1916] Chandler: Structure of Feathers 305 
ture as compared to those of the species already described. The 
distal barbules for the greater length of the barbs have well-formed 
bases with no flexules, only two or three weak hooklets, and no 
dorsal cilia. The proximals, at the base of the feather, have only 
two small, inconspicuous ventral teeth, but acquire four long and 
slightly wavy ones farther distad on the barb. Near the tip of 
the barbs the flexules are developed, beginning nearest the pen- 
nulum instead of at the proximal end of the base, the latter be- 
coming narrow and reduced, concomitant with the development of 
the flexules. This is well shown in plate 17, figures 12a and b. 
In Pelecanoides urinatrix, belonging to the genus which may be 
regarded as the least specialized member of the group, the breast 
feathers have the barbules for the greater part of the barb weak, 
but of ordinary type, i. e., without flexules. The bases of the 
distals are narrow and elongate, the ventral tooth, usually single, 
very small and simple, and the pennula hardly longer than the 
base, slender, with usually only two weak hooklets; a series of 
short ventral cilia similar to those of the body feathers of loons 
(pl. 16, fig. 8e). The proximals do not possess the elongate, wavy 
ventral teeth so characteristic of the more specialized members of 
this order, but have these structures so small and inconspicuous 
as hardly to be discernible at all. Near the tip of the barbs the 
same sort of a change takes place that occurs in Oceanodroma, i. e., 
a development of flexules with an accompanying reduction of the 
base, the ventral cilia being still well developed. The similarity 
of this type of barbule to those developed at the tip of the barbs 
of the breast feathers of loons seems highly significant. This re- 
semblance is strongly brought out by a comparison of plate 17, 
figure 126, with plate 16, figure 8f, representing the barbules of 
the tip of barbs of breast feathers of Oceanodroma and of Gavia 
respectively. 
c) Down 
The down barbules in Diomedea and Puffinus (pl. 34, fig. 97) 
are characterized by rather long, forward-curving prongs which are 
slender and cilia-like in form, sometimes nearly 0.04 mm. long and 
not infrequently forked. They are longest near the base of the 
barbule, decreasing to rudimentary prongs toward the tip. The total 
length of the barbules sometimes reaches 1 mm., but is usually some- 
what less. 
