24 COSMIG FEILOiSOFHY. [pt. il 



of colouring could be regarded as circumstances of slight 

 importance, — which they cannot. 



Since, therefore, it is natural selection which keeps up the 

 protective hues of animals, by killing off all save the least 

 conspicuous individuals, we may understand why it is that 

 animals which have for several generations been domesticated 

 no longer retain, without considerable deviation, their pro- 

 tective style of colouring, Treed from the exigencies of wild 

 life, there is no longer an imperious need for concealment, 

 and hence the unfavourably coloured individuals survive like 

 the rest, and variety appears among members of the same 

 species. In the cat family, which appears to have been 

 originally arboreal, there is a strong tendency to the produc- 

 tion of stripes and spots. In the lion, which is not arboreal, 

 and in the puma, owing to the peculiarity above mentioned, 

 these variegated markings have been almost wholly weeded 

 out by natural selection.^ But in the domestic cat, along 

 with these spots and stripes which occasionally show its 

 blood-relationship with the leopard and tiger, we more often 

 meet with colours not paralleled among the wild species; 

 now and then we see cats which are coal-black or snowy 

 white. Cows, horses, sheep, dogs, and fowl, furnish parallel 

 examples. Thuc; too we may understand why the sable and 

 the Canadian woodchuck retain their brown fur during the 

 winter ; for the one can subsist on berries, and is far more 

 agile than any of its foes, while the other lives in burrows 

 by the riverside and catches small fish that swim by in the 

 water. And thus we may understand why it is that in the 

 case of birds which build open nests, the female is dull 

 colouied like the nest ; while on the other hand, the females 

 of birds which build domed nests are often as brightly 

 coloured as the males. 



^ The variegated marking asaally appears, however, in lion-cubs ; thua 

 showincr that the variegated coloming of the leopard and tiger is relatively 

 primary, while the monotonous colouring of the adult lion is relatively 

 secondary. 



