THE FORMATION OF GERM-CEI.LS 213 



of the somatic cells was only subsequently provided with germ- 

 plasm in a latent condition in those cases in which this arrange- 

 ment was a useful one. I hold the latter view, and de \'ries the 

 former one. It is important for the theory of the germ-plasm 

 to decide between these two opinions ; for it would be incom- 

 patible with this theory for germ-substance to be present as the 

 idioplasm of the somatic cells at the phyletic origin of the 

 soma. According to my conception of the germ-plasm, the 

 phyletic origin of the somatic cells depends on the determinants 

 contained in the germ-plasm being separated into groups. It 

 would entirely contradict this assumption if those somatic cells 

 which were phyletically the first to be formed, had contained all 

 the other characters of the species in a latent condition in addi- 

 tion to their manifest specific characters. De Vries thinks that 

 the marked distinction which actually exists between the somatic 

 and germ-cells of the higher animals has led me to assume 

 the universal existence of this contrast, which is not nearly 

 of such a decided nature in the case of plants in which gradual 

 transitions from somatic-cells to germ-cells can be proved to 

 exist. 



This, however, I believe is not the case : transitions between 

 somatic and germ-cells never occur, and de \'ries's opinion 

 simply rests on the fact that he confuses germ-cells with the 

 cells of the germ-track. That the latter must be regarded as 

 somatic cells has already been shown. 



In my opinion, germ-cells were sharply distinguished from 

 somatic cells on their first appearance in phylogeny, and this 

 distinction has since persisted. In no species, whether animal 

 or vegetable, can there be any doubt as to the cells which are to 

 be looked upon as germ-cells ; and as regards the somatic cells, 

 such a doubt can only arise when cells in the germ-track are 

 regarded as germ-cells. 



I know of no more convincing proof of my view than that 

 which is furnished by the VolvocincE. These organisms consist 

 of communities of cells which may or may not exhibit a division 

 of labour, and in which a contrast between the somatic and 

 germ-cells may or may not exist. In PaHciorina all the cells of 

 the colony are similar to one another, and each performs all the 

 vital functions. In Volvox the cells are differentiated: some 

 of them have the function of maintaining the individual, and 

 others that of preserving the species : that is to say, they are 



