238 



MOUTH AND DIGESTIVE APPARATUS OF CRUSTACEA. 



(Fig. 580). In suctorial Crustacea, on the contrary, the mouth 

 is prolonged into a sort of beak, or trunk, as we have already- 

 seen in Insects of the same habits. In the interior of this tube, 

 we find thin and pointed appendages, which perform the office 

 of little lancets ; and on each side we commonly see organs, 

 which are analogous to the auxiliary jaws of masticating Crus- 

 tacea, but which are so formed as to serve to fix the animal on 

 its prey. 



851. The digestive canal extends from the head to the pos- 

 terior extremity of the abdomen ; and is composed of a very 

 short oesophagus, a large stomach (e, Fig. 572) generally armed 

 interiorly with powerful teeth, of a small intestine, and of a 

 rectum. In some Crustacea, the bile is secreted by biliary 



fo 



FIG. 572. ANATOMY OF A CRAB ; the greater part of the carapace having been 

 removed; p, portion of its lining membrane ; c, heart ; a*, ophthalmic artery ; aa, abdo. 

 minal artery ; b, branchiae in their natural position ; b', branchias turned back to show 

 their vessels ; fl, lower portion of the shell ; /, appendage of the foot-jaw ; e, stomach ; 

 m, muscles of the stomach ; fo, liver. 



vessels, like those of Insects ; but in general there is a very 

 voluminous liver, divided into several lobes, and composed of a 



