237 
1914-15.] The Reflexes of Autotomy in Decapods. 
(2) Extension of the leg at the second joint moves the point of least 
resistance to traction from the first joint to the second. By this means a 
smaller wound is secured and the probability of fatal hsemorrhage prevented. 
(3) When the source of mutilation is quickly removed from the leg, 
autotomy does not occur, but the prawn is seen to tear violently at the 
stump with its jaws, and later to flex the next sound joint. Thus excessive 
bleeding is prevented. 
(4) As far as can be judged, there is a constant time relation between 
the various reactions — extension, tail-flapping, attempts at “ autophagie ” 
(or tearing with the jaws), and flexion. 
Suborder Reptantia. 
The Lobster. 
The common lobster, Astacus gammarus (Lin.) = (Homarus vulgaris 
(Edw.)) is a very good example of this section, and a detailed description 
will be given of autotomy as it occurs in the walking-legs, because the 
animal is large, and a very suitable subject in which to record the times 
of the various reflexes. The process shows many characteristics similar to 
those present in the prawn, and, so far as autotomy is concerned, is a stage 
higher than the crayfish {Astacus), which forms a link between prawn and 
higher palinuran. 
The common method of lobster capture is the setting of creels or pots, 
and it is found that the percentage of individuals captured short of limbs 
is very small. Herrick (12) records that out of 725 lobsters caught at 
Woods Holl in December and January 1893-1894, 7 per cent, had lost one 
or both claws. He gives no figures regarding the loss of walking-legs, but 
I can state from experience that it is much less, probably between 3 per 
cent, and 4 per cent. 
It is a significant fact that if lobsters are captured and put in one tank, 
fightinggoes on amongst them till the majority have lost both chelipeds. 
The loss in walking-legs is not so great, for these are well protected by 
the large overhanging chelae. The greatest danger lobsters run of losing 
limbs is probably due, therefore, to members of their own family. In 
examination of many hundreds, very few are found which have lost a 
leg at any other point than the breaking-plane in the case of the chelipeds, 
and the region of the joint between the second and third limb-segments in 
the walking-legs. 
Mutilation of limbs by various methods produced the following results : — 
(1) If a cheliped or a walking-leg be crushed by strong pincers and held, 
the limb first becomes extended. Immediately afterwards several powerful 
