SENSES UEARING. 199 



some experiments, I found that Snails (Helix nemoralis) are 

 not affected by loud and harsh noises about them ; nor are 

 the Periwinkle and Whelk (Purpura lapillus) more suscep- 

 tible in this respect. It is aliirmed, however, by the Rev. L. 

 Guilding, that the Strombidas possess the sense of hearing, 

 or something allied to it. " I lately suspended," he says, 

 "a number of large Strombi by the spire, that the animal, 

 when dead, might fall from the shell. They had remained 

 in this situation several days, till the body, weak and 

 emaciated, hung dowai nearly a foot from the aperture, and 

 the eyes had become dim. I found that even before my 

 shadow could pass over them, they were aware of my 

 presence, and endeavoured to withdraw into the shell. I 

 then cut off the eyes, with the thick cartilaginous tentacula 

 in which they were lodged, but the animals still continued 

 to be sensible of my near approach, while hanging in this 

 mutilated and painful condition."* The experiment is not 

 conclusive, nor does it appear indeed that any noise was 

 made. The impression which gave the alarm might perhaps 

 be from the pulses of the atmosphere, thrown into motion 

 by the approach of the experimenter, and acting on a skin 

 morbidly sensible. On a summer evening I have observed 

 the common Spout-fish (Solen siliqua), extended along the 

 surface of the fine sand in which they burrow, enjoying 

 apparently the calmness and mildness of the season, take 

 alarm and instantaneously descend when I was yet distant 

 several yards : and I can explain this and similar facts only 

 on the supposition of the existence of a sense of touch 

 feelingly alive to impressions impalpable to our grosser 

 sense. " In the case of many animals," says Muller, " it 

 may be doubted whether they really hear at all : for every 

 reaction of nerves under the influence of vibrations cannot 

 be called the sensation of sound, since the sense of touch is 

 capable of perceiving the same vibrations as a tremor. "f 



Thus we explain the fear which was anciently ascribed 

 to the pearl-mussels during the thunderstorm, when they 

 were so shaken " with the feare of flashie lightenings," that 

 they cast their pearls and became " emptie ; " and thus, also, 

 we explain a fact mentioned by Baster, who, on the autho- 

 rity of the seamen engaged in cari'ying mussels to Holland, 

 tells us that these shell-fish are grievously aflected by any 

 violent motion and concussion of the air ; for if the ship 

 is overtaken by a thvmdcrstorm, or sails too near any other 

 vessel which at the moment discharges its guns, the mussels, 



* Zool. Journ. iv. 172. t Physiology, trans, p. 1129. 



