Birds. 



8489 



the others, and a great grasping power. The bill and tongue offer the 

 sole important points of difference, but, on the principles before alluded 

 to, they are of less importance than the points of agreement, because, 

 being organs directly concerned in maintaining the existence of the 

 birds, they are modified to suit the very different habits of the two 

 families. Moreover, in a very young state, the difference is scarcely 

 perceptible. In a pair of nestling hummers which I kept alive some 

 days by feeding them with minute insects, which they greedily de- 

 voured, while they showed repugnance to every kind of syrup, which, 

 therefore, probably only enters into the diet of the adult birds ; 1 ob- 

 served that the beak was short and triangular, with a very wide gape, — 

 in fact, just the beak of a swift. I am sorry I neglected to examine the 

 tongue of these young birds, but I have little doubt it would have been 

 simple, or only showing a slight approach towards the tubular form. 

 The formation of such a tongue out of one of the ordinary flat horny 

 type is very easily conceivable. It has only to become lengthened 

 and dilated at the margins, which gradually curl in on each side till 

 they meet, forming a double, or rather reniform, tube. The hummer's 

 tongue is really flat, like that of any other bird, the inrolled edges 

 not being united at their line of contact, so that, in their fresh state, it 

 may be flattened out into a long and very delicate ribband. The end 

 of this tongue is fibrous, and the act of suction would no doubt 

 secure minute flower-frequenting insects as well as pump up nectar ; 

 and that insects form the most common contents of the stomach I can 

 assert from the examination of scores of specimens of many different 

 species. 



We will now consider what are the affinities of the Nectarinidae, or 

 sun-birds of the East ; and at starting I will concede a point, which 

 you, Mr. Editor, were not perhaps prepared for. I can state, from 

 careful observation, that the tongue of the true sun -birds is really 

 tubular, and exactly similar to that organ in the hummers, and the 

 os hyoides is also partially extended over the head, so as to give some 

 degree of extensile and retractile power. From this fact, however, 

 I simply draw the conclusion that the structure of the tongue, though 

 useful in confirming the affinities of genera, is not of sufficient im- 

 portance to determine the relation of families when placed in opposi- 

 tion to other more deeply - seated anatomical and physiological 

 characters. I can imagine how the tongue may become profoundly 

 modified by variation and natural selection, to adapt it to some 

 special purpose in the economy of the bird ; but I cannot believe that 

 the sternum (whose characteristic form has no immediate connection 

 VOL. XXI. 2 A 



