ORNITHOLOGY OF SECTION D, 1850. 
disk at the extremity of each; and the webs composed of those barbs, 
are consequently both blunt and serrated at the margin. 
On examining these feathers when in a half-grown state, a singu- 
lar hair-like filament is seen to spring from their base, which explains 
the cause of these marginal serrations. This filament is narrow, flat, 
and thin, much resembling in appearance the barbs of the feathers, 
but reaching to three or four inches in length. Its distal extremity 
is free; but towards the base of the half formed feather it is seen 
to adhere to the extremities of all the barbs on one (generally the 
inner) side of the feather, forming a continuous margin or “ selvage” 
to the web. Towards the base of the feather, where the imperfectly 
formed barbs are collected, as in all young feathers, into a cylin- 
drical bundle, and inserted into a membranous sheath, the barbs be- 
longing to both webs of the feather are seen to be connected at their 
extremities to the opposite sides of this intermediate filament. As 
the feather grows and the barbs become mature, their tips are gra- 
dually released from this connecting filament, those of the lower oF 
exterior web first, and those of the interior one subsequently. Hence 
the distal portion of the filament becomes free and waves loosely in 
the air. It is probable, that when the whole feather reaches matu- 
rity, the filament is shed altogether. 
The cicatrices, or points of junction between the tips of the barbs 
and the flat surface of the filament, produce a succession of slight 
indentations on both sides of the latter, and give it a serrated ap- 
pearance, which is further increased by the alternate tufts of bar- 
bules which fringe its margin. Hence also arise the corresponding 
serrations on the margins of the feather, which haye been before 
referred to. 
It is remarkable, that these filaments, though apparently formed 
for’some temporary purpose in the development of the feather, should 
exhibit a structure ag highly complex as that of the feather-barbs 
themselves. I allude to the double row of barbules cS Strahlen” 
of German authors) which fringe the outer margin of the filament; 
they are not continuous as on the barbs (* Aeste”), but in. little 
tufts, alternating with the surfaces of attachment of the barb-tips. 
(See Fig. 2). These barbules further exhibit those ultimate fringes 
to which the name barbicels has been given. 
In ordinary feathers, the barbules on the distal side of the barD 
are, . is well known, furnished with hooked barbicels («Héilechen”): 
