KATE OF REGENERATION IN CASSIOPEA 11 



number of days during which the regeneration has been going 

 on, those along the ordinate the amount of regeneration in milh- 

 meters. The record for each specimen is carried to the time of 

 closure of the open circle in the center of the disk by the sheet of 

 regenerated tissue. 



From the start of regeneration the Aew tissue produced from 

 the side with its sense organs intact is shown to be more rapid. 

 In the early stage of regeneration this difference is more striking 

 upon a cursory examination than in the later stages although the 

 actual difference on the rate of growth of new tissue changes 

 only slightly during the entire period of regeneration. The pro- 

 portion between the amounts of new tissue formed each day, 

 taking the amount regenerated from the side without sense or- 

 gans as the unit, was respectively: First day 1 : 1.53; second day 

 1 : 1.44; third day 1 : 1.41; fourth day 1 : 1.38; fifth day 1 : 1.39. 



The regeneration from the half without sense organs is more 

 regular as is shown by the fact that for the mean of each day's 

 observation the probable error is less for that half than for the 

 one upon which the sense organs remain. This result would be 

 expected to follow from the fact that the inactive side was re- 

 lieved from the influence of the marginal sense organs which 

 would introduce many stimuH of varying intensity all of which 

 would have either a retarding or accelerating influence upon the 

 processes of regeneration. 



WTien the rates of regeneration of certain disks in table 1 are 

 compared with one another the cause of the uncertainty of the 

 results obtained in experiments with entire disks is clearly shown. 

 The closure of the open circle in disk 36, table 11, was complete 

 in two days while five days were necessary to complete the closure 

 in specimen 30, table 1. Had the latter been the active disk, 

 and the former the inactive disk, of a pair compared in an experi- 

 ment with entire disks the conclusion that an inactive disk some- 

 times degenerates more rapidly than an active one could not 

 have been avoided. 



