2^0 GERM-CELL CYCLE IN ANIMALS 



granulated protoplasm, an opinion concurred in by 

 Hasper (1911), who terms it "Keimbahnplasma." 

 The similar material in Miastor metraloas, the 

 **polares Plasma," is considered a special sort of 

 protoplasm by Kahle (1908), and I can confirm this 

 for Miastor americana. Further evidence of the 

 protoplasmic nature of the substances which be- 

 come segregated in the primordial germ cells is fur- 

 nished by Boveri's experiments on Ascaris. In 

 1904 this investigator concluded from a study of 

 dispermic oggs that the diminution process is con- 

 trolled by the cytoplasm and not by an intrinsic prop- 

 erty of the chromosomes, and that the chromosomes 

 of nuclei lying in the vegetative cytoplasm remain 

 intact, whereas those of nuclei embedded in the 

 animal cytoplasm undergo diminution. This con- 

 clusion has been strengthened by more recent experi- 

 mental evidence (Boveri, 1910) both from observa- 

 tion on the development of dispermic eggs and 

 from a study of centrifuged eggs (see p. 178, Fig. 

 53) . Boveri's results furnish a remarkable confirma- 

 tion of the conclusions reached by the writer from a 

 morphological study of the germ cells of chrysomelid 

 beetles and expressed in the following words: "All 

 the cleavage nuclei in the eggs of the above-named 

 beetles {Calligrapha multipunctata, etc.) are poten- 

 tially alike until in their migration toward the periph- 

 ery they reach the 'keimhautblastem.' Then those 

 which chance to encounter the granules of the pole- 

 disc are differentiated by their environment, i.e., the 

 granules, into germ cells; all the other cleavage 



