730 



EVOLUTION OF ANIMALS 



Part V 



Fig. 36.1. Flying geese. Drawing by Peter Scott. (Courtesy of Peter Scott: Wild 

 Chorus. London, Country Life Ltd., 1950.) 



thrust into the air in flight, streamlined, and slipping forward with no outriggers 

 to hinder. Walking birds, quail, pheasants, chickens, fold their wings and slip 

 through underbrush. The diving sea birds do likewise, driving down through 

 the water with arrowy velocity. 



Feathers 



Their covering of feathers provides birds with a light, water resistant in- 

 sulation from cold, a matchless equipment for flight, and a clothing whose 

 beauty has brought them admiration and relentless killing. 



A feather is a complex, exquisitely wrought, yet durable structure composed 

 of the horny remains of dead cells. Its growth begins, like the scale of a bird's 

 leg or reptile's body, as a nipple-shaped upgrowth of the skin that soon sinks 

 into a depression, the future follicle or sac that holds the feather in place. The 



