GERM CELLS IN THE ARTHROPODA 135 



in the autumn but return to the mitotic method in 

 the spring, later giving rise to functional spermato- 

 gonia. Vom Rath finds amitosis but contends that 

 the cells that divide in this way do not become sper- 

 matozoa but are degenerating, being used as nutritive 

 material by the other spermatogonia. The amitotic 

 divisions described by McGregor (1899) in Am- 

 phiuma differ in certain respects from those of 

 both Meves and vom Rath. In this species the 

 primary spermatogonia divide by amitosis ; their 

 products later divide by mitosis and produce func- 

 tional spermatozoa. Our knowledge concerning ami- 

 tosis in the spermatogonia of AMPHIBIA is therefore 

 in an unsatisfactory state, although the observations 

 of Meves and McGregor argue strongly in favor of 

 this method. 



CCELENTERATA. While no direct nuclear divi- 

 sions were recorded by Hargitt (1906) in the germ 

 cells of Clava leptostyla the absence of mitotic figures 

 in the early cleavage stages of the egg led him to the 

 conclusion that the "nuclear activity differs greatly 

 from the oridinary forms of mitosis, and appears 

 to involve direct or amitotic division" (p. 229). 

 If this were true, the germ cells which are derived 

 from these cleavage cells must be descended from 

 cells which once divided amitotically. This case 

 of supposed amitosis has been cleared up by the sub- 

 sequent studies of Beckwith (1909), who collected 

 material of Clava very early in the morning and found 

 typical mitotic divisions during the maturation and 

 early cleavage of the egg and no evidence of amitosis. 



