In many crabs the leg is not thrown off if simply held, but only after an injury. Even the most distal segment may be cut off and the leg remain attached, and sometimes it is not lost after the distal end of the next to the last segment is cut off. If a crab is tethered by one leg it will not throw off its leg in order to escape, unless, in the crab’s excitement, the leg is twisted or broken. How generally this holds for all crabs cannot be stated. Herrick says: “Unintentional experiments in autotomy have often been made by tethering a lobster or a crab by its large claws. The animal, of course, escapes, leaving only its leg behind. When lobsters are drawn out of the water by the claws, or when a claw is pinched by another lobster, or while they are handled in packing, especially for the winter market, they often ‘cast a claw,’ and the transportation of lobsters at this season is said to be attended by considerable loss in consequence.” The large claws of the lobster are quite heavy, the base relatively small at the breaking-joint, and it may be that simply the weight of the claw, when out of the water, may strain the leg so that it breaks off,--the leg being injured by its own weight. The lobster seems to lose its claws quite often under natural conditions. Rathburn[71] states that “out of a hundred specimens collected for natural history purposes in Narragansett Bay in 1880, fully 25 per cent had lost a claw each, and a few both claws.” Herrick[72] records that “in a total of 725 lobsters captured at Woods Holl in December and January, 1893-1894, fifty-four, or 7 per cent, had thrown off one or both claws.” The autotomy of the arms of the starfish has been often observed.[73] The arms are thrown off very near the base in many forms. If the animal is simply held by the arm it does not break off, but if injured it constricts and falls off. The lost arm does not regenerate a new starfish in most forms, but, as stated on page 102, there are recorded some cases in which the arm seems to have this power. King has found that out of a total of 1914 starfish (_Asterias vulgaris_) there were 206, or 10.76 per cent, that had new arms, and all of these, with one exception, arose from the base of the arm. The growth of the new arm from the base takes place more rapidly, as shown in Fig. 38, _A_, than when the arm is regenerated from a more distal level; but in the latter case the arm, despite its slower growth, may complete itself before another does that originates at the same time from the base of the old arm. There is, therefore, in this respect no obvious advantage, so far as regeneration is concerned, in throwing off the injured arm nearer to the disk.