208 ELEMENTARY BIOLOGY. [CHAP. 



a. The stomach ; it is marked off by a transverse con- 

 striction into a large cardiac chamber and a small, 

 posterior, pyloric one. 



b. The intestine, a straight tube leading back to the 

 anus; its wall is thrown into a series of shallow 

 folds, which take a longitudinal and slightly spiral 

 course. 



c. The ccecum ; a median dorsal upgrowth, immediately 

 behind the stomach. It is directed obliquely for- 

 wards. 



In the Lobster, this is situated far back, near the 

 anus. 



2. Some small muscles will be seen attached to the roof 

 of the stomach. Remove these. In doing so, note 

 that there comes away with them the soft cellular wall 

 of the viscus, under cover of which there is seen a 

 chitinous lining. Examine the latter with care ; it will 

 be found to be calcified to form a series of ossicles, 

 related as under. 



a. The antero-dorsal (cardiac) ossicle ; a transverse bar, 

 extending across the roof of the cardiac chamber. 



b. The postero-dorsal (pyloric) ; similarly related to the 

 roof of the pyloric chamber as is a to that of the 

 cardiac one. 



c. The antero-lateral (lateral-cardiac) ossicles; two 

 small hammer-shaped pieces, abutting, one on either 

 side, against a. 



d. The postero-lateral (lateral-pyloric) ; two long bars, 

 similarly related on either side to b as are c to a. 



They extend forwards to meet the antero-lateral 

 ossicles. 



