76 ROBERT W. HEGNER 



d. Summary of the studies of chromatin mass and cell size 



1. Measurements were made of the chromatin masses con- 

 tained in the nuclei of eighty specimens of A. dentata, forty spec- 

 imens belonging to family 150 and forty specimens belonging to 

 family 58. The two chromatin masses in any one specimen 

 were very nearly equal. The chromatin masses in the different 

 specimens varied considerably in size, but the mean quantity of 

 chromatin in the specimens of family 150, which were large, was 

 much greater than the mean quantity of chromatin in the smaller 

 specimens belonging to family 58. 



2. Similar measurements were made of the chromatin masses 

 contained in the nuclei of members of families ap. 5 and ap. 34 

 of A. polypora. It was found that in specimens of family ap. 5, 

 which were large in comparison with the number of nuclei, the 

 chromatin masses were large, whereas in specimens of family 

 ap. 34, which w^ere smaller in comparison with the number of 

 nuclei, the chromatin masses were smaller. The quantity of 

 chromatin, however, contained in specimens of the same size 

 within the two families was very nearly the same. In these 

 specimens, as in those of A. dentata, although there was consid- 

 erable variation in the chromatin masses within different speci- 

 mens, the chromatin masses within any one specimen were 

 approximately the same. 



3. Measurements of the chromatin masses in specimens of 

 two diverse lines of A. dentata indicate that the specimens in 

 the larger line all died because of the small amount of chromatin 

 they possessed in comparison with the size of the cytoplasmic 

 body. 



7. DISCUSSION 



Certain topics that have been mentioned in the foregoing 

 pages are worthy of further elaboration and are discussed in the 

 following paragraphs. 



1 . The n ucleocytoplasmic-r elation theory 



This theory is based on the idea that the nucleus is the dy- 

 namic center of the cell. The nuclear membrane is considered as 



