1916] Chandler: Structure of Feathers 367 
green of many species is produced by a brilliant green structural 
color in the ramus, accompanied by a brown pigmentation in the 
barbules, the depth and tone of the green varying with the shade 
and amount of brown pigment in the barbules. The bright emerald 
green of Melopsittacus is produced by green or blue rami, with 
lemon-yellow barbules, and the yellow olive-green of Tanygnathus 
lucionensis by green rami and barred barbules which are yellowish 
proximally (pl. 30, fig. 76a). The deep purple or blue of some 
species 1s produced by. a brilliant purple or blue structural color 
in the rami, and a dark brown pigment color in the barbules. One 
of the most interesting combinations is in the feathers on the side 
of the head of Palaeornis cyanocephalus, which are described as 
rosy, with a bloom lke that of a ripe plum. This is produced by 
a light purplish blue structural color in the rami, and a red pig- 
ment color in the barbules. 
e) Relationships 
In all respects of feather structure, the Cuculiformes are very 
closely related to the Coraciiformes, and should probably be con- 
sidered as nearly allied to the immediate forerunners of this group. 
The question of their descent is likewise easy, the only lower groups 
to which they show affinity being the peristeropode Galli and the 
Columbae; in general form of pennaceous barbules they are nearer 
to the former, but in the structure of the down and in some details 
of the structure of the pennaceous barbules, e.g., the prongs on 
the hooklets, they show affiliation with the latter. The Cuculi, 
especially the Musophagidae, come nearer the gallinaceous and 
columbid birds, while the parrots are nearer the Coraciiformes in 
the structure of their feathers. 
f) Summary 
(1) Plumules evenly distributed in Psittaci, sparse and con- 
fined to apteria in Cueuli. 
(2) Aftershaft present in Psittaci, rudimentary or absent in 
Cuculi. 
(3) Distal barbules and proximal barbules about equal in 
number. 
(4) Distal barbules with very elongate base with sinuous ven- 
tral contour, ventral teeth very small; pennulum shorter than base, 
