210 LECTURE VIII, 



Scarpa may be pardoned for overlooking tliem, though scarcely for 

 the warmth with which he repudiates their existence.* The 

 ' meatus vestibuli ' {Jig. 59, p) is provided at its bent extremity 

 with a special muscle (ib. iv). 



A true tympanic cavity and membrane, together with a cochlea, 

 are absent in all Fishes. But in many Osseous species a com- 

 munication is established, either by tubular prolongations, or by 

 chains of ossicles between the acoustic labyrinth and the air-bladder. 

 "Weber + discovered the latter interesting structure in the Carp, 

 Loach, and Sheat-fish. A canal is sent from the sac of each ves- 

 tibule {fig- 58, b), to a common ' sinus impar' (ib. //) in the sub- 

 stance of the basi-occipital : this communicates on each side by 

 a small orifice with two subspherical 'atria,' on the body of the 

 atlas, close to the foramen magnum, which 'atria' are supported 

 externally by the ossicles I and m, and, by means of the large 

 ossicle o, are brought into communication with the fore part of the 

 air-bladder (p). Both the atria and common sinus are filled by the 

 endolymph, and from the fore part of the sinus a ' canalis furcatus ' 

 (ib. i) is produced, the blind ends of which penetrate the alisphenoids. 

 In the groveling Loach {Cobitis barbatula), the air-bladder would 

 seem to exist chiefly in subserviency to the organ of hearing. 

 It is so small as to be wholly included within the singularly 

 modified parapophyses of the second and third cervical vertebrge, 

 which are expanded and coalesced so as to form a large 'bulla 

 ossea ' beneath their centrums.:}: The three ossicles on each side, 

 which bring the air-bladder into communication with the ' atria ' of 

 the labyrinth, are also concealed by the fore part of the parapophysial 

 bullae : it is plain, therefore, that they are not dismemberments of 

 those lateral or transvei'se apophyses of the vertebrae ; and, with 

 regard to their relation to the ' ossicula auditus ' of the tympanic 

 cavity in Mammalia, Weber mistook a relation of analogy for one of 

 homology, when he called them 'malleus,' 'incus,' and 'stapes.' 

 They belong, like the capsules of the special organs of sense, to the 

 ' splanchnoskeleton.' And since the vestibule is prolonged by the 

 ' ati'ia ' into the neural canal of the atlas, this vertebra must be added, 

 in the Cyprinoid and Siluroid Fishes, to the parts of the cranial verte- 



Hearing in Fishes " was printed in the volume of the Philosophical Transactions 

 for 1782, not, as Breschet states, in the year 1786. (lviii. p. 58.) 



" " Hunterum autem atque Monroum veheraenter super hac re sibi hallucinates 

 fuisse." (lx. pp. 1, 2.) 



■\ LXXIII. 



\ Mr. Yarrell, who has given a figure of these singularly modified parapophyses 

 of the Loach (i.xxix. i. p. 380.) compares them to 'scapulaj ; ' but I find tiie pec- 

 toral fins attached to the true scapular arch, and this suspended as usual to the 

 paroccipitals, in the Cobitis barbatula. 



