HOW SNAILS EAT 



After we had examined and studied the aquarium and snailery 

 to our satisfaction, Professor Parker remarked that he was ready for 

 the work of the evening, which was to prepare and examine some 

 of the teeth on the radula, or tongue, of snails. 



Selecting a good sized specimen from a number which had been 

 drowned the day previous, he showed us the oval mouth on the under 

 side of the head, with the jaw and radula protruding. " The radula," 

 he explained, u is inclosed in a rounded body called the buccal sac, 

 which is placed at the fore 

 part of the body, in the 

 lower plane of the head. If 

 we were to cut a section 

 through the head and 

 buccal body, it would pre- 

 sent the appearance shown 

 in this diagram which I 

 have prepared for you. In 

 some snails, as the apple 

 snail, the radula sac is 

 placed at the end of a re- 



gus: 2, radula; 3, core of radula; 4, new teeth forming; 



tractile rostrum, or pro- 5, cartilaginous substance beneath the radula, serving 



, . for support and for the attachment of muscles; 6, pos- 



boscis. I he apparatus IS terior cartilage muscles; 7, anterior cartilage muscles; 



nrntmsilp a n rl rn a v IIP 8, cartilage bearing jaw; 9, jaw; ;10, outer surface of mouth; 



protl 6, an nay ll, upper lip; 12, lower lip; 13, under surface of hp; 14, 



plainly seen when a snail orifice of mucous glands; 15, mucous glands; 16, mouth; 



J m 17, cells lining under surface of radula. 



is feeding. 



" The radula, or lingual ribbon, sometimes called the odontophore, is 

 a strap of chitinous, or horny matter, and occupies a place in the mouth 

 of a snail analogous to that occupied by the tongue in the cat and dog. 

 It is formed in the radula sac, and grows forward as needed, much as 

 does the human finger-nail. Just beneath the radula there is a stout car- 

 tilage to which are attached protractor and retractor muscles which move 

 the cartilage backward and forward. The radula is strongly fastened 

 to this cartilage at the anterior end. The forward action of the carti- 

 lage muscles brings the radula down between the two fleshy lips, where 



39 



Diagram of buccal organs of land snail. 1, resopha- 



