402 ZOOLOGY 



stretch of the wings and the surface exposed to the air, and thus 

 are important as aids to flight. In addition they are protective 

 in several respects. The pigment possessed by the feathers 

 serves to enhance greatly the beauty and variety of the members 

 of the group. That the color patterns are of distinct value in 



FIG. 204. 



FlG. 204. Diagram showing the tracts where the principal growth of feathers occurs (Upupo epops) 

 From Bronn. The dotted areas are the pterylce. 



Questions on the figure. Is this a dorsal or a ventral view? Find a figure 

 giving the opposite view of some bird and compare with this. Is there variety in 

 the different species of birds as to the distribution of the growth of feathers? 



sexual attraction has been believed by many naturalists. The 

 feathers, together with the scales of the shank, the claws, and 

 the beak, are epidermal growths and represent the remnants 

 of the exoskeleton so well developed in some of the lower forms. 

 Feathers are not usually produced uniformly over the body, 

 but are grouped in regions which differ in different species. 

 They also vary a great deal in form, from the down feathers of 



