DARWINISM ATTACKED. 77 



species, as Darwin himself claims, then, as he also points out, 

 it is a useful acquirement that cannot have arisen through 

 natural selection. It is not difficult to show why this must 

 be so. If two varieties were to some extent at the start 

 less fertile, inter se, than with their own kind, the only way 

 in which they could become more infertile through selection 

 would be by selecting those individuals in each generation 

 that are still more infertile, but the forms of this sort would, 

 ex hypothese, become less numerous than the descendants 

 of each species itself, which would, therefore, supplant the 

 less fertile ones." Darwin admits that this situation cannot 

 apparently be explained by natural selection, and simply 

 says that to him it appears "that the sterility both of first 

 crosses and of hybrids is simply incidental or dependent on 

 unknown differences in their reproductive systems." 



Wolff 9 has urged strongly the objection that natural selec- 



tion does not explain the degeneration or atrophy of parts, 



at least not large or nearly complete reduction. 



Objection that 



selection cannot And Weismann and other selectionists long 



conceded that some sort of auxiliary prin- 

 generationof ciple was necessary to explain degeneration on 

 a Darwinian basis. This principle was supplied 

 by Weismann, under the name of panmixia, which is, simply, 

 that a constantly active selection is necessary not only for 

 the evolutionary development or specialisation of an organ 

 but as well for its retention in specialised condition. 10 

 So. that an organ which is no longer used and is therefore 

 useless comes no longer under the supporting influence of 

 selection (on the basis of advantage) and must consequently 

 degenerate. But, as Wolff says, it seems obvious that such 

 an influence or effect of the cessation of selection or of 

 panmixia (so-called by Weismann because all variations 

 good and bad alike mix -md compensate each other) can 

 at best lead to degeneration or atrophy only when the 

 negative or reducing variations are in the majority, for when 



