376 Unwersity of California Publications in Zoology  {Vou.18 
type for their entire length, and have short internodes (pl. 37, 
fig. 112). The down barbules of a large number of genera of 
Trochilidae have been examined, and all of them have been found 
to possess this type of structure. The barbules on the outer part 
of the barbs have inconspicuous nodes, of a type similar to that 
shown in plate 37, figure 110. 
The Trogons have down very much like the Trochilidae in that 
the nodes are large and conspicuous and present for the entire 
length of the pennula, but they are not relatively as large, or the 
internodes as short, and the bases are not furnished with villi. 
The nodes are shaped more or less like the fruit of a eucalyptus 
tree and are deeply pigmented. 
The down barbules of the Pici, like the pennaceous barbules, 
show a close similarity to the Passeriformes except in the family 
Galbulidae. In the latter, as exemplified by Bucco, Malacoptera 
and Jacamerops, the down is like that of Coracias and Momotus. 
In the Rhamphastidae (Rhamphastus, Pteroglossus and Andigena) 
the barbules (pl. 37, fig. 113) have large nodes shaped like euca- 
lyptus fruits on the proximal portion, these becoming small and 
insignificant beyond the basal 6 or 7. The bases of the inner bar- 
bules have weakly developed villi. The barbets, Capitonidae, have 
down almost exactly like the Rhamphastidae. In the Picidae the 
type is similar except that the basal nodes are relatively smaller, 
and the decrease in size toward the tip of the barbules is more 
gradual and less conspicuous. The villi on the bases are well- 
developed on the barbules near the base of the barbs, as much so 
as in many Passeriformes. 
d) Color Modifications 
The variety of colors found in the Coraciiformes is unexcelled 
anywhere amongst birds, and the variety of structural modifica- 
tions correlated with color production is correspondingly great. 
Many of the Coraciiformes are characterized by the prevalence 
of deep purple and light blue colors in the wings and tail. The 
deep purple is a brilliant purple refraction color produced by the 
large dorsal ridges of the rami, combined with a blackish brown 
pigmentation in the non-refractive barbules. The beautiful light 
blue of these birds is produced by a superstructure above the 
refrangent surface of the dorsal ridges of the rami which otherwise 
produce brilliant purple, the barbules in this case being unpig- 
