14 .) NATURAL HISTORY. 



retires to some secluded spot, where he is tolerably safe from danger in the 

 defenceless condition which ensues. The first process is the absorption of 

 the limy salts from certain parts of the big claws, for the shell of these is 

 cast as well as of the rest of the body. At last the large anterior buckler, 

 or carapax, splits down the middle, and through this opening the animal 

 extricates himself, pulling out its abdomen, legs, feelers, and even leaving 

 the lining of his stomach behind. Immediately the molt has taken place 

 his new skin is very delicate, and the once formidable claws have lost their 

 power; bu1 quickly the salts of lime are deposited in the new skin, and it 

 gradually becomes even harder and thicker than before. The flesh of the 

 newl}' molted lobster is flabby and watery and not good for food, and it 

 would seem as if a large amount of water was absorbed, so as to distend 

 the new skin and allow the lobster room to grow inside it after it had 

 become so hard and dense as to have lost all elasticity. Apparently con- 

 nect id with the molting is the formation of concretionary bodies of lime, 

 one on either side of the stomach. They are of considerable size in the 

 lobster, but only weigh a few grains in the cray-fish. They are composed 

 almost entirely of carbonate of lime arranged in prismatic crystals ; and it 

 is supposed that they serve as stores of lime to harden the new integument. 

 The argument, that because of their small size in the cray-fish this explana- 

 tion ca 1 mot be the true one, lacks validity. The shell of the cray-fish contains 

 far less lime than does that of the lobsters and crabs, and besides, it is not 

 necessary that their integument harden so rapidly, for they are not exposed 

 1 i • nearly so many dangers and enemies as are their salt-water relatives. 



The cray-fishes, of which there are a large number of species, are all 

 inhabitants of freshwater. The forms are all much alike, and they so 

 intergrade that the discrimination of species is a matter of much difficulty, 

 and scarcely two authors are agreed in the limits of the various forms. 

 tndeed, one naturalist, who had paid especial attention to the Crustacea, 

 used to declare that " either we have but one species of- cray-fish east of 

 th" Rockv Mountains, or else each mud-puddle has its own peculiar species." 

 This of course was an exaggeration, but the fact that the latest revision of 

 the -roup enumerates fifty-two species in the limits named shows that lie 

 had grounds tor his statement. Some species live in rocky brooks, while 

 others -em,, to prefer muddy streams, where they burrow in the banks and 

 at times thn.w up towers of mud. This burrowing; habit renders them 

 nuisances at t imes ; tor they bore their way through dams and levees, mak- 

 ing boles which the water soon enlarges into serious breaches. 



In the southwest cray-fishes are extensively eaten, but farther north 

 1 ' l( '. v do not ,,c,-ur in sufficient numbers to render them of economic 

 importance. In Europe, and especially in France, they are cultivated for 



