OCR Text |
Show 292 MISS NEWBIGIN ON THE [Feb. 18, the main contention of the relation between the two kinds of feather-edging in Sun-birds. Microscopic examination shows that this analogy is not purely superficial. PI. X L fig. 15 represents three barbules from the yellow edging of a wing-quill of AiJthopyga seheriae, and PI. XI. fig. 16 three faintly metallic barbules from the border of the tail-quill of Anthreptes malaccensis (? represented in PI. XII. fig. IS). With these should be compared the brilliantly metallic barbules from the tail-quill of AiJthopyga seheriae (PL XII. fig. 20). Similarly the barbules from the olive tip of a contour-feather of a species of Cinnyris (PI. XII. fig. 24) should be compared with the metallic barbules of Cinnyris amethystina (fig. 5 or 14) \ These figures show that the barbules of the yellow edging of contour-feathers or quills agree with metallic barbules in having a rudimentary lamina and suppressed cilia, and in distinctly showing a system of overlapping compartments. They differ from the true metallic barbules in the absence of the great flattening visible in these, and in the want of a considerable amount of dark pigment. From the faintly metallic barbules of Anthreptes they seem to differ only in the absence of pigment. The yellow colouring, at least in the case of contour-feathers, is confined to the barbs, the barbules are only very faintly pigmented with grey. The metallic colouring of the Sun-birds is thus the result of an accentuation of a type of feather-structure widely spread in the family. I have noticed this occurrence of much modified barbules apart from metallic colour also in the male Pheasant (Phasianus colchims). Some of the long tail-quills have here a very distinct longitudinal edging of brownish colour and loose texture. Examined microscopically, the barbules of this region show distinctly the " metalhc" structure although there is no visible metallic colour. Similarly the chestnut feathers of the breast have a very distinct line across them, the distal region having a somewhat burnished surface, and terminating finally in a dark green metalhc tip. Examined microscopically the barbules of the distal region show distinctly the " metallic " structure, and except for the absence of black pigment seem to differ little from the green metallic barbules. The modification is probably a common one, and PI. X I . fig. 13 shows that it is even suggested in the Humming-birds, though in this case it does not appear to develop further. Gadow notices that metallic colour appears only on the exposed parts of feathers; apparently the "metallic" modification also occurs only on the exposed parts of feathers near the apices of the barbs. One of the most striking features of the coloration of the Sun-birds is the almost universal absence of metallic colour from the wing-quills, even though these sometimes have an edging of loose structure. In Cinnyris auriceps, according to Shelley, the wing-quills of the female have olive edgings which are absent in the male. It seems reasonable to suppose that a tendency to variation 1 See also some of Gadow's figures, e. g., of a red barbule of Mhopyga; no allusion, however, is made to these in the text. |