DIGESTIVE SYSTEM OF ISSUES. 245 



organisation for which that canal is the commissariat is the most simple 

 in the Piscine cL-iss. The Lamprey, at the head of the Dermopterous 

 order, derives from the slight spiral extension of its intestinal mu- 

 cous coat the required concomitant complexity of the digestive canal. 

 The torpid Lepidosiren, which, though of a much more advanced 

 type of ichthyic organisation, can have but little expenditure of 

 nervous and muscular force to repair, seems, in like manner, to derive 

 from a spiral extension of its thick and glandular intestinal mucous 

 membrane the equivalent of a pancreas, and no rudiment of that 

 gland exists in this fish. In several Osseous Fishes either the inac- 

 tive nature of the species, or the extent or special modifications (as 

 the long intestine and glandular palate of the Carp, for example,) of 

 the mucous membrane in the ordinary tract of the alimentai-y canal, 

 render unnecessary the presence of a pancreas. Thus there is no 

 ca3cal production of the duodenum in the Ambassis, the Wolf-fish, 

 nor the "Warty Agriope, nor in most Labroids, Cyprinoids, Lucioids, 

 Siluroids, nor in the Lophobranchs and Plectognats ; nor in the 

 genera Antennarius, Malthceus, and Batrachus. The pancreas is re- 

 presented by a single pyloric caecum in the Sandlance and Polypterus 

 (Jig. 62. k) ; by two cteca in most Labyrinthibranchs, in many 

 species of Amphiprion, in the Lophius, the Turbot, and the 

 Mormyrus {Jig. 63. k) ; by three ca^ca in the Perch, the percoid 

 Popes {Acerma), the Asprodes, and Diploprions ; of from four to 

 nine caeca in the genus Coitus ; of from five to nine caeca in the 

 genus Trigla ; of six cfeca and upwards in Scorpcena and Holocen- 

 trtcm ; and so on, increasing to a numerous group of pendent pyloric 

 pouches, as we find in the Scomberoids, Chastodonts, Gadoids, 

 Ilalecoids, Cyclopterus, and Lepidosteus. There is a difference, how- 

 ever, worthy of note, in the mode and extent of attachment of these 

 numerous ca^ca : in the Salmon (prep. 773.), the Herring, and Haddock, 

 they rank almost in a line along the whole duodenum : in the Gym- 

 notus and Lump-fish they form a circular cluster around tlie distal 

 side of the pylorus. Even in the longitudinally arranged cajca the 

 principle of concentration dawns : thus the fifty pancreatic cajca of 

 the Pilchard communicate with the duodenum by thirty orifices ; but 

 the fifty attenuated terminal blind sacs in the pancreas of the Lump- 

 fish unite, reunite, and discharge their secretion by a circle of six 

 orifices around the duodenal side of the pyloric valve. In the Tunny 

 a more subdivided bunch of pancreatic cajca empty themselves by 

 five oi'ifices ; in the Sword-fish by two orifices ; and, finally, in the 

 Sturgeon and Paddle-fish {Jig. Q\. k) by a single opening of what 

 now becomes the short and wide duct of a pancreas. The interpo- 

 sition of cellular tissue binding together longer, mure slender and 



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