CHAPTER VL 
CO-ORDINATION. 
Covered-eyed Medusa. 
From the fact that in the covered-eyed Meduse the 
passage of a stimulus-wave is not more rapid than 
that of a contraction-wave, we may be prepared 
to expect that in these animals the action of the 
locomotor ganglia is not, in any proper sense of the 
term, a co-ordinated action; for if a stimulus-wave 
cannot outrun a contraction-wave, one ganglion 
cannot know that another ganglion has discharged 
its influence till the contraction-wave, which re- 
sults from a discharge of the active ganglion, has 
reached the passive one. And this I find to be 
generally the case; for it may usually be observed 
that one or more of the lithocysts are either tempo- 
rarily or permanently prepotent over the others, 
i.e. that contraction-waves emanate from the pre- 
potent lithocysts, and then spread rapidly over 
the swimming-bell, without there being any signs of 
co-ordinated or simultaneous action on the part of 
the other lithocysts. Nevertheless, in many cases 
such prepotency cannot, even with the greatest 
care, be observed; but upon every pulsation all 
