GERM CELLS IN THE ARTHROPODA 121 



cromatico" (B). This ring passes intact to one of 

 the daughter cells (C), whereas the chromosomes are 



C D x^^ p 



FIG. 38. Differentiation of nurse cells and oocytes in Dytiscus mar- 

 ginalis. A. Oogonium with chromatin of nucleus separating into 

 two parts. B. Metaphass of oogonial mitosis ; the " anello croma- 

 tico" is situated at the lower end of spindle. C. Two-cell stage; 

 the lower cell with nucleus containing two sorts of chromatin. 

 D. Four-cell stage; "anello cromatico" in one cell. E. Eight-cell 

 stage ; cells ready to divide. F. Sixteen-cell stage ; one large cell 

 (oocyte) with chromatin from the "anello cromatico," and fifteen 

 nurse cells. (A-D, F, from Giardina, 1901; E, from Debaiseaux, 1909.) 



equally divided. During the succeeding mitoses 

 similar differential divisions occur resulting in one 

 oocyte containing the chromatic ring (Fig. 38, F) and 



