THE flXTDBNAl STEUOTUEE OF BIEDS. 155 



Bemiges. — 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 ia 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, i. e. 

 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 

 stifEesl 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 stifEer, 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 

 gradually and regularly to an obtuse point (i. e. are lanceolate). 

 Sometimes either or both webs are abruptly narrowed, or 

 emarginate, or they may be in appearance abruptly cut short 

 (fnmcate), often obliquely so, or with a curved edge {sinuate). 



