WILD LIFE OF ORCHARD AND FIELD 



[black] ball until it has been brought to within six 

 or eight inches of its eye-stalks. During the sea- 

 son of courtship snails easily perceive one another 

 at the distance of eighteen or twenty inches/' 



Organs of hearing exist in the form of little sacs 

 on each side of the subcEsophageal ganglia, con- 

 taining granules of lime (otoconites) which vibrate 

 in a clear liquid; but how sensitive these are to 

 sounds is not well known. 



The sense of taste may be present ; and that there 

 is a sense of smell is undoubted. It is probable, 

 indeed, that this sense is the most active and ser- 

 viceable of all the perceptions of these mollusks, 

 and it is believed to reside in the region of the mouth. 



Sensitiveness to touch is delicate in all parts of 

 the skin, which responds to the slightest irritation ; 

 yet little if anything is felt of what we call pain, 

 for a slug may be mutilated without exhibiting 

 any symptoms of painful disturbance, and a break- 

 ing of the shell is not only easily and frequently 

 repaired, but the loss of large parts of the body will 

 be quickly replaced. Spallanzani, whose experi- 

 ments with bats are celebrated, was the first to as- 

 certain that not only parts of the head, but even 

 the whole head, might be reproduced, although not 

 always. "It is well established by experiments 



294 



