CRUSTACEA. 



507 



leads the blood into the general body of the animals, the other directs 

 it towards the heart. These organs are enclosed in the Cephalothorax. 

 In some of the smaller species the branchiae often appear exteriorly, 

 hanging in the water like tassels. In some cases we find that the 

 Crustacea have no special organs of respiration. 



Nearly all the Crustaceans are strong, hardy, and destructive, 

 forming a horde of nocturnal brigands — merciless marauders, who 

 recoil from no trap in which they can lie in wait for their prey. 



Fig. 340. — Pisa tetraodon. 



They fight cL foutrance not only with their enemies, but often among 

 themselves, either for a prey or for a female, sometimes for the sake 

 of the fight. They struggle fiercly and audaciously with their claws. 

 The carapace generally resists the most formidable blows ; but the 

 feet, the tail, and above all the antennae, suffer frightful mutilation. 

 Happily for the vanquished, the mutilated members sprout again 

 after a few weeks of repose. This is the reason for the many Crus- 

 taceans met with having the claws of very unequal size : the smaller 

 replace those lost in battle. Nature has willed that the Crustacean 

 should not long remain an invalid. They soon return cured of their 

 wounds. " We have seen lobsters," says Moquin-Tandon, " which 

 have in an unfortunate encounter lost a limb, sick and debilitated, 



