vi A THEORY OF BIRDS' NESTS 139 



ence of the species. Colour has hitherto been too often looked 

 upon as something adventitious and superficial, something 

 given to an animal not to be useful to itself, but solely to 

 gratify man or even superior beings to add to the beauty 

 and ideal harmony of nature. If this were the case, then, it 

 is evident that the colours of organised beings would be an 

 exception to most other natural phenomena. They would not 

 be the product of general laws, or determined by ever-chang- 

 ing external conditions ; and we must give up all inquiry into 

 their origin and causes, since (by the hypothesis) they are 

 dependent on a Will whose motives must ever be unknown to 

 us. But, strange to say, no sooner do we begin to examine 

 and classify the colours of natural objects, than we find that 

 they are intimately related to a variety of other phenomena, 

 and are, like them, strictly subordinated to general laws. I 

 have here attempted to elucidate some of these laws in the 

 case of birds, and have shown how the mode of nidification 

 has affected the colouring of the female sex in this group. I 

 have before shown to how great an extent, and in how many 

 ways, the need of protection has determined the colours of 

 insects, and of some groups of reptiles and mammalia, and I 

 would now call particular attention to the fact that the gay 

 tints of flowers, so long supposed to be a convincing proof that 

 colour has been bestowed for other purposes than the good of 

 its possessor, have been shown by Mr. Darwin to follow the 

 same great law of utility. Flowers do not often need pro- 

 tection, but very often require the aid of insects to fertilise 

 them, and maintain their reproductive powers in the greatest 

 vigour. Their gay colours attract insects, as do also their 

 sweet odours and honeyed secretions ; and that this is the 

 main function of colour in flowers is shown by the striking 

 fact that those flowers which can be perfectly fertilised by 

 the wind, and do not need the aid of insects, rarely or never 

 have gaily-coloured flowers. 



This wide extension of the general principle of utility to 

 the colours of such varied groups, both in the animal and 

 vegetable kingdoms, compels us to acknowledge that the 

 " reign of law" has been fairly traced into this stronghold of 

 the advocates of special creation. And to those who oppose 

 the explanation now given of the various facts bearing upon 



