Chap. XII.] 



MEDUS/E. 



397 



Experiments on Medusae show that the seat of 

 spontaneous activity is nonfiapd to the, 



belLin 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 



