xxiii] LIFE IN LONDON 399 



characteristic of the whole group, often with metallic reflec- 

 tions ; while soft greens, and sometimes metallic greens, 

 occur in the forest regions of tropical Africa and Asia, but 

 rarely anything approaching to crests or other developments 

 of plumage. 



But as soon as we reach the Moluccas and New Guinea 

 we find a new type of coloration appearing in both groups. 

 Among the lories we find vivid red and crimson, sometimes 

 with a remnant of green on the wings and tail, but often 

 covering the whole plumage, varied with bands or patches 

 of equally vivid blue or yellow, while the red sometimes 

 deepens into a blackish-purple. Among the cockatoos we 

 have pure whites and deep black, with highly developed 

 crests, often of great beauty, so that in these two families 

 we seem to depart altogether from the usual parrot type of 

 coloration. 



Still more remarkably is this the case with the pigeons. 

 In the extensive genus of small fruit-pigeons (Ptilo?iopus) 

 the usual ground colour is a clear soft green, variegated by 

 blue, purple, or yellow breasts, and crowns of equally brilliant 

 colours. Besides these, we have larger fruit-pigeons almost 

 wholly cream white, while the very large ground pigeons 

 of New Guinea possess flat vertical crests, which are unique 

 in this order of birds. The wonderfully brilliant golden 

 green Nicobar pigeon is probably a native of the Austro- 

 Malayan islands, and may have been carried westward by 

 Malay traders, and have become naturalized on a few small 

 islands. 



These peculiarities of distribution and coloration in two 

 such very diverse groups of birds interested me greatly, and 

 I endeavoured to explain them in accordance with the laws 

 of natural selection. In the paper on Pigeons (published 

 in Tfie Ibis of October, 1865) I suggest that the excessive 

 development of both these groups in the Moluccas and the 

 Papuan islands has been due primarily to the total absence 

 of arboreal, carnivorous, or egg-destroying mammals, 

 especially of the whole monkey tribe, which in all other 

 tropical forest regions are exceedingly abundant, and are 



