28o COLOUR IN NATURE chap. 



what resembling that seen in downy feathers, and like 

 many downy feathers they have very little pigment. 

 Among these long feathers are the so-called " wires," 

 which are feathers with all the parts save the rachis 

 suppressed. The yellow feathers have no barbules, 

 and the barbs are smooth, dilated, and brightly coloured 

 with lipochrome pigment. The same pigment and 

 the same feather structure is found in the bright yellow 

 feathers forming the crest. Round the base of the 

 beak and extending over the throat there is a band 

 of green metallic colour produced by very much 

 shortened feathers, in which the barbules have under- 

 gone the same modification as those of the metallic 

 feathers of sun-birds. Speaking generally, we may 

 say that this bird shows more tendency to develop 

 additional plumes than any great brilliancy of colour, 

 but when bright colours are developed, their develop- 

 ment is associated with a tendency to suppression of 

 the barbules, and to dilatation of the naked barbs. 



The king Paradise bird {Cicinnurus regius), on the 

 other hand, shows less tendency to develop additional 

 tufts but much greater brilliancy of tint. The female 

 is a dull grayish tint, with a speckled breast, the male 

 is brilliant red on the back, with a metallic green 

 band separating the red head from the pure white 

 of the ventral surface. The tail contains two much 

 elongated wires displaying a brilliant green colour at 

 their curled tips. The red feathers are coloured by the 

 peculiar pigment zoorubin, which is practically absent 

 from the female. The feathers containing it have as 

 usual naked barbs, which are smooth, dilated, and 

 polished, so that as compared with the general 

 contour -feathers of the preceding species they are 



