272 



BRANCH CHORDATA 



Fig. 222. — Baltimore orioles and nest ; the mule in upper left-hand corner 

 of figure. (From Jordan and Kellogg, " Animal Life," D. Appleton & Co., 

 publishers.) 



large size and complicated structure of the retina, but also by the 

 highly developed power of accommodation, and by the great mo- 

 bility of the muscular iris in the dilation and contraction of the 

 pupil. 



The ear is well developed. There is no external ear, but the 

 opening to the tympanum is concealed by feathers posterior to 

 the eye. The ear has three semicircular canals, the dilated 

 cochlea, and a Eustachian tube extending to the mouth from 

 each ear. 



Of the other senses it may be stated that touch is common in 



