342 .THE WOKLD OF LIFE 



plained by it. I will therefore now add a few more consid- 

 erations to those I have hitherto set forth. 



On the question of the colour-sense I have already argued 

 that though it may exist in birds and insects, it is hardly likely 

 that it produces any such high aesthetic pleasure as it does in 

 our own case. All that the evidence shows is, that thev do 

 perceive what are to us broad differences of colour, but we have 

 no means whatever of knowing n:]iai they really perceive. It 

 is a suggestive fact that colour-blind persons, though they do 

 not see red and green as strongly contrasted as do those with 

 normal vision, yet do perceive a difference between them. It 

 is therefore quite possible that birds may see differences be- 

 tween one strongly marked colour and another without any 

 sense of what we should term colour, and at all events without 

 seeing '' colours " exactly as we see them. It is now generally 

 admitted that birds arose out of primitive reptiles, and from 

 their very origin have been quite distinct from mammals, 

 which latter probably diverged a little later from a different 

 stock and in a somewhat different direction. The eyes of both 

 were developed from the already existing reptilian eye, and 

 their type of binocular vision may be very similar. But at 

 that early period there were, it is believed, no coloured flowers 

 or edible coloured fruits, and it is probable that the perception 

 of colour arose at a much later period. It is therefore unlikely 

 that a faculty separately developed in two such fundamentally 

 different groups of organisms should be identical in degree or 

 even in nature unless its use and purpose were identical. But 

 birds are much more extensive fruit-eaters than are mammals, 

 the latter, as we have seen, being feeders on nuts which are 

 protectively tinted rather than on fruits, while their largely 

 developed sense of smell would render very accurate perception 

 of colour needless. It is suggestive that the orang-utan of 

 Borneo feeds on the large, green spiny Darian fruit ; and I 

 have also seen them feeding on a green fruit which was re- 

 pulsively bitter to myself. Our nearest relatives among exist- 

 ing quadrupeds do not therefore seem to have any need of 



