Darwin, and After Darwin.

Volume II.

by George John Romanes.

PREFACE

As its sub-t.i.tle 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 a.s.sailing 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 pa.s.sed 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 a.s.sistance. After much search I am unable to give the references to one or two pa.s.sages.

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_.

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 a.s.sisted 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 const.i.tutes 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 acc.u.mulative, 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 a.s.sociating 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 mult.i.tude 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 pa.s.ses 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 pa.s.sage from the _Origin of Species_. The first paragraph of the "Conclusion" is devoted to a _resume_ 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 pa.s.sage 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 s.e.xual

suggestion as to s.e.xual

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 ant.i.thetical 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 a.s.sisted by the co-operation of other causes.