Compensatory Regulation. 9 1 



h. The Influence of the Presence or Absence of the Opposite Chela 

 upon the Rate of Regeneration of a Removed Chela. A comparison 

 was made of the regenerated lengths of the cutting chela in cases 

 where only one chela was removed with cases where both chehe 

 were thrown off. 



When the cutting chela alone was autotomized a new cutting 

 chela was regenerated in its place. When the snapping chela 

 alone was removed there was a reversal and the old cutting chela 

 was differentiated into the new large snapping chela, while in 

 place of the removed snapping chela a typical cutting chela was 

 developed. In the second case this new cutting chela is the one 

 taken in our measurements. In a third case both chelae were 

 thrown off, a new cutting chela regenerating in place of the old 

 cutting chela and a new snapping chela in place of the old snap- 

 ping one. The lengths are taken from the moulted casts of the 

 animal, the original length being taken from the cast of the first 

 moult, the first moult condition from the cast of the second moult, 

 etc. The final measurements are taken from the alcoholic speci- 

 mens of the animals killed 57 days in each case after the operation. 

 The lengths measured in the data about to be described are the 

 greatest lengths of the cutting chela, i, e., the distances from the 

 tip of the pincher process of the fourth podomere to the farthest 

 corner of the base. (Fig. 27.) The chelae or their casts were in 

 every case drawn carefully to scale by the aid of a camera lucida 

 and the measurements are taken from these drawings. Out of 

 29 specimens kept for 59 days only 12 can serve for first moult data 

 and 13 for second moult data. The others are not valid because 

 of the death or escape of the animal or the accidental secondary 

 autotomy of one or both of its appendages. 



The relation of the regenerated chela lengths to the original 

 lengths is shown on coordinate paper (Fig. 29) for both the first 

 and the second moult. The number of individual cases is small, 

 but it is evident that the regenerated lengths of the cutting chela in 

 the cases where both chelae were removed have a distinct advan- 

 tage over the others. This is especially clear for the first moult. 



The relation comes out very clearly when we take the ratio 

 between the regenerated cutting chela length and the original 

 length in that specimen as our basis for comparison, for we see 

 that the regenerated length increases as we go from small original 

 lengths to large original lengths. As the cases given on the coor- 



