ORGAN OF HEARING IN FISHES. 



34,5 



side by a small orifice with 

 of the atlas, close to the 

 foramen magnum, which 

 ' atria ' are supported ex- 

 ternally by the ossicles I 

 aud m, and, by means of 

 the large ossicle o, arc 

 brought into commnnica- 

 tion with the fore part of 

 the air-bladder, j). Both 

 the atria and common 

 sinus are filled by the 

 endolymph, and from the 

 fore part of the sinus a 

 ' canalis furcatus,' ib. /, 

 is produced, the blind 

 ends of which penetrate 

 the alisphenoids. In the 

 grovelling Loach ( Cobitis 

 barhatula), 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 

 parajjophyses of the se- 

 cond and third cervical 

 vertebras, which are ex- 

 panded and coalesced so 

 as to form a large ' bulla 

 ossea ' beneath their cen- 

 trums.' The three ossicles 

 on each side, which bring 

 the air-bladder into com- 

 munication with the ' atria' 

 of the labyrinth, are also 

 concealed by the fore part 

 of the parapophysial bul- 

 lae : it is plain, therefore, 

 that they are not dis- 

 memberments of those 



two subsphcrical ' atria,' on the body 



229 



Organ of Heariug m situ ^\ th i i 1 1 Uder and l ssides, Carp. 

 Lwm 



XXXIX. i. p. 380. 



