NERVOUS SYSTEM, SENSES, AND SENSE ORGANS 195 



each in turn fired a gun close to the surface of the water while 

 the others observed the result. Although the gun was fired 

 eight, four, and three feet above a shallow stream, fired into 

 the air or into the opposite bank in a direct line above different 

 fishes lying either singly or in shoals from five to nine inches from 

 the bottom, in no case did the Trout take the slightest interest, 

 or give any sign of having either heard the shots or felt the 

 concussion of the bullet striking the opposite bank. Sir Herbert 

 Maxwell, howe\'er, states with equal certainty that fish in 

 Loch Ken were disturbed every time a shooting-party half 

 or three-quarters of a mile away discharged their guns. 



On the whole, it seems most probable that the sense of hearing, 

 if developed at all, is far from acute, and may be largely confined 

 to the perception of disturbances in the water. The otoliths 

 would serve to translate these disturbances into vibratory 

 movements, v/hich, by their action on the inner sensitive 

 patches, stimulate the fine endings of the auditory nerve and 

 thus convey impulses to the brain. It is difficult to understand 

 why a number of fishes should possess an elaborate apparatus 

 for the production of sound if their companions are incapable 

 of appreciating the result, and it would appear that some 

 fishes at least must be capable of perceiving sounds to a greater 

 or lesser extent. Others are perhaps almost completely deaf, 

 although they will react to violent shocks or disturbances in the 

 water. 



The arrangement of semicircular canals and the internal 

 cavities of the auditory organ with their contained otoliths 

 certainly play another part, and assist in maintaining the equi- 

 librium of the fish. In the ampulla of each canal are highly 

 sensitive cells, and by the pressure of the contained endolymph 

 on these cells a movement of the head into another plane is 

 conveyed to the brain by the auditory nerve. Similarly, if the 

 fish were to turn over suddenly on to its side, the otoliths would 

 press on the sensitive patches in the walls of the membranous 

 sacs, and thus set up nervous impulses which would promptly 

 inform the brain of the change in the inclination of the head. 



Comparatively little is known about the sense of taste in 

 fishes, but, if this exists at all, it is probably far from acute. 

 In the first place, apart from certain forms like the Carp 

 (Cyprinus) and Parrot-fishes (Scaridae), which appear to masticate 

 their food with some care, most fishes swallow the food with 

 great rapidity. Secondly, the tongue may be altogether wanting, 

 and even when this is developed, it is unprovided with muscles 



