BLOOD- VASCULAR SYSTEM, ETC., OF AMIURUS CATUS. 429 



artery. The two posterior trunk vertebrae have short and broad 

 haemal arches united by a transverse piece. The caudal vein turns 

 downwards over the posterior face of the second (sometimes the first) 

 and enters the kidney, which extends back over these arches. It 

 then passes downwaixls and forwards through the substance of the 

 kidney and near the ventral surface gives off two branches, first a right 

 and then a left vena renalis advehens, which, passing forwards and 

 outwards, distribute their blood to the kidney. 



The caudal vein, leaving the kidney, is attached to the mesentery 

 which unites the genital glands and becomes the portal vein, running 

 straight forward beneath the air-bladder to the liver. This arrange- 

 ment has not been described for any of the Teleostei, as far as I am 

 aware, and if Nicolai and Hyrtl are correct does not occur in other 

 Siluroids. According to these observers the entire vein distributes 

 itself to the kidney as the vena renalis advehens. The former 

 arrangement was constant in all specimens of Amiurus catus ex- 

 amined by me. 



The posterior cardinals (venm vertebrates posteriores of Stannius) 

 arise in the kidney and run forward on each side of the vertebral 

 column. As in other Teleosts the left vein is very small in com- 

 parison with the right, which, by a median stem, drains almost the 

 entire kidney, and issuing upon its anterior concave surface passes 

 upward and to the right, to the side of the vertebral column, where it 

 forms a large sinus-like vessel. The left cardinal receives only a few 

 branches from the horn of the kidney upon that side. Upon reach- 

 ing the fourth vertebra they narrow to pass through a triangular 

 foramen formed by the body of the vertebra at the side, the trans- 

 verse process above and an oblique bony ledge below. Having passed 

 through they turn downwards through the head-kidney and join the 

 anterior cardinals. 



The veins which drain into the vena caudalis, do not require any 

 special description, but when this vein leaves its position beneath the 

 aorta upon entering the body, it causes its branches to vary also from 

 the branches of the latter. 



The portal vein receives the genital veins in its passage between 

 these organs. It then passes above and in contact with the spleen 

 receiving the splenic veins. This point also forms a sort of nucleus 

 for the entry of a number of veins from the left mesenteric fold. 

 Those on the right unite into a mesenteric vein which in some speci- 



