230 PISCES. 



mucous membrane a glistening epithelium ; it does not perforate the 

 mouth, but terminates in a small blind pouch, having its mucous 

 surface increased by folds. 



Organs of Taste. 



THE tongue is absent in Fishes, and the anterior part of the lingual 

 bone, which frequently supports teeth, exhibits neither in its exter- 

 nal condition, nor in the distribution of its nerves, any analogy with 

 the tongue of the other Vertebrata. In cases where the glosso-pha- 

 ryngeal nerve is developed, as in the Sturgeon, it only gives twigs 

 to the branchial arches and palate, which last is in Fishes probably 

 the seat of the sense of taste. No branch arises from the fifth pair 

 that can be compared to the lingual nerve. 



That the gustatory function is probably seated in the palate, ap- 

 pears to be confirmed by the fact that in many Fishes, e. g. the 

 Cyprini and in C. carpio, peculiar organs, richly supplied by nerves, 

 are developed in that situation. In the Carp there is found at the 

 base of the skull, in front of the excavated plate, which is met with 

 on the body of the sphenoid, and supports what has been called the 

 Carp's stone, and also in front of the pharyngeal jaws, a single white 

 spongy mass, which receives numerous large branches from the 

 glosso-pharyngeal nerve, and is possessed of such a high degree of 

 irritability, that it becomes erect and turgescent upon mechanical 

 and chemical stimulants being applied. This organ forms a very 

 broad cushion immediately above the inner edges of the branchial 

 arches. 



Organs of Touch. 



As organs of touch in Fishes, we must unquestionably regard the 

 beard-like filaments that occur in many, as in sundry species of 

 Cobitis, upon the chin and at the commencement of the mouth ; they 

 receive large branches from the fifth pair of nerves. 



DIGESTIVE SYSTEM. 



IF throughout the class of Fishes we have seen the hard parts of 

 the body assuming the greatest variety of structure as compared 

 with those of other Vertebrata, so also in the Teeth that form the 

 armature of the jaws, and other facial bones, shall we find the same 



