DIGESTIVE SYSTEM. 237 



those Fishes that do not possess a perfectly-formed stomach, as in 

 the Cyprini, Gobii, and Syngnathi, but they are wanting also in 

 other Fishes with that organ properly developed, e. g. the Pike. As 

 a rule, however, they are present in the latter instances, and vary 

 exceedingly in number. It is very rare to meet with a single caecum, 

 as in Ammodytes tobianus ; there are sometimes two, as in several 

 Plaice (Pleuronectes), while other species of this genus have, like 

 the River Perch and Common Loach, three of them ; four occur, e. g. 

 in Mugil cephalus and Cottus gobio, five in Salmo spirinchus, six in 

 Perca lucioperca and in Sargus annularis, seven to eight in Trachi- 

 nus Draco, ten to thirty or more in many Salmons and Herrings, and 

 from eighty to ninety in the Salmon ; but these appendages are most 

 numerous in Gadus and Scomber, for in the Mackerel about two 

 hundred may be counted. These caecal appendages either encircle 

 the pylorus, or occupy longitudinally a greater or less extent of the 

 commencement of the intestine. In some of the Fishes already 

 named, as in the Herring and Mackerel, the caeca begin to divide, 

 and two of them open by a single aperture into the intestine. In 

 Gadus Lota two or three of the twenty caeca unite to form a common 

 trunk ; in the Tunny (Scomber thynnus) they divide so as to form 

 tufts ; in Cyclopterus, Gymnotus, and others, those of the second 

 row are further subdivided. In the Sword-fish (Xiphias gladius) 

 the finely-divided caeca are united by cellular tissue, and invested 

 externally by a common membranous covering, so that the whole 

 organ resembles a gland. In the Sturgeon, indeed, the pyloric ap- 

 pendages, by being still more subdivided and again united, acquire 

 the form of a true parenchymatous pancreas. The mucous mem- 

 brane lining the pyloric appendages exhibits a reticulated appear- 

 ance similar to that of the intestines. No nutritive matter is found 

 in these caeca, but only some slimy fluid ; chyme, however, has been 

 frequently observed in them. Their function is in other respect highly 

 problematical, though it is possible they may secrete a fluid analogous 

 to the pancreatic juice. 



In the Osseous Fishes, e. g. the Eel, Pike, Trout, we constantly 

 find a true compact and glandular Pancreas of a yellowish-white 

 color, which sends from two to three excretory ducts into the intes- 

 tine ; these are frequently accompanied by the biliary ducts, but are 

 so closely attached to the latter as to be easily overlooked. In the 

 Sturgeon a second kind of pancreas has been described as also ex- 

 isting. The Rays and Sharks possess a lobulated and reddish-yel- 



