Sprencer— Zhe Blood Vessels of Ceratodus. 19 
The two of each side unite together, just behind the cloacal region, to form a 
single vein which runs forward to the outer and ventral edge of the kidney on each 
side; into the kidney each gives off branches from its inner surface and anteriorly 
each enters into connection with the true renal portal vein. 
Just anterior to the level of the anus a transverse vessel passes across above the 
ureters and intestine and unites the two posterior trunk veins. This is a well-marked 
transverse vessel and by injecting from the vein along the kidney of either side the 
kidney of the other side can be easily injected. Between this anastomotic vessel 
and the kidney on either side, the posterior trunk vein receives two branches (a) one 
from the terminal intestine walls and (b) one from the terminal parts of the ureter 
(fig. 19). 
(2) LZutercostal verns. 
These, to the number of seven or eight, arch across to the kidney of each 
side from the body wall, traversing the remarkable development of cellular tissue 
which lies between the kidney and alimentary canal and the body wall in this part as 
noted by Dr. Giinther. The arrangement of these intercostal veins in one particular 
specimen of Ceratodus is shown in fig. 19, where the lobulated external surface of 
the kidney is shown the organ having been pressed over towards the median line. 
This shows the exact relationship of the vessels as present in the particular specimen. 
(3) Renal portal vein (figs. 7, 16, and 19). 
This name is given to the vein to be now described since it corresponds in origin 
closely to the renal portal vein of Amphibia. It is the one described by Giinther as 
the specially strong posterior intercostal vein of each side. 
In fig. 17 it is represented as a large vessel passing across, as do the intercostals, 
from the body wall to the outer edge of the kidney where it joins the longitudinal 
vein passing forwards from the posterior trunk vein. 
By injecting this vein at the point where it enters the kidney its relationship 
can be made out. Tracing it by this means away from the kidney it is found to 
penetrate the body wall slightly dorsad of and at the level of the attachment of the 
hind limb. It runs downwards in the muscles and is, just before reaching the angle 
of the pelvic plate with which the hind limb articulates, joined by a vessel passing 
directly forwards. It then enters the hind limb. 
This may be called the z/ac vezn and must be regarded from its relationships as 
the equivalent of the vessel returning blood from the hind limb to the united 
posterior part of the posterior cardinal vein during the early developmental stages of 
Amphibia and subsequently to the kidney. 
