146 American Fisheries Society 



are lacking in all fishes dissection shows that an internal 

 ear is always present deeply imbedded in the bone or 

 cartilage of the skull. In some sharks and skates a slen- 

 der tube leads from the internal ear to the top of the 

 head and its outer end is visible there. With this excep- 

 tion the internal ear of fishes does not reach the surface. 



If fish hear, the sound waves must get to the internal 

 ear by traversing the solid bone or cartilage. Since wa- 

 ter is a medium 775 times as dense as air, vibrations in 

 it possess many times the energy of similar vibrations 

 in air — and may therefore easily traverse the tissues of 

 the head and reach the internal ear. At the old swim- 

 ming hole it is a favorite pastime of boys to crack to- 

 gether stones under water after another boy has dived. 

 The painful effect on the submerged human ear of the 

 sounds thus produced is evidence enough of the greater 

 energy of vibrations in water compared with those in 

 air. 



But although fish have the essential organ of hearing 

 much like our own, and although sound waves may reach 

 this organ through the solid tissues of the head, it by 

 no means follows that fish hear. Earlier observers (e.g. 

 Hunter, 1782), thought that fish must hear because they 

 have internal ears. Later Kreidl (1895), removed the 

 internal ears of gold-fishes and, finding that they were 

 sensitive to certain sounds, concluded that these sounds 

 were felt or perceived by the skin, as we may feel cer- 

 tain sound waves when the hand is held in water through 

 which they are passing. He believed that the ears of 

 fishes were not organs of hearing. At the monastery 

 of Krems in Austria it had long been the custom to ap- 

 proach a certain pond and ring a bell. At the ringing 

 of the bell trout assembled to be fed. This was taken as 

 evidence that the fish heard the bell. Kreidl investigated 

 this report, but found that the fish assembled when the 

 pond was approached even though the bell was not rung. 

 He concluded that they came at the sight of the bell 

 ringer not at the sound of the bell. It appeared then that 

 fish in water did not sense the sounds of a bell in air. 



