178 Venous System of Didelphys Marsupialis (L) 
lateral to the aorta and ventral to its segmental branches, appear to be 
formed through a longitudinal anastomosis between branches of the post- 
cardinals and undoubtedly represent a portion of the future azygos sys- 
tem of veins. 
Try > m P / a ) a aL) 
Lhe Postcavax—The posteava of the 8 mm. embryos of Didelphys 
PRECARDINAL 
PRECARDINAL 
DUCT OF CUVIER DUCT OF CUVIER 
AZYGOS 
AZYGOS - 
POSTCARDINAL 
POSTCARDINAL 
POSTCAVA. - 
LEFT 
UMBILICAL HEPATIC VEIN 
VEIN 
OMPHALOMESENT ERIC 
RIGHT HEPATIC VEIN 
VEINS 
LEFT 
SUB AL 
HEPATICO-SUBCARDIN ANT. REVEHENT 
JUNCTION MEIN 
SUBCARDINAL 
POSTCAVA 
PARS SUBCARDINALIS OMPHALOMESENTERIC 
ARTERY 
CROSS ANASTOMOSIS 
RIGHT 
POST. REVEHENT MESONEPHRIC ARTERY 
MEIN POST. REVEHENT 
ARDINA VEIN 
CARDINAL 
COLLATERAL SUBCARDINAL 
VEINS POSTCARDINAL 
POSTCARDINAL UMBILICAL, ARTERY 
P——EXT. ILIAC VEIN 
INT. ILIAC 
S RIN 
VENOUS G VEIN 
Fig. 10. 
Fic. 10. Reconstruction of the venous system of an 8 mm. embryo of Didel- 
phys. Ventral view. 
(Text Figs. 10 and 11), which represents only a portion of this vein as 
met with in the adult, is a vessel of relatively greater size than that 
found in the Dasyurus embryo. It extends as an unpaired vessel between 
the sinus venosus and a point slightly caudad of the origin of the ompha- 
lomesenteric artery where it anastomoses with the right and left post- 
cardinal veins which form its principal caudal continuation, and where 
it also receives the left anterior and the two posterior revehent veins. 
