RATE OF REGENERATION IN CASSIOPEA 13 



For the experiments of type 2a (fig. 5) where the disks con- 

 sisted of an active and an inactive half there was shown a con- 

 stancy of results. The active half invariably showed the first 

 evidences of regeneration and maintained a higher rate through- 

 out the entire period until the cavity in the center of the disk 

 had been closed. So far as is shown by a comparison of the 

 amount of tissue regenerated in a given time by disks under the 

 conditions in experiments of type 2 and type 2a there was no 

 noticeable difference in the rate of regeneration when only a 

 single sense organ is left on the active half disk or when the full 

 number of sense organs was present. 



The results of these studies on the influence of the sense organs 

 on the rate of regeneration confirm Mayer's observations that a 

 single sense organ is sufficient to supply the nervous influences 

 that control the normal activities of a medusa. 



EXPERIMENTS OF TYPE 3 (ANESTHETICS) 



In the experiments of type 2 and 2a it was shown that the 

 active half of a medusa disk prepared as shown in figures 3 and 5 

 has a higher rate of regeneration than does the inactive half of 

 the same specimen. While this point is clearly shown in all the 

 experiments of the two types just mentioned, the results ob- 

 tained by this method throw no light upon the nature of the con- 

 trol exercised by the marginal sense organs, as to whether it is 

 exerted through the higher metabolism brought about by mus- 

 cular activity, or through some other less apparent metabolic 

 process under the control of the sense organs. 



Two other types of experiments were undertaken to ascertain 

 the nature of the nervous control. In the first set of experi- 

 ments (type 3) disks prepared with insulated active and inactive 

 halves (fig. 3) were allowed to regenerate in sea water to which 

 fifteen per cent by volume of 0.6 m MgS04 had been added. In 

 this solution the disks will live for an indefinite time and will for 

 several hours retain the capacity to regain their normal activity 

 within a few moments after being returned to fresh sea water. 

 Mayer (op. cit) has shown that in a weak MgS04 solution in sea 

 water the effect of the magnesium is for a time confined almost 



