122 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



prehension is certainly a secondary function of those claws. The only 

 purpose they serve, besides that already described, is as weapons of de- 

 fense or attack. The holes, scooped out from under shelving rocks, or 

 excavated when the bottom is soft, often to a depth which is truly as- 

 tonishing, are made in this manner. Having selected a spot, the lob- 

 ster commences and carries out the operation solely by means of his 

 tail, its great contractile power acting much the same as that of the 

 human fingers would in a similar employment. The tail is slowly drawn 

 up at first, taking as much of the mud as possible on its under side; 

 then, when well under the body, a final, powerful jerk sends the mud 

 or sand from out in front, and at the same time draws the lobster 

 farther back into the cavity thus made, enabling him to get a better 

 grasp for repeating the process over and over again, till by degrees he 

 disappears from sight, and rests only when he finds his curious chamber 

 sufficiently retired for safety or comfort. These holes are for the shelter 

 of the lobster during the period of exuviation. As the shell of the lob- 

 ster cannot increase in diameter, the creature soon grows too large for 

 its coat, and some means must be provided to accommodate it to the 

 increasing bulk of the body. This is effected by the yearly exuviation, 

 or the throwing off" of the old shell, and the formation of a new one. It 

 should be remarked, however, that full-grown lobsters are subject to no 

 such change. Professor Bell states that exuviation takes place an- 

 nually until growth is completed, and alludes to his having seen the 

 carapace of the living lobster covered with barnacles so large that sev- 

 eral years must have been required for attaining their existing size. 

 This statement of Professor Bell I have verified by observation. The 

 season for casting the shell is generally from June to September. A 

 lobster about to exuviate is readily detected by his sluggish move- 

 ments and the dull red color of the membrane in his joints. He evi- 

 dently feels sick, and sometimes takes refuge in mud-holes, sometimes 

 under locks, and often under a bunch of marine weeds. Usually in 

 less than a week from the first indications, the process of working off 

 the old integument is completed. It is extremely interesting to watch 

 the performance. The shell inclosing the trunk splits down the back 

 in aline always discernible as a faintly marked seam. It gradually 

 falls apart, and is separated from the rings of the tail, but never from 

 1 he covering of the legs or big claws, from which those appendages are 

 slowly drawn, apparently with great pain and difficulty, and no wonder, 

 since the bulk of the claw, immediately after its extraction, is out of 

 all proportion to the diameter of the joint through which it is made to 

 pass. lint the fleshy part is very soft, almost semi-liquid, and can be 

 compressed into small space. As the last act in the process, the lob- 

 ster crawls forward feebly, leaving the shell of his tail behind him. For 

 a few days he is alraosl incapable of motion, and not until his new 

 shell, which is formed by a mucous exudation containing much cal 





