NESTLING DOWN OF PENGUINS. 11 



tions of the penguins herein descril)ed. The nestlings of these birds, as has already 

 been pointed out (p. 6), Ijcfore attaining the typical contour feathers, develop two 

 distinct down plumages. Inasmuch as these neossoptiles are commonly split up l)y the 

 succeeding contour feather, so that each of the terminal rami of the latter is surmounted 

 by a ramus of the disintegrated down feather, it has been suggested that these down 

 feathers are really a part of the actual contour feather. 



Though Studer (20), Davies (4), Klee (9), and others have contributed some valuable 

 observations on the development of nestling down and contour feathers, there is much 

 work yet to be done on the embryonic history of the feather — much that as yet remains 

 obscure, but is essential to a thorough grasp of this question. But there can be no 

 doubt that the neossoptyles represent distinct feather generations. That later they 

 become, in so many instances, disintegrated, so that the several rami of which they are 

 composed are borne out on the tips of the rami of the succeeding definitive feather, is 

 due to the fact that the growth of the definitive feather is begun before that of the 

 neossoptile has finished, and consequently the bases of the rami of the first become 

 welded on to the tips of those of the second, as will be made apparent presently. Let 

 this be assumed as proved for the moment, and it will be seen that a new and important 

 light is thrown not only on the sequences of the plumages of the penguins in particular, 

 but of the nestling and later plumages of all birds. The penguins then develop two 

 successive down plumages before assuming the normal definitive feathers. The point 

 to be discovered is the significance of this sequence ; and this can best be done by a 

 general and brief survey of what obtains in other groups. 



Up till the present it has never been suspected that more than one generation of 

 nestling down was ever developed,* though it has long been known that the succeeding 

 generation of definitive feathers, in some species, presents a character intermediate 

 between down and the contour feathers which eventually succeed them. Further, as I 

 have already pointed out on more than one occasion, these down feathers present very 

 difiereut grades of perfection, such for example as may be seen in the umbelliform tufts 

 of loose, woolly down of, say, an owl, the semi-plumous type of the Galli and Anseres, 

 and the strongly pennaceous type of some Tinami. It has now become necessary to 

 re-interpret the significance of these differences. It would seem, then, that the full 

 sequence of plumages is represented (1) by neossoptyles, composed of (A) pre-pennae, 

 divisible into a — protopti/les and /S — mesoptyles; (B) pre-plumul?e, and (2) teleoptyles 

 or definitive feathers. 



In how many groups of birds these three plumages are represented I am at present 

 unal)le to say, but I have undertaken, in conjunction with my friend Mr. J. L. Bonhote, 

 a thorough examination of this problem. Consequently, I propose to do little more 



* Since this was written, a paper has appeared (" Ibis," Jan. 1906) from tlie pen of Mr. W. Eagle Clarke, on 

 the results of the Scottish National Antarctic Expedition. He therein briefly refers, without special comment, to 

 the fact that in the young of the Gcntoo Penguin, Pygoscelis papua, the down of the newly-hatched chick "soon 

 gives place to a darker coat of down, to the tips of which the paler down of the first coat is attached 

 for a time." 



