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 with 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 chelipeds 
of the lobster. When this animal is seized by the claws, and struggles to escape, ampu- 
tation is likely to occur in both limbs. 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 alive 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 P er 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 limb 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 limb are cast off, fracture taking place 
in the walking legs at the free third joint, between second and third podomeres, and in 
the great chelipeds 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 antenna-like 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 vn. 
Autotomy can be experimentally produced by seizing the animal by its claw or 
slender legs, or by stimulating the nerve of the limb directly, the reflex nerve center 
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