124 THE DARWINIAN THEORY 



looked, but through being mistaken for something 

 else. Of these cases some extraordinary instances are 

 known. The resemblance may be to another animal 

 or to a plant, flower, or leaf, or to inorganic sub- 

 stances. 



Furthermore, the protective colouring may be 

 either constant or variable ; a good example of 

 variable protective colouring being shown by the 

 Octopus and Chameleon. Again, in animals such as 

 insects, which undergo metamorphosis, and in which 

 the form, structure, and habits are widely different in 

 the larval and adult stages respectively, both these 

 stages may be protectively coloured, but the resem- 

 blance will be to entirely different objects. 



Let us take examples from the different groups of 

 animals, and we shall see that the reality of protec- 

 tive colouring is impossible to doubt. 



Mammals. — The whiteness of Arctic animals has 

 already been referred to. The American polar bear 

 is white all the year round ; the ermine or stoat 

 changes to white in the winter, and the Arctic fox 

 usually does this also. The Alpine hare always 

 becomes white in the winter in Scandinavia, and 

 usually in Scotland, although rarely so in Ireland. 

 This change consists in an actual blanching of the 

 hairs from the tips inwards, with a new growth of 

 additional white hairs. The general tawny colour 

 of deer is also protective ; the protection afforded 

 by spots is seen by their resemblance to the 

 circular spots of light caused by sunlight passing 

 through the leaves of a wood, while stripes facilitate 

 escape in long grass or reeds. 



