780 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



mandible.* Both arteries meet in front of the symphysis, and return by a single median 

 vein along the floor of the mouth. The later developments of the haemal system at a 

 stage — in, say, Gadus morrhua — when the caudal artery extends along fully two-thirds 

 the length of the tail, are as follow : — Four branchial arteries oan be made out, and 

 a submaxillary artery passes beneath the eyes, while a return-current is directed over 

 the e} 7 es, along the supraocular vein. The cceliac artery, before described as leaving 

 the aorta in the pectoral region, passes over the liver, along the ventral surface of the 

 intestine, and sends an arterial branch upward, which, bifurcating, supplies the walls of 

 the intestine, — the main trunk continuing its ventral course, and ascending in front of the 

 urinary vesicle, — over the walls of which it passes to the vena vertebralis. The venous 

 trunks form a more complex system — the simple subintestinal loop which breaks up into 

 an elaborate hepatic capillary network still continues, but it is joined by a large visceral 

 trunk on the posterior side of the liver. This latter vessel leaves the caudal vein at the 

 root of the tail, passes ventrally in front of the urinary vesicle and over the walls of the 

 rectal portion of the intestine to the termination of the mid gut. At this point a 

 large venous trunk branches off dorsally to join the posterior cardinals. Minor venous 

 branches run from the walls of the stomach and pyloric portion of the intestine, forming 

 the first indication of the portal system — all their blood finally passing in front of the 

 liver into the sinus venosus by the hepatic veins. The liver, the dorsal lobe of which 

 lies above the alimentary canal and behind the swim-bladder, is seen chiefly as a rounded 

 mass (the left and ventral lobe) projecting boldly into the surface of the yolk below, and 

 lying immediately in contact with the posterior pericardial wall. The proximity of the 

 liver with its rich vascular plexus, and of the large ductus Cuvieri pouring a stream into 

 the capacious sinus, suggest the possibility that it is at this point that the assimilation 

 of yolk-matter is most active. It is absorbed and conveyed to the heart by the venous 

 blood. The continuity of the wall, limiting the pericardial chamber (pd, PI. VII. fig. 9), 

 appears to be unbroken, and roofs over a sub-pericardial space (ss) filled with a serous plasma 

 and disintegrated yolk. A suboral chamber in many cases seems also to be shut off by 

 this membrane (PL VIII. figs. 6, 7). The heart's pulsations partake of a progressive 

 vermiform movement, the auricle, continuous with the sinus venosus, contracting first, 

 and the successive parts (of the auricle) contract in order, the ventricle dilating as the last 

 part of the auricle closes. As the ventricle contracts, the open end of the auricle dilates. 



The progressive systole being triple, . .12 3 



/a • r \ /a\ /-d\ {C\ contract 



(See accompanying diagram,) . . . (A)— (B)— ^J dilateg 



The diastole also is threefold, and D contracts ) (A) — (B) — (C) dilate 

 simultaneously with the dilatation of A, . j (D) contracts. 



The delicate pelagic forms chiefly considered in these pages present a great contrast to 



* Gotte is certainly incorrect, as Balfour pointed out (No. 11, p. 645), in denying that a mandibular artery is 

 ever developed in Teleostei (No. 59). 



