Amount of Tail Regenerated to Removed in Tadpoles 429 
to regenerate; for the animals used in Experiment 3 were collected 
in February, while those used in Experiment 2 were taken early in 
December. 
Experiment 4. Food, Spirogyra. Temperature, 78° F. 
In this experiment the relation between the amount removed and 
that regenerated was obtained every third day throughout the 
period of regeneration. 
Five series, O, P, R, S, and T, were established, twenty tad- 
poles in a series, body length 37 to 42 mm.; and a control series of 
forty other uninjured tadpoles arranged. Series O was injured by 
the removal of three mm. of tail from each individual; Series P, 
5 mm.; Series R, 10 mm.; Series S, 15 mm.; and Series I’, 20 mm. 
The regenerated part was measured every three days and the whole 
experiment maintained for thirty two days. Individual records of 
the amount regenerated by each tadpole were kept. (See Tables 
Avie, 02,.and 13. Also Hig: s.) 
It was found that Series T behaved differently from the other 
series of this experiment, accordingly itis considered separately. At 
the end of the first three days after the operation, almost half of the 
tadpoles in Series T (20 mm.) were dead, and those living were 
sluggish and weak. ‘The survivors had not regenerated any of the 
lost tail, the wound not being even healed over in several cases. 
By the end of the sixth day, seven more of this series had died and 
the death of another individual on the eighth day reduced the 
number of living to four. These four continued to live and each 
one regenerated a part of the removed tail. This regenerated tail, 
however, was not normal, being twisted and very irregular of out- 
line. It is evident that with a death rate of 80 per cent and 
abnormal regeneration by those four surviving the operation, the 
injury was too severe in Series T. The final amount regenerated 
by the four survivors of this series averaged 20 per cent of the 
amount removed. 
The average regeneration of the four remaining series on the 
third day after the operation were: 
