No. 584] REGENERATION IN ENCHTTRJEUS 497 



was used to determine the number of regenerated seg- 

 ments is accurate to within one or two segments, for it 

 will be noted that the results by the two methods never 

 differ by more than two segments, usually by only one. 

 The worm's body is so short that it was found impracti- 

 cable to secure exactly eight, sixteen, etc., segments in 

 every piece used in the whole series of experiments. 



The results obtained in each of the six sets of experi- 

 ments have been condensed, for convenience, and are 

 shown in Table II. In the first vertical column of this 

 table the Roman numerals designate the number of the 

 set of experiments. The horizontal lines corresponding 

 to each of these sets give in succession, (1) the number of 

 segments in the pieces used in the experiments, (2) the 

 number of worms operated on, (3) the number that sur- 

 vived long enough to be observed, (4) the per cent of 

 worms that survived and were observed, (5) the period 

 during which the regeneration took place, (6) the number 

 of segments (0to24) regenerated by the surviving worms, 

 (7) the average number of segments regenerated in each 

 set of experiments, and (8) the mean rate of regeneration 

 per day of the worms in each set expressed in segments. 

 This mean rate of regeneration was obtained by first com- 

 puting the rate of regeneration per day (in segments) 

 for each worm in the set, and then averaging all the re- 

 sults. In some worms the number of segments regen- 

 erated was observed twice, several weeks elapsing be- 



