88 THE PROBLEMS OF EVOLUTION 



cells differentiated to carry on the necessary func- 

 tions of the individual constitute the soma. Ac- 

 cording to the Weismannian interpretation the 

 germ plasm thus has power to perpetuate itself 

 while developing in successive generations the so- 

 matic tissues through which it is associated with 

 the environment. The somatoplasm is therefore 

 discontinuous while the germ plasm is continuous. 

 In contrast to this condition, the association be- 

 tween cytoplasm and nucleus is never interrupted; 

 the continuity is twofold. A true parallel would 

 exist if the chromosomes alone carried on the 

 reproduction of cells and if daughter groups of 

 chromosomes gave rise to the cytoplasm of the 

 new cells, but this is not known to occur in any 

 case and as a rule is obviously not the method of 

 cell division. As cell division actually proceeds it 

 is parallel only with fission and to some extent 

 with budding but not with sexual reproduction. 

 Another point of view admits the parallel un- 

 conditionally and permits the recognition of the 

 germinal cytoplasm as a connecting link between 

 the somatoplasm of successive generations; it 

 would be difficult to defend this interpretation. 

 Nevertheless there is a parallel in the fact that 

 neither chromosomes nor germ cells, in themselves, 

 express their own potentiality; they must accom- 

 plish this end through interaction with the cyto- 

 plasm on the one hand and the somatic cells on the 



