Amount of Tail Regenerated to Removed in Tadpoles 435 
data too inaccurate to be of value. It will be noticed in Table 14, 
which gives the individual data of this experiment, that various 
individuals do not have complete records. ‘These were killed to be 
used in the volume and surface calculations. By the plan adopted, 
camera lucida drawings were made of the regenerated parts as 
whole and also of two typical cross-sections of the same. From 
these the other values were calculated; the results, however, very 
unsatisfactory. 
Experiment 7. Temperature 82° F. No Food Given 
Eighteen tadpoles, body length 27 to 31 mm., were divided into 
two series, CC and DD. From Series CC an average amount of 
5-4 mm. was removed; from Series DD, 9.8 mm. This experi- 
ment was to ascertain two things: (1) the relation between the 
amount removed and that regenerated during the first few days 
after the operation; (2) the average per cent regenerated by tad- 
poles of this size. (See Tables 15,16and17. Also Fig. 2.) 
Fig. 2 shows the same regions in each of its curves as those 
found in the curves of Experiment 4. There are, as before, four 
distinct regions. A first, of slow regeneration; a second, of rapid 
regeneration; a third, of slower regeneration than the second; and 
the fourth, in which regeneration gradually ceases. Both series 
regenerated 50 per cent of the amount removed, making the 
relation between the amount removed and that regenerated, a 
proportional one. ‘The final average amounts regenerated by these 
two series here follow, to wit: Series CC, 2.7 mm., 50 per cent; 
Series DD, 5.0 mm., 50 per cent. Series CC ceased to regener- 
ate on the sixth day after the operation; Series DD, on the tenth. 
The regeneration in these two series ceased when the amount 
removed was proportional to the amount regenerated; and the 
time consumed in regenerating this amount varied with the level 
of injury. ‘The point of largest interest in this connection is the 
first part of the curves of the two series. Neither curve showed 
great regeneration during the first two or three days after the 
operation; the rapid regeneration coming several days after the 
operation in both cases. This experiment was maintained 
twelve days. 
