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diff --git a/37759.txt b/37759.txt new file mode 100644 index 0000000..8079614 --- /dev/null +++ b/37759.txt @@ -0,0 +1,11467 @@ +The Project Gutenberg eBook, Darwin, and After Darwin, Volume II (of 3), +by George John Romanes + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: Darwin, and After Darwin, Volume II (of 3) + Post-Darwinian Questions: Heredity and Utility + + +Author: George John Romanes + + + +Release Date: October 15, 2011 [eBook #37759] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK DARWIN, AND AFTER DARWIN, VOLUME +II (OF 3)*** + + +E-text prepared by Marilynda Fraser-Cunliffe, L. N. Yaddanapudi, and the +Online Distributed Proofreading Team (http://www.pgdp.net) + + + +Note: Project Gutenberg also has an HTML version of this + file which includes the original illustrations. + See 37759-h.htm or 37759-h.zip: + (http://www.gutenberg.org/files/37759/37759-h/37759-h.htm) + or + (http://www.gutenberg.org/files/37759/37759-h.zip) + + + + + +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. + 1. THE DARWINIAN THEORY. 460 pages. 125 illustrations. Cloth, + $2.00. + 2. POST-DARWINIAN QUESTIONS. Edited by Prof. C. Lloyd Morgan. + 338 pages. Cloth, $1.50. Both volumes together, $3.00 net. + + AN EXAMINATION OF WEISMANNISM. 236 pages. Cloth, $1.00. + + THOUGHTS ON RELIGION. Edited by Charles Gore, M.A., Canon of + Westminster. Second Edition. 184 pages. Cloth, gilt top, $1.25. + + +THE OPEN COURT PUBLISHING COMPANY, +324 DEARBORN STREET, CHICAGO. + + * * * * * + + +[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 _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 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 _role_ 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'etre_ 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] _Pflueger'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-Sequard 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-Sequard 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-Sequard'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-Sequard'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 Jahrbuecher_, 1875, 179. + +In view of Obersteiner's corroboration of Brown-Sequard'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-Sequard'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-Sequard'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-Sequard'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-Sequard'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-Sequard, 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-Sequard'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-Sequard. + +First, with regard to Brown-Sequard'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-Sequard 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-Sequard'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-Sequard'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-Sequard'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-Sequard 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-Sequard'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-Sequard, 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-Sequard; 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-Sequard 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-Sequard 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-Sequard 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-Sequard'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. Carriere[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, demontree 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 reussi surtout pour le _Lepidium sativum_ cultive en 1888; + j'ai obtenu pour la meme plante des resultats plus nets encore dans + la culture de 1889, entreprise en semant les graines recoltees avec + soin des pots de l'annee precedente et traitees exactement de la + meme facon[76]." + + [76] _Rev. Gen. 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-Sequard'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-Sequard'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-Sequard'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 Schaefer), +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, Naegeli, Kerner, Sachs, +De Vries, Focke, Henslow, Haeckel, Koelliker, 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 +_resume_ 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. Anfaenglich mueht 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 Fuessen, die bisher fuer unverrueckbar 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 kuenstliche sind, gewinnt immer mehr und + mehr die Oberhand, und wer nicht gerade zu den hartgesottenen + Eigensinnigen gehoert, und wer die Wahrheit hoeher stellt als das + starre Festhalten an seinen frueheren Ansichten, geht schliesslich + bewusst oder unbewusst in das Lager derjenigen ueber, in welchem + auch ich mir ein bescheidenes Plaetzchen 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 +(Artsbestaendigkeit) 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 +Gaertner, De Candolle, Naegeli, 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 Suedwestlichen + 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 +Delboeuf'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 _qua_ 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 Precurseurs + Francais_ 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, _qua_ 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'etre_ 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 Wuertenberger, 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 Haeckel) 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, Haeckel, 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:[infinity]. 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 Linnaean 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 Naegeli 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 Naegeli 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 Naegeli, 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-SEQUARD, 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. + +CARRIERE, 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 Precurseurs Francais_, 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. + +DELB[OE]UF, 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. + +GAERTNER, 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. + +KOELLIKER, 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. + +NAEGELI, 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 Jahrbuecher_, 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, demontree 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. + +_Pflueger'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 Generale 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. + +SCHAEFER, Prof., referred to, 145. + +_Schmetterlinge des Suedwestlichen 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. + +WUERTENBERGER, Dr., referred to, 254. + + +Y. + +YARRELL, Mr., referred to, 186. + + + + +LIST OF OPEN COURT PUBLICATIONS ON SCIENCE + + +The Primary Factors of Organic Evolution. By E. D. Cope. Second +edition. Pages, 550; illustrations, 121; tables, bibliography, and +index. Cloth, $2.00 net. + + A comprehensive handbook of the Neo-Lamarckian theory of Evolution. + + +A Mechanico-Physiological Theory of Organic Evolution. By Carl von +Naegeli. Translated by V. A. Clark and F. A. Waugh. Price, cloth, 60c; +paper, 30c net. + + A synopsis of his great work on evolution. + + +Darwin and After Darwin. An exposition of the Darwinian Theory and a +Discussion of Post-Darwinian Questions. By George J. Romanes. 3 vols. +Price, $4.00 net. + +Part I. The Darwinian Theory. Price, cloth, $2.00 net. + +Part II. Post-Darwinian Questions: Heredity and Utility. Price, cloth, +$1.50 net. + +Part III. Post-Darwinian Questions. Isolation and Physiological +Selection. Price, cloth, $1.00 net. + + +An Examination of Weismannism. By George J. Romanes. Price, cloth, +$1.00 net; paper, 40c net. + + "The best criticism of the subject in our language."--_The + Outlook._ + + +On Germinal Selection. By August Weismann. 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Cloth, per volume, $4.00. + + This is de Vries' great book on a new explanation of the evolution + theory, accounting for the formation of species not by the struggle + for existence but by mutation. + + +Intracellular Pangenesis. Including a paper on Fertilization and +Hybridization. By Hugo de Vries. Translated from the German by C. +Stuart Gager. Cloth, $3.00 net. + + This is de Vries' first important book. It is not very large, but + ought to be read by all students of botany, and also by those who + are interested in the theory of evolution. + + +On Orthogenesis and the Impotence of Natural Selection in +Species-Formation. By Th. Eimer. Translated by T. J. McCormack. +Price, paper, 30c net. + + Another critic of Darwin who claims that organisms develop through + transmission of acquired characters. + + +On the Inheritance of Acquired Characters. By Eugenio Rignano. +Translated by Basil C. H. Harvey. With an Appendix "On the Mnemonic +Origin and Nature of Affective Tendencies." Cloth, $3.00 net. + + Rignano calls his theory "centro-epigenesis" and is greatly + influenced by Weismann. + + +On Double Consciousness. Studies in Experimental Psychology. By +Alfred Binet. Third edition. Pages, 93. Cloth, 50c net; paper, 20c +net. + + "A most valuable contribution to this important subject which none + of its students can afford to leave unread."--_Public Opinion._ + + +The Psychic Life of Micro-Organisms. By Alfred Binet. Authorized +translation. Pages, xii, 120. Cloth, 75c net; paper, 30c net. + + "He fortifies his theory by such a wealth of exact observation and + experiments that the reader who follows his demonstration carefully + can hardly fail of conviction."--_New York Tribune._ + + +The Psychology of Reasoning. By Alfred Binet. Translated from the +second French edition by Adam Gowans Whyte, B.Sc. Pages, 191. 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