8 ANIMAL COLOEATION. 



Another pigment, whicli seems to be of equal importance to 

 liEemoglobin, is chlorocruorin, found in certain green marine 

 Annelids ; it colours their blood, and performs the office of an 

 oxygen carrier. 



It is very possible that the brightly coloured oil globules 

 which are found in the epidermis of certain Turbellarian worms, 

 and in the small fresh-water annelid ^olosoma, play a part 

 analogous to that of chlorophyll or tetronerythrin. 



The Coloration of Animals. 



It is important, as has already been said, to distinguish 

 between " Colour " and " Coloration " — that is to say, between 

 the actual tints and their arrangement and distribution. It is no 

 doubt the fact, as Mr. Wallace states, that colour is " a normal 

 product of organisation," entirely independent of utility; on the 

 other hand, it will be pointed out in the following pages that 

 there is a good deal of evidence to show that " coloration " 

 bears often a distinct relation to the needs of the animal ; it 

 may therefore have been modified by natural selection. 



One example will sufiice to render this matter clearer: the 

 common Peacock butterfly has wings adorned with the most 

 varied and beautiful colours, with which are associated duller 

 browns and black ; if these different tints were scattered 

 generally over the surface of the wings, the insect would be 

 conspicuous to its enemies at all times, — the coloration might, 

 if it were palatable to birds, render its extinction a matter of a 

 very short time. But in the actual butterfly the most brilliant 

 colours are concentrated upon the upper surface of the wings, 

 and particularly to form four eyelike markings, one at the 

 corner of each wing; the under surface is entirely mottled with 

 dull shades ; accordingly, when the insect is at rest and therefore 

 more accessible to its foes, the inconspiciwus underside is alone 



