46 ILLINOIS BIOLOGICAL MONOGRAPHS [46 



Experiment III Amblystoma punctatum Series 3962-3999 



Material and Method Eggs of Amblystoma punctatum in the cleav- 

 age stages were collected on March 18, 1913, and hatched in the labo- 

 ratory on April 9. The first operations were made on April 23, 

 at which time also five controls were killed and preserved. These when 

 measured gave an average total length of 13.1 mm. and an average tail 

 length of 5.3 mm. Ninety individuals were used for the regeneration 

 study. In thirty individuals two-thirds in length of the tail was re- 

 moved on April 23. The regenerated portion in these was removed 

 on May 10 and at the same time in a second thirty individuals two- 

 thirds of the tail was removed. On May 21 the first thirty were 

 operated on for the third time, the second thirty for the second time, 

 and the third thirty for the first time. To insure as accurate a compari- 

 son as possible the ninety individuals though they were approximately 

 of equal size were divided into thirty groups of three each, a selection 

 being made so that the three members of a group were as much alike 

 as possible. In each group one of the three members was used for the 

 first regeneration, one for the second and the third for the third regen- 

 eration. This procedure gave a possibility of comparing the first, second 

 and third regenerations without error due to difference in size, age, or 

 in external conditions. 



Three individuals from each thirty were killed two days after the 

 last operations, 'four in four days, five in six days, five in eight days, 

 six in ten days and seven in fourteen days. 



At the end of the experiment, control individuals gave an average 

 total length of 31.5 mm. and an average tail length of 10.5 mm. 



Data The data are given in Tables 31 and 32. The specific amounts 

 of regeneration were not determined because the removed lengths were 

 alike and hence the comparison of absolute lengths gives the same re- 

 sults as a comparison of specific amounts. 



The average regenerated lengths at each of the six different times 

 will be taken up first. At two days the average regenerated lengths 

 for the first, second and third regenerations are respectively 0.22, 0.25 

 and 0.26 mm. At four days the corresponding amounts are 0.66, 0.75 

 and 1.00. At six days they are 1.36, 1.40 and 1.36, but the low value 

 of the third regeneration is due to a single exceptional individual. At 

 eight days the figures are 2.18, 2.68 and 2.68. At ten days they are 

 3.55, 3.82 and 4.20 and at fourteen days 5.34, 6.12 and 6.08. In all 

 cases, except the one at six days explained above, both second and third 

 regenerations are ahead of the first. The third regeneration is greater 

 than the second at two, four and ten days, is equal to the second at eight 

 days and less than the second at six and fourteen days. Since the low 



