The structure of the intestinal tract of _Teleosteous_ fishes is subject to so numerous modifications that we should go beyond the limits of the present work if we would attempt to enter into details. Great differences in this respect may be found even in groups of the same natural families. Frequently the intestinal tract remains of nearly the same width throughout its course, and only the entrance of the various ducts serves as a guide for the distinction of its divisions. An intestine of such uniform width may be straight and short, as in _Scombresocidæ_, _Symbranchidæ_, or it may be more or less convoluted and long, as in many _Cyprinidæ_, _Doradina_, etc. On the whole, carnivorous fishes have a much shorter and simpler intestinal tract than herbivorous. In the majority of Teleosteans, however, œsophagus, stomach, duodenum, small intestine and rectum, can be more or less distinctly, even externally distinguished. There are two predominant forms of the stomach, intermediate forms being, however, numerous. In the first, the _siphonal_, it presents the form of a bent tube or canal, one-half of the horse-shoe being the cardiac, the other the pyloric portion. In the second, the _cæcal_, the cardiac division is prolonged into a long descending blind sac, the cardiac and pyloric openings of the stomach lying close together (_Clupea_, _Scomber_, _Thynnus_, etc.) [Illustration: Fig. 56.--Siphonal Stomach and Pyloric Appendages of a Female Salmon, 3⅓ feet long. _a a a_, Pyloric appendages; _ch_, ductus choledochus; _oe_, œsophagus; _st_, lower end of stomach; _p_, pyloric region; _i_, ascending; and _í’_, descending portion of intestine.] The duodenum receives always the hepatic and pancreatic secretions, and, besides, those of the appendices pyloricæ, which, in varying numbers (from 1 to 200), are of very common occurrence in Teleosteans (Fig. 56). They vary also in length and width, and whilst the narrowest serve only as secretory organs, the widest are frequently found filled with the same contents as the intestine. When few in number, each opens by a separate duct into the duodenum; when their number is greater two or more coalesce into a common duct; in the latter case the appendages cease to be free, and are connected with one another by a more or less firm tissue. Cœcal appendages at the end of the intestinal tract are of exceedingly rare occurrence in fishes (_Box_). There is no _cloaca_ in Teleosteans. In the majority of Teleosteous fishes the _vent_ is situated on the boundary between trunk and tail, behind the ventral fins. In a few it lies farther backwards, not far from the caudal fin; more frequently it is advanced forwards, under the middle of the abdomen or to the scapular arch. In two fishes, _Aphredoderus_ and _Amblyopsis_, it lies before the pectoral fins.