286 MISS NBWBiGiir ON THE [Feb. 18, 



then metallic quill-feathers must be useless for purposes of flight. 

 Owing to the absence of cilia, the barbules are wholly unconnected, 

 and so can offer little resistance to the air. The unconnected 

 nature of the barbules may frequently be observed in metallic 

 feathers by the unaided eye, e. g., in the feathers of the Peacock. 

 In confirmation of the belief that such metallic feathers must be 

 useless for purposes of flight, we find that the long metallic 

 feathers of the Peacock or Quezal are not the tail-quills, but 

 merely the tail-coverts, and that the wing- quills in both cases are 

 non-metallic. While endeavouring to continue this chain of 

 reasoning, however, the writer was struck by the fact that in 

 Humming-birds, where the power of flight is so marked, not 

 only are the rectrices frequently metallic, but they displayed a 

 closeness of texture which seemed incompatible with Gadow's state- 

 ment that ciliae are always absent from the radii of metallic 

 feathers. The metallic feathers of Sun-birds, on the other hand, 

 show always a certain looseness of texture as compared with the 

 non-metallic. On examining the respective feathers of Sun-birds 

 and Humming-birds microscopically, it was found that marked 

 differences exist between them. 



We will first describe a purple metallic feather of the Sun-bird 

 Ginnyris amethystina. When examined by the unaided eye (PI. XI. 

 lig. 1), this feather is seen to be divided into three regions. 

 There is a distinct terminal band of metallic colour, distinguishable 

 by its deep pigmentation and peculiar structure. Next we have a 

 band of close texture and brown colour, which has an indentation 

 at its lower end. Finally, the base of the feather is of an ashy 

 colour and downy structure. The basal indentation of the brown 

 band possesses some interest, because Darwin (' Descent of Man,' 

 2ud edition, p. 430 et seq.) regarded a similar indentation in the 

 centre of the ocellus of the Peacock as evidence of its origin from 

 two confluent ocelli. 



It is possible to obtain from the feather described a single barb 

 which bears barbules belonging to each of the three regions : in 

 this way transition forms can be very readily seen. 



The basal barbules exhibit the usual structure of downy barbules, 

 that is to say the distal portion, which from its (apparent) shape 

 may be called the lamina, is more or less rudimentary, while the 

 distal or filamentous region is greatly elongated and very slender, 

 has only rudimentary cilice, and consists of a series of joints slightly 

 overlapping one another (PI. XI. fig. 2). 



The barbules of the middle region possess a well-developed 

 lamina and a long filamentous region furnished with cilia and, in 

 the case of the distal barbules, with distinct hamuli (PI. XI. fig. 3). 



The barbules of the metallic region are metamorphosed into short, 

 wide, club-shaped bodies, supported on broad stalks (PI. XI. fig. 4). 

 These clubs are deeply pigmented with brown, and show very 

 distinctly transverse bars— the compartments of Gadow. Although 

 to the unaided eye the transition between the metallic and the 

 non-metallic barbules is abrupt, yet microscopically it is suftioiently 



