G W. P. PYCRAFT. 



series, though more detrenerate than tliose of the distal, overlapping series, still preserve 

 their characteristic forward curvature, but they have l)ecomc rod-shaped, losing the 

 peculiar scroll-shaped curve which these proximal radii present in functional remigcs. 

 Finally, these radii grow fewer and shorter as the free end of the ramus is approached, 

 leaving this, eventually, as a simple rod. 



III. — The Nestling Down. 



The nestling penguin, on emerging from the egg, is Init sparsely clad in down 

 feathers which rather resemble, superficially, fine silky hair than feathers. This is 

 quickly succeeded l»y a second growth of down feathers, longer and thicker ; and this, 

 later, is followed by the adult feathers or teleoptiles. This development of two 

 successive down plumages is a feature which has hitherto escaped our notice in the life 

 history of the penguin. Further, it has never been suspected to obtain, so far as I 

 know, either in this or in any other group of birds, though, as will be shown presently, 

 it occurs in a number of instances, and is likely to lead to some important modifications 

 of our conceptions of plumages and their history. 



The colour of the down in the Emperor, King, and Adelic Penguins has already 

 been described by Dr. Wilson in his report. Consequently, I .shall describe here only 

 its structural features, and such other peculiarities as may be necessary. 



The Nestling Doimi of the Adelie Penguin. 



I propose to describe the nestling down of this species first, because in this I 

 have been able to trace the whole developmental history from the very young nestling 

 to the adult bird, while in the case of other species some link in the chain has always 

 been wanting. The down of the newly hatched nestling is short, and of a texture 

 recalling velvet-pile. JMicroscopically, the rami are short, arise from a common base, 

 and bear very short, straight, ribljon-shaped radii, which have but few fila, arranged, 

 as usual, in pairs. 



This down is rapidly succeeded by a long, dense, woolly covering, so dense that it 

 is difficult to expose the skin. Except that it is shorter on the head and neck, it is of 

 a uniform character throughout. If examined carefully, the earlier, shorter down tufts 

 will be found adhering, here and there, to the tips of this second generation. The 

 peculiar characters of this down may best be studied in birds which are just developing 

 contour feathers. In such specimens it will be found that the tufts of these originally 

 umbelliform pre-pennas arc in part attached to the rami of the main shaft of the 

 contour feathers, and in part to the aftershaft thereof. In situ the tips of all the rami 

 of each down tuft reach the same level, that is to say, the rami borne by the aftershaft 

 extend to the level of those borne by the main shaft. To effect this, those rami which 

 are supported by the aftershaft of the contour feather are connected therewith l^y a long 

 ribbon-shaped stem, and this apparently on account of the fact that the after-shaft is so 



