A Typical Univalve Mollusk 



Hearing is a very poorly developed sense in mollusks. Its 

 special organ has been discovered in many genera of univalves 

 and bivalves. A pair of sacs filled with liquid in which micro- 

 scopic pebbles float, have nerves connecting them with the cere- 

 bral ganglia. There is no denying the auditory function of these 

 organs. As they are imbedded in the tissues, the vibrations re- 

 ceived are modified by the medium of the flesh through which 

 they pass. Possibly such impressions ought not to be called sound, 

 but touch, instead. 



Taste as a special sense may exist, with nerve ends in the 

 pharynx or back of the mouth. 



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