1916] Chandler: Structure of Feathers 299 



tional remiges, although the birds are adapted for aquatic life. 

 They also possess typically developed pennaceous barbules. The 

 aftershaft is present with a short weak shaft, and numerous 

 spreading barbs. 



a) Gavia immer 

 ( 1 ) Remex 



Development very high, totally different from primitive condi- 

 tion in penguins. Shaft slightly broader than deep, distinctly 

 quadrangular, with narrow median groove on ventral side and 

 barbs attached nearer dorsal surface, as in all other flight birds. Rami 

 of both vanes, though narrow at junction with shaft, immediately 

 become very wide, with a broad, membranous ventral ridge, the 

 total width of ramus then equivalent to that of shaft, i. e., about 1.6 

 mm., the translucent ventral ridge constituting approximately one- 

 fourth the width of the ramus. Rami taper rapidly and become narrow. 

 Lower edge of ventral ridge almost if not quite smooth, no villi pro- 

 jecting ventrally. About 20 barbules per centimeter, usually a few 

 less on outer vane, a few more on inner. 



Inner vane. — Distal harhules (pi. 16, fig. 8a) characterized by a 

 broad, well-formed base about 0.27 mm. long, narrowing proximal 

 to ventral teeth ; latter 1 or 2, narrow and fingerlike ; pennulum 

 moderately long; booklets 4 or 5, moderately long and slender, well- 

 formed; ventral cilia moderate, straight, more or less appressed to 

 shaft; basal two or three dorsal cilia stout and triangular, the 

 transition to rudimentary distal ones gradual. Total length of 

 barbule about 0.6 mm. Proximal Ijarhules (pi. 16, fig. 85) rather 

 stout, about 0.43 mm. long by 0.05 mm. wide, with about 4 long, 

 slender, conspicuous ventral teeth ; pennulum filamentous, with 

 rudimentary barbicels. 



Outer vane. — Distal harhules (pi. 16, fig. 8c) with elongated 

 base (0.33 mm. by 0.033 mm.) with 2 rather small ventral teeth, 

 Hooklet region of pennulum very broad (pi. 16, fig. 8c, this barbule 

 being twisted to show this characteristic). Hooklets considerably 

 increased in number, 6 or 7 present; ventral cilia very much as in 

 inner vane, and dorsal cilia absent entirely. Towards inner part of 

 barbs, bases of barbules much shorter and hooklets gradually chang- 

 ing over to curved ventral cilia, strongly hooked, reminiscent of 

 those in penguins. Proximal harhules of distal part of outer vane 

 (pi. 16, fig. did) with considerably narrower bases than those of inner 

 vane, and pennulum with a complete series of ventral cilia, the more 

 proximal ones strongly curved and hooked. The more basal proxi- 

 mal barbules very similar to those of inner vane, the ventral teeth 

 elongating on more distal barbules, ultimately forming the 4 or 5 

 proximal hooklike ventral barbicels, the more proximal cells of pen- 

 nulum adding more barbicels to these until a complete series is 

 formed. 



(2) Other Feathers 



Back feathers with well-developed interlocking vanules basally. 

 Distal barbules with both base and pennulum elongated, the former 



