On the Nervous System of Cassiopea Xamachana. 



139 



When medusae are treated with a weak solution of oxaHc acid in 

 magnesium-free artificial sea-water it is possible to destroy the activity 

 of the sense-organs for a considerable time without seriously injuring 

 the other tissues. In all my experiments, however, recovery of func- 

 tional activity by the sense-organs took place within 24 hours if the 

 oxalic-acid solution was of such a strength that the ectodermal tissues 

 were not injured. In such experiments there was at first an equal rate 

 of regeneration for each of the halves of a disk until the sense-organs 



1234.56769 



Fig. 7. — Showing the rates of regeneration of active and inactive half-disks regen- 

 erating in sea-water to which has been added 15 parts of 0.6 m MgSO^. The 

 upper line represents the half with sense-organs; the lower line represents those 

 without sense-organs. The divisions along the ordinate represent the amount 

 of regeneration in millimeters; those along the abscissa the time of regeneration 

 in days. 



regained their functional activity, after which the half-disk with sense- 

 organs regenerated most rapidly. 



The experiments with jMg solutions show that there is an influence 

 of the sense-organs on the rate of regeneration which is apparently 

 exercised for a considerable time after muscular activity has been 

 suppressed. It was impossible, however, by this method to differentiate 

 w^th any certainty between the two effects, since there is no visual 

 means of ascertaining the exact time at which the sense-organs lose their 

 power of sending out the stimuli necessary for normal contraction. 

 Since, as was shown by ]Mayer {op. cit.), it is possible to maintain a 



