452 TRANSACTIONS OF THE 



my ponds, that their sense of smell is exceedingly acute, and their 

 hearing sujQ5ciently developed to be perfectly susceptible of all 

 simple sounds, having the same acoustic aj^paratus that is found 

 in the centre of an animal's ear, but being enclosed in the bones 

 of the skull in such a manner that the vibratory motion iu water 

 of sound comes in contact with the auditory nerve, and thus pro- 

 duces the selisatiou of hearing. The eye of the sucker, and many 

 other fishes, is globular, with a flat cornea, and is consequently 

 not extended as far into the field of vision as the eyes of terres- 

 trial animals, which require an extraneous aqueous humor to 

 keep the eye convex; fish do not, because the element in which 

 they live is equivalent, and keeps the outer tunics always moist. 

 Therefore, there being no tears for lubricating purposes, I have 

 never found a lachrymal sac. There is a wonderful contrivance 

 of nature in the constitution of voracious salt water fishes' eyes, 

 enabling them to bear against the pressure of water at great depths 

 in the ocean, consisting of a hard bone with an opening into it for 

 the optic nerve. Fish tliat inhabit shoal water possess a mem- 

 braneous eye, and if forced into deep water they would immedi- 

 ately become blind — consequently you can judge accurately how 

 deep any species of fish are enabled to swim. Fish having no 

 eyelids, must necessarily sleep with their eyes wide open, and 

 are probably always enabled to see when danger is at hand ; they 

 see to a very great distance in clear water^ but turbid water ren- 

 ders their vision indistinct. The whale can distinguish a boat 

 nearly two miles off. I have noticed on removing the sucker 

 from water, that the light at first appears to paralyze the optic 

 nerve, but soon thereafter the pupil diminishes in size, and the 

 fish probably sees as well as a person would with his eyes im- 

 mersed in water. On replacing him in his proper element, he 

 appears to be confused, and swims against any object that may be 

 opposite to him. This experiment I have often tried, and never 

 knew it to fail. The sucker is acutely sensible to the touch of 

 the human hand, and his sense of smelling enables him to detect 

 food, or enemies, at a very great distance. I have placed food 

 with the oil of rhodium on it, at one end of a large pond, and 

 have noticed the sucker, accompanied by the carp, perch and 

 shiner, at the other end, immediately turn and swim to it. I 



