THE CELLULAR BASIS 169 



1. Nuclear Correlations. — Many biologists 

 maintain that the nucleus and more particu- 

 larly the chromosomes are the exclusive seat 

 of the "inheritance material" and that the cyto- 

 plasm serves merely as environment for the 

 nucleus. Against the extreme form of this 

 theory many general and specific objections 

 may be urged. General objections are based 

 upon the consideration that the entire cell, 

 cytoplasm as well as nucleus, is concerned in 

 differentiation and that neither is capable of 

 embryonic development in the absence of the 

 other. Differentiation is indeed the result of 

 the interaction of nucleus and cytoplasm, and 

 how then can it be said that the nucleus is the 

 only seat of the inheritance material? If held 

 rigidly, this theory involves the assumption 

 that the cytoplasm and all other parts of the 

 cell are the products of the chromosomes, and 

 that therefore the chromosome and not the cell 

 is the ultimate independent unit of structure 

 and function. Furthermore, since heredity in- 

 cludes a series of fundamental vital processes 

 such as assimilation, growth, division and dif- 

 ferentiation, there is something primitive and 



