SEA-FISHERTES LABORATORY. 387 



oesophageal glands. In the cardiac region of the fore-gut 

 the food is broken up in a very effective manner. Passing 

 back into the pyloric chamber, the food encounters the 

 cardio-pyloric valve. Here the large pieces are prevented 

 from passing into the pyloric chamber. The food which 

 passes into the latter chamber probably undergoes a 

 further process of sifting 1 , the useless material passing 

 along the dorsal portion of the pyloric chamber and the 

 food being passed along the ventral portion. In this 

 ventral region the food first comes into contact with the 

 digestive ferments. Both are well mixed by the action 

 of the muscles of the pyloric chamber. 



As already stated, the probable regions of absorption 

 are the mid-gut, mid-gut caeca and the tubules of the 

 digestive gland. The waste products pass down the long 

 hind-gut to the exterior. 



Ossicles of the Fore-Gut. 

 (PI. VI, figs. 40, 41, 43, 44.) 



In certain regions of the fore-gut the chitinous lining 

 is thickened and strongly calcified to form ossicles. These 

 ossicles give attachment to muscles. One set of ossicles 

 in the dorsal and lateral walls of the cardiac region are 

 connected with three tooth-bearing ossicles. This system 

 of plates which is worked by the anterior and posterior 

 gastric muscles (see section on Muscles of the Fore-gut) 

 forms a very effective apparatus for breaking up the food 

 which has passed into the cardiac fore-gut. Hence the 

 name gastric mill. 



In addition to the ossicles of the gastric mill there 

 are " supporting ossicles }■. in both the cardiac and pyloric 

 regions. To these supporting ossicles are attached the 

 various muscles of the fore-gut. 



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