158 An Examination of Weismannism. 



germ-plasm is such that in no case can amphimixis 

 have had anything to do with the oidgin of congenital 

 variations, he continues to regard the stability of 

 germ-plasm sufficiently great to necessitate, in all 

 cases, the occurrence of amphimixis in order to 

 promote the development of congenital variations. In 

 other words, notwithstanding that he now thinks all 

 congenital variations must be begun by external 

 conditions acting directly on an unstable germ-plasm. 

 he also thinks that the amount of variation thus 

 produced is likely to be exceedingly minute, and 

 must therefore be increased by subsequent amphi- 

 mixis in order to fall within the range of natural 

 selection. So that, although powerless to initiate 

 congenital variation, amphimixis must still play an 

 indispensable part in the process of evolution, as in 

 all cases a necessary condition to the occurrence of 

 natural selection. External conditions first cause 

 slight changes in the determinants of a species ; but 

 these are so slight that they have to be augmented by 

 amphimixis before they constitute material on which 

 natural selection can act, and hence before they can 

 become of any significance either in ontogeny or 

 phylogeny. 



Such. I take it, is what Professor Weismann would 

 now have us to understand ; for otherwise I should 

 have expected from him as frank a surrender of his 

 theory of evolution (or the remnant thereof in his 

 theory of variation) as he has made of its funda- 

 mental postulate. But, if such is his meaning, I may 

 mention the reasons which appear to me to render 

 it nugatory. 



In the first place, it is evident that in thus 



