Till: nl:..AXB OF Tl! ..I KM I \ 



507 



tion of tin- pharwix, tlii> \i.-\v U..p|.x, ,1 i t ,,i ,,nly to COmpam 

 ;ui;itoniical 01 -n^. hut nl- > to 



MOI.M.NH \i i:u, an. I Hoi IM \\N. \\ In to the dcvolopmci 



llrjitilrs. I'.inls :ilil Maliiln 



In tin- classes of Vertebrates just m< first visceral 



Fig. 284. Diagrammatic re pre ten tat ion of the who> organ of hearing to Han, from WlCDObUreiM. 

 <. M, M, auricle ; Atae, motni aoditoi ^ ; O, iU wail; JJt, BMCubnui* 



l>ain ; O 1 , its wall ; SAf, ooad-oooditctiBf 



appara | drawn as a 1 M of ib auditory oaiclc*; the 



place t correspond* to the stapedial plate, which cloae* the feneatra oralU ; . 

 Eustachii ; Tb\ iu opening into the pharynx ; (/'. iU wall. Iniur mr : the bony labyrinth 

 (HI.. A'/.-) for the moat part cut away ; S, aacculus ; a, A, the two rertiad nMtnbranoaa and 

 osseous semicircular canals; S.e, V.e, saccus and ductus odolympbatictu, of which the 

 two arms; Cp, cavum periljrmphaUcum ; O, eanalk rranieo* ; 



Con, membranous cochlea, which produce* at -t- the resUbalar ootctitu ; Con', bony cochlea ; 

 Sv and St, scala vestibuli and scala tjmpani, which at cuwmunioaU with each other at the 

 rulis(a); D.p, ductus )icrilymphaticos, which arises from the scala tyupani 

 at The huruwmtal semidrealar canal is not specially iJMsgiMtsH, 



but is easily recognisable. 



dft't ifl i-l. Bed in it- upju-r part also, contrary to the cor<. 

 Selachians.' 



The clo>uiv IKV..IIH-S more lilia ami i-oiii] 



^louth of ;t 'iiimrti\- i- between tlu> inner and outer 



epithelial plates. Remnants of the first visceral deft are preserved 



* See the statements discussed in a previous chapter (p. 2*7), concerning 

 the mooted question wht : fts remain closed by means of 



an epithelial membrane or are temporarily open. 



