8490 



Birds. 



with the habits of the species) should almost exactly resemble that of 

 quite an unconnected family, and differ altogether from that with 

 which it is really allied ; still less that the independent evidence of 

 the egg should confirm the same false relationship. 



A further examination, too, will show us that the sun-birds are 

 quite as sharply separated by the tubular tongue from their undoubted 

 allies, as the hummers are from the swifts. The little birds of the 

 genus Diceum have always been considered to come in the family of 

 the sun-birds, and are undoubtedly closely allied to them, yet their 

 tongue is short, simple, and merely split at the point. The honey- 

 suckers of Australia and India agree closely with the sun-birds in 

 general structure, in the form of the sternum, the shortness of wing, 

 the length and strength of the leg (in which they both exceed most 

 birds of their size), the large toes, the very long and powerful hind toe 

 and claw, and in having twelve tail-feathers (in all which characters 

 they are totally opposed to the hummers), yet the tongue is flat, of 

 moderate length and terminating in a brush, produced by repeated 

 splittings of the tip. 



Now if the one solitary character of the retractile tubular tongue is 

 sufficient to bring together two families so totally distinct in every 

 other respect as the sun-birds and the hummers, it must also be held 

 sufficient to separate them from every other family and to constitute 

 them a distinct order of birds. 



But I think I have shown that we have no reason whatever to give 

 such importance to the modifications of the tongue. We have here, 

 it appears to me, a most instructive example of how — when two totally 

 distinct groups of organized beings, with some general resemblances 

 of size and outward form, come to be specialised for a similar mode 

 of life — Nature by means of natural selection may occasionally modify 

 the same organ in each, in the same way, quite independently of each 

 other. 



The case of the sun-birds confirms my view of the true function of 

 the tubular extensile tongue being primarily the capture of minute 

 flower-frequenting insects ; for those possessed of this organ and the 

 almost equally extensible brush-tipped tongue, make insects a common 

 part of their food, whereas the simple-tongued genera — as Diceum, 

 Phyllornis and the American Careba — feed almost exclusively on soft 

 fruits. The Arachnotherae, the most highly developed of the true sun- 

 birds, live principally on spiders and nectar, and I have often seen 

 them fluttering in the air at flower-bunches or a sap-exuding palm, 



