1889. ] CARDINAL VEIN IN THE FROG. 149 
Hochstetter’s discovery concerning the paired connection between 
the cardinals and hepatic veins in certain Elasmobranchs, they con- 
firm his general views as to the development of the posteaval in 
other types. 
My statement concerning the two veins in Protopterus which take 
their origin in the kidneys and also receive blood from the body-walls 
and generative organs was only partially correct: that is, it was 
correct so far as the left vessel and the renal portion of the right one 
are concerned. ‘There can be little doubt that the vein of the left 
side corresponds entirely with the left posterior cardinal of Fishes 
(fig. 2, p. 148, died). It extends along the ventral surface of the 
kidney, partially imbedded in the lymphatic tissue which surrounds 
that organ, and then passes along the dorsal border of the corre- 
sponding gonad, between the latter and the lung, to enter the precaval, 
being packed in by lymphatic tissue all along its course. 
The vein of the right side (pt.c) is considerably larger than that 
of the left (/.cd), and as it passes along the kidney it is connected 
with its fellow by three or four transverse anastomoses. A similar 
asymmetry of the two cardinals is very common amongst Fishes, and 
there seems often to be a tendency for one or the other to become 
obliterated, as occurs to a greater or less extent with such remains 
of them as may persist amongst the Anura and Amniota. 
The liver (() of Protopterus abuts closely against the anterior end 
of the right kidney (4), and at this point the right cardinal (pt.c’) 
is continuous with a vein (pé.c'!) which passes forwards imbedded in 
the dorsal border of the liver, from which it emerges anteriorly and 
turns medianwards so as to extend for a short distance as an indepen- 
dent vessel, which perforates the pericardium in the middle line to 
enter the sinus venosus. The liver is supported by a net-like 
peritoneal fold, which is connected with the mesogastrium and is 
continued on to the vein in its independent portion. This ‘* Hohl- 
venengekrése ”’ is characterized, according to Hochstetter ', as being 
the bearer of the independently developed portion of the post- 
caval. 
The number and arrangement of the hepatic veins (4.v) is rather 
curious. In several specimens examined there were one or two large 
ones entering the main vein just before it becomes free from the liver 
anteriorly, but besides these there are numerous small vessels all 
along the course of the vein through the liver. 
These facts seem to prove conclusively that the right vein described 
above is a true vena cava inferior, which is made up of the renal 
section of the right cardinal and of an independently formed hepatic 
portion. In fact, the figure given by Howes (loc. cit.) of the veins 
of a Frog in which the left azygos persisted resembles very closely 
the state of things in Protopterus, except that the fusion of the renal 
section of the two cardinals does not take place, but only a reduction 
of that of the left side, and its connection with what must now be 
called the renal portion of the postcaval by transverse anastomoses. 
* “Ueber das Gekrése der hinteren Hohlvene,” Anat. Anzeiger, iii. Jahrgang, 
1888, p. 965. 
Proc. Zoou. Soc.—1889, No. XI. 1] 
