vi ORIGIN OF THE COLOUR-SENSE 415 
appearance ; and this seems quite in accordance with the vari- 
ous facts set forth by Mr. Gladstone and the other writers 
referred to. The fact that colour-blindness is so prevalent 
even now is, however, an indication that the fully-developed 
colour-sense is not of primary importance to man. If it had 
been so, natural selection would long ago have eliminated the 
disease itself, and its tendency to recur would hardly be so 
strong as it appears to be. 
Concluding Remarks on the Colour-sense 
The preceding considerations enable us to comprehend 
both why a perception of difference of colour has become 
developed in the higher animals, and also why colours require 
to be presented or combined in varying proportions in order 
to be agreeable to us. But they hardly seem to afford a 
sufficient explanation either of the wonderful contrasts and 
total unlikeness of the sensations produced in us by the chief 
primary colours, or of the exquisite charm and pleasure we 
derive from colour itself, as distinguished from variously- 
coloured objects, in the case of which association of ideas 
comes into play. It is hardly conceivable that the material 
uses of colour to animals and to ourselves required such very 
distinct and powerfully-contrasted sensations ; and it is still 
less conceivable that a sense of delight in colour per se should 
have been necessary for our utilisation of it. 
The emotions excited by colour and by music alike seem 
to rise above the level of a world developed on purely utili- 
tarian principles. 
