THE URINOGENITAL SYSTEM 



389 



FIG. 225. Sections of the embryonic metanephros of the chick 

 to show developing tubules. (After Schreiner.) 



A. Nephric vesicle or primordium of secreting tubule (ur. t.) 

 and collecting tubule (col. T.); 9 days and 4 hours. 



B. Elongation of nephric vesicle ; same embryo. 



C. Indication of renal corpuscle at the distal end of the 

 forming tubule. 



D. The secreting tubule appears S-shaped. 



E. Secreting tubule well formed; 9 days and 21 hours. 



F. Secreting tubule opening into collecting tubule ; 1 1 days. 



