CHAPTER IV. 



Examination of Weismann's Theory 

 of Evolution (1891). 



HAVING now considered germ-plasm as perpetually 

 continuous, we have next to regard it as unalter- 

 ably stable. 



First, let it be noted that these two fundamental 

 and distinctive postulates of the whole Weismannian 

 system are so mtimatefy connected as to be in large 

 measure mutually dependent. For, on the one 

 hand, if germ-plasm has not been perpetually con- 

 tinuous since the first origin of life, it cannot have 

 been absolutely stable " since the first origin of sexual 

 propagation " : every time that its hereditary characters 

 are modified by its containing soma (whether or 

 not representatively so), its stability has been so 

 far upset. On the other hand, if germ-plasm has 

 not been absolutely stable, it cannot have been per- 

 petually continuous " since the first origin of life." 

 As often as its stability has been upset, its " mo- 

 lecular structure" has been modified by causes ab 

 extra, as distinguished from mixtures of germ-plasms 

 in sexual unions. Therefore, it can no longer have 

 been continuous in the sense of having borne an 

 ineffaceable record of all congenital variations, due to 

 sexual unions t throughout the entire phylogeny of 



