80 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
continuity—it thus becomes a possibility that in 
these cases no such anatomical continuity exists, 
but that the physiological continuity is maintained 
by some such process of physiological induction as 
probably takes place among the nerve-fibres of 
Aurelia.* 
I have now to detail another fact of a very 
puzzling nature, but one which is certainly of 
importance. When the spiral section is performed 
on Aurelia aurita, and when, as a consequence, the 
contraction-waves which traverse the elongating 
strip become at some point suddenly blocked, if the 
section be stopped at this point it not unfrequently 
happens that after a time the blocking suddenly 
ceases, the contraction-waves again passing from 
the strip into the umbrella as freely as they did 
before the section reached the point at which the 
blocking oceurred. The time required for this 
restoration of physiological continuity is very 
variable, the limits being from a few seconds to an 
hour or more; usually, however, it is from two 
to four minutes. This process of re-establishing 
the physiological connections, although rapid, is 
not so instantaneous as is that of their destruction 
by section. In general it requires the passage of 
several contraction-waves before the barrier to the 
passage of succeeding waves is completely thrown 
* That it can scarcely be electrical induction would seem to be 
shown by the fact that such effects can only be produced on 
nerves by strong currents, and also by the fact that the saline 
tissuesof the swimming-bell must short-circuit any feeble electrical 
currents as soon as they are generated. 
