STUDIES ON GERM CELLS 



461 



their connection with the primordial germ cells." The list as 

 given includes representatives of the Coelentei^ta, Chaetognatha, 

 Nematoda, Arthropoda, and Vertebrata. The terms applied 

 to the various substances have been chosen evidently because 

 of their genesis, position in the egg, or supposed function. 



a. From nuclear substances: Nucleoli. It is certain that bodies 

 of a nucleolar nature behave as Keimbahn-determinants. Three 



TABLE 1 

 Principal cases of visible substances concerned in differentiation of germ cells (in 



chronological order) 



