336 THE WORLD OF LIFE 



very different, and the exact nature of their senses being un- 

 known. Even a considerable percentage of men and women 

 are more or less colour-blind, yet some diversity of colour is 

 perceived in most cases. The purpose of colour in relation 

 to insects is that they should distinguish between the colours 

 of flowers which are otherw^ise alike and which have no per- 

 fume. It is not at all necessary that the colours we term blue, 

 purple, red, yellow, etc., should be seen as we see them, or 

 even that the sight of them should give them pleasure. 



Again, the use of colour to us is by no means of the same 

 nature as it is to insects. It gives us, no doubt, a greater 

 facility of differentiating certain objects, but that could have 

 been obtained in many other ways — by texture of surface, 

 by light and shade, by diversity of form, etc., and in some 

 cases by greater acuteness of smell ; and there are very few 

 uses of colour to us which seem to be of " survival value ''- — 

 that is, in which a greater or less acuteness of the perception 

 would make any vital difference to us or would lengthen our 

 lives. But if so, the exquisite perception of colour we nor- 

 mally possess could not have been developed in our ancestors 

 through natural selection ; while what we call the '^ aesthetic 

 sense,'' the sense of beauty, of harmony, of indescribable charm, 

 which nature's forms and colouring so often gives us is still 

 further removed from material uses. Another consideration 

 is, that our ancestors, the Mammalia, derived whatever colour- 

 sense they possess almost wholly from the attractive colours 

 of ripe fruits, hardly at all from the far more brilliant and 

 varied colours of flowers, insects, and birds. But the colours 

 of wild fruits, which have been almost entirely developed for 

 the purpose of attracting birds to devour them and thus to 

 disperse their seeds, are usually neither very brilliant nor 

 very varied, and are by no means constant indications to us 

 of what is edible. It might have been anticipated, therefore, 

 that our perception of colour would have been inferior to that 

 of birds and mammals generally, not, as is almost certainly 

 the case, very much superior, and so bound up Avith some of 



