Compensatory Regulation. 8 1 



V. REGULATION OF THE RATE OF GROWTH AND NATURE OF DIF- 

 FERENTIATION DURING REGENERATION OF THE CHELAE OF 

 GELASIMUS AND ALPHEUS. 



I. Introduction. 



The general problem to be taken up in the experiments on the 

 chelae of the two Decapod Crustaceans mentioned corresponds 

 with that already given for the Serpulids. The interactions of 

 the two chelae naturally constitutes the principal point of study. 

 Likewise the influence of the removal of one or both chelae upon 

 the rate of moulting of the animals will be discussed and some 

 further incidental points will be touched. 



In Gelasimus pugilator the two chelae are of nearly the same 

 size and character in the female but differ widely in the male. In 

 Alpheus dentipes the chelae differ both in size and character in 

 both male and female. 



2. Gelasimus Pugilator. 



In Gelasimus the male has one of the two chelae enormously 

 developed. This large chela is nearly equally distributed between 

 right and left sides in a group of individuals taken at random. In 

 the female the two chelae are small and equal in size. The animals 

 readily autotomize their legs if a needle is inserted between two 

 of the joints distal to the "breaking joint" so as to touch the 

 nerve. In the following experiments the animals were made to 

 throw off their chelae in the way mentioned. They were kept in 

 glass dishes with just sufficient water to keep them moist and fed 

 with bits of the horse-mussel, Mytilus. Under these conditions 

 they lived very well, though unfortunately the growth of the new 

 legs was extremely slow and the experiments could not be com- 

 pleted as satisfactorily as was wished. 



I. Experiments on Males. 



a. Large Chela Alone Removed. The first object of the work 

 was to determine whether reversal of the character of that of 

 Hydroides takes place in these forms. The large chela was autoto- 

 mized in the manner already indicated. In the great majority 

 of the cases the animals lived through the 62 days after the opera- 

 tion, but in only a few did a moult take place so that the results are 



