4 6 CRUSTACEA. 





and first abdominal ring, or by splitting open the cara- I 

 pace along the middle line of the back (Fig. 6, sur). 

 In a specimen observed at the island of Martinicus, I 



off the coast of Maine, the fissure occurred between 

 the carapace and the first ring of the abdomen, as in 

 the crayfish. Through this opening the large arms, the 

 walking-legs, and whole forward part of the body were 

 drawn. This operation was performed, apparently, with- 

 out the slightest difficulty. The animal laid on its side, 

 and its tail was bent sharply under the carapace, and no 

 motions of the abdomen were seen. The whole opera- 

 tion was accomplished by the muscles of the forward 

 part of the body, which, gradually bending and bulging 

 more and more outwardly, finally withdrew the cephalo- 

 thorax completely, and with a motion or two switched 

 off the abdominal casing. The whole time occupied 

 by the moulting did not exceed fifteen minutes. Im- 

 mediately after the moulting, the size of the large 

 arms was considerably less than the outside measure- 

 ments of the shell, ami so also were all the parts. 

 They were exceedingly hard and firm at first, the 

 watery aspect usually attributed to the newly-moulted 

 Crustacean not appearing until some hours after the 

 shell was actually cast off. The effort to keep the 

 animal alive until his new shell had completely hard- 

 ened, failed, and at the end of two days he was found 

 dead. The operation of forming a new shell takes 

 probably about a week, though the time is very variable, 

 according to the conditions under which the animal is 

 living. The ease with which the lobster withdraws its 

 body and limbs is owing to the absorption which takes 

 place, especially on the inner sides of the great arms, 



