128 GENERAL ORNITHOLOGY part ii 



place of barbicels, and no booklets. 3. The hairy, bristly, ovfiloplum- 

 aceous (Lat. filum, a thread), with a very long, slender stem, and rudi- 

 mentary or very small vanes composed of fine cylindrical barbs and 

 barbules, if any, and no barbicels, knots, or booklets. There is no 

 abrupt deiinition between these types of structure ; in fact, the same 

 feather may be constructed on more than one of these plans, as in 

 Fig. 19, which is partly pennaceous, partly plumulaceous. All 

 feathers are built upon one or another, or some combination, or 

 modification, of these types ; and, in all their endless diversity, may 

 be reduced to four or five 



DiffeFent Kinds of Feathers. — 1. Contour -feathers, penrtm or 

 plumce proper, have a perfect stem composed of calamus and rhachis, 

 with vanes of pennaceous structure, at least in part, usually plumu- 

 laceous toward the base. These form the great bulk of the surface- 

 plumage exposed to light ; their beautiful tints give the bird's 

 colours ; they are the most modified in detail of all, from the fish-like 

 scales of a penguin's wings to the glittering jewels of the humming- 

 bird, and the endless array of the tufts, crests, ruflfs, and other 

 ornaments of the feathered tribes ; even the imperfect bristle-like 

 feathers above mentioned may belong among them. Another 

 feature is, that they are usually individually moved by subcutaneous 

 muscles, of which there may be several to one feather, passing to 

 be attached to the sheath of the tube, inside the skin, in which the 

 stem is inserted. These muscles may be plainly seen under the 

 skin of a goose, and every one has observed their operation when a 

 hen shakes herself after a sand-bath, or any bird erects its top-knot. 

 2. Down-feathers, plumulce, are characterised by a downy structure 

 throughout. They more or less completely invest the body, but 

 are almost always hidden beneath the contour-feathers, like pad- 

 ding about the bases of the latter ; occasionally they come to 

 light, as in the fleecy ruff about the neck of the condor, and then 

 usually replace contour-feathers ; they have an after-shaft, or none ; 

 and sometimes no rhachis at all, the barbs then being sessile in a 

 tuft at the end of the quill. They often stand in a regular quin- 

 cunx (" ') between four contour-feathers. 3. Semvplumes, semi- 

 plumes, may be said to unite the characters of the last two, possess- 

 ing the pennaceous stem of the former, and the plumulaceous vanes 

 of the latter; they are with or without after-shaft. They stand 

 among pennse, as the plumulae do, about the edges of patches of the 

 former, or in parcels by themselves, but are always covered by 

 contour-feathers. 4. Filoplumes, filoplumm, or thread-feathers, have 

 an extremely slender, almost invisible stem, not well distinguished 

 into barrel and shaft, and usually no vane, unless a terminal tuft of 

 .barbs may be held for such. Long as they are, they are usually 

 hidden by the contour-feathers, close to which they stand as access- 



