320 ELEMENTARY BIOLOGY. [CHAP. 



C. The alimentary organs. 



1 . Remove the valve, mantle-lobe, gills and labial-palps 

 of the left side, and open up the pericardium. 



Pin down under water (preferably without remov- 

 ing the right valve) and dissect away the body -wall; 

 the coils of the intestine will come into view, two 

 which lie parallel to one another at the posterior 

 end of the body, being probably those first seen. 

 Note, lying within the body- 



a. The digestive gland ; a large greenish-brown mass, 

 filling the interspace between the anterior adductor 

 muscle and the pericardium. 



b. The reproductive gland ; a yellowish-white mass 

 lying around the coils of the intestine, and filling 

 the greater portion of the body-cavity. 



2. Remove one half of the digestive gland piecemeal 

 and pick away the reproductive gland, until as much 

 as possible of the course of the intestine is exposed. 

 Work out the whole alimentary tube in detail, com- 

 mencing at the mouth; examine in order 



a. The gullet; a spacious tube lying immediately 

 behind the anterior adductor muscle; it runs 

 upwards and backwards to enter 



b. the stomach, a large irregular sac lying immediately 

 in front of the pericardium. 



Both a. and b. are buried up in the substance of 

 the digestive gland ; the ducts of this will be seen 

 opening into b. by a series of very large orifices. 

 Examine the relationship of one or more of these 

 to the lobes of the gland itself. Cf. Sec. L. d. 



c. The intestine. It arises by a wide aperture from 

 the floor of the stomach; insert a scissors blade 



