THE GENITAL GLANDS AND DUCTS OVARY 221 



tubules anastomose and form the tubuli contorti. Their proximal portions remain 

 straight as the tubuli recti. The rete testis becomes a network of small tubules 

 which finally unite with the collecting tubules of the mesonephros (see p. 225). 



The primitive genital cells of the testis cords form the spermatogonia of the 

 spermatic tubules and from these at puberty are developed the spermatogonia 

 (p. 24). The indifferent cells of the tubules become the sustentacular cells (of 

 Sertoli) of the adult testis. Primitive genital cells of the intermediate cords are 

 transformed into large pale cells which, after puberty, are numerous in the inter- 

 stitial connective tissue and hence are called interstitial cells. The intermediate 

 cords themselves are resorbed, but. the connective tissue sheaths of the tubules 

 unite to form septula which extend from the mediastinum testis to the tunica 



Mesorchium 



Ductui deferens 



EpHheliutn 



Tunica. 



albuyinea. 



|p 



FIG. 219. Section through the testis of a 100 mm. fetus. X 44. 



albuginea. The latter becomes a relatively thick layer in the adult testis and is so 

 called because of its whitish appearance. 



Anomalies. The testis may be congenitally absent, the glands may be fused or they may 

 fail to descend into the scrotum (cryptorchism). Duplications of the testis are of rare occur- 

 rence. 



The Differentiation of the Ovary. The primitive ovary, like the testis, 

 consists of an inner epithelial mass and an outer epithelial layer. Much more 

 slowly than in the testis the ovarian characters appear. In embryos of 50 to 80 

 mm. the inner epithelial mass composed of indifferent and primitive genital cells 

 becomes less dense centrally and bulges into the mesovarian (Fig. 220). There 

 may be distinguished a dense outer cortex beneath the epithelium, a clearer 

 medullary zone containing large genital cells, and a dense cellular anlage in the 

 mesovarium, the primitive rete ovarii, which is the homologue of the rete testis. 



