28 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
EXPLANATION OF FIGURES. 
1. Three transverse sections of a secondary quill of Columba livia. a at 
the base close to the primary quill; b in the middle; c at the tip on the outer 
edge of the broad feather vane. Magnified 1: Ioo. 
' 2. Three transverse sections of a secondary quill of Caprimulgus europaeus. 
a at the base close to the primary quill; b in the middle; c at the tip near 
the outer margin of the broad feather vane. Magnified 1: 100. 
3. Transverse section of a secondary quill of Columba livia from the outer 
margin of the proximal feather vane. Magnified 1: 600. 
4. Transverse section of a secondary quill of Caprimulgus europaeus, from 
the middle of the proximal feather vane. Magnified 1: 600. 
5. Section through the feather vane vertical to the secondary quills; 
through the wing covert of Garrulus glandarius. Magnified 1: 190. 
6. Section through the narrow vane of the proximal part of the hand-remex 
of Columba livia, vertical to the secondary quills. Magnified 1: 25. 
7. Section through the proximal part of the broad vane of a hand-remex 
of Caprimulgus europaeus, vertical to the secondary quills. Magnified 1: 8o. 
8. Hook-fiber of Columba livia. Magnified 1: 220. 
9. Hook-fiber of Diomedea exulans. Magnified 1: 125. 
10. Hook-fiber of Columba livia. Magnified 1: 125. 
11. Hook-fiber of Cypselus apus. Magnified 1: 125. 
12. Hook-fiber of Nyctea nivea. Magnified 1:125. 
13. Hook-fiber of Podargus humeralis. Magnified 1: Ioo. 
14. Hook-bearing part of a hook-fiber of Turacus albocristatus, showing the 
spines of the proximal hooks. Magnified 1: 480. 
15. Hook-bearing part of a hook-fiber of Cuculus canorus, showing the 
spines on the proximal hooks. Magnified 1: 480. 
16. Proximal portion of a hook-fiber of Cypselus apus, showing the cell 
boundaries and the swelling on the upper margin. Magnified I: 400. 
17, 18, 19. Surface views of the upper side of a hand-remex of Cypselus 
apus, focussed at three different levels. Magnified 1: 270. 
17. Highest level showing the terminal threads of the hook-fibers. 
18. Middle level showing the proximal portions of the hook-fibers. 
19. Lowest level showing the curved fibers. 
20. The points of origin of the hook-fiber in a hand-remex of Columba 
livia, seen from above. Magnified 1: 400. 
2t. A secondary quill with hook and curved fibers of Columba livia. Mag- 
nified 1:60. 
22. Hook-fibers of a secondary quill of Columba livia. Magnified 1: 110. 
23. Surface view of the upper side of a hand-remex of Cygnus olor, showing 
the terminal parts of the hook-fibers. Magnified 1: 270. 
24, 25. Schematic representation of the connection of the hook and curved 
fibers. 
