1916] Chandler: Structure of Feathers 307 
flying fish-eaters, differ so little from typical limicoline birds that 
a special description of their feathers would be superfluous here. 
Comparison on plate 28 of figures 61a, b, c, d and e, with figures 
57a, b, c, d and e respectively, will make the similarity strikingly 
clear. It is interesting to note that the bluish-gray colors of gulls 
are produced by an uneven distribution of pigment in the barbules, 
as shown by the figures of Larus occidentalis (pl. 28, figs. 6la, d). 
In lighter-colored gulls, such as Larus argentatus, the lght spaces 
between the dark bars in the bases of the barbules are more ex- 
tensive. Terns and jaegers have an even distribution of pigment 
in the barbules. In the former, as exemplified by Sterna maxima, 
the outer vane of the remiges has a hoary appearance due to the 
ereat length of the pennula of the distal barbules, which have ex- 
ceedingly numerous and slender ventral cilia (pl. 28, fig. 62a). 
The auks, guillemots, murres, ete., representing the Alcidae, 
seem, according to their feather structure, to form a sort of con- 
necting link between the Colymbiformes and Laridae. The resem- 
blance of the structure of the remiges to that of both the gulls 
and grebes is well brought out by a comparison of plate 28, figures 
63a, b and c, representing barbules of the remiges of Uria troille, 
with figures 6la, b and c of the same plate on the one hand, and 
plate 16, figures 9a, b and ¢ on the other. 
The structure of the breast feathers is remarkably similar to 
that of grebes and Sphenisciformes. The more basal distal barbules 
(pl. 28, fig. 63d) could very readily be mistaken for those of Aech- 
mophorus (pl. 16, fig. 9e). The middle part of the barb is fur- 
nished with twisted barbules and is exactly similar to that shown 
in plate 16, figure 9h, while on the more distal third the barbules 
(pl. 28, figs. 68e, 63f) are strikingly similar to those developed in 
the outer portion of the barbs of breast feathers of loons (pl. 16, 
figs. 8e, 8f). 
c) Down 
In the Charadriidae the down barbules are quite different in 
different forms, usually of rather moderate length, i. e., from 1 to 
2 mm. long, sometimes pigmented. The nodes are always swollen 
and more or less distinct, in pigmented types often very distinct 
with the pigment present in it as a dark spot, almost as in pas- 
serine birds (pl. 37, fig. 114). Im Cuwrsorius the barbules are of 
this type, and unusually dense, there being as many as 70 barbules 
per millimeter on each side. 
