198 SENSES HEARING. 



a strong pressure, the otolites crack in radiating lines, sepa- 

 rating often into four pyramidal pieces. This separation 

 also ensues, after a longer time, when the otolites are im- 

 mersed in a diluted uitric acid ; and if we touch them with 

 the concentrated acid, they suddenly dissolve witli the disen- 

 gagement of a gas, whence Siebold concludes them to be 

 composed of carbonate of lime. The size of the otolites 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 otolites in the centre have the appearance of 

 being pressed together so as to form a sort of solid nucleus ; 

 and towards this centre the otolites towards the circumfe- 

 rence seem ever to be violently urged, their centripetal rush 

 being invariably repulsed, and as often driven again into a 

 centrifugal direction. Removed from the capsule, the mo- 

 tions of the otolites instantly cease. The cause of these 

 curious oscillations remains undiscovered. Siebold could 

 detect no vibratile ciHa on the surfaces of the capsule ;* and 

 the cessation of the motion when the otolites are removed 

 proves them to be unciliated themselves, and, at the same 

 time, distinguishes the motion from that of inorganic mole- 

 cules as described by Mr. Brown, j- 



And in these discoveries you have a lively example of the 

 nicety of anatomical researches in our times. In my student 

 days, it was questioned whether any mollusk besides the 

 cuttles had eyes ; J and it was agreed on all hands that they 

 were earless and surd.§ Behold the change a few years has 

 made in our knowledge of this branch of physiology ! They 

 have eyes and they see ; and ears have they, yet, from the 

 very rudimentary condition of the organ, it is adapted to 

 communicate to the possessors only the most limited jier- 

 ception of sonorous undulations. Amusing myself with 



* '' Kolliker has observed, that the motion of the otolites in the mollusca 

 is dependent npon cilia, with which the internal surface of the cyst is cover- 

 ed." — Reports on Zoology for 1843-4, printed for the Ray Society, p. 216. 



t Observations sur I'Organe Auditif des Mollusques, par C. Th. V. Sie- 

 bold, in Ann. des Sc. Nat. (1843), xix. p. 193—211. 



X " Vermium genus omne oculis caret ; Plin. nisi forte Sepia ejvisque 

 Cymbium. Limaces videntur etiam oculis instructi, modo veri sint oculi, a 

 nostris certe diversi." — Linn. Sijst. Nat. 1069. 



§ " None of the mollusca appear to possess, even in the smallest degree, 

 the sense of hearing, if we except the highly organized Cephalopoda." — 

 Roget's Bridgew. Treat, ii. 436. 



