128 The Animal Mind 



auditory. In the squeteague (542), he infers from the 

 results of operation that one part of the ear, the utriculus, 

 functions in the maintenance of equilibrium, while the other 

 part, the sacculus, is the organ of hearing. The otoliths, 

 or statoliths, in the ears of the squeteague and dogfish 

 Parker thinks have actually an auditory function, contrary 

 to what is known of their use in invertebrate animals; 

 when they were removed from the ear of the dogfish, he 

 reports, there was no disturbance of equilibrium, but a 

 reduction in the reaction to blows on the aquarium wall, 

 and when the large otolith in the sacculus of the squeteague 

 was pinned down, a similar result was obtained. Most 

 sounds made in the air are extremely faint under water, but 

 to so,unds really propagated through water, Parker thinks 

 many fish are sensitive. Certain sounds may actually 

 attract them : the squeteague, for instance, itself makes 

 sounds which may serve to bring the sexes together. 

 Tests by Zenneck on Leuciscus mtilus, L. dobula, and 

 Alburnus lucidus also led to the conviction that these fish, 

 at least, could hear. A bell was struck by electricity under 

 water, and occasionally a piece of leather was placed upon it 

 at the point where the clapper struck. In the latter case 

 the mechanical vibrations produced were, it was held, the 

 same as those occasioned by the actual ringing of the 

 bell, but the sound vibrations were destroyed. The fish 

 reacted by swimming instantly away from the neighbor- 

 hood of the bell when it was rung, but not when the 

 leather was used; hence, apparently, they reacted to 

 sound (840). These experiments, however, have been 

 repeated on trout and eels by Bernoulli (43) with nega- 

 tive results. 



Widely distributed among fishes is a curious set of struc- 

 tures known as the lateral-line canals. Along each side of 



