MASCHA] STRUCTURE OF WING—FEATHERS 15 
Each succeeding hook is a little longer and directed more obliquely 
forward. While further differentiations of the hooks in general do 
not occur, in Turacus albocristus and in Cuculus canorus, on the 
anterior margin of the proximal hooks I found one to three small 
spines which gave them a peculiar appearance (figs. 14, 15). In 
the proximity of the hooks the transverse sections of the fiber itself 
changes. They are regularly oval where the last lobes of the ventral 
membrane arise. Farther out they become curved again, but the 
curvature is here far slighter than in the proximal portion of the 
fiber and the concavity turned toward the opposite side. The hooks 
are ventral projections of the successive cells forming the fiber. 
Beyond the last hook the fiber becomes rapidly thinner and gives 
off upward and downward, not as Nitzsch (1840, p. 14) erroneously 
supposed laterally, pairs of spine-shaped projections and terminates 
in a thin thread of varying length. The spines are the most variable 
parts of the whole hook-fiber. They are paired projections of the 
cells which form the distal portions of the fiber, each cell having two, 
a ventral and a dorsal one. The ventral spines are as a rule longer 
than the dorsal. The spines extend obliquely outward, the upper 
ones upward, the lower ones downward. They are broadest at their 
origin, become thinner distally and terminate in fine points. The 
proximal, ventral spines lying next to the hooks are blunt and fre- 
quently slightly curved in the form of a hook. They are transi- 
tions between the hook-shaped cell processes and the spines with 
straight-pointed ends. While, however, in the region of the hooks 
the fiber cells have no dorsal processes, in the distal, spined part of 
the fiber the cells have dorsal as well as ventral processes (spines). 
The spines originate from the distal, broader side of the cells, which 
here have the shape of flattened cones and are attached to each other 
in such a way that the narrow, proximal end of each is inserted into 
the broad, distal end of the next foregoing. The first two proximal, 
dorsal spines sometimes become very large and attain a lobose shape. 
This is especially well developed in the Cypselomorphze and in most 
water birds (figs. 17, 22, W,). These lobes lie horizontal, are 
directed towards the margin of the feather and extend as far as 
the next hook-fiber. In the hook-fibers of the proximal portions of 
the secondary quills, these lobes are smaller and more pointed than 
in the distal portions, where they become larger and relatively 
broader. Fatio (1886, p. 257) says of the spines of the hook-fibers 
of the feathers of water birds in general that “they are very long 
and numerous and by their irregular arrangement make the feather- 
ing bulky and so afford protection against the water.” In the 
