Sensory Discrimination: Hearing 117 



kingdom, and the mineral bodies in the otocysts were 

 called otoliths. 



But experiments upon coelenterates have entirely failed to 

 show that animals of this class react to sounds (205, 741, 

 521). And in some coelenterates, as well as in higher 

 animals having the same type of organ, the removal of the 

 so-called otocysts has been found to mvolve disturbance of 

 the animal's power to keep its balance and maintain a 

 normal position. Hence Verworn has suggested that for 

 "otocyst" and "otolith" the terms "statocyst" and "stato- 

 lith" might appropriately be substituted (741). In 

 jelly^sh, indeed, even the balancing function of the stato- 

 cyst organs appears doubtful ; and it is possible that they 

 function in response to shaking and jarring (514, 521). In 

 any case, there is no evidence whatever of a specific auditory 

 sensation in the consciousness, if such exists, of coelenterate 

 animals. 



Nor has any reaction to sound been demonstrated in either 

 the flatworms or the annelid worms ; their sensitiveness to 

 vibrations seems to be an affair of mechanical stimulation. 

 Darwin's experiments on this point are well known. The 

 earthworms which he observed were quite insensitive to 

 musical tones, but when the flower pots containing their 

 burrows were placed on a piano, the worms retreated hastily 

 as soon as a note was struck (171). Most observers agree 

 that moUusks also react only to mechanical jars {e.g., 190), 

 and that the statocyst organs found in some mollusks have 

 no auditory function. Batesen, however, records that a . 

 certain lameUibranch, suspended by a thread in a tank, re- 

 sponded by shutting its shell when a sound was produced 

 by rubbing a finger along the glass side of the tank (25). 

 The echitioderms are apparently insensitive to auditory 

 stimuli (617, 641). 



