266 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
sections) the connection can be made out, but it is of small diameter; 
in series 7 (frontal sections) the connection is absent, and the right 
umbilical vein breaks up and is lost in the liver substance. From 
these observations we must conclude that it is at about this stage 
that the abortion of the right umbilical vein as a continuous blood 
channel through the liver is completed, but it varies in individual 
embryos. The portal vein is a well-developed vessel, which enters 
the right upper lobe of the liver, and there ramifies. 
The relations of the cardinal veins are essentially alike upon the two 
sides. As shown in Fig. 1, the cardinal, Card , and jugular, Jug , veins 
unite and form the Ductus Cuvieri, JJ. C., which descends obliquely 
towards the liver; on the right side, Fig. 1, the Ductus Cuvieri is 
joined also by the Vena Cava Inferior, V. C. Z, which ascends 
through the liver—compare also, Figs. 2 and 3 — to the heart. 
Between the liver and the heart the venous channel is homologous 
with the sinus venosus. A sagittal section, such as Fig. 1, shows 
the wide cardinal vein abruptly closed by the mass of tubules of the 
Wolffian body, TP. B., so that one receives the impression that the 
vein suddenly becomes a sinus in which the tubules are lodged. 
Closer examination with higher powers reveals that this conception 
is essentially correct. 
Fig. 2 represents a sagittal section from the same series as Fig. 1, 
but is from the opposite side of the embryo, namely the left. It illus¬ 
trates the connection of the vascular channels of the primitive kidney 
with the Vena Cava Inferior, Fi C. I. This connection is established 
on the medial side of each mesonephros by a short wide channel, 
which shows well in transverse sections, Fig. 4, in frontal, Fig. 3, 
and also of course in reconstructions, Fig. 5. If we consider the 
Wolffian body as to its length the mesonephric branches of the 
cava inferior will be found near the middle so that they may be said 
to divide the cephalad from the caudad half of the organ. These 
venous stems being of enormous size, see Fig. 2, in comparison with 
the Wolffian body, renders this division a true anatomical division, 
and later when the true kidney grows headwards from its position 
at the caudal end of the Wolffian body, where it lies at this stage, it 
approaches the branches of the vena cava, and there results a com¬ 
plete interruption of the continuity of the Wolffian body, which 
thereafter is represented by a cephalic division and a caudal division. 
The former is presumably tjie anlage of the organ of Rosenmiiller 
(Parovarium, Epididymis), and the latter is presumably the anlage 
