REPORT OF COMMISSIONERS OF INLAND FISHERIES. 97 



marked in young lobsters — the leg would be "shot off" almost 

 simultaneously at the moment of injury. Great difficulty was ex- 

 perienced with the fourth and fifth stage lobsters because the stumps 

 were almost always cast off at the breaking plane, no matter at what 

 leA'el the cut had been made. By the exercise of considerable care, 

 hoAvever, the legs could usually be cut off, with a sharp instrument, 

 near the tip mthout a loss of the total limb through autotomy. But 

 if the cut was made near the base of the appendages, say in the region 

 of the ischiopodite or meropodite, the remaining stumps were fre- 

 quently dropped. 



In all these experiments it is to be observed that a crushing in- 

 juiy resulted in the autotomy of the whole limb, and that success in 

 preventing autotomy was only obtained by a quick cut of the in- 

 strument. This suggests a clue for the explanation of the fact that 

 under natural conditions the lobster's limb is usually gone at the 

 breaking plane. 



Even a superficial examination of the construction of the lobster's 

 claws will show that they are adapted for holding and crushing. 

 Their effectiveness in removing an opponent's limb may be seen at 

 any time in the lobster cars; indeed, their ferocious combats so often 

 result in the loss of appendages that it is necessary to tie or "plug" 

 the claws. It is perhaps safe to assume that the injuries sustained 

 in other phases of the lobster's struggle for existence are of a similar 

 character; that the lobster in the conflicts with his enemies more 

 often suffers a crushing, tearing injury than a clean-cut amputation, 

 and this results in the autotomy of the whole limb. This assump- 

 tion is farther justified by the fact that the animals with which the 

 lobster would most naturally contend are much better equipped for 

 crushing and holding than for cutting. Thus both experiment and 

 olDservation indicate that the breaking plane is the region of the 

 lobster's limb at which it is usualh' severed from the body as the 

 result of an injury to the limb. 



It would seem, therefore, that the power of regeneration is most 

 highly developed at the breaking plane, i. e., the region at ichich the limb 



