72 An Examination of Weismannism. 



stages of transposition are repeated, with the result 

 that during the individual lifetime of one of these 

 animals the germ-cells migrate through the body, from 

 what used to be their ancestral situation to what is 

 now the normal situation for that particular species. 

 Such being the facts, Weismann argues from them 

 that the germ-cells of the Hydromedusae are thus 

 proved to present properties of a peculiar kind, which 

 cannot be supplied by any of the other cells of the 

 organism ; for, if they could, whence the necessity for 

 this migration of these particular cells? Of course 

 it follows that these peculiar properties must depend 

 on the presence of some peculiar substance, and that 

 this is none other than the "germ-plasm." which here 

 exhibits a demonstrable "continuity" throughout the 

 entire phylogeny of these unquestionably very ancient 

 Metazoa. 



The second line of direct evidence in favour of the 

 continuity of germ-plasm which Weismann has ad- 

 duced is, that in the case of some invertebrated animals 

 the sexual apparatus is demonstrably separated as 

 reproductive cells (or cells which afterwards give rise 

 to the reproductive glands) at a very early period of 

 ontogeny — so early indeed, in certain cases, that this 

 separation constitutes actually the first stage in the 

 process of ontogeny. Therefore, it is argued, we may 

 regard it as antecedently improbable that the after-life 

 of the individual can in any way affect the congenital 

 endowments of its ova, seeing that the ova have been 

 thus from the first anatomically isolated from all the 

 other tissues of the organism. 



The third and only other line of direct evidence is, 

 that organisms which have been produced partheno- 



