CRABS, HERMIT-CRABS, AND OTHER CRUSTACEANS. 141 



pairs of claws of the lobster, and in studying the crustaceans 

 generally an infinite variety of modification will be found in 

 these parts. In the crab which is so much sought after for 

 food, and which is known as the soft-shell crab (a condition 

 which indicates that the crab has just moulted, or shed its 

 hard shell), the hinder pair of legs have the last or terminal 

 joints flattened, and these flattened joints are used as fins by 

 means of which the creature swims through the water. 



FIG. 130. EIGHT HIND-LEG OP THE EDIBLE CRAB. 



The above figure shows the appearance of the right 

 hind-leg of one of these crabs. Compare this with the com 

 mon crab shown in Fig. 128. 



130. A curious little crab, called the oyster-crab, makes its 

 home within the shell of the oyster, living in the gill-cavity 



FIG. 131. OYSTER-CBAB. The Tail is hidden beneath the Body, one Segment only showing. 



of the animal. Specimens may sometimes be found in 

 canned oysters, and, to those who do not have access to the 

 sea-shore, these creatures will furnish objects from which 

 an idea of the crabs or short-tailed crustaceans may be 



