PDF - Wallace Online

340 TROPICAL NATUREand emotions may not be another and perhaps more importantuse which they subserve in the great system of the universe ?We now proposeto lay before our readers a general accountof the more recent discoveries on this interesting subject ;andin doing so it will be necessary first to give an outline of themore importantfacts as to the colours of organised beings ;then to point out the cases in which it has been shown thatcolour is of use ;and lastly, to endeavour to throw some lighton its nature and on the general laws of its development.Among naturalists, colour was long thought to be of littleimport, 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 blackleopards, of white blue-bells, and of white, blue, or pink milkworts,led to the belief that colour was essentially unstable,that it could therefore be of little or no importance, andbelonged to quite a different class of characters from form orstructure. But it now begins to be perceived that thesecases, though tolerably numerous, are, after all, exceptional ;and that colour, as a rule, is a constant character. The greatmajority of the species, both of animals and plants, are eachdistinguished by peculiar tints which vary very little, whilethe minutest markings are often constant in thousands ormillions of individuals. All our field buttercups are invariablyyellow, and our poppies red, while many of our butterfliesand birds resemble each other in every spot and streak ofcolour through thousands of individuals. We also find thatcolour is constant in whole genera and other groups of species.The Genistas are all yellow, the Erythrinas all red; manygenera of Carabidae are entirely black whole families of birds;as the Dendrocolaptidse are brown while ; among butterfliesthe numerous species of Lycsena are all more or less blue,those of Pontia white, and those of Callidryas yellow. An extensivesurvey of the organic world thus leads us to the conclusionthat coloiir isby no means so unimportant or inconstanta character as at first sight it appears to be and the more we;examine it the more convinced we shall become that it mustserve some purpose in nature, and that, besides charming usby its diversity and beauty, it must be well worthy of ourattentive study, and have many secrets to unfold to us.