DIGESTIVE SYSTEM. 235 



nished with smaller and insignificant convolutions, we meet with a 

 well-defined stomach, as in Gasterosteus, Gobius, and some species 

 of Blennius and Pleuronectes. In other instances the stomach is 

 not developed directly in the course of the intestine, but to the side 

 of the latter, and forms either an oval or spherical dilatation, as in 

 Cobitis and Blennius viviparus, or passes from this form into that of 

 a retort, examples of which may be seen in the majority of Bony 

 Fish, e. g. the Salmon. The cardiac portion of the stomach is fre- 

 quently extended into a more or less elongated caecum, e. g. in the 

 Eel, in Gadus, Scomber, Clupea, and many other Fish, but more 

 especially in Ammodytes tobianus. To the stomach, when present, 

 succeeds the intestine properly so called ; it makes either few or 

 many convolutions, and is not unfrequently continued backward to 

 form a thicker portion that may be regarded as the large intestine, 

 the limits of this being defined frequently by a caecal valve, as 

 those of the pylorus are by a constriction. Beyond this point, 

 however, the intestine frequently narrows toward the cloaca, as in 

 many Carps and Salmons, and it is not rare for the valve to be 

 wanting. Occasionally a valve is found upon the cardiac orifice of 

 the stomach. Anomalies also occur of a peculiar kind, e. g. in Le- 

 padogaster biciliatus ; for here to a short narrow pharynx succeeds a 

 dilatation from four to five times wider, which occupies the greatest 

 part of the ventral cavity, and represents at once both the stomach 

 and the small intestine, while after it comes another bag of a more 

 oval form, the large intestine. Applicable as they may so far 

 appear, we shall find that in other cases the names of divisions 

 borrowed from those of the intestinal canal in the human subject 

 are not applicable to Fishes any more than they are to some of the 

 naked Amphibia, and that it is better to adopt the terms oral, 

 meso, and anal intestine, as expressing the regions of the body to 

 which the portions of intestine may happen to belong. An equal 

 amount of variety is displayed also by the mucous membrane lining 

 the canal ; thus it is often simply disposed in longitudinal folds, as 

 in Pleuronectes, Silurus, Blennius, Cyclopterus, Petromyzon, or in 

 zigzag folds, e. g. in several Cyprini, while in other Carps, and in 

 Gasterosteus, transverse folds are observable, that are particularly 

 developed in the Salmon-tribe, in the terminal portion of the intes- 

 tine. Most Fishes, however, exhibit a very varied net- work formed 

 by confluent longitudinal and transverse folds of mucous membrane. 

 It is more rare for true papillae, or tongue-shaped prolongations of 

 the folds, to be met with, as in the Pike, and many species of 



