271 



how well birds are protected by their colors, especially the fe- 

 male birds at nesting time. 



The Nervous System and Special Senses. — The braiii (Fig. 

 223) of birds is larger and more highly developed than that of 

 reptiles. The cerebrum and cerebellum are larger. The cere- 

 brum is smooth, but the cerebellum is convoluted transversely. 



Fig. 221. — Tailor-bird (Orthot'omus suto'rius) and nest. (From Jordan 

 and Kellogg, " Animal Life," D. Appleton & Co., publishers.) 



The eyes of the bird are large, to meet the demands of far vision 

 in flight. There are two movable eyelids and a third membrane 

 called the nictitating membrane, which the bird can draw over 

 the eye by a peculiar muscular arrangement. This membrane 

 protects the eye from too bright light (Fig. 196). The pecten, 

 "a. comb-shaped growth of the coroid into the vitreous body," 

 is a peculiar avian characteristic. The avian eye is character- 

 ized not only by the sharpness of vision consequent upon the 



