ALIMENTARY CANAL OF FISHES. 421 



vulgaris) and the Flounder, there is a small crecal process at 

 the commencement of the large intestine ; there are two short 

 caeca at the same part in Box Salpa. 1 The large intestine is 

 usually short and straight in Fishes, answering to the rectum 

 of higher animals,, fig. 282, f,y. In some Fishes, e. g., Salmo, 

 Clupea, Esox, Anableps, Anarrhichas, and the Gymnodonts, it 

 preserves the same diameter as the small intestine, and the 

 term ( large ' becomes arbitrary : in Gasterosteus, Centriscus, Ostra- 

 cion, Balistes, and Syngnathus, it is even narrower than the 

 ( small intestine ; ' but most commonly it is wider, as in the 

 Percoid family, the Gurnards (Triylidce), the Breams (Sparidae), 

 Scicena, Scomber, Coitus, Labrus, Pleuronectes, Gadus, Lophius, 

 Cyclopterus, the Siluridce, the Plagiostomi, and the Planirostra, 

 fig. 276, h. 



The tunics of the intestinal canal consist in Fishes, as in other 

 Vertebrates, of the peritoneal or serous, the muscular, and the 

 mucous coats, with their intervening cellular connecting layers, 

 and the epithelial lining; the muscular and mucous coats are 

 commonly thicker and of a coarser character than in the warm- 

 blooded classes ; pigmental cells are not unfrequently developed 

 in the serous coat; the epithelial scales of the intestine of the 

 Lancelet support vibratile cilia. 



The muscular fibres are arranged in a thin outer longitudinal and 



O CJ 



a thick inner circular stratum (Sturgeon) ; 2 the elementary fibres 

 in general present the smooth character of those of the involun- 

 tary system ; but Reichert 3 has detected the transversely striated 

 fibre in the muscular tunic of the whole tract of the intestine 

 in the Tench. 



The mucous membrane presents numerous modifications, some 

 of them more complex and remarkable than in any of the higher 

 Vertebrates. It is commonly thick and glandular, and always 

 highly vascular. In the small intestines it presents, in some 

 Fishes (Cod), 4 a smooth and even surface ; in some it is 

 produced into obliquely longitudinal or wavy folds ; 5 in the 

 Herring it presents feeble transverse rugae ; in many Fishes it is 

 reticulate, as in the Wolf-fish 6 and Murcena ; 7 this character is 

 present in the peculiarly thick and parenchymatoid mucous tunic 

 of the small intestine of the Sturgeon, where the larger meshes 

 include irregular spaces, subdivided into smaller cells. 8 In a few 

 Fishes the mucous membrane is coarsely villose or papillose. In 



1 xxxm. t. vi. pp. 624, 270. 2 xx. vol. i. p. 200, preps, nos. 637, 639. 3 xcm. p. 26. 

 4 xx. vol. i. p. 199, prep. no. 633. 5 Ib. Turbot, prep. no. 634, Salmon, prep. no. 635. 

 6 Ib. prep. no. 630. 7 Ib. prep. no. 631. 8 Ib. prep. no. 638. 



