148 TROPICAL NATURE, AND OTHER ESSAYS. 



all other birds, no less tlian the abundance and variety 

 of their generic and specific forms, clearly point to a 

 very high antiquity. 



The Relaiions and Affinities of Humming-hirds. — The 

 question of the position of this family in the class of 

 birds and its affinities or resemblances to other groups, 

 is so interesting, and affords such good opportunities for 

 explaining some of the best- established principles of 

 classification in natural history in a popular way, that 

 we propose to discuss it at some length, but without 

 entering into technical details. 



There is in the Eastern hemisphere, especially in 

 tropical Africa and Asia, a family of small birds called 

 Sun-birds, which are adorned with brilliant metallic 

 colours, and which, in shape and general appearance, 

 much resemble humming-birds. They frequent flowers 

 in the same way, feeding on honey and insects ; and all 

 the older naturalists placed the two families side by side 

 as undoubtedly allied. In the year 1850, in a general 

 catalogue of birds. Prince Lucien Bonaparte, a learned 

 ornithologist, placed the humming-birds next to the 

 swifts, and far removed from the Nectarinidse or sun- 

 birds ; and this view of their position has gained ground 

 with increasing knowledge, so that now all the more 

 advanced ornithologists have adopted it. Before pro- 

 ceeding to point out the reasons for this change of 

 view, it will be well to discuss a few of the general 

 principles which guide naturalists in the solution of 

 such problems. 



Hoiv to Determine Doubtful Affinities. — It is now 

 generally admitted that, for the purpose of determining 

 obscure and doubtful affinities, we must examine by 



