Chap. IX.] 



FEA THERS. 



367 



the latter similarly give off much finer radii or 

 barbules, which, interlocking by "cilia" and booklets 

 with those that are found 011 neighbouring barbs, 



c/ 



Fig. 155. Feather from the Back of Argus giganteus. 



a, Shaft (rachisV, b, aftershaft; c, branches to form the vexillum, removed 

 from one side of both shaft and undershaft ; d, shaft (scapus). (After 

 Nitzsch.) 



form the connected vane or vexillum of the feather 

 (c) ; the shaft, which in its upper portion is often 

 called the rliacliis, frequently gives off near its base 

 a smaller feather or aftersliafl (6). It has been 

 calculated (by Gadow) that the feather of an eagle 

 contains about two thousand barbs, five millions and a 



