CHAPTER XVII 



THE VIBRATORY SENSE 



Calling the fishes! Of all the varied occupations of 

 the fish-breeder which seem so extraordinary to the 

 novice or the visitor, this, more than any other, is 

 calculated to arouse interest. There is such an occupa- 

 tion, and it is a very practical one; the breeder actually 

 does call his fishes which have been scattered; collects 

 them, and urges them to come to him. The shepherd 

 whistles to his dog with the same intent; the farmer's 

 wife calls her chickens ; both make use of the auditory 

 sensations. These are addressed to the ear. The 

 fish-breeder does the same thing. But he makes use 

 of a sense related to the auditory, peculiar to fishes, 

 which influences them sufficiently to turn them from 

 their course, and finally bring them to one place. 



The means is simple; he has only to impress upon 

 the water a series of slight concussions. The fish- 

 breeder taps his foot several times on the edge of his 

 tank; or claps his hand against its brim; or, if he is 

 in a boat, he taps the bottom. Nothing more is needed. 

 The concussions, transmitted to the water, form 

 vibrating waves which reach the fishes and are per- 

 ceived by them; they obey the instruction and come 

 to the place whence the waves set out. They possess 

 a special sense which gives them knowledge of the 

 waves, teaches them the direction from which they 

 come, and enables them to take their bearings, and 

 finally, to govern their behaviour according to these 

 vibrations in the surrounding medium. 



Various factors make this easier than it would seem 

 at first sight. Their body, suspended in a medium 

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