Amount of Tail Regenerated to Removed in Tadpoles 431 
next series to cease regeneration was Series R, on the fifteenth 
day after the operation. The final amount regenerated by it 
was 5 mm., 48 per cent of the amount removed. Series S 
stopped regenerating on the eighteenth day with an amount of 7.2 
mm., 48 per cent of the amount removed. From the eighteenth 
day until the close of the experiment all of the series remained con- 
stant and did not regenerate beyond the limit they first reached. 
Because of this fact, the curve for all of the series from this time on 
are straight lines parallel to the base of the plot. 
An examination of Fig. 1 shows each curve to be composed of 
four distinct regions. ‘The first, one of slow regeneration, lasts 
for the first three days after the operation; a second, of rapid regen- 
eration, which is of several days’ duration; a third, of regeneration 
distinctly slower than that of the second region; and a fourth, in 
which the regeneration gradually ceases. At the end of the 
fourth region, the regeneration probably ceases entirely; although, 
there is some evidence of very slight regeneration for many days 
after the apparent cessation of regeneration. ‘[heaverageamounts 
regenerated by the various series up to the time when regenera- 
tion ceased, are to be found in the following table: 
TABLE 5 
FINAL FINAL PER 
AMOUNT AMOUNT CENTUM 
REMOVED REGENER- | REGENERA- 
| ATED ATED 
| mm, | mm. 
Santee Ok aa supodon.c iano aad COCR OO aT CORE UgOAOBOBe Taos | 3.2 | 14 44 
SEES Logos mor Go HAAR AtOn Dino oe BODE Eee niCioD SOSae ohne Ba Dek | 44 
DOLIESt crate cic create apace ote aicieietateis ctereiuieisys. + sista phe Greets seco | 10.4 5.0 48 
CTIES Se Eee ue Me Lala ote ol ha bala anelb etaele latte choles Greochatane ehavene 14.8 7 Ae 48 
Sexicendy (UG) ie. nce mevee Mache dolor ara el aie- seer weirs ahs 20.2 died 
Seniesil(4) sesh acre area eat. ee eclacet «Sede eee enetoee> 4.1 20 
The two Series T mentioned in the above table, are two divisions 
of that series; the numbers in parenthesis after each refer to the 
number of individuals. From this table it is to be seen that the 
amount of regeneration at the time regeneration ceased, was pro- 
