THE ALIMENTARY CANAL, 



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FIG. 45. Anatomy of a Gasteropod (Snail): a, mouth; b, foot; e, anus; d, lung; e, 

 stomach, covered above by the salivary glands; /, intestine; g, "liver"; k, heart; 

 i, aorta ; j, gastric artery ; k, artery of the foot ; I, hepatic artery ; m, abdominal 

 cavity, supplying the place of a venous einus; n, irregular canal communicating 

 with the abdominal cavity, and carrying the blood to the lung ; o, vessel carry- 

 ing blood from the lung to the heart. 



by a narrow "pyloric" orifice, or valve, but is not so clearly 

 distinguished from the gullet, so that regurgitation is easy. 4 * 



h i k 



8 I k r b 



FIG. 46. Anatomy of a Lamellibranch (Mactra) : a, shell ; 6, mantle ; c, tentacles, or 

 lips; d, mouth : e, nerves ; /, muscles; g, anterior, and n, posterior ganglion; h, 

 "liver"; i, heart; k, stomach; I, intestine passing through the heart; m, kid- 

 ney; o, anal end of the intestine; p t exhalent, and g, iuhaleut respiratory tubes, 

 or siphons ; r, gills ; , foot 



6 



