1916] Chandler: Structure of Feathers 323 
cilium, and presence of a rudimentary fourth one. The dark green 
feathers of the back are somewhat modified. The bases of both 
distal and proximal barbules of these feathers are lone and nar- 
row, and deeply pigmented, while the ventral teeth in both are 
poorly formed and lightly pigmented. The hooklets of the distals 
are weak and reduced, the ventral cilia are short and blunt, and 
there are no dorsal cilia. The proximals have three or four 
progressively diminishing blunt ventral cilia on the pennulum, thus 
ereatly resembling in general form the distal barbules. 
Botaurus and Butorides very closely resemble Ardea in all the 
details of their feather structure. The distal and proximal barbules 
of the outer vane of Butorides virescens are shown in plate 20, 
figures 21a and 21b, and comparison with figures 20a and 206 of the 
same plate will show the similarity. The sheht separation and for- 
ward curve of the ventral teeth of the proximals of the distal part 
of the outer vane, as shown in plate 20, figure 21b and slightly 
less prominently in plate 20, figure 20d, are very characteristic of 
the entire family. 
The most interesting birds of the entire group from a popular 
point of view are the egrets, Egretta candidissima and Herodias 
egretta, from which are derived the famous ‘‘aigrettes’’? of com- 
merce. In the structure of its remiges Herodias egretta differs 
from the typical forms of the genus Ardea in the reduction of the 
dorsal cilia. The first one is fairly well developed, the second smaller, 
and the third very minute. They thus differ from Ardea herodias in 
the opposite direction from Nycticorax, which has the dorsal cilia a 
little better developed. 
The aigrettes of both species of egrets are too well-known to 
need a general description, the barbs being very widely separated 
on the shaft, reaching a length of 15 em. or more, and appearing as 
filamentous strands entirely separate from each other. Although to 
the naked eye the barbs appear destitute of barbules, closer examina- 
tion shows that there is a complete series of closely appressed, 
non-interlocking barbules, the distal and proximal ones very similar, 
except that the latter are a little longer. They are flat and taper- 
ing, with no well-developed barbicels, as shown in plate 20, figure 22. 
The distal and proximal barbules are spaced 21 and 18 per milli- 
meter respectively. The barbules of the aigrettes of Herodias egretta 
differ from those of Egretta candidissima in the length, the former 
being under 0.65 mm. long while the latter are normally at least 0.7 
