Reighard. — Senses and Learning in Fishes 147 



Kreidl concluded that they did not use the ears for 

 hearing. 



Later an American, Parker (1903, 1903a, 1910a, 

 1910b, 1911a, 1912a), held that this view was wrong. 

 He found, as had Kreidl, that fish responded to sound. 

 He used the killifish (Fundtdatus heteroclitus) , and sque- 

 teague (Cynoscion regalis). The killifish were placed in 

 a cage suspended in an aquarium. One end of the aqua- 

 rium was a sounding board to which was attached a bass- 

 viol string string the vibrations of which were transmit- 

 ted through the water. In other experiments he placed a 

 vibrating tuning fork against the sounding board. When 

 normal fish were tested in this apparatus they responded 

 to the sound by breathing more rapidly, by movements 

 of the pectoral or tail fins oi." by springing. Fishes in 

 which the nerves of the ear had been cut rarely gave 

 these responses. They sometimes responded when the 

 bass-viol string was used, but this was probably because 

 it gave rise not only to sound waves, but also to slower 

 vibrations which affected the lateral-line organs of some 

 of the fish. Fish with cut ear nerves gave no response 

 to the sound waves from the tuning fork, for it produced 

 no disturbances in the water except sound waves. 



Fishes in which the ears were intact, but in which all 

 the nerves to the skin and lateral line had ben cut, re- 

 sponded to the sounds in the only way possible for them, 

 by increased rate of breathing. Such responses as they 

 gave were hardly to be distinguished from those of nor- 

 mal fish. It was clear then that the killifish could hear 

 so long as the nerves to the ear were intact even when 

 all the nerves supplying the skin and lateral line had been 

 cut. The only possible conclusion is that fishes use the 

 internal ears, but not the skin or lateral-line, as organs 

 of hearing. How then explain the fact that the goldfish 

 from which Kreidl had removed the internal ears, were 

 still able to hear? Kreidl performed this operation by 

 making a small opening in the top of the head and pull- 

 ing out the internal ear with a pair of forceps. It re- 

 mained for Bigelow (1904), a pupil of Parker, to show 



