118 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
ing between the bell and the manubrium. Never- 
theless, in many cases, irritating any part of the 
band a J has the effect of causing the manubrium 
to perform the active random motions previously 
described. In such cases, however, it is observable 
that the further away from the manubrium the 
stimulus is applied, the less active is the response 
of this organ. In very many instances, indeed, the 
manubrium altogether fails to respond to stimuli 
applied at more than a certain distance from itself. 
For example, referring to Fig. 25, the manubrium 
might actively respond to irritation of any point 
in the division d, e, f, g, while to irritation of any 
point in the division f, g, h, 7 its responses would 
be weaker, and to irritation of any point in h, 1, 7, k, 
they would be very uncertain or altogether absent. 
Hence in this form of section we have reached 
about the limit of tolerance of which the non-radial 
connections between the bell and manubrium are 
capable. 
Another interesting fact brought out by this form 
of section is, that the radial tubes are tracts of 
comparatively high irritability as regards the manu- 
brium; for the certainty and vigour with which 
the manubrium responds to a stimulus applied at 
one of the severed radial tubes, f, g, or h, 4, or J, k, 
contrast strongly with the uncertainty and feeble- 
ness with which it often responds to stimuli applied 
between any of these tubes. Indeed, it frequently 
happens that a specimen which will not respond 
at all to a stimulus applied between two radial 
tubes, will respond at once to a stimulus applied 
