MOLLUSC A: THEIR EARS 73 



tion also ensues, after a longer time, when the otolithes 

 are immersed in diluted nitric acid ; and, if we touch them 

 with the concentrated acid, they suddenly dissolve with the 

 disengagement of a gas, whence Siebold concludes them 

 to be composed of carbonate of lime. The size of the 

 otolithes is not equal, and in the same capsule there are 

 always some which are smaller than others. "Within the 

 capsule they have, during life, a very remarkable, and in 

 some respects peculiar, lively, oscillatory movement, being 

 driven about as particles of any light insoluble powder 

 might be in boiling water. The otolithes in the centre have 

 the appearance of being pressed together so as to form a 

 sort of solid nucleus, and toward this centre the otolithes 

 toward the circumference seem even to be violently urged, 

 their centripetal rush being invariably repulsed, and as 

 often driven again into a centrifugal direction. Eemoved 

 from the capsule, the motions of the otolithes instantly 

 cease. The cause of these curious oscillations remains un- 

 discovered. Siebold could detect no vibratile cilia on the 

 surfaces of the capsule, and the cessation of the motion 

 when the otolithes are removed proves them to be uncili- 

 ated themselves, and, at the same time, distinguishes the 

 motion from that of inorganic molecules. 



It has been more recently ascertained that the move- 

 ments of the otolithes are due to very minute cilia with 

 which the interior surface of the capsule is -covered. This 

 had been long suspected, and some eminent physiologists, 

 as Wagner and Kolliker, have distinctly seen the cilia 

 themselves. 



If you ask what can be the use of ears to a class of 



animals which are invariably dumb, I answer that though 

 15 SCIENCE 4 



