124 ^- n Examination of Weismannism. 



independently : it appears to be always the case that 

 in the phenomena of variation a smaller or a larger 

 group of cells is concerned. Now there must be 

 something that determines the similar and simul- 

 taneous variation of such a whole group of cells ; 

 and, in all cases where such a variation is congenital, 

 it is certain that this something must be contained 

 in the substance of heredity. So far. I think, we 

 must all agree, whether or not we regard this sub- 

 stance as "germ-plasm." In other words, whether 

 we regard the carriers of heredity as proceeding 

 centrifugally | germ-plasm ) or centripetally (gemmules), 

 it seems to me that we ought to accept Weismann's 

 doctrine of determinants. Indeed, pathologists have 

 already furnished a foreshadowing of such a doctrine 

 in regard to the phenomena presented by certain 

 diseases, such as cancer ; but it is an important step 

 to have extended the idea from pathology to biology 

 in general — and. at the same time, to have given it 

 a more definite shape than it has hitherto presented. 

 In Weismann's hands it serves to render more con- 

 ceivable — if not also more intelligible — that process 

 of marshalling cell-formations, which, be our theories 

 what they may, is assuredly the most distinctive and 

 remarkable fact of ontogenetic organization. 



Again, as regards the id, I do not see how any one 

 can attentively read Professor Weismann's discussion 

 without acknowledging that, if we once accept his 

 doctrine of determinants, his sequent doctrine of ids 

 becomes a logical necessity. 



On the other hand, however, I do not see that 

 such is the case with respect to idants ; and still less 

 do I see any reason for identifying the latter with 



