact which he
has thus himself unconsciously suggested, namely, that the young of the
only talking animal should be alone in presenting--and in unmistakably
presenting--the instinct of articulation. Well, such being the state of
matters as regards this particular case, in the course of a debate which
was held at the Newcastle meeting of the British Association upon the
heredity question, I presented this case as I present it now. And
subsequently I was met, as I expected to be met, by its being said that
after all the faculty of making articulate sounds might have been of
congenital origin. Seeing of how much importance this faculty must
always have been to the human species, it may very well have been a
faculty which early fell under the sway of natural selection, and so it
may have become congenital. Now, be it remembered, I am only adducing
this case in illustration of the elusiveness of Weismann's theory. First
of all he selects the faculty of articulate speech to argue that it is a
faculty which ought to be instinctive if acquired characters ever do
become instinctive; and so good does he deem it as a test case between
the two theories, that he says _from it alone_ we should be prepared to
accept the doctrine that acquired characters can never become
congenital. Then, when it is shown that the only element in articulate
speech which possibly could have become congenital, actually has become
congenital, the answer we receive is a direct contradiction of the
previous argument: the faculty originally selected as representative of
an acquired character is now taken as representative of a congenital
one. By thus playing fast and loose with whatever facts the followers of
Darwin may adduce, the followers of Weismann bring their own position
simply to this:--All characters which can be shown to be inherited we
assume to be congenital, or as we term it, "blastogenetic," while all
characters which can be shown not to be inherited, we assume to be
acquired, or as we term it, "somatogenetic"--and this merely on the
ground that they have been shown to be inherited or not inherited as the
case may be. Now, there need be no objection to such assumptions,
provided they are recognized as assumptions; but so long as the very
question in debate has reference to their validity as assumptions, it is
closely illogical to adduce them as arguments. And this is the only
point with which we are at present concerned.




NOTE B TO PAGE 89.


In answer to this illustration as previously adduced by me, Mr. Poulton
has objected that the benefit arising from the peculiar mode of stinging
in question is a benefit conferred, not on the insect which stings, but
upon its progeny. The point of the illustration however has no reference
to the maternal instinct (which here, as elsewhere, I doubt not is due
to natural selection); it has reference only to the particular instinct
of selective stinging, which here ministers to the purposes of the other
and more general instinct of rearing progeny. Given then the maternal
instinct of stinging prey for the use of progeny, the question is--What
first determined the ancestors of the Sphex to sting their prey only in
nine particular points? Darwin's answer to this question is as
follows:--

     "I have been thinking about Pompilius and its allies. Please take
     the trouble to read on perforation of the corolla by Bees, p. 425
     of my 'Cross-fertilization,' to end of chapter. Bees show so much
     intelligence in their acts, that it seems not improbable to me that
     the progenitors of Pompilius originally stung caterpillars and
     spiders, &c., in any part of their bodies, and then observed by
     their intelligence that if they stung them in one particular place,
     as between certain segments on the lower side, their prey was at
     once paralyzed. It does, not seem to me at all incredible that this
     action should then become instinctive, i.e. memory transmitted from
     one generation to another. It does not seem necessary to suppose
     that when Pompilius stung its prey in the ganglion it intended or
     knew that their prey would keep long alive. The development of the
     larvae may have been subsequently modified in relation to their
     half-dead, instead of wholly dead prey; supposing that the prey was
     at first quite killed, which would have required much stinging.
     Turn this over in your mind," &c.

Weismann, on the other hand, can only suppose that this intensely
specialized instinct had its origin in fortuitous variations in the
psychology of the species. But, neglecting the consideration that, in
order to become fixed as an instinct by natural selection, the
particular variation required must have occurred in many different
individuals, not only in the first, but also in the sequent generations,
the chances against its occurring only once, or in but one single
individual case, are many thousands if not millions to one.




INDEX


A.

Acceleration and retardation, 16.

Acquired characters, heredity of, 39, 103, 133.

Adaptation, 7, 13, 55, 62, 67, 71, 159, 165;
  of species and of specific characters, 166.

ALLEN, Mr., referred to, 209.

_All-sufficiency of Natural Selection_, referred to, 65, 95.

_Alone with the Hairy Ainu_, referred to, 26.

American and European trees compared, 201.

_American Journal of Science_, referred to, 273.

_American Naturalist_, referred to, 35, 58.

Ammonites, species of, 254.

_Animal Intelligence_, referred to, 93.

_Animal Life_, referred to, 101.

_Animal Life and Intelligence_, referred to, 33, 36.

_Apparent Paradox in Mental Evolution_, referred to, 90.

Appendages of Normandy and Irish pigs, 188.

Articulation and inheritance, 335.

Artistic faculties of man, 27.


B.

BABINGTON, Prof., referred to, 252.

BACHMAN, Dr., referred to, 186.

BAILEY, Prof., referred to, 127.

BAKER, Mr., referred to, 252.

Balancing of brainless frog, 78.

BALL, Mr. Platt, referred to, 3, 95; quoted, 50.

BATESON, Mr. W., referred to, 36.

BEDDARD, Mr. F., referred to, 174.

BENTHAM, Mr., referred to, 252.

Birds, diagnostic characters of, 176;
  of Australia, effect of climate on, 210;
  influence of food on, 218.

Blastogenetic, 123, 242, 245, 250.

Blending of adaptations, 67.

_Brain_, referred to, 80.

BROCA, Prof., referred to, 64, 67, 174, 318.

BRONN, Prof., referred to, 174.

BROOKS, Prof., referred to, 14.

BROWN-SÉQUARD, referred to, 104, 122, 142; quoted, 104.

BUCKLEY, Mr., referred to, 147.

BUCKMAN, Prof. James, referred to, 125.

BUCKMAN, Prof. S.S., referred to, 24.

BUTLER, Mr. A. G., referred to, 254.

BUTLER, Mr. Samuel, referred to, 87.

Butterfly, seasonal changes of, 210;
  influence of food on, 217.


C.

Carnivora, instincts of, 89.

CARRIÈRE, M. L. A., referred to, 123.

Cave animals, colour-changes in, 211.

_Cave Fauna of North America_, quoted, 211.

Cessation of Selection, 99, 199, 212, 292.

Characters, adaptive and specific, 159, 307;
  specific, due to Natural Selection, 171.

_Charadriidae, Geographical Distribution of the Family_, quoted, 173.

Chimpanzee, counting of, 31.

Climate, influence of, on plants, 200;
  on animals, 209.

Co-adaptation, 64.

COCKERELL, Prof., referred to, 218.

Colour, 269.

Colour-changes in butterflies, 210.
  in cave animals, 211.

_Colours of Animals_, referred to, 36.

Congenital, as opposed to acquired characters, 134.

Constancy of characters not necessarily due to Natural Selection, 186.

_Contemporary Review_, referred to, 60, 65, 95

Continuity of germ-plasm, 44, 61, 133;
  absolute and relative, 134, 155.

_Contributions to the Theory of Natural Selection_, referred to, 2;
quoted, 180.

COPE, Prof., referred to, 14, 15, 20, 63, 256; quoted, 16.

Correlation, 171, 184, 211, 222, 268.

COSTA, M., quoted, 217.

CUNNINGHAM, Mr. J. T., quoted, 103; referred to, 95, 122.


D.

DALL, Prof., referred to, 14.

DARWIN, Charles, referred to, 1-13, 20-22, 25, 44, 45, 51-53, 56, 66,
67, 74, 87, 88, 93, 95, 96-100, 149, 159, 160, 167, 173, 174, 181-183,
187-191, 193, 195, 198, 200-202, 213-216, 218, 219, 226, 256, 261-265,
268, 271, 277, 283, 287, 291, 305-307, 313-332, 337; quoted, 11, 53, 66,
96, 181, 182, 186-191, 193, 195, 201, 202, 213-215, 261, 262, 265,
313-316, 319-322, 324-326, 328-331, 337.

_Darwin et ses Précurseurs Français_, referred to, 234.

_Darwinian Theory of the Origin of Species_, quoted, 254.

_Darwinism_, quoted, 22, 27, 67, 181, 182, 186, 189-191, 221, 222, 235,
236, 252, 253, 269, 270, 273, 313, 316; referred to, 7, 12, 15, 20, 70.

DE CANDOLLE, Prof., referred to, 206.

Deep-sea faunas, 212.

DELBŒUF, referred to, 224.

_Descent of Man_, quoted, 25, 322-324, 331.

_Development of the Hard Parts of the Mammalia_, referred to, 14.

DE VRIES, Prof., referred to, 122, 174.

Diagnostic characters of birds, 176;
  Marsupials, 178.

Divergent Evolution through Cumulative Segregation, quoted, 224.

DIXON, Mr. Charles, referred to, 174; quoted, 177, 223.

_Doctrine of Descent and Darwinism_, quoted, 260.

Dogs, scratching, reflex of, 80;
  shaking off water, 84;
  transplantation of ovaries, 143.

DORFMEISTER, Dr., referred to, 211.

Ducks, use-inheritance in, 96;
  losing true plumage, 187.

DUPUY, Dr., referred to, 105.

DYER, Mr. Thistleton, quoted, 325, 327.


E.

_Effect of External Influences upon Development_, referred to, 66, 95.

_Effects of Use and Disuse_, quoted, 50.

EIMER, Prof., referred to, 14, 174, 217.

_Entomological Society, Trans. of_, quoted, 211; referred to, 217.

Epilepsy of guinea-pigs, 104.

_Essays on Heredity_, quoted, 56, 91, 97, 107, 152; referred to, 12, 36,
65, 105, 110.

EUDES-DESLONGCHAMPS, M., referred to, 188.

European and American trees, compared, 201.

EVEREST, Rev. E., quoted, 213.

_Evolution without Natural Selection_, quoted, 177.

_Examination of Weismannism_, referred to, 39-42, 44, 100, 122, 123,
134, 136, 138-140, 156.

_Experiments in Pangenesis_, referred to, 145.


F.

FABRE, M., referred to, 88.

Factors of organic evolution:
  Natural Selection, 2, 5, 6;
  use-inheritance, 3, 11.

_Factors of Organic Evolution_, referred to, 8.

Faculties and organs, 29.

Fertility, 229.

Flat-fish, Mr. Cunningham on, 103.

_Floral Structures_, referred to, 19.

FOCKE, Dr., referred to, 174.

_Fonctions du Cerveau_, referred to, 109.

Food, influence of, 217.

Foot, of man, 23.

Frog, brainless, balancing of, 78.


G.

GALTON, Mr. Francis, referred to, 40-48, 100, 103, 134-139, 145, 146,
152, 154, 156, 300, 303-305; quoted, 46, 100.

Gangrene, effects of, 54, 105.

_Gardener's Chronicle_, quoted, 127.

GÄRTNER, Dr., referred to, 206.

GEDDES, Prof., referred to, 15, 20,174.

Gemmules, 47, 145, 155.

Genera and species, 261.

Germ-plasm and Stirp, 40;
  and pangenesis, 42;
  isolation of, 137;
  stability of, 243.

_Germ-plasm_, referred to, 128.

GIARD, Prof., referred to, 14, 174.

Giraffe, co-adaptation in, 64.

GOLTZ, Prof., referred to, 80, 84.

GOULD, Mr., referred to, 210.

Graft-hybridization, 143.

Growth, laws of, 222, 226, 248, 270, 321.

Guinea-pigs, epilepsy of, 104.

GULICK, Mr., referred to, 174, 259, 260, 271; quoted, 224, 273.

_Gute und schlechte Arten_, quoted, 203.


H.

Habit, hereditary, 87.

_Habit and Intelligence_, quoted, 225.

Hand, of man, 24.

_Handbook of British Flora_, referred to, 252.

HAYCRAFT, Prof., referred to, 80.

HEAPE, Mr. Walter, referred to, 147.

HENSLOW, Prof. George, referred to, 18-20, 127-132, 174, 208; quoted,
19, 130, 131.

Heredity, problems of, 39.

HERING, Prof., referred to, 87.

HEWITT, Mr., referred to, 187.

HILL, Prof. Leonard, quoted, 132.

HAECKEL, Prof., referred to, 174, 260, 282.

HOFFMANN, Dr., referred to, 123, 280.

Horse, callosities of, 265.

HUXLEY, Prof. T. H., referred to, 167-170, 185, 256, 275, 283, 307-312;
quoted, 307-309.

Huxleyan doctrine of species, 167.

_Hyatt_, Prof., referred to, 14, 15.

Hymenoptera, social, 92.


I.

_Inadequacy of Natural Selection_, referred to, 65, 95.

_Inconsistencies of Utilitarianism as the Exclusive Theory of Organic
Evolution_, quoted, 273.

Indifferent characters, 171, 185, 208, 247.

Insects, instincts of, 91.

Instability of useless characters, 186.

Instinct and hereditary habit, 87;
  of Sphex, 88;
  of carnivora, 89;
  of man, 89;
  Prof. Weismann's views on, 90;
  of insects, 91.

Intercrossing, 67-71.

Isolation, 223 _et seq._


J.

JORDAN, Dr., referred to, 206, 252.


K.

Karyokinesis, 140.

KERNER, Prof., referred to, 174, 202-206, 231, 239, 260, 282; quoted,
203.

KOCH, Dr., referred to, 217.

KÖLLIKER, Prof., referred to, 174.


L.

Lamarck, referred to, 9-15.

Lamarckism, 9, 61, 113.

LANDOR, A. H. Savage, referred to, 26.

Language and Weismannism, 334.

LANKESTER, Prof. Ray, quoted, 245, 299; referred to, 305.

LESAGE, M., referred to, 126.

_Life and Letters of Charles Darwin_, quoted, 319, 320; referred to, 11.

LUCIANI, referred to, 109.


M.

_Making of Flowers_, referred to, 19.

_Manual of British Botany_, referred to, 252.

_Manual of Dental Anatomy_, figure from, 267.

Marsupials, diagnostic characters of, 178.

_Materials for the Study of Variation_, referred to, 36.

MEEHAN, Mr., referred to, 201.

MELDOLA, Prof., referred to, 68.

_Mental Evolution in Animals_, referred to, 25, 88, 89, 92.

_Mental Evolution in Man_, referred to, 31.

MERRIFIELD, Mr., referred to, 211.

Mice, mutilation of tails of, 148.

MIVART, Prof. St. George, referred to, 4, 174, 217.

Monstrosity, in turkeys, 181;
  in cattle, 196.

MORGAN, Prof. Lloyd, referred to, 33, 36, 174, 271, 300-305; quoted,
300, 303.

MOSELEY, Prof., referred to, 26.

MURPHY, Mr. J. J., referred to, 224.

Mutilations, inheritance of, 53, 148.


N.

NÄGELI, Prof., referred to, 174, 206, 318.

Naked skin of man, 25.

NATHUSIUS, referred to, 188.

Natural Selection, range of, 2, 5, 51, 62, 92;
  a theory of species, 161, 169;
  and cave animals, 211;
  and Porto Santo rabbits, 214.

_Natural Selection and Tropical Nature_, quoted, 23.

_Natural Science_, quoted, 104.

_Nature_, quoted, 132, 223, 245, 299, 325; referred to, 68, 98, 218.

Neo-Darwinian school, 10, 61.

Neo-Lamarckian school, 13, 62, 63.

_Neuer Beitrag zum geologischen Beweis der Darwin'schen Theorie_,
quoted, 254.

_Neuter Insects and Darwinism_, referred to, 95.

_Neuter Insects and Lamarckism_, referred to, 95.

Neuters of hymenopterous insects, 92.

NEWMAN, Cardinal, referred to, 20.

Niata cattle, 191.


O.

OBERSTEINER, Dr., referred to, 105, 106.

_Oesterreichische medicinische Jahrbücher_, referred to, 105.

_On Truth_, referred to, 217.

Orang-utan, teeth of, 267.

_Organic Evolution_, referred to, 217.

_Origin of the Fittest_, quoted, 16; referred to, 14.

_Origine des Plantes Domestiques, démontrée par la culture du Radis
sauvage_, referred to, 123.

_Origin of Sex_, referred to, 17.

_Origin of Species_, quoted, 3, 4, 181, 182, 186, 188, 190, 261, 262,
265, 321, 322, 325, 326, 329; referred to, 67, 159, 227, 286.

OSBORN, Prof., referred to, 14, 58, 63.

OWEN, Sir Richard, referred to, 191.

Oxen, skulls of, compared, 192.

Oysters, change of, 217.


P.

PACKARD, Prof., referred to, 14, 213.

Pangenesis, 11, 42.

Panmixia, 97, 212, 291.

Parsimony, law of, 51.

Parsnips, variation of, 125.

PASCOE, Mr., referred to, 174; quoted, 254.

PERRIER, Prof., referred to, 14, 93, 95.

PETER, Dr., referred to, 206.

PFEFFER, Herr, referred to, 15.

_Pflüger's Archiv_, referred to, 80.

_Philosophical Transactions_, referred 10, 103.

_Physiological Selection_, referred to, 187, 307, 313, 324; quoted, 188,
308.

_Pickard-Cambridge_, Rev. O., quoted, 221.

Pig, old Irish, 188.

Plants, influence of climate on, 122-207.

Porto Santo rabbits, 214.

POULTON, E. B., referred to, 36, 217, 337.

_Presidential Address to the Bristol Naturalists Society_, 1891; quoted,
300, 303.

_Proceedings of the Royal Society_, referred to, 145, 147; quoted, 307.

Protective resemblance, 72.

Protrusion of eyeball, in epileptic guinea-pigs, 111.


Q.

QUATREFAGES, M., referred to, 234.


R.

Rabbits, and use-inheritance, 96;
  transplantation of ovaries, 143;
  Porto Santo, 214.

Radish, variation of, 123.

Rats, scratching, reflex of, 81.

_Raupen und Schmetterlinge der Wetterau_, referred to, 217.

Reflex action and use-inheritance, 64-87.

_Rejoinder to Prof. Weismann_, referred to, 95.

Reversal of selection, 101, 292.

_Revue Générale de Botanie_, referred to, 126.

RICHARDSON, referred to, 188.

ROUX, Prof., referred to, 298.

Rudiments, 294.

RYDER, Prof., referred to, 14.


S.

SACHS, Prof., referred to, 15, 174.

"Sally," counting of, 31.

SAUERMANN, Dr., referred to, 218.

SCHÄFER, Prof., referred to, 145.

_Schmetterlinge des Südwestlichen Deutschlands_, referred to, 217.

SCHMIDT, Dr. Oscar, quoted, 260.

Schools of Evolutionists, 12-20.

SCOTT, Prof., referred to, 63.

Scratching, reflex, in dogs, 80;
  in rats, 81.

Seasonal changes of butterflies, 210.

SEEBOHM, Mr. Henry, quoted, 173; referred to, 174.

Selection, cessation of, 99, 292;
  reversal of, 101, 292.

Selection, sexual, 219 _et seq._

Selective value, 73.

Self-adaptation, 18.

SEMPER, Prof. Karl, referred to, 101.

Sexual selection, 219 _et seq._

Sole, pigment of, 104.

Somatogenetic and somatoplasm, 123, 137, 155, 242-249.

_Some Laws of Heredity_, referred to, 24.

Species, stress laid on origin of, 159;
  necessarily due to natural selection, 168.

---- definitions of, 229.

SPENCER, Herbert, referred to, 8, 64-68, 95.

Sphex, instincts of, 88, 337.

STEBBING, Rev. T. R., quoted, 25.

Sterility, 8.

Stirp and germ-plasm, 40, 47, 138.

_Struggle for Existence between the parts of an Organism_, referred to,
299.


T.

Theory of Heredity, referred to, 40, 47, 137, 154; quoted, 46, 47.

THOMAS, Mr. Oldfield, referred to, 178.

THOMSON, J. A., referred to, 15.

TODD, J. E., referred to, 35.

TOMES, Mr., referred to, 267.

Transfusion of blood in rabbits, 145.

Transplantation of ovaries in rabbits, 143, 147.

Trees, comparison of European and American, 201.

Turkey, tuft of hair of, 181;
  losing metallic tints, 186.


U.

Use-inheritance, 3, 49, 77, 95, 151.

Utility, law of, 8, 20, 159;
  universality of, 166;
  of specific characters, 172;
  of specific characters in birds, 176;
  of specific characters in Mammals, 178.


V.

_Variation of Animals and Plants under Domestication_, quoted, 3, 4, 53,
66, 96, 187, 189, 191, 193, 195, 213-216, 330, 331.

Varieties, climatic, 228.

Vestigial characters, 171, 184, 261, 294.

VINES, Prof., referred to, 297.

Vitality, plumes of birds due to surplus, 270, 25.

Voice, of man, 25.


W.

WAGNER, Moritz, referred to, 217.

WALLACE, Mr. A. R., referred to, 2, 6, 9, 11, 15, 20-35, 50, 66-70, 167,
169, 172-175, 180-198, 210, 218-227, 235-237, 252, 256, 258, 263-278,
285, 313-322, 328, 331, 332; quoted, 22-24, 27, 67, 180-182, 185, 186,
190, 191, 221-223, 235, 236, 269, 273, 313.

Wallacean doctrine of species, 167, 169.

WEISMANN, Prof., referred to, 2, 7, 9, 12, 13, 39-60, 65, 66, 90-105,
112, 128, 134-142, 148, 149, 151, 152, 155, 156, 173, 241, 243, 244,
246, 279, 280, 291, 294, 297, 298, 300, 311, 338; quoted, 56, 91, 97,
152, 243, 244, 297.

Weismannism, diagram of constituent theories, 43, 136;
  elusiveness of, 334.

_Weismannism once more_, referred to, 66, 95.

WELBY, Hon. Lady, referred to, 90.

WESTPHAL, Prof., referred to, 105, 107.

Withdrawal of foot by reflex action, 75.

WÜRTENBERGER, Dr., referred to, 254.


Y.

YARRELL, Mr., referred to, 186.




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       *       *       *       *       *

       
       
       
Transcriber's note:

The following typographical errors were correctred.

    |Page |Error         |Correction    |
    |10   |dicussion     |discussion    |
    |45   |thoughout     |throughout    |
    |229  |pyschological |psychological |

The following inconsistent hyphenations were changed.

    |Page |Original       |Changed to    |
    |34   |inter-crossing |intercrossing |
    |46   |re-appear      |reappear      |
    |123  |re-act         |react         |
    |132  |eye-lid        |eyelid        |
    |216  |lifetimes      |life-times    |
    |217  |lifetime       |life-time     |
    |317  |threefold      |three-fold    |

The following inconsistent hyphenations were not changed.

    "somatoplasm" (3 instances) and "somato-plasm" (2 instances)
    "twofold" (2) and "two-fold" (1)
    "interaction" (1) and "inter-action" (1)
    "supernatural" (1) and "super-natural" (1)

Other changes:

    Page 16 Footnote 10 - double quotes around "acceleration" and
    "retardation" changed to single quotes. A double quote inserted at
    the end.

    In the Index - Entries "On Truth" and "Orang-utan, teeth of" moved
    from under "M" to under "O".