THE LATER DEVELOPMENT OF THE CHICK 363 



of a lumen in each sexual cord, which thus puts the cav- 

 ities of the testis into communication with the mesonephric 

 tubules. The sexual cords thus become the rete efferentia. 

 The primordial germ cells, or spermatogonia as they may now 

 be called, lie in the walls of the dilated inner ends of the rete 

 efferentia (sexual cords), into the cavities of which their cell 

 products may be discharged and pass thence, by the vasa 

 efferentia and the vas deferens, to the cloaca. The original 

 "germinal epithelium" becomes converted into a flat covering 

 layer continuous with the peritoneal folds (mesorchia) slinging 

 the testis from the dorsal body wall. 



Ovary. The early development of the ovary parallels that 

 of the testis. Like the right oviduct, the right ovary, after 

 developing for a time, degenerates and disappears. In the 

 left or definitive ovary the primordial germ cells behave as in the 

 testis, at first, but after a brief period their migration ceases 

 and those which have left the primitive germinal epithelium 

 degenerate, together with the sexual cords. The epithelial 

 cells, and the primordial germ cells contained in the epithelium, 

 continue to multiply rapidly, and the mesenchymal stroma 

 becomes abundant. The inner surface of the germinal epi- 

 thelium forms strands of cells projecting into the stroma of the 

 ovary, and containing primordial germ cells or oogonia. These 

 strands segment into separate cell masses or nests, each includ- 

 ing an oogonial cell; the further growth and development of the 

 oogonia have been described in the beginning of the preceding 

 chapter. 



The mesonephros thus has no share in the formation of the 

 reproductive system of the female; its posterior section may be 

 recognized in the vestigial paroophoron, while the homolog 

 of the epididymis of the male is to be seen in the parovarium. 



C. THE ADRENAL BODIES 



Brief reference to the development of the adrenal bodies may 

 be made here, although they are not a part of the renal system. 

 These bodies have a double origin, arising in part from periton- 



