34 ILLINOIS BIOLOGICAL MONOGRAPHS [34 



At the four-day period the amount of regeneration is so small that 

 there is a large probable error and these data should be used with cau- 

 tion. For the 1 / 18 and % removals the number of individuals is so 

 small that the data for these levels do not compare in accuracy with the 

 others and they will therefore be passed over for the present. 



The data are presented in Tables 21 to 30. Tables 21 to 26 give 

 respectively the regenerations for the six different levels beginning with 

 the shortest removal. Table 27 collects all the data of amounts regen- 

 erated and Table 28 all the data of specific amounts regenerated. 

 Figure 2 gives in graphic form the specific amounts regenerated 

 for each regeneration. Table 29 gives the differences between 

 the first and second regenerations for each of the different levels at each 

 of the seven times of measurement. It includes the differences in specific 

 length as well as those in absolute length. The specific lengths furnish 

 the better basis for comparison and will be used in the following discus- 

 sion unless otherwise stated. Table 30 compares the specific rates in 

 the first and second regenerations and Figure 3 gives the results in 

 graphic form. 



Taking up the regeneration from the different levels and leaving 

 out of consideration for the present the two levels with too small a 

 number of individuals, the data for the 1 / 10 level as given in Table 4 

 are the first to be considered. There are five individuals for first and 

 seven for second regenerations. The second regeneration is ahead in 

 specific length from the fourth to the tenth day. At 121/2 days the two 

 are tied and at 56 days the first is ahead. Regeneration is completed in 

 12% days and beyond this time there is a decrease in regenerated ma- 

 terial. The decrease is greater in the second than in the first regenera- 

 tion, hence the ascendency of the latter at 56 days. During the whole 

 period of active regeneration the second regeneration remains ahead. 



There are eight individuals for the first regeneration and eleven for 

 the second at the Ys level (Table 24). The specific amounts of regenera- 

 tion are strikingly similar throughout the whole period of regeneration. 

 The two departures from equality are an advantage of 0.01 for the second 

 regeneration at 8 days and a disadvantage of 0.02 at 18 days. These 

 •departures are in the direction of the general rule observed at other 

 levels that the second regeneration tends to be ahead at the earlier pe- 

 riods and the first at later periods, the advantage in the later case being 

 due to the earlier completion of regeneration and absorption of regener- 

 ated material in the second regenerations than in the first ones. In this 

 instance the first regeneration does not gain an advantage until after the 

 second has reached its maximum. 



At the ^2 level there are 5 individuals for the first regeneration and 

 8 for the second (Table 25). The second is ahead until the eighth day. 



