88 Journal of Travel and Natural History 



is subject to such numerous and rapid variations. The case I have 

 now endeavoured to illustrate is exactly analogous to what occurs 

 among butterflies. As a general rule, the female butterfly is of 

 dull and inconspicuous colours, even when the male is most 

 gorgeously arrayed ; but when the species is protected from attack 

 by a disagreeable odour, as in the Heliconidas, Danaidse and 

 Acroeidse, both sexes display the same or equally brilliant hues. 

 Any general theory of the phenomenon of colour in animals must 

 deal with both these cases, as well as with the whole series of facts 

 presented by every degree and kind of protective and imitative 

 tinting. 



To some persons it will perhaps appear that the causes to which 

 I impute so much of the external aspect of nature are too simple, 

 too insignificant, and too unimportant for such a mighty work. 

 But I would ask them to consider that the great object of all the 

 peculiarities of animal structure is to preserve the life of the indi- 

 vidual, and maintain the existence 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 organized beings would be an ex- 

 ception to most other natural phenomena. They would not be 

 the product of general laws, or determined by ever-changing exter- 

 nal 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 subordin- 

 ated to general laws. I have here attempted to elucidate some of 

 these laws in the case of birds, and have shewn how the mode of 

 nidification has affected the colouring of the female sex in this 

 group. I have before shewn (in the article on " Mimicry " already 

 alluded to) 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. Lastly, I would 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 shewn 

 by Mr Darwin to follow the same great law of utility. Flowers do 



