ORUSTACEOUS ANIMALS. 



399 



the shell is restored, which is effected by a deposition of calcareous 

 matter on the external membrane of the skin. They all also pos- 

 sess the curious power of reproducing a lost or injured limb. In 

 the former case, a fresh limb supplies the place of that lost; and 

 in the latter case, the animal itself shakes off the injured joint, 

 and a new one soon takes its place. Lobsters, when alarmed, fre- 

 quently throw off their claws. 



In some of the Crustacea, near the lower end of the stomach, 

 where it begins to narrow, are situated a number of teeth, or sub- 

 stances of a bony nature resembling teeth, usually five in number, 

 placed upon the opposite sides of the organ. These, being moved 

 by muscles attached to them, thoroughly grind the food passing 

 between them, which is then discharged through an orifice into 

 the intestines. 



Ordinarily the animals of this class reside in the water, 

 though some few are found upon the land. Upon being taken 

 from the water, the former do not immediately die, but live for 

 some time thereafter. Their flesh furnishes a very delicious food, 

 but it is heavy and very diificult of digestion. 



The Common Crab 

 is abundantly taken on 

 our coasts by fishermen, 

 who employ for its cap- 

 ture a wicker basket 

 called a " creel " or crab- 

 pot. The crab-pots are 

 made each with an aper- 

 ture which permits the 

 animal to enter, but for- 

 bids its egress — just like 

 a common wire mouse- 

 trap. A piece of a fish 

 is fastened at the bottom 

 of the creel, and the whole apparatus let down to the bottom of 

 the water, guarded by a line connected with a float, by means of 

 which the fishermen draw it up and then remove its contents. 



Crab. 



