248 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



nerve-enrliiigs so far sensitive that only by tlieir 

 excitation can the reflex mechanism be thrown 

 into action. But if such is the expUmation in 

 this case, it is curious that in Tiaropsis indicans 

 eveiy part of the beli should be equally capable of 

 yielding a stimulus to a precisely similar reflex 

 action. 



" In 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 ivhole margin of the bell was re- 

 moved ; but that it made ineflTectual efforts to find 

 the oflPending 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 tlie stimulus su})plied to the mutilated part is 

 spread over the bell, and falsely referred by the 

 manubrium to some part of the sensitive — i.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. 



