90 PARKER— A CRITICAL SURVEY OF 



telephone. If the hand of the experimenter was held in the aquarium 

 water, be it ever so carefully done, the Aminnis immediately de- 

 scended to the deeper parts and responses to the more delicate forms 

 of stimuli were completely inhibited. Hence Korner's method of 

 operating a " cri-cri " by hand under water could have had no other 

 result that that of rendering the fishes quite unresponsive and it 

 would have been surprising if he had obtained anything but nega- 

 tive results. As this responsive phase of Amiiirits seems to have en- 

 tirely escaped Korner's attention, it is natural that he should also 

 have failed to observe the reaction of this fish to whistles, and to 

 other sound-producing devices. Hence so far as Amittrus is con- 

 cerned Korner's negative results, as contrasted with those of Maier 

 (1909), of Haempel (1911) and of Parker and Van Heusen (1917), 

 are quite clearly due to defective technique and as this technique 

 was also the basis of his tests of the twenty-five kinds of fishes first 

 reported by him as without hearing, it follows that these tests can 

 no longer be regarded as valid and that Korner's statements based 

 upon them are, therefore, without weight. 



Another source of error in the testing of fishes for hearing is 

 the assumption that their only form of response to sound is flight. 

 From the time of Aristotle this has been known to be a typical re- 

 sponse, but that it is the only method of reaction to sounds is far 

 from true. Kreidl (1S96, p. 585) in his experiments at the fish 

 basins in Krems got evidence that certain fishes .would approach a 

 center of vibratory disturbance and Parker (1912, p. 103) showed 

 that Prionotus, which produces a loud grunting noise, approaches a 

 sound center rather than retreats from it. Thus, though fishes 

 under most experimental conditions commonly are put to flight by 

 sounds, they occasionally may do the reverse and under more nat- 

 ural conditions this may be a much more usual form of response 

 than has been suspected. But whether fishes approach or avoid a 

 source of sound, their responses in such activities are chiefly through 

 their fins. It is, therefore, not surprising that in experimental tests 

 sound, and particularly slight sounds, call forth very characteristic 

 fin movements. As these movements follow with such regularity 

 on the application of this stimulus, to deny them as a sign of effec- 

 tive stimulation is to ignore that very feature which may be of prime 



