228 DARWINISM chap. 



or dead leaves on or among which they habitually live. Then 

 we have the innumerable special adaptations to the tints and 

 forms of leaves, or twigs, or flowers ; to bark or moss ; to rock, 

 or })cl)l)le ; by which such vast luimbers of the insect tribes 

 obtain i)votection ; and we have seen that these various forms 

 of coloration are equally prevalent in the waters of the seas 

 and oceans, and are thus coextensive with the domain of life 

 upon the earth. The comparatively small numbers which 

 possess "terrifying" or "alluring" coloration may be classed 

 under the general head of the protectively coloured. 



But under the next head — colour for recognition — we have 

 a totally distinct category, to some extent antagonistic or 

 complementary to the last, since its essential principle is 

 visibility rather than concealment. Yet it has been shown, I 

 think, that this mode of coloration is almost equally im- 

 portant, since it not only aids in the preservation of existing 

 species and in the perpetuation of j^ure races, but was, per- 

 haps, in its earlier stages, a not unimportant factor in their 

 development. To it we owe most of the variety and much 

 of the beauty in the colours of animals ; it has caused at 

 once bilateral symmetry and general permanence of type ; 

 and its range of action has been perhajis equally extensive 

 with that of coloration for concealment. 



Influence of Locality or of Climate on Colour. 



Certain relations between locality and coloration have long 

 been noticed. Mr. Gould observed that birds from inland or 

 continental localities were more brightly coloured than those 

 living near the sea-coast or on islands, and he supposed that 

 the more brilliant atmosphere of the inland stations was the 

 explanation of the phenomenon. ^ Many American naturalists 

 have observed similar facts, and they assert that the intensity 

 of the colours of birds and mammals increases from north to 

 south, and also wdth the increase of humidity. This change 

 is imputed by Mr. J. A. Allen to the direct action of the en- 

 vironment. He says : "In respect to the correlation of intensity 

 of colour in animals with the degree of humidity, it would 

 perhaps be more in accordance with cause and effect to express 

 the law of correlation as a decrease of intensity of colour with 

 ^ See Origin of Species, -p. 107. 



