1916] Chandler: Structure of Feathers 323 



cilium, and presence of a rndimentary fourth one. The dark green 

 feathers of the back are somewhat modified. The bases of both 

 distal and proximal barbules of these feathers are long and nar- 

 row, and deeply pigmented, while the ventral teeth in both are 

 poorly formed and lightly pigmented. The booklets 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 

 greatlj^ 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 21&, and comparison with figures 20a and 20& of the 

 same plate will show the similarity. The slight 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 21& 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 cm. 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 



