Reighard. — Senses and Learning in Fishes 149 



tense sounds produced directly in water. Because they 

 do not appear to hear sounds produced in air does not 

 justify us in concluding with Haempel that they are deaf. 



The sounds audible to fishes are then probably not 

 usually those produced in air — for ordinary sound waves 

 travelling through air have too little effect on the much 

 denser water. But the evidence indicates that sound 

 waves set up in water or those reaching water from some 

 solid like a boat are sensed by fishes. Hence the fisher- 

 man may talk in a boat without appreciably disturbing 

 the fish, but he may not produce sounds by striking the 

 boat itself. No doubt the sound of his own voice travels 

 through his body and through the boat to the water, but 

 it then has probably too little intensity to be effective. 

 Since we have little experimental knowledge as to how 

 any of the game fishes react to sounds produced in water, 

 it is as well for the sport fishermen to be as silent as he 

 can. 



It is quite possible that certain fishes may be attracted 

 by sounds. This is indicated by the facts that some of 

 them produce sounds. The male squeteague (Cynoscion 

 regalis) has the ability to make sounds, but the female 

 has not. It is not impossible that these sounds attract 

 the female. Haempel (1911), relates that in parts of 

 Europe fishermen are wont to attract catfish by means 

 of sounds. In one case a wooden instrument is used, in 

 another the hook is baited with a live frog and the water 

 then struck with an instrument which produces a sound 

 like the croaking of a frog. 



3. The Visual World and the Sense of Sight in Fishes. 



The appearance of its visual world to the fish is deter- 

 mined in part by the medium through which it looks and 

 in part by the peculiarities of its eyes. 



A. The Visual World. The human eye is not adapt- 

 ed for clear vision when immersed in water, but it is 

 possible to use an instrument like an inverted periscope 

 (Reighard, 1908), and by means of it to see objects 

 under water while the head remains in air. When such 

 an instrument is used the clearest ocean water looks 



