248 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
nerve-endings so far sensitive that only by their 
excitation can the reflex mechanism be thrown 
into action. But if such is the explanation in 
this case, it is curious that in Tiaropsis indicans 
every part of the bell should be equally capable of 
yielding a stimulus to a precisely similar reflex 
action. 
“Jn pursuance of this point, I tried the experi- 
ment of cutting off portions of the margin, and 
stimulating the bell above the portions of the mar- 
gin which I had removed. I found that in this 
case the manubrium did not remain passive as it 
did when the whole margin of the bell was re- 
moved; but that it made ineffectual efforts to find 
the offending body, and in doing so always touched 
some part of the margin which was still unmuti- 
lated. I can only explain this fact by supposing 
that the stimulus supphed to the mutilated part is 
spread over the bell, and falsely referred by the 
manubrium to some part of the sensitive—z.e. un- 
mutilated—margin. 
“But to complete this account of the localizing 
movements, it is necessary to state one additional 
fact which, for the sake of clearness, I have hitherto 
omitted. If any one of the four radial tubes is 
irritated, the manubrium will correctly localize the 
seat of irritation, whether or not the margin of the 
bell has been previously removed. This greater 
ease, so to speak, of localizing stimuli in the course 
of the radial tubes than anywhere else in the 
nectocalyx, except the margin, corresponds with 
what I found to be the case in Tiaropsis indicans, 
