12 Mr. W. P. Pycraft un the 



course, is due to the structure of the radii. The calamus is 

 entirely embedded in the skin. 



Under a high power of the microscope the radii are seen to 

 be given off in pairs along the rami. Those of the proximal 

 end of the feather are deeply pigmented, the colouring-matter, 

 of the tint of sepia, being dispersed in granules of unequal 

 size and distribution, and imparting a somewhat striated 

 appearance to the radius. Structurally they cannot be said 

 to differ from the downy radii of the definitive feather 

 (PI. III. fig. 3, p. 7). 



The radii of the distal end of the feather are in no wise to 

 be distinguished from those of such pennaceous feathers as 

 do not interlock (PL III. fig. 2), yet, by reason of their 

 stiffness and close arrangement, form a vexillum. They are 

 deeply pigmented ; the colouring-matter, of the tint of vau- 

 dyke-brown, is broken up into oblong masses separated from 

 each other by narrow transparent zones (PI. III. fig. 2). 

 Towards the tip these radii bear tolerably long cilia. At the 

 proximal end of the rami the radii cross each other, after 

 the fashion of the typical interlocking feather. 



The aftershaft, as previously stated, is almost as long as 

 the main stem, and structurally diff'ers only iu that the distal 

 rami are pointed so much forward that they run almost 

 directly parallel with the shaft, and this has resulted in a 

 feeble development of the radii, which have been crowded 

 almost out of existence (PI. III. fig. 1, H.). 



The presence of an aftershaft, and so greatly developed, is 

 a feature of considerable interest, inasmuch as it had pre- 

 viously been known to occur only in Dromaus. Thus, 

 Dr. Gadow says of it (14) : — "In Dromceus each neossoptile 

 .... has a short calamus carrying a long dorsal rhachis and 

 a much smaller ventral aftershaft — each of them furnished 

 with from 5 to 6 rami .... and these again beset with 

 numerous radii without cilia. This is the only known 

 instance of a neossoptile with an appendage, and it is signifi- 

 cant that the latter is smaller than the principal shaft, and 

 only in its final stage equals the rhachis in size.^' Quite 

 recently, however, 1 have found a fairly well-developed after- 



