1916] Chandler: Structure of Feathers 297 
dorsal surface as in other birds. Barbs very numerous, about 30 or 
40 per centimeter on each side, thus in some measure making up for 
weakness of structure by strengthening vanes. More or less of inner 
portion of barbs, usually about one-half, furnished with primitive 
pennaceous barbules; outer portion downy, compactness of vanes 
being maintained only by stiffness of rami. Terminal portion of 
feather devoid of barbules, rami becoming cylindrical and _ bristly. 
Inner and outer vanes similar. Distal barbules of pennaceous 
portion (pl. 15, figs. 6a, 6b) with poorly developed base. Pennulum 
with a series of ventral barbicels extending to tip, not differentiated 
into ventral teeth, hooklets, and cilia. Usually all of them much 
eurved and hooklike, but not hooked merely at tip as in other 
birds. Proximal barbules (pl. 15, figs. 6c, 6d) with no bend or 
sharp differentiation between base and pennulum, the latter dis- 
tinguishable only by presence of outward-curving, dorsal and ventral 
barbiecels, which hardly differ in form from prongs of down barbules, 
though usually longer. Distal barbules reaching length of about 
0.35 mm., the proximals about 0.6 mm., the base in each case 
occupying about half total length. 
2. Down 
Transition from pennaceous to down barbules simple and easy, 
the hooked form of barbicels of distal barbules being lost and size 
of those of proximal barbules reduced. Typical down barbules (pl. 15, 
fig. 6e, and pl. 34, fig. 96) characterized by unusual shortness, not 
exceeding 0.8 mm. in length, and usually considerably less. Base 
very narrow and poorly differentiated from pennulum. The latter 
naked and filamentous basally, but furnished with comparatively 
long and conspicuous prongs towards tip. As usual in typical 
down, barbules inserted in four instead of two rows, those of either 
side alternately projecting in different directions (pl. 15, fig. 6e). 
Counting all four rows, there are about 60 barbules per millimeter. 
b) Other Types 
The dark feathers of Hudyptes chrysocome are very familiar, differ- 
ing chiefly in having longer pennaceous barbules (pl. 15, figs. 7a, 7b), 
which have a dark pigment segregated into transverse bands, as in the 
feathers of gulls and some pigeons. This probably accounts for the 
bluish tinge which the feathers of this species have. Im Spheniscus 
mendiculatus the distal barbules are relatively short, while the proxi- 
mals are long, with a well-developed series of ventral baricels; they 
are about 0.25 mm. and 0.68 mm. lone respectively. 
The stiff, spinelike rectrices of the latter species have a broad, 
shallow concavity on the ventral side of the shaft, although in the 
body feathers the shaft is very thin and almost perfectly flat both 
above and below. 
