126 The Animal Mind 



35. Hearing in Fishes 



Throughout the vertebrate animals there exist structures 

 bearing analogy to our own ears, whose function might 

 therefore be supposed to be auditory. But in the lowest 

 vertebrates the only structures of the human ear represented 

 are the semicircular canals, and these suggest a static rather 

 than an auditory organ. The cyclos tomes, eel-like and 

 semiparasitic forms classed below the true fishes, have a 

 pair of sacs one on either side of the head, containing 

 mineral bodies, and each leading into one or two semi- 

 circular canals. In the true fishes the sac has two chambers, 

 marked off from each other by a constriction. Three semi- 

 circular canals open from the foremost chamber, two lying 

 in the vertical plane, and one in the horizontal plane. 

 The chambers contain "statoliths" and fluid. 



That the semicircular canals in fishes have a static 1 func- 

 tion has been shown by experiments to be described later. 

 Is the fish ear also an organ of hearing ? Again authorities 

 disagree, and it is probable that species differ. Kreidl got 

 no response from goldfish when vibrating rods were placed 

 either in the water or in the air near the water. Only 

 when the fish were made more sensitive by strychnin did 

 they react, and only to noise, not to tone. They reacted 

 quite as well, moreover, when the ears were removed; 

 whence it was concluded that their sensitiveness to noise 

 resided in the skin (408, 409). A similar negative con- 

 clusion regarding auditory sensation has been reached by 

 F. S. Lee (416), by O. Korner as a result of experiments 

 on twenty-five species (404), and by Marage (460 a), using 



J The word "static" is here used to mean "relating to equilibrium" 

 in general, not to static equilibrium as distinguished from dynamic 

 equilibrium. 



