450 Charles R. Stockard 



respond in dissimilar manners and finally to attempt to harmonize 

 the results. 



Seventy-five healthy medusae were selected and arranged in 

 five groups of 15 individuals each. The average size of individ- 

 uals in all the groups v^as approximately equal since the medusae 

 were first arranged in lots of five equal sized specimens and one 

 from every lot w^as put into each group. The groups w^ere then 

 operated upon. In the first group one oral arm was cut at its 

 base from each medusa, in the second two arms were similarly 

 removed from each, in the third four arms were cut away, in the 

 fourth six arms were amputated and in the fifth group all of the 

 eight oral-arms were cut off at their bases. The groups are thus 

 alike in every respect except that they are injured to successively 

 greater extents. None of the specimens were fed during the experi- 

 ment. 



Table III presents the record of regenerative growth from the 

 individuals with one arm cut away. The first vertical column 

 contains the original diameters in millimeters of the medusae disks 

 on the day of operation, May 20; the second column shows the 

 disk diameters 17 days later when the new growing tissue was 

 first measured. The third column shows the lengths of the new 

 arm-buds and the fourth and fifth columns contain the specific 

 amounts of regeneration which are calculated in the fourth column 

 by dividing the length of new tissue by the original disk diameter 

 in each case, and in the fifth column by dividing by the diameters 

 after ij days. The figures of the fifth column are with one excep- 

 tion greater than those in the fourth since the disks decreased in 

 diameter during the experiment. 



The sixth column of the table gives the diameters of nine in- 

 dividuals measured 24 days after the operation. The size of the 

 disks have continued to decrease and the new arm buds have 

 lengthened as shown in column seven. The specific amounts of 

 regeneration, therefore, have also increased. It is unnecessary 

 to calculate a specific rate of regeneration per day since the growth 

 was continuous and each column of specific amounts is given for a 

 certain number of days; obviously the specific amounts are to one 

 another as the quotients would be if they were all divided by the 

 same number of days. 



