THE URIXOGEXITAL 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 davs and 21 hours. 



F. Secreting tubule opening into collecting tubule; 11 days. 



