THE SENSE OF HEARING IN FISHES. 79 



concluded that though dogfishes are not responsive to ordinary 

 musical tones, they do possess hearing. 



Tests carried out by Parker (1910a) on Ammoccctes by the 

 same means as those used with the dogfish yielded similar results. 

 This fish is sensitive to sound not only through the skin but also 

 through the ears. 



Parker (igiob) also studied the ears of Cynoscion. In this fish, 

 as in many other acanthopterygians, the sacculus and the utriculus 

 are entirely separate structures, there being no utriculo-saccular 

 canal. Cynoscion, after having been in a large wooden tank for 

 some time, became adjusted to its new environment and when the 

 side of the tank was tapped vigorously, it responded by a slight 

 forward spring. The utriculus and semicircular canals were then 

 destroyed through a small incision on the top of the head, leaving 

 the sacculus intact. Such fishes showed at once disturbed equilib- 

 rium, after which they recovered their upright position. On having 

 blinders put over their eyes, however, they swam with great irregu- 

 larity. Thus both eye and ear are involved in their responses for 

 equilibrium. During all these tests, however, they reacted as normal 

 fishes do to taps on the wall of the tank, showing that the destruc- 

 tion of the utriculus and semicircular canals had not interfered with 

 their responses to sounds. It was found impossible to reverse the 

 operation just described and destroy the sacculus leaving the utric- 

 ulus intact. But by forcing a strong pin through the paper-thin 

 bone between the roof of the mouth and the sacculus, it was possible 

 to fix the large otolith of the sacculus, the sagitta, firmly against the 

 outer or non-nervous wall of the sacculus and thus prevent its inde- 

 pendent motion. Fishes treated in this way were only occasionally 

 responsive to taps on the wooden wall of the tank. If a normal 

 fish and one with the sagitta pinned down were tested in the same 

 tank, the greater responsiveness of the normal individual was easily 

 noticed. Although the experiments on Cynoscion leave open the 

 question of the extent to which the skin may participate in sound 

 reception, they show very clearly that the sacculus of the ear, as 

 contrasted with the utriculus, has a well-defined part in this activity. 



Meyer (1910), whose work was chiefly concerned with the capac- 



