The Dissection of the Fish 



31 



lived, and some may be even annual, dying after spawning, per- 

 haps at the end of the first season. 



Teeth are wholly absent in several groups of fishes. They 

 are, however, usually present on the premaxiUary, dentary, and 

 pharyngeal bones. In the higher forms, the vomer, palatines, 

 and gill-rakers are rarely without teeth, and in many cases the 

 pterygoids, sphenoids, and the bones of the tongue are similarly 

 armed. 



No salivary glands or palatine velum are developed in fishes. 

 The tongue is always bony or gristly and immovable. Some- 

 times taste-buds are developed on it, and sometimes these are 

 found on the barbels outside the mouth. 



The Alimentary Canal. — The mouth-cavity opens through the 

 pharynx between the upper and lower pharyngeal bones into the 



Fig. 19. — Sheepsheac 



(with incisor teeth), Arcliosiirgiix iirnhn'.oreiihaliis 

 baurn). Beaufort, X. C. 



fWal- 



oesophagus, whence the food passes into the stomach. The intes- 

 tinal 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 ceso]ih- 

 agus with many longitudinal folds and the intestine with but 



