REPORT OF COMMISSIONERS OF INLAND FISHERIES. 311 



Chelipeds. Second Pair of Legs. Third Pair of Legs. 



Right. Left. Right Left. 



papilla papilla papilla papilla 



7 mm. 2 mm. papilla papilla 



13 mm. 8 mm. 5^ mm. papilla 



Both Non- 



functional Functional functional 



It may be seen from these data that the six limbs were all removed 

 49 days before the next molt, and that five of these appendages 

 regenerated and molted as functional limbs, while on the other hand 

 the slight regenerative activities in the third left leg merely produced 

 a structure which molted as the very small non-functional papilla 

 shown in Fig. IT. 



This case, therefore, shows that it may be possible for the regenera- 

 tive process to start up without resulting in the reproduction of a 

 functional limb by the time of molting, even when the mutilation is 

 made early in the molting period. But since it is extremely rare to 

 find such a partially developed non-functional limb after a molt, 

 it is evident that a partial regeneration of this character must be 

 regarded as exceptional rather than typical. This, together with the 

 fact that the process of regenerating does not respond readily to 

 mutilation in the latter part of the molting period, seems to support 

 the conclusion that there is a tendency in the regenerative process to 

 begin only when the conditions are such as to favor the development of 

 a functional structure before the act of molting takes place. 



5. While the present experiments were being made, Zeleny,* 

 published the results of some experiments on regeneration in adult 

 crayfishes. The experiments consisted in the comparison of the 

 rate of regeneration and the rate of molting in two series of regenerat- 

 ing crayfishes, in which the degree of injury in one series was greater 

 than in the other. 



The results in the crayfish, with reference to the rate of molting, 



*(Journal of Experimental Zoology, II, 1905.) 



