243 
1914-15.] The Reflexes of Autotomy in Decapods. 
autotomy the remaining part of the leg is rigidly extended much beyond 
that degree of extension which it could obtain if the whole of the chela 
were present (fig. 15). 
The following conclusions can be drawn from the above study of the 
processes of autotomy in the lobster : — 
In the walking-legs there is a distinct advance on what was found in 
the prawn. In both the second limb-segment is sharply extended, but in 
the latter a new element is added. The break, instead of wholly involving 
a tough membraneous structure, is partly through brittle calcareous matter. 
This, of course, is due to contraction of the flexor of the third segment, 
and an indrawing of the ring of integument central to the groove 
described above. Regarding the limb-segment as a rigid cylinder, it is 
Fig. 15. — Basal parts of the chelipeds showing breaking-furrow in 
the right chela and stump extended after autotomy on the 
left. B.f., breaking-plane. 
easily seen that the combined result of contraction of the two muscles is 
to make the region of the groove the weakest part. If, therefore, the 
traction set up by tail-flapping cannot be resisted, breaking must occur at 
the groove. The graphic recording of m usd e-contraction has established 
the fact that a definite time-relation exists between the different parts of 
the reflex. 
The reflex is plurisegmental, for autotomy does not occur when the 
nerve connection to the tail is severed. If the influence of upper neurons 
be removed, the reflexes are more powerful. This demonstrates that even 
in an animal with so little cerebral development as the lobster the 
inhibitory action of the upper ganglia is manifest. 
Evasion of an enemy would seem to be the most powerful factor in the 
production of autotomy in the lobster, for it is necessary that the walking- 
leg be held in order that amputation may be effected. The movements of 
retreat suggested by tail-flapping also make it highly probable that escape 
is the real purpose. In the prawn, if the limb was not held after mutilation. 
