240 FEATHERS 
the inner web of one of the primaries of a Crane (Grus), 38 em. 
long, I found about -650. 
(5) The radi or barbules are attached in two opposite rows to the 
i thick upper rim of the 
| i wy rami, and like them point 
: toward the tip of the 
i feather. Hach radius is a 
thin lamella, about 1 mm. 
in length, the upper sur- 
face of which is not, how- 
ever, thickened like that 
of the rami, but doubled 
up. Their number is 
enormous: every ramus 
of the Crane’s feather just 
mentioned bore about 
600 pairs—making nearly 
800,000 radii for the 
inner web alone, and cer- 
tainly more than a million 
for the whole feather. 
(6) The cilia or barbicels 
with their hamuli or hooks 
areoutgrowths of the radii. 
The hamuli are of the 
greatest importance in 
regard to the faculty of 
FLicut, because by their 
means alone the radii, and 
consequently the rami, 
are connected to form a 
coherent almost air-tight 
surface. The hamuli grow 
only on the distal rows of 
the radu, that is, the rows 
which look toward the tip 
of the feather, and those 
of one radius reach over 
Part of the barrel has been cut away to shew the and hook on Lo thedoubled- 
series of horny cups (p) continued (as p’) through the Up Margin of the radii 
wnbiliciform pit, whence arises the Aftershaft. D, (themselves hookless) of 
downy portion of the web. the proximal row of the 
next ramus, as shewn in the opposite figures. Cilia which are not 
furnished with hooks frequently have shapes which may possibly 
prove to be characteristic of different groups of birds. 
From their varying forms feathers are usually divided into 
hy 
i! 
' 
i 
' 
i) 
<— + ~~~ 
; Ne 
ConTOUR-FEATHER, WITH AFTERSHAFT. 
