FISHES. 319 



may be observed. In the cyclopteri this organ is thoracic, 

 of a circular form, and consists of numerous soft papillae. 

 In the lampry, the mouth contracts, and the lips act as a 

 sucker. 



The use of this organ to the fish, it is difficult to ascertain. 

 When, by its means, the fish attaches itself to the sides of 

 other fishes, or to the bottom of ships, it is carried forward 

 without any exertion of its own ; and, during storms, adhe- 

 sion to rocks may save a weak fish from being tossed about 

 by the fury of the waves; but there may, perhaps, be other 

 purposes to which it is subservient, which still remain to be 

 discovered. 



The sucker furnishes to the ichthyologist^ characters for 

 the discrimination of the species which are obvious and 

 permanent ; but these have seldom been described with ac- 

 curacy or minuteness. 



The organs of motion are extensively employed by the 

 systematic ichthyologist, in the formation of his divisions. 

 It does not appear, however, that naturalists have deter- 

 mined the exact value of the characters which they furnish, 

 either for generic or specific distinctions. La Cepede, in 

 some instances, has formed genera from a difference in the 

 number of the dorsal fins ; while, into the genus Gadus, 

 species with one, two, and even three fins are admitted. 

 As the number of the fins is invariably the same, in the 

 same species, and as these organs may be supposed to ex- 

 ercise considerable influence on the habits of fishes, the cha- 

 racter thus exhibited may be safely employed in generic 

 distinctions. The characters furnished by the structure of 

 the fins have not been overlooked, especially the rays. The 

 circumstance of being bony or jointed, is often noticed in 

 specific distinctions, although well entitled to regulate divi- 

 sions of a higher kind, as the character furnished is perma- 

 nent. Those characters furnished bv the fins, which are 



