PHYLOGENY OF THE PAL^EOGNATH^E AND NEOGNATH.E. 167 



the surface of the feather a very soft, silky appearance ; towards the tip they decrease 

 in length, and finally disappear. The distal end of the feather — about one-sixth of its 

 whole length — is peculiar, in that the rami bear no radii, but fuse more or less com- 

 pletely into one common laminate mass. Separate rami may, however, be distinguished 

 here and there under the microscope. The radii are very long, filamentous, and bear 

 only minute pointed fila, for the most part unpaired. 



On the neck the feathers are of a looser structure, the radii being shorter, and 

 disappearing much sooner than in the back-feathers. 



The contour-feathers of the Apterygidce appear at first sight to differ but little from 

 those of many Neognathce, the vane of the feathers, seemingly, being continuous. The 

 fact that it is discontinuous is only proved after microscopic examination. 



The rami are paired, set close together, and moderately long. The radii are long, 

 filiform, more or less distinctly jointed, and armed with numerous minute fila, set in 

 pairs, following close one upon another. These run in this fashion through almost the 

 entire length of each radius, only the extreme proximal end lacking such appendages. 

 According to Parker [71] they are longer in the embryo than in the adult. The entire 

 absence of hooklets at once distinguishes this from a laminate feather. 



There is no aftershaft. (See also p. 163.) 



In the Struthionidce the adult contour-feather more nearly resembles that of the 

 Neognathce than is the case with any other of the Palceoqnathce. 



The rami are set closely together, precisely as in the typical Carinate feather. The 

 radii take the form of narrow blade-shaped bands, directed upwards and outwards, so 

 that the rami from which they spring form the bottoms of V-shaped troughs. The 

 distal end of each radius bears fila disposed as in normal Neognathce, but none are 

 sufficiently elongated to form hooklets : they are probably, however, vestiges of these. 

 Moreover, the radii differ from those of more perfect feathers in that the distal and 

 proximal radii do not differ one from another : both series are alike, long and blade- 

 shaped. Thus, the. vane is discontinuous — a probably degenerate condition. 



In the Mheidce the contour-feathers of the trunk are characterized by the markedly 

 discontinuous character of the vane ; the rami appearing as a number of hard lines, 

 between which radii are only faintly traceable. 



The remiges are of very considerable size, though far inferior to those of the Ostrich. 

 The rami bear numerous short and fairly conspicuous radii. 



The radii of the track-feathers, under the microscope, appear to have degenerated 

 rather less than have those of the remiges. They approach those of the Ostrich. At 

 its proximal end, each radius is laterally compressed, the resultant lamina bearing some 

 4 or 5 long fila, probably vestiges of hooklets, and of the processes which occur on the 

 ventral edge of the lamina in the proximal radii of Neognathine feathers. 



The radii of the remiges are filiform, but distinctly flattened- from side to side. The 

 fila suggest vestiges of hooklets ; they are frequently bifid. 



2b 2 



