their Food and Digestive Organs. 



77 



Fig. 7., 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 ; h h, salivary glands, the 

 parts are laid open. — Fig. 8., Alimentary canal of the Pleurobranchus : a, first stomach j 

 c, second stomach j d, third stomach ; e, fourth stomach. — Fig. 9 , Alimentary canal of the 

 Patella : a, the mouth j b, the buccal mass ; c, the tongue ; d, the stomach ; e e, the intes- 

 tine. 



chus {Jig. 8**); and, again, contrast these with the same 

 parts in Patella {Jig. 9.). That these contrasts in structure 

 are accompanied with decided peculiarities in the quality of 

 food, can scarcely be doubted ; but we know nothing of what 

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

 even add, their kind of food, are almost conjectural. Blain- 

 ville gives it as his opinion, that all the species destitute of 

 jaws must swallow soft and decayed vegetable and animal 

 matter : being, by their structure, incapacitated from chewing 



* " In the Pleurobranchus the oesophagus dilates into a membranous 

 crop {fig- 8. a), at the lower part of which (b) the bile is poured in. It 

 communicates by a narrow cardia with the second stomach (c), which is a 

 gizzard with thin but muscular parietes. The third stomach (d) is mem- 

 branous, and precisely resembles the plicated stomach of ruminants, in 

 being disposed in large but delicate folds, by means of which the alimentary 

 matter contained in it is moulded into long whitish cords. The fourth 

 stomach (e) is membranous, like the crop, but smaller. It is remarkable 

 that the gizzard contains a narrow groove running through its whole 

 length, leading from the first to the fourth stomach, and probably subser- 

 vient to a species of rumination." (Carus, Comp. Anat. } trans., ii. 10.) 



