294 MISS NEWBIGIN ON THE [Feb. 18, 
velvety black. The black region extends further up the vane on 
one side of the rachis than on the other. In mounted specimens 
the overlapping of the quills occurs in such a manner that the 
successive feathers cover over the black region of the feathers in 
front. There seems to be no difference in the amount of pigment 
present in the two regions. Remembering the, as yet, unexplained 
fact that metallic colours occur only on exposed parts of feathers, 
it seems impossible to doubt that the black region is associated 
with the overlapping of the feathers. The tail is forked, and in 
consequence it is hardly probable that the rectrices can be 
separated and spread out to form the “ parachute ”-like structure 
which has been described in other forms; the black area is thus 
permanently covered up. 
In Sappho sparganura the conditions are almost reversed, the 
exposed parts of the tail-quills are brilliantly metallic, with a band 
of black at the apex. It seems most probable that in this case, as 
in Topaza pella, the black colour is produced by an excess of 
melanin pigment. 
Summary.—From the account given above it is seen that in the 
metallic feathers of Sun-birds the radii are without cilia and their 
distal regions are more or less completely modified into flattened 
club-shaped bodies containing a large amount of brownish pigment, 
and consisting of a series of ‘overlapping compartments,” as 
described by Gadow. It is also seen, however, that the barbules 
near the apices of the barbs tend throughout this family to become 
modified in this way, so that the distinction between male and 
female, or specialized and unspecialized forms, is less in the struc- 
ture of the barbules than in the amount of brownish pigment 
present. From the fact that similar conditions are observed in the 
Pheasant it seems probable that this occurs not infrequently. 
In the case of the Humming-birds the metallic colour is confined, 
like the brownish pigment, to the proximal part of the barbules, 
and its presence is not associated with any modification of the 
barbules which affects their efficiency in the feathers of flight. In 
their case, therefore, metallic colours may occur in the quills of the 
tail or (rarely) wing without interfering with the powers of flight. 
Further, as the metallic colour is associated with a specialization of 
the proximal region of the barbule, it cannot in contour-feathers 
primitively form a terminal band; the apparently terminal position 
is produced by the gradual suppression of the apical barbules, in 
which the proximal region is never well-developed. 
The examination of specimens upon which this paper is based 
was chiefly carried on in the Museum of Science and Art, Edinburgh, 
and I have to record my obligations especially to Mr. Eagle Clarke 
for his kindness in affording me facilities for doing so, and espe- 
cially for furnishing me with several feathers for microscopic 
investigation. 
The systematic part of the paper is based on Shelley’s ‘Monograph 
of the Sun-birds’ (London, 1876-80), and Salvin’s Catalogue of 
Humming-birds (B. M. Catalogue of Birds, vol. xvi, 1892). 
