406 



ZOOLOGY 



SUM. 



its posterior portion, including the middle and posterior turbinals, 

 is invested by tlie one-layered epithelium of the Schneiderian 



Fig. 1047. — Columba livia. The eye. A, in sagiltal section ; B, the entire organ, external 

 aspect. Cii. cornea ; ch. choroid ; cl. pr. ciliary processes ; ir. iris ; t. lens ; opt. nv. optic 

 nerve ; j)ct. pecten ; rt. retina ; set. sclerotic ; scl. pi. sclerotic plates. (After Vogt and Yung.) 



membrane to which th 

 Tlie eye (Fig. 1047) 



-&i— 



Fig. 1048.— Columba livia. 



The right membranous laby- 

 rinth, outer aspect. i^..4, am- 

 pulla of posterior canal ; FB, 

 posterior canal ; HA, ampulla 

 of horizontal canal ; HJi, hori- 

 zontal canal ; laff. cochlea or 

 lagena ; mr. membrane of 

 Reissner ; pb, basilar part of 

 cochlea ; -S. sacculus ; SA, am- 

 pulla of anterior canal ; SS, 

 anterior canal. (From Wieders- 

 heim, after Haase.) 



e fibres of the olfactory nerve are distributed. 



is not even approximately globular, but has 

 the form of a biconvex lens. Sclerotic 

 bony plates (B.,scl.2Jl.) are present, and there 

 is a large pecten (p>ct.), in the. form of a 

 plaited and strongly pigmented membrane, 

 pi'ojecting 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 soQle 

 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 lony 

 labyrinth is applied. The tympanic cavity 

 and columella have the same arrangement 



