531 



RATE OF REGENERATION— ZELENY 



53 



TABLE 34 (Continued) 



Experiment VI Bufo americanus Series 6283-6323 



This series was designed for the study of the effect of successive 

 removal of the tail upon the rate of metamorphosis. The lengths of 

 the removed regenerating tails however are of some value in a com- 

 parison of successive regenerations though here as in Experiment V 

 age and external factors are not eliminated. 



The eggs were laid on April 20-21, 1915. The tadpoles were col- 

 lected on April 27 and the first removals were made on April 28. 

 The first metamorphosis was completed on June 11. The average 

 total length at the time of the first removal Avas 10.9 mm. and the 

 average tail length 6.4 mm. The average removed length was 3.8 mm., 

 which is approximately 60 per cent of the tail length. The second 

 removal was made on May 7 and gives a nine-day period for the first 

 regeneration. The third removal of May 17 gives a ten-day period 

 for the second regeneration. The fourth removal on May 26 gives a 

 nine-day period for the third regeneration. As in the case of Experi- 

 ment V the cuts could not in practice be made to come exactly at the 

 border line between old and new tissue and the accuracy of the meas- 

 urements is therefore not as great as in those cases in which the 

 lengths were taken directly from the animal without removal of the tail. 



The data are shown in Table 35. The first, second and third re- 

 generation lengths are given for sixty individuals. The first and third 

 regenerations have the same time interval and are therefore directly 

 comparable. The average for the first regeneration is 1.94 ^0.02 mm. 



