228 DARWIXISM chap. 



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

 we have the innumerable special adaptations to the tints and 

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

 or pel)ble ; by which such vast numbers of the insect tribes 

 obtain protection ; 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 

 imder 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 

 thiidv, 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 pure 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 perhaps ec^ually extensive 

 Avith that of coloration for concealment. 



Influence of Locality or of Climate on Colour. 



Certain relations between locality and coloration have long 

 been noticed. IVIi*. Gould observed that birds from inland or 

 continental localities were more brightly colom-ed 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 Avith 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 AA'ith the degree of humidity, it Avould 

 perhai^s be more in accordance Avith cause and effect to exj^ress 

 the laAV of correlation as a decrease of intensity of colour AA'ith 

 ' Se& Origin of Species, yi. 107. 



