INTIIODUCTIOX. 9 



that tliere exists another yellow-shafted species with red niystacal strific and red nuchal 

 crescent, viz., Volnptcs c/iri/soh/vs. If this theory Ik- correct, we would ha\c a clew to 

 another class of dichromatic siiecies, viz., those which now are stereotyped into two 

 invariable forms or species, .separated geo<iraphically, but still identical in structure. 

 We .shall only mention an example recently brouijlit forward by ."Mr. Ritli^way, that of 

 the sc.-irlet and the white ibises {Gxara ntlmi and aNid), of which he very character- 

 istically remarks that they are now so different in color that jirobalily nobody would 

 deny their specific distinction, thoujih structurally so alike that a sjiecinien of the 

 white one dyed scarlet would be indistinguish;il)le from G. ruhra. The (piestion which 

 hnally impri'sses itself upon the iiuiuirer, in view of the above facts, is this: ,\re not 

 the two or tiirt'c 'phases' of dichromatic or trichromatic species 'inci]>ient 8j)ecie8,' 

 the linal fate of which will be that of the white and the scarlet ibises? 



We have eidarged considerably upon this subject, because it is one of the most 

 ])erplexing, and, consequently, most interesting questions in modern ornithology. It 

 shows what we know, and ])articularly what we do not know ; it shows that ornithology 

 nie.ans more than a mere description and naming of birds, that one of its aims is to con- 

 tribute to the solution of the great problem of the age: "The origin of species." 



Besides feathers, we recognize in birds other e])idennal appendages, as tlie horny 

 sheaths of the beak, the teeth in some extinct forms, the scaly covering of the feet, spurs, 

 and nails. Most of these dil'ferent structures vrijl be more advantageously treated of in 

 other connections, and under the head of such groups in whicli they may be of si)ecial 

 interest, although we wish here to call attention to the fact that parts of the horny 

 beak and the nails of the toes may be shed in a way analogous to that of the molt 

 of the feathers, referring, as Ave do, to the deciduous nature of the basal jiarts of the 

 1)111 in sc\ci-,il members of the auk family (puffins and dwarf-auks), to the 'centre- 

 board' of the white jielican's bill, and to the .seasonal claw-molt iti the grouse-family, 

 j)articularly the jitarniigans. The most jiriniitive form of the horny covering of the 

 feet seems to be its division into uniform hexagonal scales, and is called reticidate ; the 

 next stage is when some of these scales fuse together, forming what is termed scuta, 

 or scutella, which particularly cover the anterior ])art of the tarsus and the upper sur- 

 face of the toes; still further specialization is indicated l»y the tarsal scuta fusing into 

 a continuous covering which, in its extreme development, embraces both the front and 

 the back of the tarsus, as in some of the higher group of passerine birds ; sueli a 

 tarsus is said to lie 'booted.' 



It has already been remarked that the skin has no sudoriferous glands nor sebnceous 

 follicles ; but we cannot dismiss the dermal .system before having mentioned the bilobed 

 oil-i^lanil placed at the base of the t;iil-feathers on the 'pope's nose,' and sehlom miss- 

 ing, as it is in the ostriches ami some few other binls. When '])reeiiing' their 

 feathers, birds press the fatty substance out of liiis oil-box with their beaks, and by 

 pa.ssing each feather between the mandibles, anoint the whole |ilumage in order to 

 keep it in rejiair and protect it against g<tting wet, as |>articularly noticeable in water 

 birds. 



Turning now to the other structural systems of the bird's body, it is not our inten- 

 tion to eidarge upon or even mention such gineral features as are regularly found in 

 the text-books, only those being deemed worth our .attention, in the present connection, 

 which are of ]iarticular importance for an intelligent imderst.-mding of modern orni- 

 thological classificati<in, or questions which .it jircsent are most occupying the lovers 

 of our beautiful science. 



