194 A HISTORY OF FISHES 



of depth is not very great, it is improbable that it is concerned 

 with changes in pressure, and it may be concluded that it 

 probably serxes to intensify the impulses of sound waves and 

 movements received from the surrounding water. Of its 

 importance to the life of the fish there can be no doubt, since 

 the elaborate Weberian mechanism is possessed by every 

 member of the dominant group of fresh-water fishes living 

 to-day. 



Some authorities have expressed doubt as to whether fishes 

 really hear at all, at least in the sense in which higher animals 

 hear. Aristotle was quite certain that they are able to perceive 

 sounds in the water, "for they are observed to run away from 

 any loud noises like the rowing of a galley." A number of 

 experiments have been conducted to ascertain the extent to 

 which fishes are able to hear, but a brief survey of the more 

 interesting of these will show the contradictory nature of the 

 results obtained. Dr. Bateson found that loud reports or 

 explosions made by blasting operations near Plymouth were 

 followed by sudden movements in some fishes, whilst others 

 seemed to be unaffected. He concluded that fishes perceive 

 the sound of sudden shocks when sufficiently severe, but do 

 not hear the sounds made by striking two objects together 

 under water out of sight of the fish. Cases have been described 

 of Carp, Gold-fish, and other fishes assembling for feeding at 

 the sound of a bell, but Dr. Kreidl found that Trout assembled 

 equally readily at the sight of a person even when the bell was 

 not rung, and that they took no notice if they could not see the 

 person ringing the bell. If, however, a stone or piece of food 

 was thrown into the water, the fish hurried to the spot where 

 the water was disturbed. This author agreed with Dr. Bateson 

 that the fishes responded, not to sounds made in the water, but 

 only to a shock such as a blow on the sides or top of an 

 aquarium. What is even more interesting, however, is the fact 

 that they were said still to react to similar shocks when the ear- 

 sacs and auditory nerves had been removed. Two American 

 investigators, however, obtained somewhat different results. 

 They found that certain fishes responded to sounds made by a 

 tuning fork or by a bass viol string by characteristic movements 

 of the fins and other organs, but that when both the auditory 

 nerves were cut these responses disappeared. Another German 

 worker concluded that Roach, Dace, and Bleak definitely 

 responded to sound vibrations. Mr. Radcliflfe states that he 

 and some friends, in order to test the sense of hearing in Trout, 



