THE URINOGENITAL SYSTEM 



393 



Two other epithelial constituents enter into the composition of 

 the indifferent gonad, viz.: the rete tissue or cords of the urino- 

 genital union, and the sexual cords. These lie between the ger- 

 minal epithelium and the glomeruli of the Wolffian body. Between 

 these elements is a sparse mesenchyme continuous with the sur- 

 rounding mesenchyme, constituting the stroma of the gonad. 



"■/ .S' 







'X 







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

 cephala. (After Hoffmann, from>ehx and Biihler.) 



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



Germ., Germinal epithehum. Mst., Mesentery. S. C., Rete cords, 

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



Some primordial germ-cells occur in the stroma, though most are 

 in the germinal epithelium. 



The rete cords appear within the gonad on the fifth day; 

 they are solid cords of epithelial cells that fill up the interior 



