EXPLANATION OF PLATE (AFTER BURMEISTEK.) 



Fig-. 1. A dorsal feather of Argus giganteus of the natural size, seen from beneath, in 

 which the left series of barbs on the main shaft, and also the right series on the after- 

 shaft, have been removed, in order to render the relations of the two shafts more dis- 

 tinctly perceptible, a. The thickened portion of the main shaft, with its longitudinal 

 furrow, b. The after-shaft, c, c, c. The barbs of both shafts, d. The short, obtuse tube. 



Fig. 2. Four barbs of the same feather from the upper part, with their barbules, seen 

 from above under a moderate magnifying power, a. The barbs, b. Uarbules of the 

 anterior series, on which the hooklets are seated, c. Barbules of the posterior series, 

 without hooklets. 



Fig. 3. Six barbs (a, a, a] in transverse section, viewed from the cut surface, with 

 their anterior (b, b, b) and posterior (c, c, c) barbules. From the outer side of the vane of 

 one of the remiges of a goose, moderately enlarged. 



Fig. 4. An anterior barbule of the same feather, strongly magnified, with its hooklets 

 (b) and cilia (a). 



Fig. S. A posterior barbule of the same feather, equally magnified. 



Fig. 6. A portion of the feather shown in fig. 1, seen from above, in which a is the 

 main shaft and b, b, two of its barbs, from which issue the curiouslj' curved laminar bar- 

 bules, still without hooklets or cilia. This figure is particularly intended to show that 

 even the main shaft bears barbules when the barbs stand far apart. 



Fig. 7. The filoplume of a goose, moderatelj' enlarged. 



Fig. 8. The upper extremity of the same, with the tips cut off, more strongly magnified. 



Fig. 9. A barbule of the same feather, very strongly magnified. The cavities of the 

 cells may still be recognized in it. 



Fig. 10. A young goose-feather, seen from in front, just protruding the apex of the 

 vane (?) from the follicle (a). 



Fig. 11. The same from behind, opened longitudinall}'. a. The follicle. b,b. Feather- 

 material, c. Matrix, with its blood-vessels, d, d. Cast-off and desiccated portions of the 

 latter. 



Fig. 12. An immature barbule, of the posterior series, of a grey pigeon's feather. 



Fig. 13. An immature barbule of the anterior series of the same feather. 



Fig. 14. The lower portion of a barb, in which no distinction can yet be recognized 

 between it and its barbules, consisting of homogeneous cells and their nuclei. Taken 

 from the feather represented in fig. 10. 



Fig. IS. A portion of an immature barb, in which the barbules are already indicated, 

 but not yet divided off; on the left those of the hinder and on the right those of the ante- 

 rior series. Taken from a grey pigeon's feather. 



Fig. 16. Modified cells, becoming converted into solid horny substance, from the 

 uppermost layer of a young barb of this same feather. 



Fig. 17. The cells of the epithelium of which the follicle consists, with their nuclei 

 and nucleolar corpuscles. 



Fig. 18. The lower extremity of one of the wing-feathers of a pigeon, in which the tube 

 has been laid open by a cut, and the main shaft and barbs are cut off short; the lowest 

 barbs immediately above the tube are also removed, a. Dry cast-off remains of the 

 matrix which project from the upper opening of the tube and lie in the furrow of the 

 shaft, b. The position of the orifice, which has been removed by the cut. c. Dry cast-off 

 portions of the matrix in the interior of the tube, which, like the preceding, are placed 

 one within the other, like a row of thimbles, d. The outer, and e, the inner, side of the 

 vane. 



Pig. 19. White down-barbules of the domestic Duck, magnified 100 diameters. Taken 

 from Nitzsch, in 'Voigt's Magazine,' &c., Bd. xi, Taf. 6. 



Fig. 20. Down-barbules from the lower part of a contour-feather of the same Duck. 

 Ibid. 



Fig. 21. Beginning of a down-barbule from the lower part of a contour-feather of 

 Corvus glandarius. Ibid. 



Fig. 22. The same from Sylvia rubccula. Ibid. 



Fig. 23. The same from the domestic Duck. Ibid. 



Fig. 24. The same from Strix otiis. Ibid. 



Fig. 25. The same from the Turtle Dove. Ibid. 



