238 LECTURE IX. 



valve. In the Bogue-bream {Box vulgaris) and the Flounder there 

 is a small ca^cal process at the commencement of the large intestine ; 

 there are two shoi*t c^ca at the same part in Box Salpa* The large 

 intestine is usually short and straight in Fishes, answering to the 

 rectum of higher animals. In some Fishes, e. g., Salmo, Clupea, 

 Esox, Anahleps, Anarrhichas, and the Gymnodonts, it preserves the 

 same diameter as the small intestine, and the term ' large,' becomes 

 arbitrary : in some fishes, e. g., Gasterosteus, Centrisciis, Ostracion, 

 Balistes, and Syngnathus, it is even narrower than the ' small in- 

 testine ;' but most commonly it is wider, as in the Percoid family, the 

 Gui'nards ( TriglidcB), the Breams ( Sparidcs), Scicena, Scomber, 

 Cottus, Labrus, Pleuronectes, Gadus, Lophius, Cyclopterus, the 

 SiluridcB, the Plagiostomi, and the Planirostra (ib. A). 



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

 tebrates, 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 Lancelot support vibratile cilia. 



The muscular fibres are arranged in a thin outer longitudinal and 

 a thick inner circular stratum (see preps. 637. 639. from the 

 Sturgeon) ; the elementary fibres in general present the smooth 

 character of those of the involuntary system ; but Reichert t 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 Verte- 

 brates. It is commonly thick and glandular, and always highly 

 vascular. In the small intestines it presents, in some Fishes (Cod, 

 prep. 633.), a smooth and even surface ; in some it is produced into 

 obliquely longitudinal or wavy folds (Turbot, prep. 634., Salmon, 

 prep. 635.) ; in the Herring it presents feeble transverse ruga? ; in 

 many Fishes it is reticulate, as in the Wolf-fish (prep. 631.) and 

 Murcena (prep. 630.) ; this character is present in the peculiaidy thick 

 and parenchymatoid mucous tunic of the small intestine of the Stur- 

 geon, where the larger meshes include irregular spaces, subdivided 

 into smaller cells (prep. 638.). In a few Fishes the mucous membi'ane 

 is coarsely villose or papillose. There is often a well-marked dif- 

 ference in the character of the lining membrane of the small and 

 large intestine : thus, in the Salmon, the rugag become fewer, larger, 



* xxxiii. t. vi. pp. 624. 270. f xciii. p. 26. 



