CHAPTER VI. 



CO-ORDINATION. 



Covered-eyed MeduscB. 



From the fact that in tlie covered-eyed Medussethe 

 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 dischar^je of the active o^anHion, 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 



