Amount of Tail Regenerated to Removed in Tadpoles 427 
From these averages it is to be seen that the relation of the 
amount regenerated to that removed is clearly not a proportional 
one at the end of five days, as was the case at the end of twelve 
days in Experiment 1. All of the series were continued until the 
twelfth day after the operation, a second set of measurements 
being taken at that time. Series F and G again showed no 
regeneration. All of the tadpoles in these two series were still as 
active as any of the others in the experiment, but the condition of 
the tail externally was precisely the same as when observed on the 
fifth day. ‘There were no deaths in any of the series during the 
twelve days they were maintained and the general health of all 
the tadpoles seemed good. As all of the other conditions of the 
experiment were the same for Series F and Gas for Series D and E, 
which did regenerate, this lack of regeneration was ascribed to the 
effect of temperature upon the processes producing regeneration. 
Series D and E both made accretions to the amount regenerated 
during the seven days intervening between the fifth and the 
twelfth, excepting the first set in each series from which but two 
millimeters had been removed, which remained constant. As 
was noted in Experiment 1, the per cent regenerated by the 
various sets of each series during the twelve days was approxi- 
mately the same, showing the amount regenerated to be propor- 
tional to the amount removed at the end of the twelfth day. The 
per centum regenerated, however, was not the same in Series D 
as in Series E, the latter being about fifteen per cent less than 
the former. ‘This difference was evidently due to the lower tem- 
perature at which Series E was kept, as the other factors were the 
same. ‘Three things are evident from the data of Experiment 2. 
(1) Temperature affects the amount of regeneration, other factors 
being constant. (2) There is a temperature limit below which 
tadpoles live but do not regenerate the tail. (3) The percentage 
of regeneration is not proportional at all times throughout the 
period of regeneration. Measurements of the control series show 
that the tadpoles did not grow during this experiment. 
