THE CELLULAR BASIS 179 



by the interaction of nucleus and cytoplasm, 

 and most probably the chromosomes are an 

 important factor in this process. But in no 

 case is the cytoplasm a neglible factor, in no 

 case does it serve merely as food for the 

 chromosomes. The entire cell, nucleus and 

 cytoplasm, is concerned in heredity and 

 differentiation. 



D. THE MECHANISM OF DEVELOPMENT 



Development consists in the transformation 

 of the oosperm into the adult. What is the 

 mechanism by which this transformation is 

 effected? There is progressive differentiation 

 of the germ into the developed organism but 

 by what process is this differentiation ac- 

 complished? 



Many different processes are concerned in 

 embryonic differentiation. From the stand- 

 point of the cell the most important of these 

 are (1) the formation of different kinds of 

 substances in cells, (2) the localization and 

 isolation of these substances, (3) the trans- 

 formation of these substances into the various 



