[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.]
[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"since the first origin of sexual reproduction," was another very important point of difference, but this has now been withdrawn.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.
[27] Theory of Heredity (Journ. Anthrop. Inst. 1875, p. 346).
[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.
[29] Variation under Domestication, ii. 392.
[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.
[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.