176 Venous System of Didelphys Marsupialis (1) 
THE DEVELOPMENT OF THE VENOUS SYSTEM IN MARSUPIALS. 
All of my marsupial embryos, as stated above, are too advanced to 
definitely determine the earliest stages in the development of the postcaval 
vein, as well as the condition presented by the subcardinal veins at a 
PRECARDINAL 
DUCT OF CUVIER 
POSTCARDINAL 
POSTCARDINAL 
AORTA 
LEFT 
ANT, REVEHENT VEIN 
SUBCARDINAL 
LEFT HEPATIC VEIN 
POSTCAVA 
RIGHT HEPATIC 
VEIN UMBILICAL VEIN 
HEPATICO-SUBCARDINAL- 
JUNCTION 
OMPHALOMESENTERIC 
VEIN 
MESONEPHRIC ARTERY 
MESONEPHRIC ARTERY ‘ 
ESONE c ANT. REVEHENT VEIN 
SUBCARDINAL 
MESONEPHRIC ARTERY 
POSTCAVA 
PARS SUBCARDINALIS 
OMPHALOMESENTERIC 
ARTERY 
MESONEPHRIC ARTERY 
EEFar 
RIGHT 
POST. REVEHENT POST. REVEHENT VEIN 
VEIN SUBCARDINAL 
SUBCARDINAL 
AORTA 
POSTCARDINAL POSTICARDINAL 
UMBILICAL aRTERY 
Fia. 9. 
Fig. 9. Reconstruction of the venous system of a 6 mm. embryo of 
Dasyurus. Ventral view. . 
time before the posteava is formed. There can be no doubt, however, so 
far as the subcardinal system is concerned, that it plays the same role in 
the marsupials, as thus far examined, as in the rabbit (Text Fig. 6), in 
which it enters into the formation of a portion of the postcava, as well as 
