60 ILLINOIS BIOLOGICAL MONOGRAPHS [60 



The time intervals vary somewhat in each set but it is evident in both 

 cases that there is a decrease in rate of regeneration from the first to 

 the third and fourth regenerations. This decrease is undoubtedly due 

 to increase in age and not to successive removal. 



9. In Experiment VII a comparison of the completeness of re- 

 generation in single individuals of Rana clamitans shows a progressive 

 decrease in amount regenerated from the first to the fourth regener- 

 ation and an increase from the fourth to the fifth. In this experiment 

 also the age factor is not eliminated and the decrease is probably due 

 to increase in age. 



