Regeneration of the Chelcc of the Gnlf-zi'eed Crab. 113 



in age of the animal, however, shows that it is ckie not to the successive 

 removal and regeneration, but to other factors connected with the increase 

 in age. In animals of equal size the first and second regenerations are 

 equal, and successive removal neither accelerates nor retards the rate of 

 regeneration. 



It is interesting to compare this with former results. As stated above, 

 the general statement has been made again and again that successive re- 

 moval in many animals does not affect the power of regeneration. In none 

 of the cases upon which this conclusion is based, however, was any correc- 

 tion made for change due to increase in age. If the present experiments 

 had been left on a similar basis the data would have shown an increase 

 in rate of regeneration with successive removal. It is only after the correc- 

 tion for increase in age is made that successive removal is seen to have no 

 influence upon the regeneration of the right chela. The single case of the 

 sciatic nerve of the dog mentioned by Stewart would probably, however, 

 still show an increase in the rate of regeneration after correction for age 

 increase. The general significance of a single case is, however, doubtful, 

 because of the possibility of some physiological change apart from succes- 

 sive injury. 



A discussion of the facts of successive regeneration is reserved until the 

 writer has worked up other experiments which are now under way. It is 

 obvious that an exact determination of the effect of successive removal of 

 an organ upon its power to regenerate is of importance in a study of the 

 character of the mechanism at the basis of the process of regeneration. 



The effect of removal of the right chela upon the condition of the left 

 chela. Numerous experiments and general observations point to the conclu- 

 sion that the removal of one of a pair of organs in cases where regenera- 

 tion does not take place is followed by an increase in size and efiiciency of 

 the remaining organ. Thus, when an arm is removed the other arm in- 

 creases in size and strength. The same holds for the kidney and other 

 organs. It is of interest to determine whether in case the removed organ 

 starts to regenerate the uninjured organ still undergoes a similar increase 

 in size or efficiency. This matter is of considerable importance in a dis- 

 cussion on the one hand of the factors involved in hypertrophy and on the 

 other hand of the factors concerned in the regeneration of the new organ. 

 If the hypertrophy is due to an excess of production of certain formative 

 or food materials, due to the absence of one of the consuming organs, and 

 a regenerating appendage uses the same material, it is probable that in case 

 regeneration takes place the uninjured organ will not increase in size. This 

 is the result obtained in the case of the chels of Portunus sayi. The left 

 chela is not larger in animals with a second or a first regeneration of the 

 right chela than in animals of the same size with the right chela uninjured. 

 This result is of special interest, because in Portunus the regenerating chela 



8 



