8 



W. P. PYGRAFT. 



neossoptiles represent distinct feather generations, and that therefore the pre-pennse, as 

 I have elsewhere (11) called those neossoptiles preceding contour feathers, are not, as 

 some apparently hold, a part of " agents in advance " of the contour feathers which 

 succeed them. Consequently, the fact that the bulk of the rami of the pre-pennse in 

 Pygoscelis adelise are directly attached to the tips of the rami of the after-shaft of the 

 succeeding teleoptile is a somewhat remarkable fact, especially since in all other 

 instances yet known the nestling-down, when attached to contour feathers, is attached 



to the rami of the main shaft. In the case now under 

 discussion the rami of the pre-penna, which are borne by 

 the main axis of the contour feather, are few in number 

 and take no appreciable part in the formation of the pre- 

 penna as a whole, which is composed of rami connected 

 by means of the long ribbon-shaped stalk with the rami of 

 the aftershaft, and forming the large tuft of woolly down 

 such as is seen in Fig. 3. The significance of this relation 

 to the aftershaft must be referred to again later. 



Microscopically the rami of these " pre-pennse " are 

 of considerable length, and have short, ribbon-shaped 

 spirally-twisted radii which bear only about four pairs 

 of minute fila. The spiral twist acts as a kind of felting 

 arrangement, whereby the downy covering is " knitted," as 

 it were, into an almost homogeneous coat. 



The Nestling Down of the Emperor Penguin. 



This differs not only in colour but also in certain small 

 structural details from that of the Adelie Penguin. The 

 first down-plumage differs from that which follows, in 

 that it is short, barely covers the body, and resembles 

 silky hair more than feathers ; that is to say, when 

 superficially examined. Under the microscope each down 

 feather is found to be made up of several rami, umbelliform 

 in arrangement, and of moderate length, each ramus being 



produced into a long filament beyond the radii, which are short. The fila of these radii 

 are much larger than in Pygoscelis. This first down-plumage is rapidly succeeded by 

 similar umbelliform tufts of much greater length and volume. The rami are about 

 twice as long as those which preceded them, but the radii are only, relatively, slightly 

 longer, and bear from eight to ten pairs of fila. This generation of down feathers 

 differs from the corresponding generation in Pygoscelis, firstly, in that the radii are 

 straight instead of spirally twisted, so that the down is less " felted," and secondly, 

 in that instead of being of a uniform character throughout, the rami of the. down 



FIO. 4. THE FIRST 



SECOND (MESOPTYLE) DOWN 

 EKS OF Aptenodytes forsteri. 



MESOPTYLE. 



M = 



