90 JELLY-FISH, STAR-FISH, AND SEA-URCHINS, 
now stimulating the end w, or on watching the 
lithoeyst there discharge, the resulting contraction- 
wave would be observed to bifureate at b,and then 
Fig. 14, 
pass on as two separate waves through the zones, 
bc,bd. Now, as these two waves were started at 
