104 An Examination of Weismannism. 



been perpetually continuous " since the first origin of 

 life," and absolutely stable " since the first origin of 

 sexual reproduction." It is clear that these two 

 additional postulates are not needed for his theory of 

 heredity, but only for his additional theory of evolu- 

 tion. There have been other theories of heredity, 

 prior to this one, which, like it, have been founded on 

 the postulate of" continuity " (in Weismann's sense) of 

 the substance of heredity ; but it has not been needful 

 for any of these theories to postulate further that this 

 substance has been always thus isolated, or even that 

 it is now invariably so. For even though the isolation 

 be frequently invaded by influences of body-changes 

 on the congenital characters of this substance, it does 

 not follow that the body-changes must be transmitted 

 to offspring exactly as they occurred in parents. They 

 may produce in offspring what we have agreed to call 

 " specialized " hereditary changes, even if they never 

 produce " representative '"' hereditary changes, — i.e., 

 the transmission of acquired characters. But it is 

 essential to Weismann's theory of evolution that body- 

 changes should not exercise a modifying influence 

 of any kind on the ancestral endowments of this 

 substance ; hence, for the purposes of this further 

 theory he has to assume that germ-plasm presents, 

 not only continuity \ but continuity unbroken since tlie 

 first origin of life. 



Similarly as regards his postulate of the stability of 

 germ-plasm as absohite. It is enough for all the 

 requirements of his theory of heredity, that the sub- 

 stance in question should present the high degree of 

 stability which the facts of atavism, persistence of 

 vestigial organs, &c, prove it to possess. But for his 



