MASCHA | STRUCTURE OF WING—FEATHERS 7 
vane about half way between the primary quill and the margin of 
the feather, or nearer to the former. Here also the ventral ridge 
suddenly becomes lower in the region where the height of the quills 
themselves abruptly becomes less. In the vanes with uniformly de- 
creasing secondary quills the central margins of these quills stand 
out free, so that one clearly sees the ribbing on the under side of 
the feathers of which Parseval (1889, p. 70) has spoken. It is quite 
different in the Striges, Accipitres and Diomedea, birds described 
by Ahlborn. Here the secondary qnills are very high and 
markedly concave at their point of origin and the ventral ridge is 
of considerable size in the basal part of the secondary quill; being 
nearly vertical to the quill itself it lies almost horizontally, and ex- 
tends to the convex rear side of the secondary quill in front of it 
(fig. 33). In the middle of the length of the secondary quill the 
ridge becomes so small and the angle between it and the quill to 
which it belongs so large, that the ventral connection of the second- 
ary quills formed by these ridges ceases. Outside this well marked 
line their ventral margins are free. If one looks at the ventral side 
of the feather it is noticed that in the proximal third of the vane 
the light is reflected from the ridges producing a silvery luster which 
ceases rather suddenly at a line parallel to the primary quill, an 
appearance which can be observed more or less clearly in the remiges 
of all these birds. 
In the development of this ventral ridge two types can be distin- 
guished. One is represented by the remiges of Columba, the other 
by those of the Striges, Tubinares, and Accipitres. In the first the 
ridge is a stout, low ventral projection of the cortex of the secondary 
quills and appears wedge-shaped in transverse sections (figs. I, 3). 
In the second it is a band-shaped membrane thin down to its base, 
attached vertically to the high and markedly convex secondary quill 
(fig. 29). These types are connected by transitional forms. A 
peculiar development is observed in the secondary quills of the 
remiges of the Caprimulgi in which the ventral ridge is not sharp 
but blunt, of uniform thickness throughout and rounded at the 
margin. On the upper edge also the secondary quill bears a ridge, 
which is broad, low and rounded (figs. 3, 4, 29, Vd), and of no 
functional importance for flight. 
The tertiary fibers are attached to the secondary quills in a com- 
plicated manner. In examining sections parallel to one of the two 
kinds of tertiary fibers, I could only indistinctly make out their 
junction, but the sections vertical to the secondary quills were much 
more instructive. I could find no description of this apparatus in 
