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 



Fig. 52. — The gemmeous dragonet (Callionymus lyra), the male above, 

 the female beneath. (From Darwin.) 



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

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

 eaten. Strange are some of large appetite (e.g. Chiasmodon niger), 

 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. 



