Analysis of Rate of Regeneration 403 
for four days at one time and allowed to live in foul water for 
four days at a later period. The set was discontinued April 28, 
fifty days after operation. Table I gives the averages of the 
results of the measurements made on this set. 
Experiment 11. Tadpoles used in Experiment II were 33-35 
mm. long; the average for the set was 34.6 mm. ‘The operated 
series was composed of twenty-three individuals, and the control 
series of twelve. The average amount of tail removed by the 
operation performed, April 27, was 11.5 mm. The extremes of 
operation were 9.7 mm. in one and 12.6 mm. in two cases. ‘These 
series were discontinued on May 27, thirty days after the opera- 
tion. Table II gives the complete data for the set and shows that 
individual variation is not sufficiently great to affect the validity 
of the averages. Table III gives the averages of the results 
obtained in Experiment II. 
Table II gives the complete individual data for Experiment II. 
The first column gives the body lengths of the individual tadpoles. 
The first twelve belong to the control series. The second column 
gives the tail lengths of the tadpoles. The third, the amount, in 
millimeters, that was removed by operation on April 27. The 
next seven columns give the amounts regenerated upon the dates 
indicated at the heads of the columns. ‘The remaining four 
columns give measurements of the tail and body length upon 
the dates indicated. The average for the series is given at the 
base of each column. Separate averages for the body lengths 
and tail lengths of each series and an average body length for the 
entire set 1s given. . 
_ Experiment III was made upon ten tadpoles 41.4-44.9 mm. 
long, the average for the series being 43.7 mm. All ten individuals 
were operated upon October 1, an average amount of 14.8 mm. 
was removed, the extremes of operation being 14 and 16 milli- 
meters. The experiment is of interest in this paper, because, 
(1) measurements were made more frequently immediately after 
the operation than in the other experiments; and (2) a change 
of food later in the course of development of the new tails pro- 
duced a change in the rate. The series was discontinued Novem- 
ber 3d, but, as two individuals were killed for the histological 
