GYMNOTUS ELECTRICUS. 417 



tough ; it is thickest on the back and sides, becomes thinner towards 

 the belly fin, and upon this fin is quite thin and not nearly so strong. 

 It is attached to the parts which it covers by cellular membrane, which 

 is of a finer texture where it unites the skin to the large electrical 

 organ, than on the back, where it unites the skin to the muscles, &c. 

 Upon the skin, especially about the head, are a great many openings of 

 the excretory ducts which contain the mucus for lubricating the skin, 

 as in other fishes. The line which passes along from the head to the 

 tail in fishes is their common excretory duct, having a great number of 

 branches which open laterally ; the glandular part for the formation 

 of the mucus generally lying on the head. Under the skin, almost 

 everywhere, lies a very thin membrane, spotted with numberless small 

 dark spots : this is more firmly united to the parts which it covers than 

 to the skin. 



The Senses. — The eyes of this fish are placed near the nose or ex- 

 tremity of the head, and are extremely small : these are, therefore, only 

 adapted to see near objects. This will probably confine the [fish's] 

 sphere of action ; which I believe is, in most animals, regulated by the 

 .senses. [Each olfactory sac of] the nose has two openings, as in the 

 eel and many other fishes; one anterior and a little projecting, the 

 other posterior, and even with the common skin of the head. These, 

 perhaps, answer to the anterior and posterior nostrils of some other 

 animals. The organ of bearing is upon the same principle with that 

 organ in fishes in general, consisting of three bent canals, similar to the 

 semicircular canals in the human subject, opening into one cavity, 

 in which lies a loose bone. This, in some fishes, is of a particular 

 construction ; it is chalky in others ; whilst a few have nothing in this 

 cavity. These canals are generally formed of a transparent cartila- 

 ginous substance. The tongue projects very little, less so than in 

 many other fishes. In the mouth there is a very singular structure, 

 consisting of four rows of regular risings ; one placed along the upper 

 surface of the tongue, one on the roof of the mouth, and one on each 

 side, which are smaller than those on the tongue and roof of the mouth 1 . 

 It is not easy to conceive a use for them ; as they are upon the tongue, 

 it may be conjectured they are for the sense of taste : if so, then taste 

 is conveyed by different nerves. The mouth is neither large nor small, 

 when compared to other fish of the same size. The teeth have nothing 

 remarkable in them. 



The oesophagus is short, strong as in fish in general, and pretty large, 

 having the air-bags opening into it. The abdomen is an oblong cavity, 



1 [Hunt. Prep. Phys. Series, No. 1449.] 

 VOL. II. 2 E 



