278 SNAILS AND SLUGS 



consisting of twelve reels of cotton, a pair of scissors, a 

 screw-driver, a key, and a knife, weighing in all seventeen 

 ounces, or more than fifty times its own weight. As 

 Mr. A. H. Cooke observes in recording this feat, it was 

 as if a twelve-stone man had drawn a load, not on 

 wheels, of three and a half tons. 



While some molluscs (Pelecypoda) have dispensed with 

 a head, and get on very fairly without it, all our land 

 molluscs have retained that organ, and some of them 

 put it to good use. Darwin quotes the instance of two 

 snails (Helix pomatia) which were placed in a small 

 garden where there was no suitable food. One of these 

 snails was sickly; the other climbed the wall into the 

 next garden, where food was abundant. Nobody expected 

 to see it back; but, behold! it returned in twenty-four 

 hours to its invalid mate, whom it induced to start at 

 once for the land of plenty. Here we have evidence of 

 tjogitation, resolution, memory, sense of direction, and 

 affection, or at least solicitude for the welfare of another. 

 And such solicitude is the more disinterested, in that 

 every individual Helix consists of a complete domestic 

 establishment in him — her — its — self. That is to say, it 

 is hermaphrodite ; and although snails comply so far 

 with convention as to pair regularly, the close of the 

 honeymoon is marked by both parents setting to work 

 to see which can lay most eggs. 



Many species of slug possess the faculty of spinning 

 threads of their own mucus or slime, which they use 

 in a manner which it is difficult to dissociate from 

 intelligence. • The tree slug {Limax arborum) not only 

 can let itself down from branch to branch by means of 

 such a thread, but can ascend again to the place whence 



