102 BLIND VERTEBRATES AND THEIR EYES. 



DOES AMBLYOPSIS "HEAR"? 

 (BY FERNANDUS PAYNE.) 



Until the time of Bateson and Kreidl, it was generally taken for granted that 

 fishes could hear because they had ears. Bateson concluded from his observations 

 on congers, flatfishes, pouting, etc., that fishes perceive the sound of sudden shocks, 

 but do not seem to hear the sounds of bodies moving in the water. Kreidl was 

 the first to make experiments to test the hearing of fishes. He experimented on 

 the gold-fish (Carassius auratus) and concluded that gold-fishes do not hear with 

 the ear, but that they do react to sound waves by means of sense-organs in the 

 skin. Lee's observations supported KreidPs results, and he further concluded 

 that the sole function of the ear in fishes is equilibration. Parker was the first to 

 get positive evidence against the conclusions of Kreidl and Lee. His experiments 

 were based on Fundulus hetcroditus. He used three classes of fishes; first, nor- 

 mal, that is, unmaimed, ones ; second, fishes with the auditory nerves cut ; and third, 

 fishes with the skin rendered non-sensitive but with the ears intact. 



His apparatus consisted of a heavy aquarium with a slate bottom, two glass 

 sides, and two slate ends, one of which he replaced by a piece of deal board to 

 serve as a sounding board. To the middle of one edge of the sounding board he 

 attached a stout beam of wood so that it stood out horizontally about i m. in 

 the plane of that end. He stretched a bass-viol string from the free end of the 

 beam over a bridge in the center of the sounding board to its opposite side. When 

 the string was plucked or bowed, it produced about 40 vibrations per second. 

 The fishes to be experimented upon were placed in a small cage suspended from 

 a cord attached at its ends to the walls of the room. The end toward the sound- 

 ing board was covered with coarse cloth. 



He subjected 10 normal fishes each to 10 tests, and from the 100 tests he got 

 96 pectoral-fin responses. Fishes with auditory nerves cut responded only 18 

 times in a total of 100 trials, and Parker thought these 18 times were in part acci- 

 dental occurrences and in part due to the slight movements of the aquarium caused 

 by the vibrating string. Instead of the vibrating string he substituted an electric 

 tuning-fork which vibrated 128 times per second. With the tuning-fork, where 

 the vibrations of the aquarium could be eliminated, he got no responses with the 

 earless fishes. Fishes in which the skin was made insensitive, but with the ears 

 intact, responded to sound 96 times in a total of 100. These fishes reacted almost 

 exactly as the normal ones did. From these results Parker concludes that the 

 killifish hears. Although his conclusion, that a fish hears, is contrary to Kreidl 

 and Lee, he does not say that the observations of these men are entirely wrong, 

 for the cars in different fishes may function differently. In fact, Parker found no 

 evidence of hearing in the smooth dog-fish (Mustelus cams') when he subjected it 

 to the same experiments as the killifish. Bigelow used Parker's methods of experi- 

 menting and re-examined the gold-fish. He concludes that the gold-fish hears. 1 



1 Since writing tin aln>ve Km TUT in Lucae's Festschrift, 1905, reviewed the evidence advanced to show that 

 fishes can hear, and con< hide . that while they react to rapidly repeated tone-vibrations such as are produced by 

 a tuning-fork or an electric bell, it is not proven that they perceive this with their ears. He used 25 species of 

 fishes and found that in no case did any of these 25 species react in any way to a single sharp click. He con- 

 cludes from these experiments that fishes do not hear. 



