436 ZOOLOGY. 



pani, above which is found a kind of vestibule filled with 

 liquid, and enclosing the termination of a special nerve. 

 Nothing is for certain known respecting the faculties of smell 

 and taste in these animals. 



565. Most crust acc;t live oh animal substances; but 

 they offer great differences in their regime; some live only 

 on liquid matters, others on solid food, and differen< 

 oWrvable in the construction of the mouth, corresponding 



Fig. 425.* 



to their varied circumstances. In the masticating Crustacea 

 there is before the mouth a short transverse lip, followed by 

 a pair of mandibles, a lower lip, one or two pairs of jaws, pro- 

 perly so called, and in general one or three pairs of auxiliaries 

 or limb-jaws, serving chiefly for the prehension of the food 

 (Fig. 123). In the Crustacea which live by suction, we find, 

 on the contrary, the mouth prolonged into a kind of beak or 



rboscis, resembling those insects whose habits are analogous, 

 the interior of this tube are slender pointed appendage-, 

 performing the functions of small lancets, and on either side 

 we find generally organs analogous to the auxiliary jaws of 

 the grinding Crustacea (crustacees broyeurs), but which are 

 formed to enable the animal to fix on its prey. 



566. The digestive canal extends from the head to the 

 posterior extremity of the abdomen, and is composed of a very 

 short gullet, a large stomach (e, Fig. 427), armed in general 

 internally with powerful teeth, a slender intestine, and a 

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

 vessels sufficiently resembling those of insects j but in general 



* Anterior portion of the inner surface of the body of a Crab (Maia) : ai, 

 internal antennae ; a, external antennae : y, eyes ; o, auditory organ ; m, 

 liml'-juws ; b, mouth ; p, base of the antenor limbs ; t, entrance to the res- 



("l.ai'irv i-avitv; , sternum. 



