CLASS CRUSTACEA. 3 1 



Let us now briefly look at the varioi:s appendages 

 carried on tliese segments, beginning at the head. 



The first segment carries a pair of eyes, which are of 

 large size and globular shape, and are supported upon 

 movable stalks. The Lobster can thus roll the eyes about 

 in different directions ; and the eyes themselves are what 

 is called "compound," each being composed of numerous 

 simple eyes amalgamated together. The eyes also are 

 protected in part by a great jagged spine or beak de- 

 veloped from the front of the shield which covers the head. 



The second ring carries a pair of feelers, which are 

 double, and composed of numerous joints (fig. 12, a). 

 From their small size, these are known as the " lesser 

 antennae" (Latin, antenna, the yard-arm of a ship). 



The third ring carries another pair of feelers («'), which 

 are known as the "great antennae," from their large size. 

 They are composed of numerous joints, like the preceding, 

 but each consists of no more than a single branch. 



ThQ fourth, fifth, sixth, and seventh segments carry each 

 a pair of jaAvs, differing somewhat in each segment, and 

 the last pair so closely approaching the true legs or " feet " 

 in structure as to receive the name of "foot-jaws." All 

 these jaws move from side to side, and are really to be 

 regarded as modified limbs. 



The eighth and ninth rings (being the first two rings of 

 the thorax) carry, each, another pair of lunb-like jaws or 

 "foot-jaws," the last pair of these (fig. 12, n) being of 

 large size and c^uite like legs. 



The tenth, eleventh, twelfth, thirteenth, and fourteenth 

 segments carry five pairs of legs, which the animal uses 

 partly in walking and partly for grasping. The first pair 

 of these legs is greatly developed (fig. 12, c), and consti- 

 tutes a pair of great pincers or "nipping-claws." One 

 claw is blunt, and is used chiefly for holding on to foreign 

 objects, and the other claw is sharply serrated, and is 

 used by the animal for biting or cutting up its food. The 

 second and third pairs of legs {d and e) also terminate in 

 nipping-claws, but these are quite of small size. The 

 fourth and fifth pairs of legs are provided with simply 

 pointed extremities. 



