SEA-SNAILS AND SEA-SLUGS. 2OQ 



from the rock. Then is the time to take him unawares, and 

 force his foot from its firm hold. Having secured him, we 

 are at liberty to inspect the owner of this strange house, but 

 we can best do this by placing him in our clear glass bottle, 

 and letting him crawl up the side. 



That which is known as the mollusk's "foot" has no re^ 

 lationship with the feet of vertebrate animals, the name being 

 suggested by the similar use to which dissimilar organs are 

 put. We have already explained that the term gasteropod 

 signifies " belly-fcot," and if we were to cut through the " foot " 

 of the Limpet, we should find that it is indeed its belly, for it 

 contains the principal portion of its viscera. We are not going 

 into the anatomy of the mollusca, just now, but will confine 

 our attention to its exterior. It has now begun to climb up the 

 glass, and we can see that the foot is spread out so that it 

 occupies the greater portion of the area covered by the shell. 

 At the fore part it has a distinct head, with a pair of tentacles, 

 ditto eyes, and a very evident mouth, for the Limpet's principal 

 occupation appears to be to lick the surface upon which it is 

 gliding. Around the foot and the head there runs a frill which 

 is really the creature's breathing apparatus, and between that 

 and the shell there is, of course, the mantle by which the shell 

 was secreted, and is enlarged as occasion requires. The 

 Limpet is now in rapid motion, and we can see that it pro- 

 gresses in exactly the same fashion as do the garden snails 

 and slugs, that is, by a series of muscular contractions, evi- 

 denced by the constant ripple along the surface of the foot. 

 The foot exudes a very tenacious slime, which enables it to 

 obtain perfect contact with the surface over which it is gliding, 

 or upon which it is resting. It is perfectly astonishing how 

 much nonsense is still written in books upon this subject by 

 persons who ought to know better, and who could easily test 

 the correctness of their views by occasionally studying Nature, 

 instead of relying so much upon academical teaching, and 

 that of an antique character. Their statement is, that the 



