104 Proceedings of the Royal Physical Society. 



As is well known the presence of a posterior vena cava is frequently 

 associated with an asymmetrical condition of the anterior portions of the 

 posterior cardinal veins. Iu Polypterus such an asymmetry exists, and this 

 suggested the desirability of ascertaining whether a posterior vena cava is 

 not present in that animal. As a matter of fact, Polypterus does possess a 

 posterior vena cava. In Budgett's paper on the anatomy of Polypterus there 

 occurs the sentence, "The [air-bladder] vein on the right side is of great 

 size, corresponding to the size of the right air-bladder, and posteriorly unites 

 with the caudal vein." 



Examination of the vein in question shows that it is not the right 

 pulmonary vein, but the hepatic vein. This vein is of great size, and the 

 main trunk of it traverses the liver right to its posterior end, and then 

 runs free for a considerable distance (about 2 inches in an adult of 14 inches 

 total length) through the splanchnocoele along the right side of the right 

 lung till it joins the interrenal vein (fused posterior cardinals). It is clear 

 that the vein which I have described is a true primitive posterior vena cava 

 of the same type as that in lung-fishes, and peculiar only in the fact that 

 its communication with the interrenal (posterior cardinal) vein is further 

 back than usual. 



(Issued separately, 23rrf May 1910.) 



