THE DOMESTIC PIGEON 365 



The mouth is inclosed by a toothless, horny beak, above 

 which are situated the two nostrils, set in a mass of soft, fleshy 

 skin called the cere (Fig. 191, 5). The eyes are large, and 

 have an upper and a lower eyelid and a nictitating membrane. 

 The external openings to the ears are a little behind and 



FIG. 189. Photograph of Rock-Dove 



below the eyes, and are surrounded with specially modified 

 feathers. At the base of the tail on the dorsal surface is a 

 gland (Fig. 191, 4) which secretes an oil for keeping the 

 feathers in good condition. 



The feathers are not scattered uniformly over the body, 

 but are arranged in definite tracts separated by areas in 

 which grow only a few hair-like feathers. As an example 



