146 THE STORY OF REPTILE LIFE. 



when the winter is cold, but they do so singly 

 and not in colonies as in the foregoing instance. 



CHAPTER VII. 



REPTILIAN LIVERIES. 



"THE existence of colour, as such," remarks 

 Professor Poulton, "is not necessarily of any 

 value to an organism." Colour is the incidental 

 result of chemical or physical structure which 

 causes certain light- waves to be absorbed ; or the 

 elements of the tissues may be so arranged that 

 the light is scattered, causing what are known as 

 interference colours, such as the metallic colours 

 of birds' feathers. The red colour of blood is an 

 instance of non-significant colour, since, hidden 

 away in the tissues of the body, its redness ceases 

 to exist, and only becomes apparent when drawn 

 from the animal. The often beautiful colours of 

 non-living bodies again serve as instances of non- 

 significant colour. 



Nevertheless, the coloration of the vast bulk of 

 living animals is fraught with a deep significance, 

 and represents the results of a long process of 

 selection. From the wide range of variation 

 offered by the inevitable production of non- 

 significant colours, the innumerable patterns 

 which form the characteristic liveries of the 

 different species of animals have been formed. 

 Animals which, by their conspicuous coloration, 

 either drew upon themselves the attention of their 



