Pabkee. — On the Ve)wus System of the Skate. 415 



from the tail, as well as part of that from the hinder part of the body, is 

 taken to the kidney and passed through the renal capillaries on its way back 

 to the heart. 



From the kidneys the blood is returned by numerous small renal veins 

 (r) into the two large cardinal veins (cd), which lie, one on the ventral face 

 of each kidney, and, uniting with one another by a cross-branch (cd") pos- 

 teriorly, pass forwards and outwards to the aperture (cd' ) abeady men- 

 tioned in the precaval sinus. After leaving the kidneys the two cardinal 

 veins run together, and form a spacious cardinal sinus (cd. sj, capable of 

 containing fully an ounce of blood, and connected on either side with two 

 almost equally extensive sjyermatic sinuses (sp. s.J, which receive the blood 

 from the reproductive organs. 



The general diposition of the cardinal veins, as here described, is per- 

 fectly well known, but their relation to the caudal vein is, I think, not 

 generally recognized. In fact, it is distinctly stated in Huxley's "Ana- 

 tomy of Vertebrated Animals,'' in Gegenbaur's "Elements of Comparative 

 Anatomy," and in Claus's " Grundziige der Zoologie," that both in Marsi- 

 pobranchii and in Elasmobranchii, the two branches of the caudal vein are 

 directly continued into the cardinals. I therefore thought, at first, not un- 

 naturally, that the true condition of the renal circulation in the skate had 

 been overlooked, but on consulting M. Jourdain's memoir on the renal 

 portal system, in the " Annales des Science Naturelles,"* I find that he has 

 described and figured the real state of things with great exactness, except 

 for the fact that he gives a wrong account of the relations of the veins from 

 the hind limbs. 



The skate has thus a true "renal portal system," quite of the same 

 nature as that of Amphibia and Keptilia : in these latter the renal portal 

 veins receive not only the blood from the tail and pelvis, but also that from 

 the hind limbs, and in the skate also the veins of the hind limbs or pelvic 

 fins are described by Jourdain as opening into the renal portal vein. But 

 I find that he has mistaken the principal pelvic vein for the femoral. 

 The latter takes a quite different and very remarkable course. 



The femoral vein (fm), in fact, debouches into a spacious trunk (il. h., 

 epgj, which lies, for a considerable part of its course, in the ventral wall of the 

 abdomen, near its outer boundary. Both anteriorly and posteriorly it passes 

 dorsalwards, becoming connected in front with the distal end of the brachial 

 vein, and behind, curving along the posterior wall of the pelvic cavity, then 

 passing on to the lateral wall of the cloaca, along which it takes its course 

 as far as to the rectal gland, where, with its fellow of the opposite side, it 

 enters a hinder prolongation of the cardinal sinus, first receiving numerous 



* Ser. IV., Tom XII., 1869. 



