406 



ZOOLOGY 



SKCT. 



its posterior portion, including the middle and posterior turbinals, 

 is invested by the one-layered epithelium of the Schneiderian 







cl.p 



FIG. 1047. Columba livia. The eye. A, in sagittal section ; B, the entire organ, external 

 aspect, en. cornea ; ch. choroid ; c.l. pr. ciliary processes ; ir. iris ; I. lens ; opt. nv. optic 

 nerve ; pet. pecten ; rt. retina ; sd. sclerotic ; scl.pl. sclerotic plates. (After Vogt and Yung.) 



membrane to which the fibres of the olfactory nerve are distributed. 

 The eye (Fig. 1047) is not even approximately globular, but has 

 the form of a biconvex lens. Sclerotic 

 bony plates (B., scl.pl.) are present, and there 

 is a large pecten (pet), in the form of a 

 plaited and strongly pigmented membrane, 

 projecting into the cavity of the eye from 

 the entrance of the optic nerve. The 

 pecten is of nervous character, and is in 

 all probability a sensory organ having some 

 function connected with the process of 

 accommodation. 



The auditory organ (Fig. 1048) is chiefly 

 distinguished from that of Reptiles by the 

 great development of the cochlea (lag). 

 The anterior canal (SB) is of great size, 

 and the whole membranous labyrinth is 

 closely invested by a layer of dense ivory- 

 like bone, which can be isolated by cutting 

 away the surrounding spongy bone, and is 

 then seen to form a sort of model of the 

 contained organ, to which the name bony 

 labyrinth is applied. The tympanic cavity 

 and columella have the same arrangement 



FIG. 1048. Columba livia. 



The right membranous laby- 

 rinth, outer aspect. FA, am- 

 pulla of posterior canal ; FB, 

 posterior canal ; HA, ampulla 

 of horizontal canal ; HB, hori- 

 ^ontal canal ; lag. cochlea or 

 lagena ; mr. membrane of 

 Be issuer ; j)b, basilar part of 

 cochlea ; S. sacculus ; SA, am- 

 pulla of anterior canal ; SB, 

 anterior canal. (From Wieders- 

 heim, after Hasse.)' 



