Amount of Tail Regenerated to Removed in Tadpoles 433 
portional to the amount removed. The time required by the 
various series to regenerate these amounts, that is, the length of 
time during which regeneration took place, was not the same for 
these several series, but varied in the same direction as the amount 
removed. 
From the experiment as a whole three things are evident: (1) 
The regeneration of the part removed is not complete; for in every 
case the regeneration ceased after about 46 per cent of the 
amount removed had been regenerated. (2) The amount regener- 
ated at the time that regeneration ceased, which was the complete 
amount laid down during the period of regeneration, varied directly 
as the amount removed, that is, was proportional to the amount 
removed. (3) The length of time through which the period of 
regeneration extended, was not the same for the various amounts 
of injury; but it grew longer the greater the amount removed. 
In this connection, the behavior of the series with 2 mm. 
removed in Experiment 2, is to be considered. Under that experi- 
ment, it was noted that the amount regenerated by the individual 
with an injury of 2 mm. was the same on the twelfth day as on 
the fifth day after the operation; in other words, in this case there 
was no additional regeneration after the fifth day. The smallest 
injury inflicted in the present experiment was the removalof 3 mm., 
that in Series O. This series ceased regenerating on the ninth day 
after the operation. Comparing these two sets of tadpoles, it is 
seen that, these with 2 mm. removed reached the end of their 
period of regeneration some four days earlier than those of Series 
O with 3 mm. removed. Although this comparison is not strictly 
accurate, it does show that the time through which regeneration 
takes place, the duration of the period of regeneration, varies in 
the same direction as the amount removed. 
The control series of Experiment 4 showed no growth during 
the time of this experiment. 
Experiment 5. Temperature, 80° F. Food, Raw Beef 
One hundred tadpoles, body length 37 to 42 mm., were operated 
upon in the same manner as those of Experiment 4. The experi- 
ment was maintained for thirty days in a brooder at 80°F. The 
