SECTION OF COVERED-EYED MEDUS&. 67 
bell, the result being, at each discharge, two con- 
traction waves, which start at the same instant, 
one on each side of the ganglion, and which then 
course with equal rapidity in opposite directions, 
WU, Sia, 
Nigy WS Wy} A 
BYif U1) SF 
Fig. 9. 
and so meet at the point of the dise which is 
opposite to the ganglion. Suppose, now, a number 
of radial cuts are made in the dise according to 
such a plan as this (Fig. 9), wherein every radial 
cut deeply overlaps those on either side of it. The 
