402 Marion L. Durbin 
decrease of the rate late in experiment II shows the effect of a 
prolonged period of reduced temperature. 
Error from individual variation was eliminated by removing 
from the series all strikingly abnormal individuals and by basing 
the results of the experiment upon an average of a large series of 
individuals. (See Table II.) 
DATA 
Experiment I, March 8, 1908, twenty individuals 40-43 mm. 
in length were operated upon. The average amount of tail 
removed was 15.1 mm., the extremes of the operation were 17 
mm. in one case and 14 mm. in two cases. The set was com- 
posed of nineteen individuals in an operated series and twelve 
individuals in a control series. The average body length of the 
operated series was 41.1 mm., of the control series 41.2 mm. 
During the last of this experiment the animals were subjected 
to two irregularities of treatment. They were left without food 
TABLE I 
MARCH | APRIL 
Dates of measurements... 8 11 15 \) Saxe it ton | 25 6 | 10 | 14 | 18 | 28 
Amounts of regeneration’ | | ; 
hy iN so oadahasabeod | 0.68 | 2.95 | 5.00 | 6.60 | 7.60 9.68 | g.20 | 9.30 | 9.60 | 9.40 
Days in period between | | 
Measurements......... res erase ca en | 3 ey age 4 4 | I6 
Gain during periods in 0.68 | 2.27 | 2.05 | 1.60 | 1.00| 2.08 | 0.52] 0.10 | 0.30 | 0.20 
Wai boosenggoaD.ooAbOLS | | | | | . 
Rate during periods...... 230-570 680 | .400 300, «170-130 «025.075 | | .020 
Measurements of control | | | | | 
series in millimeters... .| 41.20 | | 40.17 | | | 40.10 | | 38.9 
| | | 
Data for Experiment I. The first horizontal row of figures gives the dates upon which each meas- 
surement was made; below each date is the average amount of tail in millimeters regenerated by the 
operated series at that time. The third row of figures gives the number of days that have elapsed 
since the last measurement. The fourth row gives the gain in length during these periods. The 
fifth row contains the rate in millimeters per day, at which the tail grew during each period. The 
measurements of body length are the averages for the control series, and are given in the columns, 
headed by the dates upon which the measurement was made. 
