Chap. XII.] 



MEDUSM. 



397 



Experiments on Medusae show that the seat of 

 spontaneous activity is confined to the edge of the 

 bell in the Craspedote Me- 

 dusse, and to the region of 

 the marginal sense organs 

 in the Acraspedote forms; 

 if the extreme margin of the 

 bell of the former be com- 

 pletely removed, there is 

 immediately a total and 

 permanent paralysis of the 

 entire organ ; in the latter, 

 removal of the marginal 

 bodies is sufficient to pro- 

 duce a similar effect. The 

 results of these experiments 

 are, then, in 

 complete ac- 

 cordance with 

 the anatomical 

 facts. The dif- 

 fused plexiform 

 arrangement of 

 the nerve fibres 

 is, further, spo- 

 ken to by the 

 following ex- 

 periment : if all 

 the marginal 

 sense organs but 

 one be removed, 

 and if deep 

 sections be made in the substance of the bell, 

 so as to, at any rate, separate the nerve fibres at 

 many points of their course, it is found that the 

 bell is still capable of contraction ; or, in other 

 words, the stimuli sent out from the sole remaining 



