Summary. 109 



on which this theory is founded ; but he does so 

 without appearing to perceive the speculative im- 

 possibility of any longer sustaining his temple of 

 evolution if he were to remove its pillars of germ- 

 plasm. 



Ignoring, then, these inconsistencies, we proceeded 

 to examine separately, and on their own respective 

 merits, the two distinctive postulates of the theory 

 of germ-plasm — perpetual continuity since the first 

 origin of life, and absolute stability since the first 

 origin of sexual propagation. 



It does not appear to me that very much has to 

 be said, either for or against the former postulate, 

 on merely antecedent grounds, or grounds of general 

 reasoning. Therefore I relegated to an Appendix 

 my examination of what Weismann has argued on 

 these grounds, while in the text I considered only 

 what he has advanced as evidence a posteriori. Here, 

 as we saw, he has developed three distinct lines of 

 verification — viz. (A) the migration of germ-cells in 

 some of the Hydromedusae, (B) the early separation 

 of germ-cells in the ontogeny of certain Invertebrata, 

 and (C) the alleged invariability of organisms which 

 are produced parthenogenetically. But we have seen, 

 with respect to (A), that the specialized character 

 of germinal cells is a fact which every theory of 

 heredity must more or less recognize ; and, therefore, 

 that the migration of these cells, wherever it may be 

 found to occur, does not lend any peculiar countenance 

 to Weismann's theory. There may be many reasons 

 for such migration other than the one which this 

 theory assigns ; while the reason which it does assign 

 is rendered improbable by the consideration that in 



