10 SMITHSONIAN MISCELLANEOUS COLLECTIONS LvoL. 48 
of the wing, it is undoubtedly of interest that in the wings of these 
birds this curvature is developed only so far as the feathers really 
overlap each other. 
The secondary quills have the same structure in all remiges of a 
wing, but we observe a regular variation of their size in the different 
feathers of the same wing and in the different parts of each feather. 
An increase of the stiffness of the secondary quills is noticeable, 
as we proceed from the proximal to the distal part of the wing. 
Hand in hand with this goes an increase of the development of 
the ventral ridge, which is relatively small in the arm-remiges but 
attains enormous dimensions in the hand-remiges of Diomedea, 
the Accipitres, and Striges. At the same time the outer vane in 
the hand-remiges becomes constantly narrower, as compared to 
the inner, and at the same time stiffer and firmer. The secondary 
quills in the narrow vanes are’basally just as high as the sec- 
ondary quills of the corresponding broad vanes lying opposite 
them, and they do not terminate in fine threads like those of the 
broad vanes but are only slightly pointed at the end. The elasticity 
of the secondary quills contributes to keep the elements of the narrow 
outer vane in their proper position and order. 
Besides these differences of size in the secondary quills of the 
different feathers of the wing, similar variations occur also in the 
different parts of each feather as mentioned above. The supposition 
is obvious that the secondary quills are thickest and highest at the 
base, and that they should become lower towards the end of the 
feather, where the primary quill also decreases in thickness. Such 
conditions are really found in the arm-remiges of all birds and in 
the outer hand-remiges of Diomedea. In the outer hand-remiges of 
numerous birds, such as the Columbinze, Coccygomorphe, Cypselide, 
Strigide, and Natatores, however, the secondary quills are moder- 
ately high at the base of the feather, increase gradually in height 
distally and attain their maximum height at or just beyond the 
middle of the feather. Measurements in corresponding portions of 
different hand-remiges gave the following results: 
| Height of Secondar Juills. 
| Length of . y@ 
Sue | Whole Vane. | 3 cm. from the Middle of the | 3 cm. from the 
Bas Vane. | Tip. 
: AM ihe ss a es | ea z z 
Macropteryx mystaceus. | 18cm. | 300 kL | 389 uC 233 be 
Bubo maximus. 28 | 550 g1o 700 
Cygnus olor. 26 | 489 | 1,223 678 
The secondary quills are measured close to the primary quill near 
their point of origin, that is at the point of their greatest height. 
