GAD us. 



335 



kidneys it divides into two renal portals, as in the skate ; the left renal 

 portal breaks up into capillaries in the left kidney, but the right is 

 usually continuous forwards with the right cardinal vein. A branch 

 from the caudal vein, the vesicular vein, runs ventralwards and joins 

 the mesenteric branch of the portal vein. 



The portal system is well developed and consists of a mesenteric 

 vein from the intestine, a splenic from the spleen and a branch from 

 the air-bladder leading to the liver. The blood from the liver is carried 

 by paired hepatic veins into the sinus venosus. 



Fig. 237. — Lateral View of Cod's Skull. 



3., Branchiostegal Rays. 



c.h., Ceratohyal. 



d, Dentary. 



/,, Frontal. 



A.W., Hyomandibular. 



i.o.^ Interoperculum. 



/., Lacrymal. 



?«, Maxilla. 



«., Nasal. 



o. Operculum. 



p.s., Parasphenoid. 



p.m., Premaxilla. 



p.o., Preoperculum. 

 q.y Quadrate. 

 S.O., Supraocclpital. 

 S.O., Suboperculum 



(lower reference). 



The vascular system shows a peculiar asymmetry of both the arterial 

 and venous systems, and a marked tendency to anastomosis of certain 

 outlying vessels, seen also in the bird. Both the veins and arteries are 

 remarkably small compared with the size of the fish, and there is a very 

 small quantity of blood. 



Skeletal '^^^ skeleton of the cod is in marked contrast to that 



of the skate in consisting almost entirely of bone. 

 Axial. — The skull is formed of a cranium, mainly bone, and a 

 series of bony visceral arches. The cranium is formed of (i) an occipital 



