531 NATURAL HISTORY OF BIRDS. 



called 6r. religiosa by Linnaeus, but, as Jerdon informs us, probably by a mistake, as 

 he never heard of its being held at all sacred. 



Notwithstanding the enormous difference between the most extreme members of 

 the series now to follow, as, for instance, between the thin-billed flower-pecker 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 tropical 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 ' Cinnyrimorphse ' of others, chiefly embracing the sun-birds and the honey- 

 eaters. They are characterized by a thin, pointed, 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. 



This apparatus, which resembles 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 principle in these families, so distantly related that 

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

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

 World, bear a great resemblance to the hummers. We 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 apparatus is provided with very long cornua, which are bent over the 

 skull as in woodpeckers 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 splits up into two tubes, herein differing from that of the hum- 

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

 (Meliphagidas) the splitting up of the end of the tubes is continued dichotomously, 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 accomplished 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 depress the larynx 

 and the posterior part of the tongue, a vacuum will be produced between tongue and 

 palate, which will then be filled with the flower nectar, into which the tip 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 prevent air from rushing into 

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

 enter the anterior part 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 



o o 



with the rest of the Passeres in having the prrepalatine bar running on the inner side 

 of the palatal process of the prsemaxillary, while in the honey-suckers it passes on the 

 outer side. 



In regard to the geographical distribution, we may remark that the honey-eaters 

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

 striking feature in the ornithology of the latter continent, being "to the fauna what 



