274 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



into wings, and the toothless, beaked mouth are characteristic 

 and distinguishing external features. The feathers, although 

 covering the whole of the surface of the body, are not uni- 

 formly distributed, but are grouped in tracts called pterylce, 

 separated by bare or downy spaces called apteria. They are 

 of several kinds, the short soft plumules, or down feathers, the 

 large, stiffer, contour feathers, whose ends form the outermost 



FIG. 126. A body feather and a wing feather from a chicken. 



(Reduced.) 



covering of the body, the quill feathers of the wings and tail, 

 and the fine bristles, or vibrissa?, about the eyes and nostrils, 

 called thread feathers. The fore limbs are modified to serve 

 as wings, which are well developed in almost all birds. How- 

 ever, the strange kiwi, or Apteryx, of New Zealand with hair- 

 like feathers is almost wingless, and the penguins have the 

 wings so reduced as to be incapable of flight, but serving 

 as flippers to aid in swimming underneath the water. The 



