634 NATURAL HISTORY OF BIRDS. 



called G. religiosa by Linnajus, but, as Jerdon infonus us, probably by a mistake, as 

 he never heard of its being held at all sacred. 



Notwithstanding the enonuous difference between the most extreme members of 

 the series now to follow, as, for instance, between the thin-billed flower-j>eeker and 

 the heavy-headed grosbeak, the link of intermediate forms which combine them seems 

 so unbroken that we can entertain no doubt but what they are only different develop- 

 ments of the same common stock. We commence with several trojiical forms which, 

 though highly specialized in one direction to be presently spoken of, are probably, on 

 the whole, more ancestral than those which we have placed at the end. 



The forms here referred to are the so-called ' Tenuirostres,' corresponding to the 

 group 'Cinnyrimoqihw ' of others, chiefly embracing the sun-birds and the lioney- 

 eaters. They are characterized by a thin, ])oiiited, more or less lengthened and 

 curved bill, and the two families mentioned by having the tongue long, protractile, 

 ending in a suctorial tube anteriorly bifid. 



Tliis apj)aratus, which reseinliles considerably the tubular tongue of the humming- 

 birds, deserves a little attention, and it is worth while to note that not only is the 

 tongue constructed on a similar )irinci])le in these families, so distantly related that 

 they are justly placed in different orders, but tliat also externally, in shape, size, and 

 coloration, the tubilingual tenuirostres, which are exclusively confined to the Old 

 World, bear a great rcscnd)]ance to the hummers. AVe have here an illustration of 

 the fact "that similar functional requirements frequently lead to the development of 

 similar structures in animals which are otherwise very distinct." 



The hyoid a]ii)aratus is provided with very long cornua, which are bent over the 

 skull as in woodjicckers and humming-birds, though not reaching further forward 

 than the frontal bones. The horny sheath of the tongue itself forms first a single 

 tube, which then s])lits uj) into two lubes, herein differing from that of the hum- 

 mers, which is 'double-barreled' to the very l>ase ; but in the true honey-suckers 

 (Melijihagida') the s])lilting up of the end of the tul)es is continued dichotomuusly, so 

 as to form a sort of ' brush.'' Several sets of muscles effect the protrusion of the tongue 

 and the sucking action, which by Dr. Gadow is ascertained to be accom]ilished auto- 

 matically in about the following manner : The whole tongue and larynx is first pressed 

 upwards against the palatal roof of the mouth by the contraction of one set of mus- 

 cles, thus filling the mouth wholly. By the action of other muscles the tongue is pro- 

 truded. If, now, the former muscles relax, and their opponents de|)ress the larynx 

 and the ]iosterior jiart of the tongue, a vacuum will be jiroduced between tongue and 

 palate, which will then be filled with tlie flower nectar, into which the ti]) of the 

 'tongue may have been inserted. The object of the terminal vibrissas in the sun-birds, 

 and tubular brush in the honey-suckers, seems to be to ])revent air from rushing into 

 the tube if there should not be enough nectar to till it, inasmuch as the fluid will then 

 enter the anterior ])art of the tube by capillary action, and then be sucked up. 



Professor Parker has pointed out a considerable difference in the palatal structure 

 of the two tubilingual families referred to. He has found that the sun-birds agree 

 with the rest of the Passeres in having the |>ra'palatine liar running on the inner side 

 of the palatal j)rocess of the priemaxillary, while in the honey-suckers it passes on the 

 outer side. 



In regard to the geographical distribution, we may remark liiat the honey-eatei"8 

 chiefly inhabit Oceania and Australia. They are, as Gould says, the most peculiar and 

 strik ins feature in the ornithokx'v of the latter continent, beinc; "to the faima what 



