THE VIBRATORY SENSE 



their behaviour on the basis of these vibratory im- 

 pressions which the water transmits to them; they 

 come, they turn aside, or avoid and flee, according to 

 the reflex provoked. 



This sense, like the others, varies considerably. 

 According to circumstance and in different species, 

 its keenness is sometimes excessive and sometimes 

 dulled. In rod-fishing, a duel between the fish and 



Fig 51. — Simplified and very much enlarged view of a transverse section 

 of the tube which perforates the scale, so as to show the walls 

 which, at intervals, contain groups of sensitive elements, both 

 elongated and oval in shape. This wall is embedded in the sub- 

 stance of the scale, which itself is covered by the epidermis. 

 Linear magnification, 375 times. 



the fisherman, it often works in an unexpected way 

 and plays a part which has not been taken into account. 

 Sometimes its importance is less. In other cases it is 

 exaggerated, as in the fresh-water roach. One of 

 them, the rudd {Scardinius erythrophthalmus), stands out 

 among the others on account of its extreme sensitivity. 

 It is both greedy and distrustful ; its appetite draws it 

 to the bait, and its auditory sense drives it away; its 

 behaviour, based upon both impulses at once, seems to 

 leave it in a continual state of indecision. If one is 

 fishing for it from the river-bank, it must be very 



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