26 



VI. 



KEMAEKS ON THE OTOLITHS OF CERTAIN EISHES, 



Extracted from a paper read before the Dover Field Club and 

 Natural History Society, 29th January, 1890, 



BY 



Mr. SYDNEY WEBB. 



The mechanism of the human ear consists of an outer organ with 

 convolutions for the purpose of arresting and detaining sounds, and an 

 internal series of complex arrangements for their conveyance to the brain. 



To effect this, there is a receiving tube closed at the inner end by 

 the tightly-stretched membrane vre usually call the di-um, behind which 

 is a little chain of bones, the last of which is stirrup-shaped and fastened 

 to another thin skin which closes the cavity within which these bones are 

 placed Beyond the stirrup is a bony chamber in which are winding 

 passages ; from its fancied resemblance to a snail-shell the spiral part of 

 this organ is called the cochlea. All the passages and tubes are filled 

 with a watery fluid. The nerve by which sounds are communicated to 

 the brain, extends from it to this winding chamber, and the extremely 

 sensitive ends arc ramified and spread throughout the passages and cells. 



From the outer ear, the vibrations pass down the tube to the drum, 

 which latter (like the tinfoil curtain of the telephone) communicates the 

 infinitely minute air wave to the chain of bones, these set the fluid into 

 motion within the winding passages throwing it into undulations, which, 

 acting upon the nerve, produce the complicated phenomenon we call 

 hearing. 



On either side of the skull of a codfish, within the cavity, lies a 

 small bone detached fi'om the others, slightly curved and flattened, of an 

 elongate oval shape. This is the otolith, cr receiving medium, which 

 corresponds to the cochlea in man, and the same term might be used as 

 instancing the same relative functions, were it not for its very dissimilar 

 appearance. It is often called, in ignorance,- a shell, thus oddly enough 

 associating to itself the English meaning of cochlea. It is to the diversity 

 of form in these bones I propose to direct your attention. 



There is much difference in opinion amongst anglers, whether fishes 

 really hear or not. One argues that they will almost listen to a 

 conversation about the bait and mode of attack, and act accordingly ; 

 whilst another lays too much stress on the vibration of the ground from 

 approaching footsteps, as the sole cause of taking alarm. That some 

 fishes have this sense very well developed has been fully proved, and 

 those persons who study the otoliths of purely fresh water fishes, such as 

 roach, tench, bream, or carp, will notice a complication of structure over 



