VASCULAR SYSTEM 323 



vein, as already mentioned (Fig. 190), but more or fewer of them, 

 especially those from the dorsal wall of the organ, open into the 

 posterior cardinals. They may, as in Polypterus, even join the 

 hepatic veins. 1 



The veins from the gonads are very variable in their destina- 

 tion, sometimes joining the posterior cardinals, as in the Salmon 

 (Salmo salar) ; or the hepatic portal vein, as in Amiurus ; or, as 

 in the Perch (Perca flumatilis\ forming by their union a single 

 trunk, which communicates directly with the left Cuvierian 

 duct. 



Eepresentatives of the great lateral veins of Elasmobranchs 

 appear to be absent in the Teleostomi, the veins from the 

 pectoral and pelvic limbs joining the Cuvierian duct and the 

 posterior cardinal veins- respectively. 



The two large anterior cardinal veins, which collect the blood 

 from the head and brain, occupy their usual position directly 

 above the branchial apparatus, and are sometimes connected by 

 transverse anastomoses as they pass backwards to join the 

 Cuvierian ducts. The inferior jugular vein is either single (e.g. 

 Gadus); or paired, as in Perca (Fig. 190). 



In the Dipnoi the venous system is distinguished by an 

 interesting combination of characters, some of which are either 

 primitive or peculiar to the group, while others exhibit a distinct 

 transition to the embryonic or the adult condition of the lower 

 air-breathing Vertebrates. 



In Neoceratodus z (Fig. 191) the renal portal system is unusually 

 complex, the veins distributing venous blood to the kidneys being 

 derived from several sources, as follows : (1) from each of the 

 two branches into which the caudal vein divides on its exit from 

 the haemal canal (af.r.v} ; (2) from a common trunk (pt.v) which, 

 on each side, is formed by the union of segmental veins from 

 certain of the post-cloacal myotomes and is united with its fellow 

 by a transverse anastomosis ; (3) from more anteriorly situated 

 intercostal or segmental veins (i.c.v) which enter each kidney 

 directly'; and (4) from a vein on each side corresponding to the 

 renal portal vein of Amphibia. The latter vein (rp.v) is formed 

 by one of the two branches of the iliac or femoral vein, and joins 



1 Budge tt, Trans. Zool. Soc. xiv. Pt. vii. 1901, p. 332. 



2 Giinther, Phil. Trans. 161, 1872, p. 535 ; Baldwin Spencer, Macleay Memorial 

 Volume, 1894, p. 17, 



