Rate of Regeneration. 369 



influence exerted either upon the other organ or organs directly 

 or else upon the mechanism for carrying food materials to those 

 organs. The retardation influence is brought out in a somewhat 

 different light when considered as a manifestation of the inertia 

 of the organism. This idea also tends to unite the two suggestions 

 of positive stimulation as a result of injury to the animal and the 

 negative or retardation stimulus exerted by the uninjured organs. 

 The former acts after the operation in overcoming the inertia of 

 the organism. The latter on the other hand is merely a mani- 

 festation of the same inertia acting before removal. 



The crayfish data when taken alone furnish no evidence in favor 

 of either one of these two views as opposed to the other. The 

 experiments on the Serpulid opercula and Alpheus chelae, however, 

 cannot be as well explained by the positive stimulation theory as 

 by the retardation view. 



The foregoing speculations are evidently of but small direct 

 value. Their purpose is accomplished if they have emphasized 

 the importance of the discovered relation between the degree of 

 injury and the rate of regeneration in any general theory of regen- 

 eration. 



6. SUMMARY. 



A comparison was made of the rate of regeneration and the rate 

 of moulting in two series of crayfish with different degrees of 

 injury. In one series the right chela alone was removed. In the 

 other series the two chelae and the last two pairs of walking legs 

 were removed. It was found that the rate of regeneration of each 

 chela in the series with the greater injury is greater than that of 

 the single removed chela in the series with the lesser injury. 

 Likewise the rate of moulting of the animals is greater in the 

 former series than in the latter. 



Indiana University, 

 May 31, 1905. 



