366 University of California Publications in Zoology Vou. 138 
proximally, but very minute distally. In the aftershaft the nodes are 
not quite so globular, and show rudiments of prongs. In the majority 
of the Psittaci, the nodes are shaped more like the fruit of a 
eucalyptus tree, and have the pigment in them instead of proximal 
to them, thus closely approaching some of the coraciiform birds. 
The nodes in the Psittaci are somewhat closer together than in the 
Cuculi, there being usually 15 or more per millimeter, instead of 10 
or 12 as in the Cueuli. 
d) Color Modifications 
There are a number of interesting color modifications in this 
order. The steel-blue feathers of Hudynamis honorata have a warm 
brown pigment, and are highly reflective, the blue color being prob- 
ably due, at least in part, to the selective transmission and reflec- 
tion of the pigment. There are raised ridges at the junction of 
the cells of the bases of both distal and proximal barbules, and also 
on the broad pennula of the latter. A similar modification is to 
be found in the glossy green feathers of Geococcyx californianus. 
In this case the green color seems to be primarily produced by the 
reflective bases of the distal barbules, but the pennula of the prox- 
imals are conspicuously broadened, with distinct raised ridges at 
the junction of the cells (pl. 30, fig. 73a). 
In the Musophagidae, represented by Turacus corythax, the 
barbules of the remiges owe their deep purplish crimson color to 
an evenly distributed pigment known as turacin, which, according 
to Church (1893), is somewhat soluble in water and contains a 
considerable percent of copper. By transmitted light this pigment 
in thin layers, e.g., in a single barbule, is of a distinct green 
color, but in thicker layers, as where the flange overlaps the rest 
of the base, or where two barbules lie on top of each other, it is 
a deep red. It is, therefore, a fluorescent color, with color proper- 
ties somewhat similar to those of eosin. The dull glossy green and 
delicately lined feathers of the back are produced by barbs in 
which the barbules are evenly pigmented with a brownish color and 
are green by refraction, while the rami are whitish. 
In the Psittaci a number of interesting color modifications are 
found. Yellows, reds, and oranges are produced by a pigment 
evenly distributed in both rami and barbules. Green, blue, and 
purple are produced by a refraction from the dorsal ridges of the 
rami, modified by pigmentation in the barbules, e. g., the soft deep 
