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Show 420 DR. H. GADOW ON THE COLOUR OF FEATHERS. [May 2, Position B, in which the bird is placed vertically to the eye, a position in which objects are usually described. Position C, in which the bird is held in the same level with, but between tbe eye and light. The three positions in which metallic colours should be observed. Fig.l EXPLANATION OF T H E PLATES. PLATE XXVII. s, scapus or shaft: 2. 3. 4. Part of a belly-feather of Pitta moluccensis. r, ramus or barb; p, radius or barbule. The blue part of the ramus at * (fig. 1), a s seen under the microscope with transmitted light. The same, but magnified 640 times, s*, transparent surface-coating or sheath; c, the layer of cones, with their sheath (s) and with the fine ridges (r). The same of Ccereba. 5. Yellow radius of Pitta, pp, pigment-corpuscles, the shaft of the radius showing the longitudinal ridges. 6 fl. Part of another yellow radius of Pitta. No pigment present. 6 b. Transverse section through 6 a at *. 7. Yellow radius of Picus. 8. Part of a metallic golden-green to blue feather of Nectarinia famosa s, shaft; p, radius ; r, ramus. 9 fl. Distal half of one radius of Nectarinia, showing the transparent sheath which surrounds the compartments. 9 b. The same, but seen from the edge. 10. End of a metallic radius of a Jacamar. cc, the suppressed cilia;. 11. J art of a metallic violet barbule of Sturnus vulgaris 12. Part of a barbule of a red non-metallic feather of Nectarinia. PLATE XXVIII. Fig. 1. One metallic violet barbule of Mthopyqa 2. One barbule of a green feather of Palceornis. 6. Barbule of a yellow crest-feather of Parus sultaneus. 4. Fart of a colourless barbule of Parus sultaneus. "aSmaVro^o^ ' ""^ <°W-J*«* to bluish) feather of BhowhS its h i X v l r 0 1 " P a r t m e ? t 8 B 6Pa r a t e d f M m the others, and snowing its highly convex-concave shape ; r, barb or radius. |