OUTLINES OF ICHTHYOLOGY. 159 



their acuteness of smell. The nostrils, which are 

 simple cavities near the end of the muzzle, divided 

 by a membrane, are generally pierced with two 

 holes, but both openings lead to the same common 

 canal. 



The sense of Taste is more developed in the 

 herbivorous than in the carnivorous fishes ; but it is 

 in general probably of a low order, as a great part 

 of the tongue is bony, and frequently furnished 

 with teeth, placed there for the purpose of retain- 

 ing food or prey. Obliged necessarily to open and 

 close their jaws in respiring, they cannot long 

 retain food in the mouth when quite shut, and the 

 substance, if of small size, must be swallowed 

 quickly and without much mastication. 



It has been thought possible, from the bony 

 nature of the tongue and the shape of the teeth, 

 which are calculated to assist in conveying food to 

 the back of the mouth, that the sense of taste may 

 reside in the soft, fleshy portions of the throat. A 

 low sense of taste generally, however, would ap- 

 pear to be inferred from the fact that fish are often 

 unable to distinguish poisonous substances, and 

 are accordingly frequently destroyed wholesale by 

 poachers. 



In regard to the organs of digestion, the intes- 

 tines of fish generally are short, and the digestive 

 process very rapid — so rapid, in fact, in some of 



