1916] Chandler: Structure of Feathers 361 
more emphasized, the cells being exceedingly short, the crowded 
ventral cilia being long and slender, the dorsal ones in close juxta- 
position to each other, and of a peculiar blunt, heavy form (pl. 29, 
fig. 71b). The proximal barbules (pl. 29, fig. 71c) are similar to 
those of the inner vane of the remiges. The barbules of the breast 
feathers resemble those of the scapulars but are weaker and less 
perfectly developed. 
c) Down 
The down barbules of typical Columbae are long, as in galli- 
naceous birds, frequently 3 or 4 mm. in length. On the basal part 
of the pennula there are a number of very large, expanded, and 
conspicuous nodes, usually from 3 to 8 of them of full size, then a 
similar number of smaller and less conspicuous ones, decreasing 
in size until they almost entirely disappear, the whole distal por- 
tion of the pennulum being smoothly filamentous or with very minute 
swollen nodes (pl. 36, fig. 109). Very similar down barbules are 
found in Tinamus and Nothocercus among the Crypturiformes. 
This structure of down has been found in all species of Colum- 
bidae which have been examined except Goura coronata. It has 
been found in Columba, Melopelia, Zenaidura, Columbigallina, Did- 
unculus, Macropygia and Osmotreron. In Goura the down bar- 
bules are shorter than in other Columbidae, not over 2 mm. long, 
and are smoothly filamentous with the nodes not swollen at all, 
although the junction of the cells is indicated by the uneven distri- 
bution of pigment, the latter being located in the distal portion of 
the internodes. Nitzsch (1867, pl. 1, fig. 25) figures the basal 
portion of a down barbule from a turtle dove. 
In Pteroclis the down barbules are between 1 and 2 mm. long, 
very slender and delicate, with no indications whatever of nodes, 
except towards the tip where rather large prongs are developed. 
ad) Color Modifications 
There are a number of special color modifications in the Colum- 
bidae which are worthy of special mention. The blue-grays, rang- 
ing from light pearl gray in the breast of Melopelia asiastica to a 
slate blue in Gowra, are very common in birds of this group, as 
in the Laridae, and are produced in the same way, namely, by a 
segregation of the black pigment into transverse bars (pl. 29, figs. 
64c, 66a-c, and 70c-e) the lighter colors produced by barbules with 
