Crustaceans . 



45 



is earned bent below the carapace, although not fitting into a 

 groove as in the Brachyura. Other forms of this group bear a 

 strong resemblance to the true crabs. On lifting up stones 

 on a rock)' coast we cannot fail to come across the little creatures 

 known as Porcelain Crabs {Porcellana flatychelcs) in which the 

 appearance is absolutel)' Brachyurous (Fig. 47) ; yei, if the 

 abdomen be spread out, it will be found to terminate in a tail-fan 

 as in the Macrura, and the peculiar reduction of the fifth pair of 

 legs is carried so far as to con\'ey the impression, at first sight, 

 that only three pairs of legs are present in addition to the large 

 flattened pincers. The porcelain crab exhibits very well the 

 phenomenon knov.ii as self-mutilation or autotomy, which is 

 common to many Crustaceans. When disturbed it takes up a 

 quite pugna- 

 cious attitude, 

 raising its 

 pincers ; if, 

 howe^•er, one 

 of these be 

 seized, it is 

 promptly cast 

 off while the 

 crab, thus re- 



t'lG. 47. PORCELLANA PLATY- 



CHELES (after BELL). 



FIG. 48. COMMON HERMIT 



CRAB (after bell). 



leased, makes its escape, and, in the course of time, regenerates 

 the voluntarily amputated limb. When the hmb of a crab 

 IS injured at some point it is cast oft by a sudden jerk, to provide 



