84 BULLETIN OF THE UNITED STATES 1'TSH COMMISSION. 



term " black lobster," used by the fishermen on the coast of Maine, is not altogether 

 inappropriate. The old shell is also brittle, owing to the absorption of organic matter, 

 and if the carapace or large shield wnich covers the anterior half of the body is 

 pressed between the fingers, it will sometimes split down the back in the longitudinal 

 median furrow. In most cases the shell does not crack in this place unless artificially 

 compressed. In the course of the preparation for the molt the lime salts of the 

 shell are absorbed along the middle line of the carapace, leaving a narrow perfectly 

 straight gutter, extending from the spine or rostrum to the posterior margin of the 

 shield. The chitinous portion of the cuticle still remains, forming an inelastic hinge, 

 on which the lateral halves of the carapace bend without breaking asunder. In the 

 molted shell there is also a linear membranous area on either side of the rostrum. 

 Absorption of the hard matter of the shell at these points tends to give greater latitude 

 to the movements of the two halves of the carapace. If you examine a hard-shell 

 lobster you will find in place of the median furrow a blue line, drawn as if with a fine 

 pen and rule. Below this line the epidermic cells of the skin become so modified as to 

 bring about the total absorption of the lime salts of the cuticle. In sections of the 

 skin, however, it is difficult to detect any histological change in this linear area. 

 Other areas of absorption, to be described hereafter, occur, which are of even greater 

 importance to the success with which the lobster comes out of his old covering alive 

 and whole. 



The period of uneasiness, which foreshadowed the molt and was very marked, 

 ended in this lobster by its rolling over on its side, agitating its appendages, and 

 bending its body in the shape of the letter V, the angle of the V coinciding with the 

 gaping chink between the dorsal shield and " tail." Presently the old cuticle, holding 

 these parts together and through which the new shell is seen, began to stretch, the 

 wall of the body pressing against it with considerable force, and the hinder end of the 

 shell being slowly lifted up, while its anterior part remained attached to the rest of 

 the skeleton. The slow but sure pressure of the parts within cause an increasing 

 tension in the yielding cuticular membrane, which finally bursts, revealing the brilliant 

 colors of the new shell. The legs and other appendages are occasionally moved, but 

 no marked convulsive movements are to be seen. The carapace has now become raised 

 upward to an elevation of perhaps 2 inches behind, in consequence of which, the 

 anterior end being fixed, the rostrum is bent downward and the animal now has a 

 very singular appearance. 



When this much has been achieved the lobster becomes quiet for a few seconds 

 and then resumes its task with renewed vigor. From this time on until free its 

 muscles work intermittently. The doubled-up fore part of the body is with each effort 

 of the animal more and more withdrawn from the old shell, and this implies the 

 separation of the skin from the complicated linkwork of the internal skeleton and the 

 freeing of the twenty-eight separate appendages, which are attached to this portion of 

 the body, from their old cases, and at the same time the release of the muscles from the 

 internal tendons of the large claws and other parts. The cuticnlar part of every ecto- 

 dermic structure is stripped off. This exoskeleton folded up to fit such a complicated 

 mold is in reality a continuous structure, and from the method of its regeneration the 

 sloughing of one part necessitates the shedding of the whole. 



The carapace is now elevated to such an extent behind that the rostrum is 

 directed obliquely downward and backward. The lobster is still lying in comparative 



