586 



ZOOLOGY 



SECT. 



Development. The ova of Mammals (Fig. 1213), like those 

 of Vertebrates in general, are developed from certain cells of 

 the germinal epithelium, the primitive ova (pr. ov.}. Each of 



Jbr.ov 



bl.V 



Joti 



FIG. 1213. Part of a sagittal section of an Ovary of a new-born child, bl. v. blood-vessels ; foil. 

 strings and groups of cells derived from the germinal epithelium becoming developed into 

 follicles ; g. ep. germinal epithelium ; in. ingrowing cord of cells from the germinal epithelium ; 

 >/-. oo. primitive ova. (From Hertwig, after Waldeyer.) 



these, surrounded by smaller unmodified cells of the epithelium, 

 sinks into the stroma of the ovary, in which it becomes embedded, 

 the small cells forming a Graafian follicle (foil.) which encloses it. 



cap 



ov 



FIG. 1-214. Two stages in the development of the Graafian follicle. A, with the follicular 

 fluid beginning to appear ; B, after the space has largely increased, caps, capsule ; disc. 

 cumulus proligerus ; memb. membrana granulosa ; ov. ovum ; sp. space containing fluid. 

 (After Hertwig.) 



Spaces filled with fluid soon appear among the follicle cells (Fig. 

 1214, Asp.), and these eventually coalesce to form a single cavity. 

 This cavity, which in some Mammals is crossed by strings of 



