THE EXTERNAL STRUCTURE OF BIRDS. 155 
Remiges—These feathers are implanted into bones of the 
pinion and the arm, and belong to distinct categories accord- 
ingly. They mainly determine the size and shape of the wing, 
in conjunction with the development of the solid parts which 
support them. They are very little developed in the Cas- 
sowary and Emeu, and are still more rudimentary in the Apteryx. 
In the Penguins, however, they are peculiarly reduced, being 
no more in them than so many short scale-like feathers closely 
investing the arm, and forming a“ flipper.” In the Ostrich 
they are large, but, as every one knows, soft and loose, 7. ¢. 
plumaceous in composition. 
The remiges are very often so formed as to make the wing 
a structure strongly convex above and concave below—a con- 
dition which determines the noise made by Partridges when 
they rise. They may, however, form a nearly flat surface, 
though they are generally more or less concave underneath. 
The Divers afford an example of short wings with fully 
developed feathers, while the wings are at their maximum of 
relative length in the Frigate-bird. 
As might be expected from their use, the remiges are the 
stiffest and strongest of all feathers, being most thoroughly 
“¢pennaceous” and coherent in their elements and the rachis 
always bears a web on either side. Of these the anterior or 
outer web is the narrower and stiffer, and the posterior or 
inner web the broader and softer. They vary in number (apart 
from the very exceptional forms such as the Apteryx or the 
Penguin) from sixteen to more than fifty, as may be seen in 
Humming-birds and Albatrosses respectively. 
The feathers are so placed that the softer inner vane of 
each of the remiges underlies the stiffer external or anterior 
vane of that next to it. It is now ascertained that, in flight, 
a certain rotation of the long axis of each large quill-feather 
takes place, so that the air can pass between the feathers as 
the wing is raised. In the down-stroke they become closely 
applied, and the stiffer vane of each feather then helps to 
keep from yielding to the pressure of the air the broader soft 
vane of the feather external to it. They generally taper 
eradually and regularly to an obtuse point (7. e. are lanceolute). 
Sometimes either or both webs are abruptly narrowed, or 
emarginate, or they may be in appearance abruptly cut short 
(truncate), often obliquely so, or with a curved edge (stnuate). 
