202 



THE SCIENCE OF LIFE. 



The mouth of Gasteropods possesses a peculiar strap- 

 like organ, the odonto- 

 phore, (pdous, tooth ; phero, 

 I bear.) It is studded with 

 three or more rows of lin- 

 gual teeth, formed of sili- 

 ca, which are the serrated 

 edges of minute plates, the 

 number of which varies in 

 different species; the gar- 

 den Slug has one hundred 

 rows with one hundred 



o/-J <irrV4"tr f*a<fVi in e*ir\\ 



FIG. too. 



structure of tentacles: a. Right inferior ten- j-QW. (Fig". IOI.) The Strap 

 tacle retracted within the body. b. Right su- ' \ S* V 



perior tentacle fully protruded, c. Left superior or " tOngUC," playS OVCr 3. 

 tentacle partially inverted, d. Left inferior 



tentacle. /. Optic nerve, g. Retractor mus- CartilaginOUS Cushion, Of 

 cle. k. Optic nerve in loose folds. /.Retractor . . . . , 



muscle of head. *. Nerve and muscle of left pulley, Connected With the 



lower jaw, and the teeth 

 are renewed by fresh growths 

 from the membrane beneath. 

 The gullet is long, and frequent- 

 ly expands into a crop ; the 

 stomach is often doable, the an- 

 terior being a gizzard provided 

 with teeth for mastication ; the 

 intestine passes through the liv- 

 er, and ends in the fore part of 

 the body, usually on the right 

 side. The heart is double, and 

 FIG. loi. Palate of Buccinum a capillary system intervenes be- 



undatum, as seen under polarized 



light. tween the arteries and veins, but 



inferior tentacle. /. m. Nervous collar. 



