242 LECTUEE IX. 



lower organised Mollusks : other members of the Piscine class do 

 not show by permanent structures the gradational steps in the develop- 

 ment of the hepatic, as in that of the pancreatic gland. Passing to 

 the Myxinoids we find the liver to be, as in all higher fishes, a well- 

 defined conglomerate, or acinous parenchymatoid organ, with a portal 

 and an arterial circulation, with hepatic ducts, and generally a gall- 

 bladder and cystic duct, by which the bile is conveyed to the duodenum, 

 from which the stomach is divided by a pyloric valvular orifice.* 



The texture of the liver is soft and lacerable ; its colour usually 

 lighter than in higher Vertebrata, being whitish in the Lophius, 

 in many other fishes of a yellowish-gray or yellowish-brown : it is, 

 however, reddish in the Bream ; of a bright red in the Holocentrum 

 orientale, orange in Holocentrum hastatum, yellow in Atherina 

 presbyter, green in Petromyzon marinus, reddish-brown in the 

 Tunny, dark brown in the Lepidosiren ; almost black in the Paddle- 

 fish. In most fishes the liver is remarkable for the quantity of fine 

 oil in its substance, under which form almost the whole of the adi- 

 pose tissue is there concentrated in the Cod-tribe, the Rays, and 

 the Sharks.j Fishes which, like the Salmon and Wolf-fish, have oil 

 more diffused' through the body have comparatively little oil in the liver. 



The liver is generally of large proportional size : it is attached at 

 the fore-part of the abdomen to the aponeurotic wall partitioning off" 

 the pericardium (yjig. 61. I, o), and extends backwards, with a few 

 exceptions, further on the left than on the right side : in the Carp, 

 the Bream, and the Stickleback, the right lobe is longest. Its shape 

 varies with that of the body or of the abdominal cavity : it is broad- 

 est, for example, in the Eays, longest in the Eels ; not, however, 

 elongated in the Gymnotus, in which apodal fish, by reason of the 

 peculiar aggregation of the organs of vegetative life in the region of 

 the head, the liver is divided into two short and broad lobes con- 

 nected by a transverse lobule. The liver consists of one lobe in 

 most Salmonoid and Lucioid Fishes, in the Gymnodonts and Lopho- 

 branchs, in the Mullets, Loaches, and Bullheads. It is long and 

 simple in the Lamprey and Lepidosiren ; long and bilobed in the 

 Conger. The Lump-fish has a lobulus besides the chief lobe, which 

 is round and flat. Thei'e is a short thick convex lobe to the right of 

 the long left lobe in the Lophius. In many fishes the two lobes are 

 subequal : they are rarely quite distinct, as in the Myxinoids ; but 

 commonly confluent at their base, as in the Wolf-fish ; or connected 

 by a short transverse portion, as in most Sharks, the Siluroids, the 



* The Bream is the only fish in which I have found the cystic duct terminating 

 directly in the stomach. 



f The myriads of Dog-fish captured and commonly rejected on our coasts show 

 that the fishermen have not yet taken full advantage of tliis anatomical fact, which ex- 

 poses to them an abundant source of a pure and valuable oil. 



