240 



MICROSCOPIC ANATOMY OF THE ORGANS. 



structures, the Schlauche of Pfliiger. The primordial ova are 

 thus collected into groups, called egg nests (Eiballen). 



The egg nests are divided into smaller cell groups by the 

 ingrowth of connective tissue. In each of these primordial 

 follicles we find at least one ovum, and often three or four, 

 which are surrounded by a layer of germinal epithelium cells, 

 the follicular cells. Later, each primordial follicle contains 

 only one ovum, partly because the others disintegrate, and 

 partly because a follicle containing more than one ovum is 

 usually split up by connective tissue into as many follicles as 

 there are ova. The follicular cells tend to increase greatly in 

 number. 



Further changes which usually occur in post-embryonal 

 life consist in the great increase in the follicular cells by karyo- 



Fio. 184. 



Prim (in/ 

 follicle 



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Blond- 



epithelium 



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From a section through the cortex of an ape's ovary. X 150. 



kinesis and the production by these of several layers around 

 the ovum (Fig. 184). In the layers of follicular cells there 

 occur during the growth of the follicle certain changes. The 

 ovum increases in size and there is developed around it a deli- 

 cate membrane the zona pellucida which, according to some, 

 is a product of the follicular cells, while others hold that it 

 arises from the ovum itself. At the same time the egg proto- 



