INHERITANCE 215 



parents, it follows that in some sense there is a sort of 

 continuity of material as long as there is life at least in 

 the forms we know of. The theory of the continuity of 

 " germ-plasm ' therefore would be true, even if germ-cells 

 were produced by any and every part of the organism. That, 

 as we know, is not actually the case: germ-cells, at least 

 in the higher animals and in plants, are produced at certain 

 specific localities of the organism only, and it is with regard 

 to this fact that the so-called theory of the " continuity of 

 germ-plasm " acquires its narrower and proper sense. There 

 are distinct and specific lines of cell-lineage in ontogenesis, 

 so the theory states, along which the continuity of germ- 

 protoplasm is kept up, which, in other words, lead from one 

 egg to the other, whilst almost all other lines of cell-lineage 

 end in " somatic " cells, which are doomed to death. What 

 has been stated here is a fact in many cases of descriptive 

 embryology, though it can hardly be said to be more than 

 that. We know already, from our analytical and experi- 

 mental study of morphogenesis, that Weismann himself had 

 to add a number of subsidiary hypotheses to his original 

 theory to account for the mere facts of regeneration proper 

 and the so-called vegetative reproduction in plants and in 

 some animals, and we have learned that newly discovered 

 facts necessitate still more appendixes to the original theory. 

 In spite of that, I regard it as very important that the fact 

 of the continuity of some material as one of the foundations 

 of inheritance has clearly been stated, even if the specialised 

 form of the theory, as advocated by Weismann in the 

 doctrine of the " germ-lineages " (" Keimbahnen ") should 

 prove unable to stand against the facts. 



The important problem now presents itself : What is the 



