TROPICAL NATURE 



ment are much more numerous than the internal changes ; as 

 seen in the varied character of the integuments and append- 

 ages of animals hair, horns, scales, feathers, etc., etc. and 

 in plants, the leaves, bark, flowers, and fruit, with their 

 various modifications as compared with the great uniformity 

 in the texture and composition of their internal tissues ; and 

 this accords with the uniformity of the tints of blood, muscle, 

 nerve, and bone throughout extensive groups, as compared 

 with the great diversity of colour of their external organs.. 

 It seems a fair conclusion that colour per se may be considered 

 to be normal, and to need no special accounting for ; while 

 the absence of colour (that is, either white or black}, or the 

 prevalence of certain colours to the constant exclusion of 

 others, must be traced, like other modifications in the 

 economy of living things, to the needs of the species. Or, 

 looking at it in another aspect, we may say that amid the 

 constant variations of animals and plants colour is ever tend- 

 ing to vary and to appear where it is absent ; and that natural 

 selection is constantly eliminating such tints as are injurious 

 to the species, or preserving and intensifying such as are 

 useful. 



This view is in accordance with the well-known fact of 

 colours which rarely or never appear in the species in a 

 state of nature, continually occurring among domesticated 

 animals and cultivated plants ; showing us that the capacity 

 to develop colour is ever present, so that almost any required 

 tint can be produced which may, under changed conditions, 

 be useful, in however small a degree. 



Let us now see how these principles will enable us to 

 understand and explain the varied phenomena of colour in 

 nature, taking them in the order of our functional classifica- 

 tion of colours. 



Theory of Protective Colours 



We have seen that obscure or protective tints in their 

 infinitely varied degrees are present in every part of the 

 animal kingdom ; whole families or genera being often thus 

 coloured. Now the various brown, earthy, ashy, and other 

 neutral tints are those which would be most readily produced, 

 because they are due to an irregular mixture of many kinds 



