THE CELLULAR BASIS 187 



protoplasm out of the protoplasm of the germ 

 cells. It is plain that different kinds of proto- 

 plasm are present in the two germ cells before 

 they unite in fertilization, but in the course of 

 development the number of substances present 

 and the degree of difference among them 

 greatly increase. 



Actual observation shows that by the inter- 

 action with one another of substances or parts 

 originally present and by their reactions to 

 external stimuli new substances and parts ap- 

 pear which had no previous existence just as 

 new substances result from chemical reactions. 

 This is "creative synthesis" in philosophy, 

 epigenesis in development. Differentiations 

 appear chiefly in the cytoplasm but only as the 

 result of interaction between cytoplasm and 

 nucleus. Similarly, it may be argued, smaller 

 units of organization such as chromosomes or 

 chromomeres do not in themselves give rise to 

 any adult part, but only as they interact upon 

 other units are new parts formed. 



In many cases the first formation of such 

 new substances appears in the immediate 

 vicinity of the nucleus and, like assimilation 



