340 TROPICAL NATURE 



and emotions may not be another and perhaps more important 

 use which they subserve in the great system of the universe ? 



We now propose to lay before our readers a general account 

 of the more recent discoveries on this interesting subject ; and 

 in doing so it will be necessary first to give an outline of the 

 more important facts as to the colours of organised beings ; 

 then to point out the cases in which it has been shown that 

 colour is of use ; and lastly, to endeavour to throw some light 

 on its nature and on the general laws of its development. 



Among naturalists, colour was long thought to be of little 

 import, and to be quite untrustworthy as a specific character. 

 The numerous cases of variability of colour led to this view. 

 The occurrence of white blackbirds, white peacocks, and black 

 leopards, of white blue-bells, and of white, blue, or pink milk- 

 worts, led to the belief that colour was essentially unstable, 

 that it could therefore be of little or no importance, and 

 belonged to quite a different class of characters from form or 

 structure. But it now begins to be perceived that these 

 cases, though tolerably numerous, are, after all, exceptional ; 

 and that colour, as a rule, is a constant character. The great 

 majority of the species, both of animals and plants, are each 

 distinguished by peculiar tints which vary very little, while 

 the minutest markings are often constant in thousands or 

 millions of individuals. All our field buttercups are invari- 

 ably yellow, and our poppies red, while many of our butter- 

 flies and birds resemble each other in every spot and streak of 

 colour through thousands of individuals. We also find that 

 colour is constant in whole genera and other groups of species. 

 The Genistas are all yellow, the Erythrinas all red; many 

 genera of Carabidae are entirely black ; whole families of birds 

 as the Dendrocolaptidse are brown ; while among butter- 

 flies the numerous species of Lycsena are all more or less blue, 

 those of Pontia white, and those of Callidryas yellow. An ex- 

 tensive survey of the organic world thus leads us to the conclu- 

 sion that coloiir is by no means so unimportant or inconstant 

 a character as at first sight it appears to be ; and the more we 

 examine it the more convinced we shall become that it must 

 serve some purpose in nature, and that, besides charming us 

 by its diversity and beauty, it must be well worthy of our 

 attentive study, and have many secrets to unfold to us. 



