1896.] METALLIC COLOURS OF BIRDS. 295 
EXPLANATION OF PLATES XI. & XII. 
Fig. 1. Violet metallic feather of Cinnyris amethystina, showing three zones: 
a=apical metallic zone; b=brown pigmented zone with closely 
connected barbules and basal indentation ; c=downy basal zone. 
Fig. 2. Two downy barbules from same: /=rudimentary lamina; f=filament- 
ous region, much elongated and with rudimentary cilix. Objective 
2", Ocular B. 
Fig. 3. Proximal radius from region 6 of same, showing well-developed lamina, 
slightly pigmented and marked with cross-bars, and filamentous 
region with well-developed cilia. Ob. 3", Oc. B. 
Fig. 4. Proximal radius of same, showing transition to metallic condition. The 
lamina is rudimentary, and the filamentous region is pigmented and 
somewhat expanded. Ob. 2’, Oc. B. 
Fig. 5. Metallic radius of same, showing shape, compartments, and peculiar 
flattening. The last three figures are all of radii taken from different 
levels on the same barb, 
Fig. 6. Fragment of metallic barb under low power, to show position of 
barbules: p=proximal radii; d=distal. Ob. 1", Oc. B. 
Fig. 7. Metallic feather from gorget of Basilinna leucotis: a=naked barbs, 
corresponding to zone a of fig. 1; 5=metallic region of feather, 
corresponding to zoned of fig. 1; c=downy region. 7 a is a diagram- 
matic cross-section of a single barb, to illustrate the formation of the 
7s gaa of the feather: d=distal radius; p=proximal radius; 
= barb. 
Fig. 8. Proximal radius from the base of one of the metallic barbs of above 
feather. The lamina is only faintly pigmented. Ob. 3”, Oc. B. 
Fig. 9. Distal radius from brilliantly metallic region of same. The lamina is 
deeply pigmented and has a folded-in edge. The filament is without 
pigment. Ob. 3”, Oc. B. 
Fig. 10. Fragment of metallic barb of same with distal barbules only, to illus- 
trate normal position of barbules. Owing to the angle of insertion of 
the filamentous region, this is not visible in surface view. Ob. 1", 
Oc. B. 
Fig. 11. Tip of barb of breast-feather of Lustephanus fernandensis 9, to illus- 
trate apical modification of barbules. The lower barbules in the 
figure are metallic. Ob. 1", Oc. B. 
Fig. 12. Tip of barb of gorget-feather of Basilinna leucotis, with naked barb 
furnished only with rudiments of apical barbules. Ob. 1", Oc. B. 
Fig. 13. Barbules from three different levels on a barb of a contour-feather of 
Phaethornis eurynome to show details of the modification of the original 
apical barbules. Note in passing towards the apex of the barb the 
reduction of the lamina and flattening of filamentous region. Tho 
filamentous region is, however, unpigmented. Ob. }'’, Oc. B. 
Fig. 14. Fragment of barb of Cinnyris amethystina for comparison, and to show 
junction of metallic and non-metallic regions. Ob. 1", Oc. B. 
Fig. 15, Three barbules from the yellow edging to a quill of Zthopyga seherie, 
Ob. 4", Oc. B. 
Fig. 16. Three barbules from metallic edging of quill of Anthreptes malaccensis, 
Ob. 3", Oc. B. 
Fig. 17. Tail-quill of Anthreptes malaccensis(?), with metallic edging on right 
side (m). 
Fig. 18. hae Sea a barbules from above. Ob. }’’, Oc. B. 
Fig. 19. Three metallic barbules from tail-quill of ELustephanus fernandensis, 
Ob. }', Oc. B. 
Fig. 20. Three brilliantly metallic barbules from central tail-quill of Zthopyga 
seherig. Ob. 1", Oc. B. 
Fig. 21. Barbules from same quill, but much nearer rachis ; they show partial 
transformation, and in their natural position exhibit a faint though 
distinct metallic sheen. This partial transformation occurs chiefly in 
the case of distal barbules, and produces a visible effect to the unaided 
eye. Ob. 4”, Oc. B. . 
