PLATE 12 



EXPLANATION OF FIGURES 



13a and 13b Schemata giving a ventral view of the relations of the post- 

 cava to the aorta in a 20 mm. and a 23 mm. Tragulus embryo respectively, as 

 shown by reconstructions of these stages. 21, cardinal collateral vein; 24, aorta; 

 40, sex vein; 41, spermatic artery; 57, renal vein; 59, inter-renal segment of the 

 cava; 60, iliac bifurcation of the aorta. 



244 



