1S89.] CARDiNAi^ Vein in the frog. 149 



Hochstetter's discovery concerning the paired connection between 

 the cardinals and hepatic veins in certain Elasinobranchs, they con- 

 firm his general views as to the development of the postcaval ia 

 other types. 



My statement concerning the two veins in Protoptenis 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, Led). Ic 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 aud 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 {I. 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 aa may persist amongst the Aiiura and Amniota. 



The liver (//■) of Protopterus abuts closely against the anterior end 

 of the right kidney (A), and at this point the right cardinal {pt.c') 

 is continuous with a vein (pt-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 veuosus. The liver is supported by a net-like 

 peritoneal fold, which is connected with the mesogastrium and is 

 continued on to the vein iu its independent portion. This " Hohl- 

 venengekrose " 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 (h.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 Gekrose der hinteren Holilvene," Anat. Aiizeiger,iii. Jalirganff, 

 1888, p. 965. 



Proc. Zool. Soc— 1889, No. XI. II 



