Chapter VIII.— DEFENSIVE MUTILATION AND REGENERATION. 

 AUTOTOMY OR REFLEX AMPUTATION. 



The casting of the big claws and of some of the smaller legs described as defensive 

 mutilation, autotomy, or "self -amputation," is highly characteristic of the lobster. 

 It is closely associated \vith the remarkable power of regeneration or replacement of lost 

 parts, and less directly with the periodical renewal of the shell. These subjects have 

 opened up wide fields for research, the borders of which we can only touch at a few 

 points. 



The power of reflex amputation is most perfectly developed in the large cheUpeds 

 of the lobster. When this animal is seized by the claws, and struggles to escape, ampu- 

 tation is Ukely to occur in both hmbs. The animal surrenders its principal weapons, 

 but may escape with its life. The powers of regeneration are at once enlisted in the 

 complete renewal of the lost members. Every stage in the process can be found in 

 animals kept aUve in floating cars or in those sent to the markets. Out of 725 lobsters 

 caught at Woods Hole, Mass., in December and January, 1893-94, 54, or 7 per cent, 

 had thrown off one or both claws. The leg is broken off, as we have already seen, at a 

 definite place, called the "breaking plane" or joint near its base, through reflex muscular 

 contraction; there is but little bleeding from the old stump, and a new Umb soon sprouts 

 and is regenerated. The slender walking legs are sometimes lost and replaced in a similar 

 way. Many, if not all, of the appendages, when mutilated or removed, are capable of 

 regeneration, the time required for the process depending upon the proximity of the 

 succeeding molt, the vigor of the animal, and the temperature of the water. 



In autotomy the five distal segments of the hmb are cast off, fracture taking place 

 in the walking legs at the free third joint, between second and third podomeres, and in 

 the great chehpeds at the corresponding breaking plane. On the second compound 

 podomere of the first pereiopod of the adult the suture of basis and ischium is marked 

 by a fine hairline or encircling groove, free from setse, and it is always in this plane that 

 disjunction occurs. If the terminal parts of the limb are amputated autotomy of the 

 remaining stump usually occurs before the work of regeneration is begun. Mutilation 

 of the claw alone, however, is not necessarily followed by the casting and renewal of the 

 limb. Parts regenerated in any of the appendages are as a rule similar to those thrown 

 off, except in the case of the eyes and big claws under certain conditions. The stalked 

 eye can sometimes be made to produce an anterma-hke structure, and while big crusher 

 claw usually reproduces crusher, and lock forceps lock forceps, this is not invariably 

 the case, and we occasionally find lobsters with both claws similar, and of either toothed 

 or crushing type, as described in chapter vii. 



Autotomy can be experimentally produced by seizing the animal by its claw or 

 slender legs, or by stimulating the nerve of the Umb directly, the reflex nerve center 



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