1916] Chandler: Structure of Feathers 357 



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 flgures 61a, h, c, d and e, with figures 

 57a, h, 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 (pi. 28, figs. 61a, d). 

 In lighter-colored gulls, such as Larus argentatus, the light 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 

 great length of the pennula of the distal barbules, which have ex- 

 ceedingly numerous and slender ventral cilia (pi. 28, fig. 62a). 



The auks, guillemots, murres, etc., 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, h and c, representing barbules of the remiges of Uria troille, 

 with figures 61a, h and c of the same plate on the one hand, and 

 plate 16, figures 9a, h and c on the other. 



The structure of the breast feathers is remarkably similar to 

 that of grebes and Sphenisciformes. The more basal distal barbules 

 (pi. 28, fig. 63d) could very readily be mistaken for those of Aech- 

 mophorus (pi. 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 

 (pi. 28, figs. 63e, 63/) are strikingly similar to those developed in 

 the outer portion of the barbs of breast feathers of loons (pi. 16, 

 figs. 8e, 8/). 



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 (pi. 37, fig. 114). In Cursorius the barbules are of 

 this type, and unusually dense, there being as many as 70 barbules 

 per millimeter on each side. 



