HAVE FISHES MEMORY. 381 



Anglers, as is well known, still lay great stress upon a sort of bait 

 whose chemical properties operate at a distance. The belief is that 

 fish can be lured to a given spot by certain substances. My corre- 

 spondence goes to prove that this supposition is open to many 

 exceptions. 



Doubtless the reception of mechanical or tactile impressions, in 

 other words, the sense of touch, occasionally has a part to play in the 

 feeding of fishes and in their life as a whole. Bateson reports that 

 the barbels are brought into requisition only after the food has been 

 reached. Protopterus, Motella^ and others distinctly make use of their 

 barbels to investigate the food whose presence has announced itself 

 through the sense of smell. Probably onW the region about the 

 mouth responds to touch irritations. An observer can readily con- 

 vince himself that, if he avoids being seen or himself moving the fish, 

 any part of its body as it lies in the aquarium may be touched, and 

 the fish will not change its position. Additional experiments on this 

 point would be highly desirable. 



That fishes are open to light impressions appears from the fact that 

 some, soles for instance, can change their colors according to the hue 

 of the subsoil above which they happen to swim. Dunn recently 

 reported his observations upon soles. (Contemporary Review, 1899.) 

 Not only did he see light colored individuals turn black over dark 

 soil, but when he carried them home in a pail with a dark bottom he 

 found them all darkened. Dunn's essay, which, it should be said, 

 ignores the results of all past investigations, also contains statements 

 about the existence of electric and magnetic sensations, but they have 

 been reached by way of pure speculation. 



In general the behavior of fishes with regard to light proves that 

 they receive light impressions. Some feed only in the dark, some 

 rise to the bait only on days of a certain degree of cloudiness and at 

 other times keep themselves far below the surface of the water, and 

 it is known that a shadow suffices to drive away a shoal of fish. 



It is universally agreed that fishes see, that is, are aware of images 

 produced optically. Their vision apparently gives rise to a compara- 

 tively acute faculty of discrimination, for, as every angler knows, 

 artificial bait is valuable only if quite up to the mark in certain respects, 

 and the price lists of dealers in sporting articles show, by the multi- 

 plicity and variety of the artificial insects, fish, etc., ofl'ered for bait, 

 how high an opinion fishermen entertain of the optical discrimination 

 of their intended victims. 



Again, fishermen carefully conceal the hook in the living bait, believ- 

 ing that fish will notice the slightest edge protruding. Doubtless fishes 

 receive the impressions of form and color, and distinguish optically 

 between rest and motion. Many are guided by optical impressions in 

 taking their food. Bateson could not decide whether fishes that respond 



