THE URINOGENITAL SYSTEM 



393 



indifferent gonad, viz., the stroma cells and the sexual cords 

 (segmental or genital cords). The stroma is formed from mesen- 

 chyme situated internal to the germinal epithelium. It is a 

 very narrow layer at first, and is formed, in part at least, by pro- 

 liferation of the germinal epithelium itself, in the same manner 

 as mesenchyme is formed elsewhere by proliferation from the 

 mesoderm. The stroma of the gonad is separated from the tubules 



W.D 



FIG. 226. Cross-section through the genital primordium of Limosa sego- 

 cephala. (After Hoffmann, from Felix and Biihler.) 



The stage is similar to that of a chick embryo of 4 days. 



Germ., Germinal epithelium. Mst., Mesentery. S. C., Sexual cords. 

 V., Posterior cardinal vein. W. D., Wolffian duct. 



of the Wolffian body by the numerous blood-vessels on the me- 

 dian aspect of the latter. Up to the middle of the period of 

 incubation, and a little later, it is extremely sparse; it increases 

 subsequently as a result of ingrowth of the blood-vessels and 

 accompanying connective tissue. 



