134 GERM-CELL CYCLE IN ANIMALS 



the formation of chromosomes and amphiaster" 

 (p. 437) and concludes from a review of the literature 

 up to the year 1900 "that in the vast majority of 

 cases amitosis is a secondary process which does not 

 fall in the generative series of cejl-di visions" (p. 119). 

 During the past ten years interest in direct nuclear 

 division has been maintained principally because of 

 the claims of certain investigators that germ cells 

 may multiply in this way and still give rise to func- 

 tional eggs or spermatozoa. 



During amitosis the chromatin remains scattered 

 within the nucleus and does not form a spireme 

 nor chromosomes, and therefore its individual ele- 

 ments, the chromatin granules, do not divide. As 

 a result of this mass-division there can be no accurate 

 segregation of chromatin granules in the daughter 

 nuclei as is demanded by the theory that the nucleus, 

 and particularly the chromatin, contains the de- 

 terminers of hereditary characteristics. Further- 

 more, nuclear division without the formation of 

 chromosomes obviously condemns the hypothesis 

 of the genetic continuity of the chromosomes, and 

 hence seriously interferes with current ideas regard- 

 ing the significance of the accessory chromosomes in 

 the determination of sex. Among the animals in 

 whose germ cells amitosis has been reported are cer- 

 tain AMPHIBIA, ccelenterates, cestodes, and insects. 



AMPHIBIA. Vom Rath (1891, 1893), Meves (1891, 

 1895), and McGregor (1899) have recorded amitosis 

 in the germ cells of AMPHIBIA. Meves claims that 

 the spermatogonia of Salamandra divide amitotically 



