Effect of Successive Removal upon Regeneration 485 
Variations due to imperfections in the carrying out of the above 
precautions or to other neglected factors can largely be eliminated 
from the general result by the use of a large number of individuals. 
This was done fairly well though not as fully as desirable. While 
the original number was sufficiently large in all the series the rigid 
exclusion of larve that were influenced by accessory factors 
reduced this considerably in some. Most of these accidents were 
in the form of additional injuries which were especially likely to 
occur at the time of changing of the water. “Though the number 
of valid individuals is not great in some of the single series the 
general result obtained from all the series is wholly reliable 
especially since all seven experiments are in entire agreement. 
Data. The salamanders were divided into six series as follows ; 
TABLE 1—AmBLyYsToMA JEFFERSONIANUM 5 
Record of Series 
APPROXIMATE POR- | LENGTH OF FINAL 
REGENERATIONS 
SERIES EGG MASSES TION OF TAIL REGENERATION 
COMPARED 
REMOVED PERIOD IN DAYS 
ae od Mare eRe A,B 2/5 | third-first 14 
NVR S82 2 Sete cir a AB 4/5 | third-first 14 
MIB Giker. Atevsrmtctots can sreha sisters GC, D, E, F, G 2/5 fourth-first | II 
Ee Rolo s'. ose GD EEG 4/5 fourth-first 11 
AMA een seeicisneclieeeee vs oy | 2/5 fourth-first 10 
FOUL (23s) Deseo codesp emacs felis |) 4/5 fourth—first 10 
The dates of the operations in the different series are given in 
Table 2. 
TABLE 2—AmBLYSTOMA JEFFERSONIANUM 
Dates of Operations 
[THIRD AND| FOURTH FINAL RE- 
CLOSE OF | 
FIRST SECOND THIRD FIRST | AND FIRST |GENERATION 
SERIES EXPERI- | 
OPERATION | OPERATION] QPERATION| OPERA- OPERA- | PERIOD 
MENT 
TIONS TIONS IN DAYS 
[tat es | | 
Ia— 16 | February 17 | March13 April 6 April 20 14 
Il a— II b.| February 22 | March 9| March 24 April 9 | Aprilzo Il 
III a—Ill b.| February23 | Marchro | March25 Aprilito | April2o 10 
