1897.] Hair and Feathers. 778 
of the pulp cavity thus making this portion of the shaft hollow ; 
while in D, taken below the vane we have no barbs and only 
the hollow quill. 
With the contour feather, as with the down feather there is 
vw the same retraction of the pulp 
z and the same formation of pith 
; as has already been described. 
5 ‘ After the feather is complete 
Ji the retracted pulp remains 
t quiet until about the time of - 
the molt when it comes to the 
front again to form the new 
feather. The feather, the de- 
velopment of which we have 
been following, is as yet cyclin- 
drical in shape and is still 
enclosed in the feather sheath. 
With the retraction of the pulp 
it dries and becomes horny as before, the sheath breaks away 
and the barbs by their elasticity straighten out and become 
arranged on either side of the shaft (see fig. 12) so as to form 
the well-known vane. 
There are here to be mentioned two points. The first is 
that the upper and lower surfaces of the contour feather do not 
Fic. 11.—Four transverse sections through fig. 9 at different levels, A, near the 
tip; D, near the base. 
correspond to the upper and lower surfaces of the papilla but 
rather to the inner and outer surfaces of the feather-forming 
epidermis, as may be seen by a comparison between figures 10 
and 12. The other matter is this: With the withdrawal of 
the pulp from the feather there is no longer any nerve or blood 
