CHAP. XVI Backboned Animals 255 



pigments, partly to silvery waste-products in the cells of the outer 

 skin, and partly to the physical structure of the scales. Some- 

 times the males are much brighter than the females, and grow 

 brilliant at the breeding season. In some cases the colours har- 

 monise with surrounding hues of sand and gravel, coral and sea- 

 weed ; while the plaice and some others have the power of rapidly 

 changing their tints. 



Fishes feed on all sorts of things. Some are carnivorous, others 



KiG. 52. — The gemmeous dragonet {Callzo7tymus lyrd)^ the male above, 

 the female beneath. (From Darwin.) 



vegetarian, others swallow the mud. By most of them worms, 

 crustaceans, insect-larvte, molluscs, and smaller fishes are greedily 

 eaten. Strange are some of large appetite {e.g. Chiasmodon inger)^ 

 who manage to get outside fishes larger than their own normal 

 size ! 



Of their mental life little is known. Yet the cunning of trout, 

 the carefulness with which the mother salmon selects a spawning- 

 ground, the way the archer-fish (Toxotes) spits upon insects, the 

 nest-making and courtship of the stickleback and others, the pug- 

 nacity of many, show that the brain of the fish is by no means asleep. 



