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 branchiz 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 @ 7outrance 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 ahtennz, 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, 
