JOURNAL OF CONCHOLOGY. 239 



HOW DOES A SNAIL CRAWL? 



By ROBERT F. SCHARFF, Ph.D., B.Sc. 



Museum of Science and Art, Dublin. 



I SUPPOSE Conchologists have oftentimes been puzzled by this 

 question. Does a snail wriggle along the ground like a worm 

 or a snake ? If this were the case we should be able to see a 

 series of wrinkles appearing upon the sole of the foot. Indeed 

 if we allow a snail to crawl on an inverted sheet of glass, so as 

 to enable us to look at it from underneath, we fancy to perceive 

 a faint indication of these wrinkles in shape of a number of 

 dark bands or waves travelling slowly from behind forward. 



The general notion is that the mechanism of locomotion in 

 the snail is essentially the same as that in many footless larvse 

 of insects, with the difference that the number of wave motions 

 produced by the foot is much greater, and that the attachment 

 of the sole to the foreign body is much firmer. As I said, the 

 waves which we recognise on the sole seem to strengthen this 

 view at first sight. However, if we examine the phenomenon 

 more closely, we find that the foot of the snail is intimately 

 attached to the glass and that the waves do not appear between 

 the sole and the glass, but in reality inside the foot, producing 

 no change of form on its surface. Hence we must look for 

 another explanation. 



There can be no doubt that the locomotion of a snail, such 

 as Helix aspersa, for instance, originates in the waves which we 

 see gliding along the foot. The animal moves as long as the 

 waves last. As soon as the play of waves disappears, the 

 motion also ceases. 



In order to obtain an interpretation of the significance of 

 these mysterious waves, a study of the anatomy of the foot is 

 requisite. Simroth is the only Zoologist, to my knowledge, 



