74 PARKER— A CRITICAL SURVEY OF 



as already described and Lee (1898, p. 138) concluded that fishes 

 do not possess the power of hearing, in the sense in which that term 

 is ordinarily used, and that the sole function of their ears is equi- 

 librium. 



These conclusions were not supported by the work of Parker 

 1903a, 19036) on Fundulus hetcroditus. Recognizing the possi- 

 bility that sound might stimulate not only the skin and the ear but 

 also the organs of the lateral-line system, three sets of Fundulus 

 were tested. One set was entirely normal. A second set was pre- 

 pared by cutting the roots of the fifth and seventh nerves, the lateral- 

 line nerves, and the spinal cord a short distance behind the skull, 

 thus rendering inoperative the lateral-line organs and the organs of 

 touch on the whole surface of the fish except in the region imme- 

 diately about the pectoral fins. In this set the ears were left intact. 

 In the third and last set the eighth nerves were cut, thus eliminat- 

 ing the ears, while the receptivity of the skin was not interfered 

 with. 



These three sets of fishes were subjected to sound stimulation in 

 a large aquarium. The sound was generated by plucking a bass- 

 viol string attached to the wooden end of the aquarium and so ar- 

 ranged that its vibrations were transmitted directly through the 

 wood to the water of the aquarium The normal fishes responded by 

 pectoral-fin movements in 96 per cent, of the trials. The fishes in 

 which the skin had been rendered insensitive, though greatly re- 

 duced in their powers of locomotion by the operations they had un- 

 dergone, nevertheless responded in 94 per cent, of the trials. Fi- 

 nally the fishes in which the ears had been eliminated responded in 

 only 18 per cent, of the trials. It was, therefore, concluded that 

 sounds called forth responses in Fundulus by stimulating not only 

 the skin but also the ears, in other words, that this fish hears. To 

 remove any doubt as to the nature of the stimulus, an electrically 

 driven tuning-fork of the rate of 128 complete vibrations per second 

 was made to replace the bass-viol string on the wooden end of the 

 aquarium. When the fork was in vibration, its base could be 

 brought in contact with the wall of the aquarium and withdrawn at 

 will. If this operation was carried out with a motionless fork, no 

 response from the fishes was to be observed, but when the fork was 



