ANIMAL COLORATION. 



CHAPTER I. 



INTRODUCTORY. THE PRINCIPAL FACTS OF ANIMAL 



COLORATION. 



WE must clearly distinguish at the outset between u Colour v 

 and " Coloration " : the two terms are frequently confused, but 

 they are obviously by no means synonymous. By colours we 

 understand the actual tints (blue, green, red, etc.) which are 

 found in animals ; by coloration, the arrangement or pattern 

 of these tints. In certain cases the two expressions colour 

 and coloration may be practically synonymous, may coincide : 

 in a perfectly green caterpillar it is only necessary to mention 

 the colour ; but in the vast majority of cases the colours are 

 more than one, and have therefore a certain arrangement : 

 there is thus a coloration. 



The Colours of Animals. 



The colours of animals are due either solely to the presence 

 of definite pigments in the skin, or, in the case of trans- 

 parent animals to pigment in the tissues lying beneath the 

 skin; or they are partly caused by optical effects due to the 

 scattering, diffraction or unequal refraction of the light rays. 



Colours of the latter kind are often spoken of as structural 

 colours ; they are caused by the structure of the coloured 



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