84 INTRODUCTION. 



consisting of olive-green, blueish-grey, or brown ; 

 none possessing one brilliant spot of any pure colour. 

 On the other hand, as soon as we cross the verge of 

 the herbivorous group, and enter the carnivorous, we 

 find such spots as those alluded to become brighter 

 and more numerous, many parts being stained with 

 yellow and red in deep and natural tints. To the first 

 genus of the group, Systomus^ the Gold-fishes be- 

 long, whose intestinal tube is only one-half the length 

 of that of the herbivorous species. In advancing 

 from this family towards another, we find, as in 

 the genus Opsarius^ the abdominal tube still fur- 

 ther diminishes; and in proportion as this takes 

 place, and the habits of the species become more 

 carnivorous, the brilliancy of the colours becomes 

 remarkable. Tlie Perilampus is another genus of the 

 same sub-family, which presents numerous bright 

 lines of various colours, but particularly blue, on 

 their sides. " They are all," says Mr. M'Lelland, 

 " small species of little or no direct utility to man ; 

 nor is it possible to account for the peculiar bril- 

 liancy of their colours in any other way (as its 

 final cause) than as an instance of that inscrutable 

 design by which it would seem that, in pursuit of 

 aquatic insects, on which they subsist, along the 

 surface of waters, they become the better marks 

 of Kingfishers, Skimmers, Terns, and other birds 

 which are destined to keep the number of fishes in 

 check, especially in deep waters, beyond the reach 

 of the waders." Analogy from other animals, more 

 especially insects, strongly corroborates these views. 



