125] 



RATE OF REGEXERATIOX—ZELEXY 



125 



and for second regenerations 0.057 as compared with 0.050 for forty 

 eight percent removals in the first regenerations of Experiment II and 

 0.050 for forty nine percent removals in the second regenerations of 

 Experiment I. 



The percentage increments per day are 26 for first regenerations 

 as compared with 29 in Experiment II and 28 for second regenerations 

 as compared with 28 in Experiment I. 



The close agreement of these values taken from a comparatively 

 large number of individuals strengthens the conclusion as to the validity 

 of the comparisons at different periods and levels in experiments I and II. 



TABLE 65 



Rana clamitans Series 3628-3765 

 First and second regenerations of the tail Six and eight days 



Experiment IV Amblystoma punctatum Tail Series 4600-5052 



Operations were made at five levels approximating 10, 21, 34, 53 and 

 74 per cent of the original tail length. The removed lengths average 

 respectively 1.1, 2.2, 3.7, 5.8 and 8.1 mm. Measurements were made 

 2, 4, 6, 8-9, 10-11, 13, 14-15 and 16-17 days after the operation. Tin- 

 rates per day for each of the levels at each of the different times are 

 given in Table 66. 



The specific rates are shown in Table 67. The averages for all the 

 levels at each of the time periods are respectively 0.032 mm. for to 2 

 days, 0.004 for 2 to 4 days, 0.053 for 4 to 6 days, 0.039 for 6 to 8 days. 

 0.064 for 8.4 to 10.3 days, 0.043 for 10.3 to 13.0 days, 0.012 for 13.0 

 to 15.2 days and 0.019 for 15.2 to 17.3 days. As in the case of other 

 salamander experiments the data are more irregular than those for the 

 frog tadpoles because of the susceptibility of the salamander larvae 

 to factors which have not so far been brought under control. The 

 character of the food is probably an important factor. The greatest 

 rate comes between 8.4 and 10.3 days after the operation for three of 

 the five levels and also for the average of all levels. This is later than 



