Rate per day in millimeters 
Analysis of Rate of Regeneration 409 
tion, when .23 mm. had been regenerated at the rate of 0.11 
mm. per day. The measurement for the fourth day (1.31 mm.) 
shows the rate for the second two days to be 0.54 mm. per day. 
This interval of initial low rate probably extends over about two 
days. The first measurements in Experiments I, I] and IV were 
not made until the third day when the tail had begun to grow 
faster. The rate for the first period in these cases is therefore 
a compound of the low rate of the first interval and the relatively 
higher rate apparent in the second region of the curve. ‘The 
second region of the rate curve represents the interval of maxi- 
Su Sear 7, 100) 12-8 ae 17 21 25 29 Sau 
Days since operation 
Fig. 4 Curve of rates of regeneration for Experiment IV. For explanation, see Fig. 1. 
mum length adding activity. It ends when the rate has reached 
its maximum and has begun to decrease. The duration of this 
interval varies in different experiments; it is shortest in Experi- 
ment IV, where it extends over four or five days ,and longest in 
Experiment I in which it ends on the tenth day after the opera- 
tion. The factors entering into the variation in the length of 
this interval and the rate at its maximum cannot be made out 
from the present data, but Ellis? has shown that they are in part 
at least dependent upon the amount removed. ‘The third region 
7 Ellis, M. M. ’og: The Relation of the Amount of Tail Regenerated to the Amount Removed in 
Tadpoles of Rana clamitans. Jour. Ex. Zodl. vol. vii, no. 3 
