120 GERM-CELL CYCLE IN ANIMALS 



one to ten. The oocytes that become eggs are those 

 that chance to lie at the periphery of the ovary and 

 hence are in a position to derive abundant nutrition 

 from the blood. The oocytes that fail to become 

 eggs are not, according to De Winter, "vitello- 

 genes" but true abortive eggs, representing a more 

 primitive stage than the nurse cells of other insects 

 which have acquired, secondarily, a nutritive func- 

 tion. 



On the other hand, Govaerts (1913) argues strongly 

 in favor of the view that the ob'gonia divide differen- 

 tially, the daughter cells becoming true germ cells 

 (the ultimate oogonia) and true somatic cells (the 

 nurse cells). He bases his position upon the condi- 

 tions existing in the ovaries of certain beetles of the 

 genera Carabus and Cicindela, and upon the dis- 

 coveries of Giardina (1901), Debaisieux (1909), 

 and Giinthert (1910) in Dytiscus marginalis. Giar- 

 dina established for Dytiscus the fact that the mito- 

 ses which result in the formation of nurse cells are 

 differential, as theoretically postulated by Paulcke 

 (1900). During the four divisions preceding the 

 formation of the oocyte a single ob'gonium gives rise 

 to one oocyte and fifteen nurse cells (Fig. 38). A 

 differentiation takes place in the chromatin of the 

 oogonial nucleus, one half consisting of a condensed 

 mass, the other half of large granules which corre- 

 spond to the forty chromosomes of the ob'gonium 

 (Fig. 38, A). During mitosis the chromosomes 

 become arranged as an equatorial plate, and the 

 chromatic mass forms a ring about it the "anello 



