330 



PHYTIVOROUS MOLLUSCA. 



companied with decided peculiarities in the quality of food, 

 can scarcely be doubted ; but we know nothing of what 



Fig. 64 



Fig. 66. 



Fig. 64. Alimentary canal of the Tethys: a, the proboscis; b, the oesophagus ; c, 

 the stomach ; d, the intestine ; e, hepatic duct ; /, the liver ; g, hepatic artery ; 7i, h, 

 salivary glands : the parts are laid open. — Fig. 65. Alimentary canal of the Pleuro- 

 branchus: a, first stomach ; c, second stomach ; d, third stomach ; e, fourth stomach. 

 — Fig. 66. Alimentary canal of the Patella : a, the mouth ; b, the buccal mass ; c, 

 the tongue ; d, the stomach ; e, e, the intestine. 



these peculiarities are : their manner of feeding, and, we 

 may even add, their kind of food, are almost conjectural. 

 Blainville gives it as his opinion, that all the species desti- 

 tute of jaws must swallow soft and decayed vegetable and 

 animal matter : being, by their structure, incapacitated from 

 chewing a fresh material.* But the conclusion is a hasty 

 one ; for I, at least, am not inclined to attach that value to 

 deductions of this kind which many seem to think they 

 merit. The Aplysia has very small obtuse mandibles, of a 

 soft cartilaginous substance ; yet that mollusck eats its sea- 



that the gizzard contains a narrow groove running through its whole length, 

 leading from the first to the fourth stomach, and probably subservient to a 

 species of rumination." — Carus, Comp. Anat. trans, ii. 10. 

 * Man. de Malacol., p. 177. 



