No salivary glands or palatine velum are developed in fishes. The tongue is always bony or gristly and immovable. Sometimes taste-buds are developed on it, and sometimes these are found on the barbels outside the mouth. [Illustration: FIG. 19.--Sheepshead (with incisor teeth), _Archosargus probatocephalus_ (Walbaum). Beaufort, N. C.] =The Alimentary Canal.=--The mouth-cavity opens through the pharynx between the upper and lower pharyngeal bones into the oesophagus, whence the food passes into the stomach. The intestinal tract is in general divided into four portions--oesophagus, stomach, small and large intestines. But these divisions of the intestines are not always recognizable, and in the very lowest forms, as in the lancelet, the stomach is a simple straight tube without subdivision. In the lampreys there is a distinction only of the oesophagus with many longitudinal folds and the intestine with but one. In the bony fishes the stomach is an enlarged area, either siphon-shaped, with an opening at either end, or else forming a blind sac with the openings for entrance (cardiac) and exit (pyloric) close together at the anterior end. In the various kinds of mullets (_Mugil_) and in the hickory shad (_Dorosoma_), fishes which feed on minute vegetation mixed with mud, the stomach becomes enlarged to a muscular gizzard, like that of a fowl. Attached near the pylorus and pouring their secretions into the duodenum or small intestine are the _pyloric cæca_. These are tubular sacs secreting a pale fluid and often almost as long as the stomach or as wide as the intestine. These may be very numerous as in the salmon, in which case they are likely to become coalescent at base, or they be few or altogether wanting. Besides these appendages which are wanting in the higher vertebrates, a pancreas is also found in the sharks and many other fishes. This is a glandular mass behind the stomach, its duct leading into the duodenum and often coalescent with the bile duct from the liver. The liver in the lancelet is a long diverticulum of the intestine. In the true fishes it becomes a large gland of irregular form, and usually but not always provided with a gall-bladder as in the higher vertebrates. Its secretions usually pass through a _ductus cholodechus_ to the duodenum. The _spleen_, a dark-red lymphatic gland, is found attached to the stomach in all fish-like vertebrates except the lancelet. The lining membrane of the abdominal cavity is known as the _peritoneum_, and the membrane sustaining the intestines from the dorsal side, as in the higher vertebrates, is called the _mesentery_. In many species the peritoneum is jet black, while in related forms it may be pale in color. It is more likely to be black in fishes from deep water and in fishes which feed on plants.