CH. X.] NATURAL SELECTION. 23 



pigeons and parrots ; while the northern snipe resembles the 

 marshy vegetation in which it lives, and the woodcock, with 

 its variegated browns and yellows, is inconspicuous among 

 the autumn leaves.^ Arboreal iguanas are tinted leafy green ; 

 and out of many species of tropical tree-snak.es thei-A is but 

 one which is not green, and this kind conceals it'?elt during 

 the daytime in holes. Flat fish, like the skate and flounder, 

 are coloured like the gravel beneath them. Fishes which live 

 among gorgeous coral reefs are magnificently tinted. The 

 brilliant red hippocampi of Australia dwell among sea-weed 

 of the same colour. And numerous other examples fro^i 

 the vertebrate sub-kingdom are given by Mr. Wallace, from 

 whose remarkable essay the examples here given are culled. 



Before going farther, let us note how completely these 

 interesting phenomena are in harmony with the theory of 

 natural selection. The variability of the hues of domestic 

 animals descended from a monotonously-coloured wild species, 

 shows that there is no direct physiological necessity for the 

 production of animals of a single given style of colouring. 

 But it is tolerably obvious that in the struggle for existence 

 the most conspicuous among those animals which serve as 

 food for others will be the soonest detected, killed, and 

 eaten; while in general the most conspicuous carnivorous 

 animals will be the most easily avoided, and hence will be 

 the most likely to perish for lack of sustenance. And while 

 it is not universally true of the higher animals, as it is of 

 the lower animals and plants, that a much greater number 

 perish than survive, the destruction of life is nevertheless 

 so great that the fate of each creature must often depend 

 upon apparently trivial circumstances. The explanation 

 would therefore be satisfactory, even if protective shades 



* The general principle is well stated by Emerson, in tliis pretty quatrain : 

 •* He took the colour of his vest 

 From rabbit's coat and grouse's breast ; 

 For as the wild kimls lurk and Iiido, 

 80 walks the liuuioin ui unespied." 



