118 REPORT OF COMMISSIONERS OF IXLAXD FISHERIES. 



tional as such. The two lateral surfaces of this compound structure 

 are each dentated by a row of serrated teeth (T, T). These two rows 

 of teeth begin near the rudimentary joint and traverse the opposite 

 lateral surfaces in a distal direction; distally they converge but do 

 not quite meet over the flattened and slightly furrowed tip of the 

 extremity. The tactile hairs are grouped more or less about these 

 dentated margins. The evidence that this abnormal structure 

 represents the double dactyl seems even more conclusive when it is 

 perceived that if we were to split the whole structure in a dorso- 

 ventral plane, each half, with its row of teeth, would form a dactyl 

 for the opposing index. 



According to the above interpretation, the abnormal structure on 

 this walking leg is morphologically a double claw, composed of two 

 extra dactyls and a compound index. That this abnormality may 

 extend farther into the proximal segments of the normal limb has 

 already been indicated in the preceding description of certain struc- 

 tural features in the meropodite and ischiopodite. In this walking 

 leg, therefore, we have a clear case of a "triple-claw" which has 

 arisen through a process of regeneration. 



2. Other Experiments and Observations on Abnormalities in Regen- 

 erating Limbs. 



Aside from the fact that the triple claw just described has arisen 

 through regenerative processes, I can add nothing further in regard 

 to the factors casually related to its origin. As a preliminary, how- 

 ever, to a further experimental study of this subject, it seems desir- 

 able to record here the following observations: 



a. An Extra Bud on Regenerating Leg. 



The first case is that of a regenerating fourth left leg. On July 27, 

 1903, in one of my experiments, an 8-inch male lobster was muti- 

 lated by cutting off the first pair of swimmerets. At this time the 

 fourth left leg of this lobster was gone, but it soon began to regener- 



