448 Morphogenetic Factors 



the chromosomes as such. It may be that all the effects now attributed to 

 chromosomes may ultimately be found to be due to their genes. 



It must regretfully be admitted that not very much of substantial impor- 

 tance has yet been contributed by genetic analysis to a solution of the 

 problems of morphogenesis. Its most significant addition to our knowl- 

 edge of development thus far is perhaps the discovery of the relation be- 

 tween the size of a cell and the degree of its internal polyploidy, with the 

 bearing this fact has on the control of histological differentiation. Behind 

 the other problems of morphogenesis still lurks the unanswered question 

 of how genes control the development of form and structure and thus 

 the orderly and integrated growth of an individual as an organism. En- 

 vironmental factors have an important influence on the character of this 

 organism, but the organizing process itself seems to be centered in proto- 

 plasm and thus to be under the control of the directive and self-multi- 

 plying elements in protoplasm, the genes. It is to this general problem of 

 organization that attention in our final chapter is directed. 



