266 University of California Publications in Zoology I Vol. 13 



ordinarily developed as a very thin, translucent film, which bends 

 distally and overlaps the following ramus, giving a smooth, glazed 

 appearance to the under surface of the feather which is conspicuous 

 at the most casual glance. It is thus developed in all of the Anseres, 

 (pi. 33, fig. 28a), and in a number of gallinaceous birds, though in 

 the latter it is by no means constant, being present, for instance, in 

 Bonasa, but absent in Lophortyx. The ventral ridge of the outer 

 vanes of some groups of birds, e. g., Anseres, Falconidae, and some 

 Ciconiae, is further modified by being furnished with irregular villi 

 (fig. C, and pi. 21, fig. 28&) on the ventral edge. The rami of the 

 inner vane always have the ventral edge entire or nearly so. 



As shown by Mascha (1904), rami are furnished with a lateral 

 ^' ledge" which is grooved for the reception of the bases of the bar- 

 bules (fig. C). These are much more highly developed and efficient 

 in some birds than in others, often making it very difficult to scrape 

 off the barbules without tearing off with them a part of the barb to 

 which they remain attached. 



c) Barbules. — The interlocking barbules of a typical remex are 

 of four distinct types, the distal and proximal barbules of the inner 

 vane, and the distal and proximal barbules of the outer vane. 



It is unnecessary here to enter into a discussion of the typical 

 structure of distal and proximal barbules, or of their manner of 

 interlocking. An excellent description of this is given by Pycraft 

 (1893), and a few additional facts of interest are added by Mascha 

 (1904). There are, however, a number of minor details of structure 

 of both distal and proximal barbules which are almost uniformly 

 different in all birds in the inner and outer vane, although apparently 

 this fact has escaped the notice of all previous observers. As a rule 

 the bases of the distal barbules of the outer vane are longer and 

 relatively narrower than those of distal barbules of inner vanes, but 

 this is not always true, the chief difference lying in the pennula. 

 On the inner vane the pennulum of distal barbules as a rule is longer 

 than it is in the outer vane, with fewer booklets, but a larger num- 

 ber of cells with cilia (compare pi. 16, fig. 8a, with fig. 8c and see 

 text-figure D). The most conspicuous difference lies in the dorsal 

 cilia on the proximal portion of the pennulum. Almost without excep- 

 tion, distal barbules of the inner vanes of remiges are characterized 

 by the specialized development of the first two (pi. 20, fig. 20a), 

 and often to a less extent of the third, dorsal cilia (pi. 20, fig. 23a). 

 These specialized cilia are developed as stout, conspicuous, lobate, or 



