LOBSTER. 71 



Diagram of the oesophagus and stomach as they 

 would appear if seen from the side. Observe : 



3. Posterior to the stomach on each side a large, 



soft, brown or greenish-yellow structure, the 

 digestive gland. 



Gently pushing it with the handle of a scalpel away 

 from the middle line, find : 



4. The duct of the digestive gland of that side, 



a short, wide, thin-walled tube which enters 



the part of the alimentary canal, the mesen- 



teron, immediately posterior to the stomach. 



Removing tJie reproductive organs and the digestive 



gland , and separating the muscles of the abdomen 



in the median line, find : 



5. The intestine : a straight tube leading from 



the mesenteron to the anus. 

 Finish the diagram of the digestive system. Cut 

 with fine scissors through the oesophagus close 

 to the stomach, and through the intestine, and 

 take out the stomach. Open the stomach and ex- 

 amine : 



6. The arrangement of the gastric teeth. 

 IV. Excretory System. 



In the extreme anterior part of the cephalic 



cavity on each side. 



1. Paired, delicate, greenish structures, the ex- 

 cretory organs (green glands). 

 (For the external openings see A. IV. 2.) 



