THE YELLOW PERCH 319 



The colors of most fishes are protective in their nature, 

 and the perch is no exception to this general rule. From 

 above, the olivaceous back is with difficulty distinguished 

 from the water itself or the bottom below ; from beneath, 

 the white under parts are colored like the surface of the 

 water or the atmosphere above. The mottled sides also 

 serve to render the perch less conspicuous in lights and 

 shadows among weeds and rocks on the bottom. It has 

 been noted that in some instances where perch live both in 

 a large lake and in its tributaries, as in Lake Michigan and 

 the rivers which flow into it, the lake fish have a tendency to 

 lighter general coloration and to disappearance of the dark 

 vertical bands. It has been suggested that this difference in 

 color is due, in part at least, to the smaller amount of light 

 in the lake, combined with the absence of dark lurking- 

 places. 



Sight is probably the best-developed sense, though, as al- 

 ready stated, the eyes are not adapted to vision at a great 

 distance. To test the power of sight discrimination, an 

 observer dropped into an aquarium pieces of wireworms 

 (larvae of click beetles) alternately with similar bits of 

 earthworms. Nearly every time one or more of the bits of 

 wireworm were seized by the perch, only to be dropped a 

 moment later. The fishes did not seem to make any per- 

 manent association between the appearance of the wire- 

 worm and its inedible character. 



Perhaps the clearest way to picture the limitations in 

 the mental organization of a fish is to sum up, as Professor 

 Sanford does, some characters in which the fish differs from 

 man: 



No fish is ever conscious of himself ; he never thinks of himself 

 as doing this or that, or feeling in this way or that way. The 

 whole direction of his mind is outward. He has no language and 

 so cannot think in verbal terms ; he never names anything ; he 



