EXPLANATION OF THE PLATES. 



PLATE I. 1 



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 aeries on the after-shaft, have been removed, in order to render 

 the relations of the two shafts more distinctly 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. 6. Barbules of the anterior series, on which the booklets are seated, 

 c. Barbules of the posterior series, without booklets. 



Fig. 3. Six barbs (a, a, a) in transverse section, viewed from the cut surface, with their anterior (b, b, 5) 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 booklets (b) and cilia (a). 



Fig. 5. 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 curiously curved laminar barbules, still without booklets 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, moderately 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 

 recognised in it. 



Fig. 10. A young goose-feather, seen from in front, just protruding the apex of the vane (4) from the 

 follicle (a). 



Fig. 1 1 . The same from behind, opened longitudinally, 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 recognised between it and its barbules, 

 consisting of homogeneous cells and their nuclei. Taken from the feather represented in fig. 10. 



Fig. 15. 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 anterior 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. 1". 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. 



Fig. 19. White down-barbules of the domestic Duck, magnified 100 diameters. Taken from Nitzsch,in 'Voigt's 

 Magazin,' &c., Bd. xi, Taf. 6. 



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



Fig. 21 . Beginning of a dowu-barbule from the lower part of a contour-feather of Corvus glandarius. Ibid. 



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



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



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



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



1 This Plate has been drawn by me chiefly from nature, and from my own investigations. Nitzsch was, even to 

 the last moment, undecided, as he told the publisher, whether he should represent upon it the different parts and 

 kinds of feathers, or give a diagrammatic representation of all the tracts, with their denominations. I chose the 

 former, as being in my opinion the most necessary and valuable, inasmuch as the position of the tracts is sufficiently 

 clear from the other plates. The latter I found completed ; they have been engraved from Nitzsch' s own drawings. 

 BURMEISTEK. 



