172 TROPICAL NATURE, AND OTHER ESSAYS. 



tints of the upper wings, which are more or less exposed 

 to the various colours of surrounding nature. 



Classification of Organic Colours. We find, then, 

 that neither the general influence of solar light and heat, 

 nor the special action of variously tinted rays, are ade- 

 quate causes for the wonderful variety, intensity, and 

 complexity of the colours that everywhere meet us in 

 the animal and vegetable worlds. Let us therefore take 

 a wider view of these colours, grouping them into classes 

 determined by what we know of their actual uses or 

 special relations to the habits of their possessors. This, 

 which may be termed the functional and biological clas- 

 sification of the colours of living organisms, seems to 

 be best expressed by a division into five groups, as 

 follows : 



i 1. Protective colours. 



2 Warning colours I " ^ cre atures specially protected. 

 Animals J 2 ' \ b. Of defenceless creatures, mimicking a. 



] 3. Sexual colours. 



( 4. Typical colours. 

 Plants. 6. Attractive colours. 



It is now proposed, firstly, to point out the nature of 

 the phenomena presented under each of these heads ; 

 then to explain the general laws of the production of 

 colour in nature ; and, lastly, to show how far the varied 

 phenomena of animal coloration can be explained by 

 means of those laws, acting in conjunction with the laws 

 of evolution and natural selection. 



Protective Colours. The nature of the two first 

 groups, Protective and Warning colours, has been so 

 fully detailed and illustrated in my chapter on " Mimicry 

 and other Protective Resemblances among Animals," 

 (Contributions to the Theory of Natural Selection, p. 45), 



