MR. E. T. HIGGI5S OK THE OTOLITES OF PISH. lijl 



Wolf fisli. On tlie one side it is situated just below the junc- 

 tion of the anterior and posterior semicircular canals, and on the 

 other side below the junction of the anterior and external. 



Professor Miiller says that sound is conveyed to the auditory 

 organs of fish by three media in succession, viz. : — 



1st. The water in which the fish lives. 



2ndly. The solid parts of the body and of the organs of hearing. 



3rdly. The fluid of the labyrinth. 



There can be no doubt that these are the principal media by 

 which sound is conveyed to the organ of hearing ; still to these 

 ought to be added the air-bladder (where it exists) ; for though no 

 doubt the principal use of this organ is to enable the fish, by the 

 generation or expulsion of its enclosed air, to rise or sink ; yet it 

 must materially assist in multiplying by resonance and conducting 

 the vibrations to the auditory nerve, thus supplying the place of a 

 tympanum, especially to those fish, such as the Cyprinidas and 

 Siluridae, w^here a direct communication exists between the ante- 

 rior air-bladder (by its tubular prolongation) and the chain of 

 ossicles communicating with the otocrane and its contained otolites, 

 semicircular canals, auditory nerve, &c. 



This chain of ossicles has, by some comparative anatomists, been 

 considered to be the representatives of the ossicula auditils in other 

 vertebrata. If they are recognized as such, we must deny to all 

 fish, except those belonging to the highly favoured groups of Cy- 

 prinidae and Silmndse, possession of those organs of hearing. This 

 subject, together with my reasons for questioning whether the 

 opercular bones should, as believed by some, be considered the re- 

 presentatives of the ossicula auditm, must form the subjects of 

 future investigations. 



Before passing on to the more immediate object of my paper, I 

 would only add that I cannot understand the necessity of search- 

 ing on the outside of the skull for these representatives, when we 

 find the otocranes containing all the essentials. 



The otolites, or ear-stones, by analysis are determined to consist 

 principally of carbonate and phosphate of lime and mucus, with a 

 very small proportion of animal matter. 



Mr. Stoddart says, " They are evidently formed by the crystal- 

 lization of carhonate of lime in a gelatinous fluid, a condition well 

 known to every chemist as interfering with the proper crystalline 

 angles and planes by altering the regular arrangement of the 

 calcareous particles." 



And in a subsequent paper he states that " otolites were de- 



LI^'N. PROC. — ZOOLOGT, VOL. IX. 13 



