SPLEEN OF LEPIDOSIREN AND PROTOPTERUS. 
237 
liver via the hepatic portal vein. There is, at first, no direct 
communication between the intestine and the liver, and no 
arterial supply to the spleen. This latter point seems to be 
general throughout the phylum, for Dr. Bryce states, in 
QuaiiTs f Elements of Anatomy/ vol. i, p. 237, that in the 
human embryo the artery develops late. 
What the chief factor of this intestinal vein is, is uncertain. 
In Pro top ter us it appears to be the intra-intestinal, while 
in Lepidosiren it is the subintestinal. This, however, is 
most likely only a question of which is most developed at the 
stage under consideration. 
At about Stage XXY in Pro top ter us, and earlier in 
Lepidosiren, there is visible a small vein which communi- 
cates directly with the liver. This is the Hepatic Portal 
Vein proper, which, in the adult, becomes a well-marked 
vessel. 
In Lepidosiren at the latest available stage I carefully 
examined the veins of this region (omitting the smaller 
tributaries from the intestine) . The arrangement is as follows, 
from before backwards. There are three veins which com- 
municate between the spleen and the hepatic portal vein, and 
behind the last of these the latter forks ; the right branch is 
confined to the liver, and the left, passing straight through 
the tissue of the pancreas and turning over the left side of 
the gut, gradually fades away in the lattePs ventral 
mesenchyme. 
I interpret this in this way. The subintestinal vein 1 runs 
round the left side of the intestine to the dorsal surface, and 
then gives off a branch running backwards into the right 
lobe of the liver. It then continues forwards and gives off 
one branch to the splenic spongework, receives two from it, 
and then disappears. After reaching the side of the liver the 
portal vein seems to give off small branches into the liver 
tissue along the entire length. 
1 Dr. Jane Robertson (‘ Quart. Journ. Micr. Sci.,’ vol. lix, p. 121) 
describes this vein as the posterior part of the original subintestinal and 
the proximal part of the left vitelline vein. 
