LO1 
and external to the epibranchial arteries, receiving in 
their course vessels conveying blood from the head and 
brain, and enter the precaval veins at the dorsal and 
anterior extremities of the latter. ; 
The Inferior Jugular Vein (V’. /ug.') is an azygos 
trunk running backwards under the ventral wall of the 
pharynx immediately above the dorsal aorta. It then 
passes upwards on the anterior wall of the pericardium, 
and may enter either the right or left side of the sinus 
venosus, though its ending on the right side seems to be 
the more common one. 
The Hepatic Veins (VV. hep.) are short wide trunks 
coming from the liver, which penetrate the posterior wall 
of the pericardium and enter the posterior part of the 
sinus venosus. 
The Renal Portal System.— The afferent vessels of this 
system are the parietal veins, the caudal vein and the 
genital veins. The caudal vein (V. cd.) runs forwards 
from the tail in the haemal canal immediately beneath 
the dorsal aorta. It enters the kidney at the most dorsal 
and posterior angle of the latter organ, and divides into 
two vessels which run forwards in the kidney and breaix 
up, but do not apparently anastomose with the cardinal 
vein. A short venous trunk comes from each ovary (or 
testis) and the adjacent portions of the body wall, and 
enters the kidney on each side near the extreme ventral 
tip of the latter organ. A series of veins from the muscles 
of the trunk enter the dorsal portion of the kidney on each 
side; these are the parietal veins. One such vessel is 
represented in fig. 22 as entering the anterior tip of the 
head kidney. 
The efferent vessels of the system are the cardinal 
veins, which run forward in the kidney. The right car- 
dinal vein (V. card.) runs along the middle part of 
