THE 



COLOURS OP ANIMALS 



CHAPTER I 

 THE PHYSICAL CAUSE OF ANIMAL COLOUBS 



Colours due to absorption 



THE colours of animals are produced in various ways. 

 By far the commonest method is the absorption of 

 certain elements of light by means of special sub- 

 stances which are called pigments, or colouring matters. 

 The colour of each pigment is due to those elements 

 of the light which it does not absorb, and which can 

 therefore emerge and affect the eye of the spectator. 

 Black is, of course, caused by the absorption of all 

 the constituents of light, so that nothing reaches the 

 eye. The colour of red pigment, like that of red 

 glass, depends upon the fact that red is less absorbed 

 than any other element of the light which passes 

 through. If a sheet of red glass be placed upon 

 white paper, the light traverses the glass, is reflected 



