272 



THE SEA SHORE 



is surrounded by its own ring of the hardened integument, and is 

 connected with its neighbours by means of a portion of uncalcified 

 skin that renders the whole very flexible. A groove in the front 

 portion of the great shield (carapace) marks the division between 



the head and the thorax, the 

 former composed of six, and the 

 latter of eight united segments. 

 The calcareous covering of 

 each segment consists of an 

 upper portion, called the tergum, 

 and a lower, named the sternum, 

 united at the sides ; the sternal 

 portion of the cephalothorax, 



FIG. 204. A SEGMENT or THE 

 ABDOMEN OF A LOBSTER 



t, tergum : *, sternum, bearing a pair of 

 swimmerets ; A, bloodvessel ; d, diges- 

 tive tube ; n, nerve chain 



which gives attachment to the 

 walking limbs, is a most com- 

 plicated and beautifully formed 

 structure. 



The six pairs of appendages 

 belonging to the head are easily 

 made out with a little care. The 

 first are the jointed eye-stalks 

 that bear the compound eyes pre- 

 viously described ; and these are followed by two pairs of antennce, 

 or feelers, the first being shorter and double, while the second 

 are very long. The former contain the organs of hearing. Then, 

 in front of the mouth, and completely hiding it, are a pair of 



FIG. 203. PARTS OP LOBSTER'S 

 SHELL, SEPARATED, AND VIEWED 

 FROM ABOVE 



