78 



CLASS PISCES. 



the air bladder in some Teleostei, which are fully described in 



the account of that sub-class. 



The Olfactory Organs are a pair of simple pits or sacs, in the 



lining of which the 

 fibres of the olfactory- 

 nerve terminate. In 

 the Marsipohranchii 

 the olfactory organ 

 is partly single and 

 presents peculiar re- 

 lations (see account 

 of Marsipohranchii). 

 In other fishes each 

 sac usually has two 

 openings, both of 

 which are external 

 except in Dipnoi. 

 In Elasmobra n c h s 

 there is usually only 

 one opening. The 

 internal surface of 

 the sacs is generally 

 increased by folds of 

 the mucous mem 

 brane. 



We know practi- 

 cally nothing about 



Fig. 40.— Right membranous labyrinth of Chimaera, seen \\iq seiise of taste. 

 from the median side (from Wiedersheim, after Retzius). 



aa ampulla of anterior vertical canal ; ac auditory nerve ; "Jiie tactile Sense is 

 ade opening of ductus endolymphaticus ; ae ampulla of 



horizontal canal ; ap ampulla of posterior vertical canal ; xiO doLlbt Specially 

 ass process of the sinus utriculi ; ca, anterior, op posterior ^ 



vertical canal ; ce horizontal canal ; er crista acustica served bv tllC lipS 

 ampullae ; de ductus endolymphaticus, which opens at ade _ "^ 



through the skin ha; mn macula acustica neglecta ; ms and their appendages, 

 macula acustica sacculi (the macula ac. utr. rec is on the . 



other side and not properly visible) ; pi papilla acustica and by special parts 

 lagenae (the lagena, however, can hardly be said to be J i- 



present in this form) ; branches of auditory nerve raa to of the appendages 

 anterior ampulla, rae to horizontal ampulla, rap to pos- . • i i 



terior ampulla, rec to macula acustica utriculi, rs to wllicll are ricllly 

 macula sacculi and lagenae, ru to macula recessus utriculi ; 



s saccule ; sp sinus utriculi posterior, ss sinus utriculi innervated (e.g. 

 superior ; u utricle. m • 7 



Tngia.) 

 The system of embedded epidermal* sense organs which are 

 found in all fishes requires a detailed description. 



* Levdig, Lehrhuch d. Histologie des Menschen u. d. Thiere, 1857. Solger, 



