A feather originates thus. A conical papilla arises in the _derma_ and pushes up the _epidermis_, a depression forming meanwhile around the base; subsequently the derma supplies a nutritive pulp, while part of the epidermal layer is converted into a tuft of stiff rays, meeting and forming a short tube below; these thereafter burst their covering and protrude as the _rami_ or barbs, on which, apparently by secondary splitting, are commonly produced _radii_ or barbules. In this state we have a plumule or "down-feather"; but in the case of the feathers that have "webs" or "vanes" (_vexilla_) often called contour feathers (_pennae_ or _plumae_), a fresh papilla forms at a deeper level, so that the earlier structure is thrust forward and eventually drops off from the apex of the later. Meanwhile the "dorsal" portions of {3}the barrel or quill (_calamus_ or _scapus_) at the base of the tuft of rays have elongated into a principal shaft (_rhachis_); this is generally accompanied by a secondary "aftershaft" (_hyporhachis_), originating from the "ventral" side, which in the Emeu and Cassowary rivals the shaft itself in size. On the rhachis a double series of _lamellae_ or barbs are developed, carrying a similar double series of barbules, much as in the down-feather, but the barbules again give rise to barbicels (_cilia_), which in the distal rows usually terminate in hooklets (_hamuli_). These catch in the folded margins of the next proximal row, and a firm surface is thus secured. An after-shaft never, and a down-feather rarely, possesses barbicels; while in some cases by the absence of these and part of the barbules a "disconnected" web and a "decomposed" feather are formed, as in the decorative tufts of many species. The barbs may even be absent, as in the wing-quills of Cassowaries, the wires of Birds-of-Paradise, the "bristle-feathers" at the gape of Night-jars or the eyelashes of Hornbills. In the hackles of _Gallus_ (Fowl), and the secondaries or even the tail-feathers of _Ampelis_ (Waxwing), the tip of the rhachis is flattened and wax-like; and similar structures are observable elsewhere. In the newly-hatched young the down is often partly or entirely suppressed, but in certain Birds this suppression is temporary, and a thick coat grows after a few days. "Powder-down" feathers are those which never develop beyond the early stage, and continually disintegrate at the tip into bluish- or greyish-white powder; they occur in the _Tinamidae_, _Ardeidae_, _Rhinochetidae_, _Eurypygidae_, _Mesitidae_, _Accipitres_ and _Psittaci_, in _Podargus_, _Coracias_, _Leptosoma_, _Gymnoderus_ and _Artamus_.