264 Unwersity of California Publications in Zoology (Vou. 18 
of a groove is a specialized condition, and that the condition of the 
groove in the shaft could be used to some extent as a gauge of 
specialization. This, however, does not hold, since a wide variation 
can be found, not only within a single group, but in the different 
feathers of a single species. In less specialized wing quills of a 
female ostrich, for instance, the shaft has a totally different ap- 
pearance from that found in the plumes of the male; in the former 
the shaft is convex above and below, with only a narrow, insignificant 
groove. In Coccyzus, as mentioned above, there is no ventral groove, 
while in Geococcyx, of the same family, there is a broad, shallow 
groove. In the penguins there is not only no groove, but a median 
keel is developed both above and below on the very broad, flat shaft. 
In cassowaries, where the remex quills are reduced to bare, stout 
spines, there is no groove, and the shaft is subcireular in cross-section. 
Aftershafts are never developed on remiges. 
b) Vanes and Barbs.—The vanes of remiges of flight birds are 
never quite equal, the outer vane always being narrower than the 
inner, very conspicuously so on the outer primaries, often subequal 
on the inner secondaries. In many of the best birds of flight, espe- 
cially those which soar and glide to a considerable extent, there is a 
further modification of the vanes of some of the outer primaries, in 
that more or less of the distal portion is narrowed down or ‘‘incised’’ 
so that the tips of these feathers, when the wing is spread, are 
separated from one another like spread fingers. In the columbid 
genus Drepanoptila, the feather plate is bifurcated, there being dis- 
tally two shafts and four vanes. This anomalous condition, character- 
istic of the trunk feathers of other genera of the same group of 
Columbidae, must be regarded as a recent, heritable mutation. 
Usually more or less of the basal portion of the vanes of remiges, 
as well as of other contour feathers, is downy in character, though 
often the innermost portion of even the most basal barbs may have 
pennaceous or transitional barbules, a larger and larger portion be- 
coming downy as the superior umbilicus is approached (fig. A). In 
flightless birds various kinds of reduction of the vanes of remiges 
takes place. In ostriches the remiges are developed in the male as 
ornamental plumes, in cassowaries they are reduced to stiff, bare spines, 
with the vanes absent entirely, while in penguins and most other 
flightless birds they are reduced to the condition of the trunk feathers, 
and are barely, if at all, distinguishable from them. 
