150 THE STRUCTURE AND LIFE OF BIRDS cuap. 
\ 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 
4 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 
uA the nestling on the top having been 
) formed even in the egg. The 
Fic. 40--Cassowary’s quill does not dry up, so that the 
eather, 
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