736 



THE NATURE BOOK 



edges of this organ the shell is built and 

 extended as growth takes place. Like- 

 wise, when the gardener gives the snail 

 a chop with his spade and smashes its 

 shell, or throws it forcibly against the 

 wall for the same purpose, from this mantle 

 oozes out the repairing fluids, and so the 

 snail becomes its own surgeon, joins up 

 its broken parts and carefully cements 



PORTION OF TONGUE OF EDIBLE SNAIL 

 (HELIX POM ATI A). 



The tonjiue of the Roman or Edible Snail possesses 140 

 rows of minute teeth. The total number of teeth is 

 more than 20,000, and these form a rasp that can in- 

 flict serious damage upon garden products. 



them together again. Then once more it 

 goes on its way rejoicing to take toll from 

 the lettuce plot, or, perhaps, to make one 

 of its destructive forays amongst the 

 young and juicy flower seedlings, and 

 so recoup its strength ; thus squaring 

 accounts with the gardener for the injury 

 he inflicted. 



Turning to the senses of the snail, it 

 is obvious that its sense of touch is very 

 keen. It will only emerge from its 

 shell in the cool of the evening when 

 moisture and dew begin to accumulate, 

 or after a shower when everything is 



damp, for moisture is essential to its 

 welfare. When kept quite dry it will often 

 remain sealed up in its shell for weeks 

 and months at a time, showing no sign 

 of life. A little water sprinkled round 

 about it, however, quickly causes it to 

 detach itself from the tree or wall to 

 which it has been clinging, and to glide 

 forth in its slow and dignified manner, 

 first extending its head slightly, and then 

 its great stomach-foot, after which appear 

 the two long " horns," quickly followed 

 by the lower and smaller pair. 



It is at the moment when the longer 

 pair of feelers are extended, that the 

 snail takes a peep to see if all is well, for 

 the tiny black specks seen at the tips of 

 the " horns " are its eyes. They wave 

 gently to and fro, but at the shghtest 

 danger are retracted into the feelers, and 

 the feelers into the head. Just what kind 

 of a view of its surroundings the snail 

 receives by means of its elevated eyes, 

 we are quite unable to understand. 

 Experiments tend to show that it is very 

 short-sighted. The fact, too, that the 

 retina is very close to the spherical lens, 

 would also point to the same conclusion. 



Near the eyes, on the tips of the feelers, 

 are some curious minute skin cells, which 

 are said to possess olfactory functions. 

 The gleaming night -tracks made by the 

 snail over the garden wall to some favourite 

 feeding haunt, may, perhaps, be taken 

 as e\ddence that the snail possesses 

 a keen sense of smell. A snail will 

 climb the bark of a tree, or a wall, night 

 after night, to reach ripe plums, or other 

 fruit, returning to its regular hiding- 

 place behind the ivy, after its meal ; 

 for snails undoubtedly possess a strong 

 homing instinct. 



Furthermore, if, when a fully developed 

 snail is seen approaching a ripe pear or 

 plum, the fruit is suddenly removed, the 

 snail will stop short and quickly extend 

 and wave its feelers, as if trying to locate 

 the scent of it. If the fruit is then put 

 in a different place, the snail will often 

 steer directly towards it. Such evidence 

 would seem to prove that the snail pos- 

 sesses very sensitive olfacttn'y organs ; 

 but that conclusion does not necessarily 

 follow. The snail may be guided by 

 something other than the sense of smell. 

 If it is that, its olfactory senses are much. 



