166 Papers from the Department of Marine Biology. 



SUMMARY. 



(1) The experiments with entire disks, when the rates of regenera- 

 tion of specimens on which the sense-organs remained are compared 

 with those of specimens from which all sense-organs are removed, are 

 inconclusive because of wide differences in physiological activity 

 between different individuals. 



(2) When we compare the insulated halves of a disk, on one of which 

 the sense-organs remain, while all of them have been removed from 

 the other half, it is found that the half-disk with sense-organs always 

 regenerates most rapidly. This is especially noticeable in the early 

 stages of regeneration. The difference in rate falls gradually through- 

 out the course of an experiment (table 1 and fig. 6) . 



(3) When disks prepared as in the experiments mentioned in the 

 previous paragraph are allowed to regenerate in sea-water plus 15 parts 

 0.6 m MgS0 4 , the regeneration is at first more rapid from the half on 

 which the sense-organs come under the influence of the anesthetic, and 

 from that time on the rate of regeneration is practically equal from 

 both halves (table 2 and fig. 7). 



(4) When all the sense-organs are removed from a disk and the 

 halves insulated, muscular activity may be maintained in one half by 

 forming an endless labyrinth of the subumbrella tissue and initiating a 

 circuit wave of contraction by induction shocks. Under these condi- 

 tions the regeneration is faster from the activated than from the 

 inactive half-disk. The difference is, however, not nearly so great as 

 when the sense-organs are removed from only one of the insulated 

 halves of a disk (table 3 and fig. 8) . 



(5) Comparison of rates of regeneration of the halves of a disk, one 

 half of which retains its sense-organs, while a circuit wave of contrac- 

 tion is maintained in the muscles of the other half, shows that the 

 half-disk the muscles of which are contracting under the control of the 

 sense-organs regenerates faster, although the rate of pulsation of the 

 activated half is more than 3 times that of the former (table 4 and fig. 9). 



(6) The influence of the nervous system on the earlier stages of 

 regeneration has been noted by several earlier investigators, but 

 apparently no importance has been attached to it. 



(7) These experiments indicate that the rate of regeneration is simply 

 one expression of the general metabolic activity of an animal, and as 

 such is subject to the influence of the nerve-centers, as are many other 

 functional activities. 



(8) When a normal medusa, a regenerating medusa, a medusa disk, 

 or half-disk is kept in water free from food material, the loss in weight 

 follows a curve of the formula y = w(l d)x. Here y = the weight for 

 anjr given day, w = original weight, x = number of days of starvation, 

 and a is a constant, the " coefficient of negative metabolism." The value 



