164 



THE WORLD OF LIFE 



CHAP. 



Markings of this character, though varied almost in- 

 finitely, occur in all classes of the higher animals, and very- 

 much in proportion as their mode of life requires them. 

 When concealment is of more importance, then the recog- 

 nition is made effective by differences of shape or of motions 

 and attitudes, or by special cries, as in the cuckoo. Among 

 the birds of the tropical forests, while the ground colour is 

 often protective, as in the green of parrots, the smaller fruit- 



Fig. 38. — QLdicnemus recurvirostris (Great Indian Stone-Curlew). 

 This species is found all over India, and also in Ceylon and Burma. This species 

 is clearly defined by the upturned bill and the compact black mark around 

 the eye. 



pigeons of the Malay Archipelago, many of the barbets, and 

 hosts of other birds, yet the different species will be almost 

 always characterised by spots or bands, or caps of brilliant 

 or contrasted colours. But as these usually break up the 

 green body into irregular portions, and as flowers of equally 

 varied hues are common on trees, or on the orchids and 

 other epiphytes that grow upon their branches, the general 

 effect is by no means conspicuous. 



Now, without this principle of the necessity for external 

 differences for purposes of recognition of each species by 

 their own kind, and especially of the sexes by each other, 

 this endless diversity of colour and marking, when not pro- 

 tective, seems difficult to explain. The Duke of Argyll, in 

 his interesting work, The Reign of Law, published six years 



