36 NATURAL SELECTION in 



This great principle gives us a clue which we can follow out 

 in the study of many recondite phenomena, and leads us to 

 seek a meaning and a purpose of some definite character in 

 minutiae which we should otherwise be almost sure to pass 

 over as insignificant or unimportant. 



Popular Theories of Colour in Animals 

 The adaptation of the external colouring of animals to 

 their conditions of life has long been recognised, and has been 

 imputed either to an originally created specific peculiarity, 

 or to the direct action of climate, soil, or food. Where the 

 former explanation has been accepted it has completely 

 checked inquiry, since we could never get any further than 

 the fact of the adaptation. There was nothing more to be 

 known about the matter. The second explanation was soon 

 found to be quite inadequate to deal with all the varied 

 phases of the phenomena, and to be contradicted by many 

 well known facts. For example, wild rabbits are always of 

 gray or brown tints well suited for concealment among grass 

 and fern. But when these rabbits are domesticated, without 

 any change of climate or food, they vary into white or black, 

 and these varieties may be multiplied to any extent, forming 

 white or black races. Exactly the same thing has occurred 

 with pigeons ; and in the case of rats and mice, the white 

 variety has not been shown to be at all dependent on altera- 

 tion of climate, food, or other external conditions. In many 

 cases the wings of an insect not only assume the exact tint of 

 the bark or leaf it is accustomed to rest on, but the form and 

 veining of the leaf or the exact rugosity of the bark is 

 imitated ; and these detailed modifications cannot be reason- 

 ably imputed to climate or to food, since in many cases the 

 species does not feed on the substance it resembles, and when 

 it does, no reasonable connection can be shown to exist 

 between the supposed cause and the effect produced. It was 

 reserved for the theory of Natural Selection to solve all these 

 problems, and many others which were not at first supposed 

 to be directly connected with them. To make these latter 

 intelligible, it will be necessary to give a sketch of the whole 

 series of phenomena which may be classed under the head of 

 useful or protective resemblances. 



