SOME NOTES ON THE FACTORS CONTROLLING 

 THE RATE OF REGENERATION IN TAD- 

 POLES OF RANA CLAMATA— DAUDIN. 1 



MAX MAPES ELLIS. 



During the fall of 1907 some experiments were undertaken at 

 the Zoological Laboratory of Indiana University at Bloomington, 

 upon tadpoles of Rana clamata as a study of factors controlling 

 the rate of regeneration. The results of this work are given in 

 part in this preliminary report. 



Tadpoles varying in body length from 35 to 40 mm. were 

 arranged in series so that comparisons showing the influence of 

 age, level of injury and location of injury (i. e., whether the 

 operation was in old or regenerating tissue) upon the rate of 

 regeneration and the relation of first to second regeneration were 

 made possible. 



1. Age. — Tadpoles, 10 mm. whose tails had been removed, 

 were used in this comparison. They were of four different ages 

 with respect to the time of operation. The first set was operated 

 upon on the date X, another on X + 10 days, a third on X -\- 12 

 days and the last on X + 22 days. Those injured on X had the 

 highest rate of regeneration and those on X -\- 22 the lowest. 

 The other two sets were both lower than the first. These differ- 

 ences in rate were not due to laboratory conditions as that point 

 had been eliminated. As all other factors were controlled it is 

 quite evident that the rate of regeneration of the tadpole tail 

 decreases as the animal grows older. The averages are given 

 here : Those of the date X regenerated at a rate of .39 of a milli- 

 meter per day; X -\- 10 days, .35 ; X -\- 22, .26. These figures 

 show a decided decrease in the rate with an increase in age, 33^3 

 per cent, of the rate being lost during the 22 days between the 

 date of the first and last operations. 



2. First and Second Regeneration. — The data collected are 

 not at all conclusive for the relation of the rate of first regener- 



1 Contribution from Zool. Lab. of Indiana University, No. 94. 



