INTEGUMENT. 3! 



glands near the ear in some rasores. The scales on the legs and the 

 claws on the feet and occasionally on the wings, are derivatives from 

 reptilian ancestors. The feathers are also derived from scales, but are 

 greatly modified. 



Feathers. There are several kinds of feathers but all may be 

 grouped under three heads: hair feathers (filoplumes), down feathers 

 (plumulae), and contour feathers (plumae). The latter have all of the 

 feather features (fig. 22) and in the typical form consist of shaft and 

 vane. The basal part of the shaft is the hollow quill, in which is a 



FIG. 23. Feather tracts of Geococcyx calif ornianus, after Shufeldt. 



small amount of loose pith. In the region of the vane the shaft, here 

 called rhachis, is solid, and running the length of its lower surface is a 

 groove, the umbilicus. The vane consists of lateral branches (barbs) 

 on either side, which have, in turn, smaller side branches (barbules), 

 these with small hooks at their sides and tips (B}. Interlocking of 

 these hooks gives firmness and continuity to the whole vane. In down 

 feathers the barbs arise directly from the end of the quill, and as hooks 

 are lacking, the barbs do not interlock and no vane is formed. Hair 

 feathers are merely long and slender shafts with no barbs, the simplest, 

 if not the most primitive kind of feather. It is still a question as to 



