THE URINOGENITAL SYSTEM OSD 
of the mesonephros are formed (Fig. 219). During its growth 
forward a series of small diverticula arise from its wall and extend 
dorsally (Fig. 223); these branch secondarily in a generally dichot- 
t 
oe Pi > 
ole as 
Ke) 
WV, 
Fig. 222.— Transverse section through the metanephros, mesonephros, 
gonads and neighboring structures of an 11-day male chick. 
a. A.S., Abdominal air-sac. Ao., Aorta. B. W., Body-wall. Coel., Coe- 
lome. Giz., Gizzard. I]., ium. M. D., Remains of degenerating Miillerian 
duct. M/’s’t., Mesentery. M’t’n., Metanephros. Sp., Spine of neural arch. 
tr. Pr., Transverse process of the neural arch. V. ¢. i., Vena cava inferior. 
W. D., Wolffian duct. Other abbreviations as before. 
