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 3Iarsipobranchii 

 the olfactory organ 

 is partly single and 

 presents peculiar re- 

 lations (see account 

 of Marsipobranchii). 

 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 

 the sense of taste. 

 The tactile sense is 

 no doubt specially 

 served by the lips 

 and their appendages. 



aa 



Fig. 40. — Right membranous labyrinth of Chimaera, seen 

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

 aa ampulla of anterior vertical canal ; ac auditory nerve ; 

 ade opening of ductus endolymphaticus ; ae ampulla of 

 horizontal canal ; ap ampuJla of posterior vertical canal ; 

 ass process of the sinus utriculi ; ca anterior, ci> posterior 

 vertical canal ; ce horizontal canal ; cr crista acustica 

 ampullae ; de ductus endolymphaticus, which opens at ade 

 through the skin ha ; mn macula acustica neglecta ; ms 

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

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

 lagenae (the lagena, however, can hardly be said to be 



present in this form) ; branches of auditory nerve raa to 01 tllC appendages 

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



terior ampulla, rec to macula acustica utriculi, rs to wlllCll are ricniy 

 macula sacculi and lagenae, ru to macula recessus utriculi ; . j. j / 



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

 superior; « utricle. THgla.) 



The system of embedded epidermal* sense organs which are 

 found in all fishes requires a detailed description. 



* Le.ydig, Lehrbtich d. Histologie des Menschen u. d. Thiere, 1857. Solger, 



