DE\ 7 ELOPMENT OF THE TESTICLE. 



J25 



distinguished, but become formed subsequently by an increase in size of one or more 

 of the cells. The further changes which take place in the Graafian follicle are 

 described with the structure of the ovary (v. Splanchnoiogy). The remainder of 



Fig. 151. TRANSVERSE SECTION THROUGH THE OVARY OP AN EMBRYO SHARK (SCYLLIUM), SHOWING THE 



GERM-EPITHELIUM FORMING PRIMITIVE OVA. (Balfour.) 



At po, the germ-epithelium and primitive ova ; the lightly-shaded part is the ovarian strotna, 

 covered elsewhere by flattened epithelium. 



the germinal epithelium which is left covering the surface after the formation of 

 the egg-tubes, constitutes the permanent epithelium of the ovary. 



Most, if not all, of the permanent ova are produced, at least in the human subject, long- 

 before birth, In the human ovary the nests of cells which are to form the Graafian follicles 



Fig. 152 SECTION OP THE OVARY OF A 



NEWLY-BORN CHILD. HlGHLY MAG- 

 NIFIED. (Waldeyer.) 



a, Germinal epithelium dipping in at 

 b, to form an ovarian tube ; c, c, prim- 

 ordial ova lying in the germ-epithelium ; 

 d, d, longer tube becoming constricted so 

 as to form nests of cells ; e, e, larger nests ; 

 /, 'distinctly formed follicle with ovum 

 and epithelium ; g, g, blood-vessels. 



are more equally diffused through the 

 substance of the ovary than in most 

 animals, in many of which the young- 

 follicles remain forming a stratum 

 near the surface. In the human 

 embryo of from four months up to 

 the period of birth, the ovary seems 

 to be formed of little else than a mass 

 of young- ova, closely surrounded by 

 flattened cells of the g-erminal epithe- 

 lium and constituting- thus minute 

 Graafian follicles ; the amount of 



stroma being at this time relatively small. It has been calculated that the ovaries may 

 at this stag-e contain as many as 70,000 primordial ova. 



Development of the Testicle. The germinal epithelium does not undergo so 

 marked an hypertrophy in the male as in the female. But it becomes thickened, 

 and enlarged cells, corresponding to the primordial ova in the female, are found in 

 it. Further, small strands of the epithelium dip down into the subjacent mesoblast, 



