AUTOTOMY 153 



this holds for all crabs cannot be stated. Herrick says : " Uninten- 

 tional 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 l states 

 that "out of a hundred specimens collected for natural history pur- 

 poses in Narragansett Bay in 1880, fully 25 per cent had lost a claw 

 each, and a few both claws." Herrick 2 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 ob- 

 served. 3 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 (Astcrias vnlgaris} 

 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. 



In the brittle-stars (ophiurians) the arm breaks off with greater 

 ease and at any level. If the arm is simply held and squeezed, it 

 will, in some forms, break off just proximal to where it is held. If 

 the broken end is again held, another small piece breaks off, and in 

 this way the arm may be autotomized, piece by piece, to its very base. 



1 The Fisheries and Fishing Industries of the United States, Washington, 1887. 



2 "The American Lobster," Bull. U. S. fish Comm., 1895. 



8 Reaumur in 1742 records the first observations. Spallanzani also described the pro- 

 cess, and many later writers have examined it. 



