xv GENERAL ADAPTATIONS 319 



gentian (Gentiana verna\ and a few others, we perceive a depth 

 and a purity of hue which seem to have reached the limits 

 of the possible. We may surely ask ourselves whether 

 these exquisite refinements of mere colour as well as the 

 infinity of graceful forms and the indescribable delicacies 

 of texture and of grouping, are all strictly utilitarian in 

 regard to insect-visitors and to ourselves. To them the 

 one thing needful seems to be a sufficient amount of 

 difference of any kind to enable them to distinguish among 

 species which grow in the same locality and flower at the 

 same time. 



Special Cases of Bird Coloration 



Coming now to birds, we find the colours with which 

 they are decorated to be fully equal in variety and purity of 

 tint to those of flowers, but extending still farther in modifica- 

 tions of texture, and in occasionally rivalling minerals or 

 gems in the brilliancy of their metallic lustre. The exquisite 

 blues and vinous purples, reds and yellows of the chatterers 

 and manakins, the glorious metallic sheen of the trogons, of 

 many of the humming-birds, and of the long-tailed paradise- 

 bird ; the glistening cinnabar-red of the king-bird of paradise, 

 appearing as if formed of spun-glass ; the silky orange of the 

 cock-of-the-rock and the exquisite green of the Malayan 

 crested gaper, are only a few out of thousands of the extreme 

 refinements of colour with which birds are adorned. 



Add to these the marvellous ornaments with which the 

 males are so frequently decorated, the crests varying from 

 the feathery dome of the umbrella-bird, to the large richly 

 coloured crest of the royal fly-catcher of Brazil, and the 

 marvellous blue plumes from the head of the fern-bearing 

 bird of paradise (Pteridophora Albertt), with a thousand others 

 hardly inferior, and we shall more than ever feel the want of 

 some general and fundamental cause of so much beauty. 



All this wealth of colour, delicacy of texture and exuber- 

 ance of ornament, has been explained hitherto as being utili- 

 tarian in two ways only : (i) that they are recognition-marks 

 of use to each species, more especially during its differentiation 

 as a species ; and (2) as influencing female choice of the 

 most ornamental males, and therefore of use to each species 



