150 THE STRUCTURE AND LIFE OF BIRDS chap. 



attention. Most birds, before they 

 are fledged, have upon them em- 

 bryo or nestling feathers, which are 

 very similar to the " downs " of 

 mature birds described above. Be- 

 ginning the history of one of these 

 from its earliest days, we find first 

 a papilla upon the skin. From the 

 epidermic covering of this springs 

 the nestling feather with a number 

 of thread-like branches, all starting 

 from the same point, so that it is, 

 in fact, a feather with the rachis 

 left out. We may look upon it as 

 a quill split uniformly the whole 

 way round into numbers of narrow 

 pieces ; it does not, like the later 

 feather, face one particular way. 

 Preparatory to this splitting, the 

 epidermic cells over the papilla 

 group themselves round the centre, 

 and their little elevations are in- 

 dications of the barbs that are soon 

 to appear. When the time comes, 

 the feather proper drives out the 

 nestling feather, and carries it on 

 its tip. The two are not really 

 distinct, but parts of one and the 

 same growth, the real feather with 

 the nestling on the top having been 

 formed even in the egg. The 

 quill does not dry up, so that the 



