474 NATURAL HISTORY. 



Their method of growth is very curious. Other animals as 

 they increase in size experience no particular inconvenience 

 Not so the Crustacea. Their bodies are closely enveloped in a 

 strong, unyielding mail, which cannot grow with them. Their 

 armour is therefore cast off every year, .and a fresh coat formed 

 1o suit their increased dimensions. Not only is the armour 

 cast off, but even the covering of the eyes, the tendons of the 

 claws, and the lining membrane of ike stomach, with its 

 teeth. 



They all also possess 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, frequently throw off their claws. 



The Decapods, as their name imports, are the fortunate 

 possessors of ten legs, five at each side. They also possess 

 three pairs of jaws, besides the teeth in the stomach. They 

 breathe by means of branchiae or gills, fixed at each side of 

 the throat, or chest, often erroneously called the head.* 



The COMMON CRAB belongs to the short-tailed Decapods. 

 It is abundently taken on our coasts by fishermen, who employ 

 for its capture a wicker basket called a " creel" or crab-pot. 

 The crab-pots are made each with an aperture which permits 

 the animal to enter, but forbids 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 sea, guarded by a line connected with a float, by means 

 cf which the fishermen draw it up and then remove its con- 

 tents. Each float has a peculiar mark, by which the fisher- 

 man knows his own. When taken, the crabs are kept alive 

 in well-boats, until wanted. 



* These animals have no distinct head; that and the thorax being merged into 

 what naturalists call " ccphclo-tjiorax," or head-thorax. 



