PISCES FISHES. 519 



the blood from being driven back again into the ventricle. In the 

 heart of Lophius (Jig. 228, A), the conformation of the cavities is 

 very peculiar. The auricle (b) is large and pyriform, and the ven- 

 tricle (c) of a globular shape ; but the most singular feature in its 

 structure is the valve between the ventricle and the bulb (d). This 

 is a soft fleshy protuberance (e), perforated in the centre, which 

 projects into the cavity of the bulb, and allows the blood to pass 

 freely in one direction ; but the sides of the canal collapse, and 

 close the orifice, if the blood is forced back from the bulb towards 

 the ventricle. 



Issuing from the pericardium, the branchial artery runs beneath 

 the centre of the branchial apparatus, dividing into as many 

 trunks as there are branchial arches, to each of which a vessel is 

 given off. 



To each branchial arch are attached a great number of vascular 

 lamellae placed parallel to each other, like the teeth of a comb. 

 The branchial artery, which runs in a groove situated upon the con- 

 vexity of the corresponding arch, sends off a twig to every one of 

 these laminae ; and this vessel, after twice bifurcating, divides into 

 an infinite number of little ramuscules, which run across both sur? 

 faces of the branchial fringe, and terminate by becoming converted 

 into capillary veins. 



The radicles of the branchial veins all open into a venous canal 

 which runs along the internal margin of each lamella, and these last 

 terminate in the great vein of the corresponding branchial arch, 

 which runs in the same groove as the artery, but is more deeply 

 situated, and, moreover, runs in the opposite direction ; that is to 

 say, that the branchial artery derived from the heart, and coming 

 from the ventral aspect of the body, diminishes in size as it mounts 

 towards the back, and gives off twigs to the branchial fringe, 

 whereas the branchial vein, on the contrary, receiving blood from 

 the lamellae of the branchia, increases in diameter as it approaches 

 the dorsal region. 



On leaving the gills, the branchial veins assume the appearance 

 and perform the function of arteries. The anterior, even before 

 escaping from the branchial arch, gives off ramifications to different 

 parts of the head, and the heart and parts adjacent likewise receive 

 their supply of arterial blood from a branchial vein. 



The veins derived from all the branchial arches ultimately unite 

 and form the aorta, which evidently corresponds to the aorta of 

 Mammalia, although it has neither auricle nor ventricle at its com- 

 mencement. 



