NATURAIy history OR AMERICAN LOBSTER. 
283 
Reflex amputation in crustaceans, whether considered in relation to shock or to fear, 
or as an independent mechanism, must be regarded as one of the most remarkable 
phenomena of invertebrate life. The loss of a considerable amount of tissue is always 
a shock to a higher vertebrate, while a lobster in autotomy of both its chelipeds may 
give up with impunity one-half the weight, or even more, of its entire body. In the 
higher animals fear may be due to inheritance or it may directly arise through asso- 
ciation, by experience. The lobster, indeed, shows fear by hiding or by its hasty retreat 
from an enemy, but reflex amputation does not appear to have any necessary relation 
to fear. The reflex center of the cord is aroused to activity by a stimulus coming direct 
through the nerves of the limb, and not from the brain. We may be sure that the 
same center does not at one moment give the order to flee, and at the very next compel 
the animal to drop any of its legs. The lobster or crab does itself a grievous injury 
automatically in order to escape a worse fate. This kind of reflex surgery thus seems 
to be an afterthought of nature, as if an attempt had been made to repair an earlier 
mistake, or a compensation, as it were, for having originally endowed the crustaeean 
with a frame too vulnerable to attack, or with a mind too feeble to successfully cope 
with its environment. 
RESTORATION OF LOST PARTS. 
The power of restoring lost or injured parts through the process of regeneration is 
very general throughout the body and appendages of the lobster. It is exercised very 
perfectly and promptly in the big chelipeds when thrown off by autotomy at the break- 
ing plane, where the process has evidently been favored by natural selection or some 
other factor of evolution. Regeneration is also very active in the fragile antennae and 
the walking legs. All of these organs are, at the same time, very liable to injury, and 
are essential to the maintenance of life by directing the animal to its food and enabling 
it to secure it. In conveying this food to the mouth and preparing it for the stomach 
the mandibles and other mouth parts are quite as important; the swimmerets also serve 
a variety of necessary functions, but all of these structures are far less liable to injury. 
Whether there is a causal relation between liability to injury and facility to restore the 
injured parts is another question. Morgan has reached a negative conclusion in his 
experimental studies on the hermit crab, and concludes that “regeneration is a funda- 
mental attribute of living beings.” The question, however, does not depend upon a 
single relation; the relations are undoubtedly very complex, and it can not be denied 
that in such animals as the lobster the external organs which are most exposed to injuries 
of every kind and which are of immediate necessity for the maintenance of life possess 
the most active power of regeneration. 
Emmel has shown (8g) that the power of regeneration varies at different levels in 
the limbs and that* even the swimmerets may regenerate more rapidly than the legs if 
the latter are cut off but a short distance below the breaking plane. Therefore the rate 
of regeneration depends upon the place of injury as well as upon the amount of surplus 
energy available at that point. 
The regeneration of a large cheliped in the fourth and fifth stages is essentially the 
same as in the adult. At the moment the limb is broken off there is but little loss of 
