lo8 JELLY-FISH, STAll-FISH, AND SEA-URCHINS. 



rhythm of the ganglion, which had previously been 

 twenty in the minute, fell to fourteen for the first 

 minute, eicfhteen for the second, and the orio-iiKil 

 rate of twenty for the third. In such experiments 

 the diminution of rate is most conspicuous during 

 the first fifteen or thirty seconds of the first minute. 

 Sometimes there are no contractions at all for the 

 first fifteen seconds after cessation of the stimulatina: 

 process, and in such cases the natural rhythm, 

 when it first begins, may be as slow as one-half or 

 even one-quarter its normal rate. All these effects 

 admit of being produced equally well, and with less 

 trouble, by faradizing the strip, when it may be 

 even better observed how prolonged may be the 

 stimulation, without causing anything further than 

 such slight exhaustion of the ganglion as the above 

 results imply.* 



Kaked-eyed Medusce. 



It would be impossible to imagine movements on 

 the part of so simple an organism more indicative 

 of physiological harmony than are the movements 

 of Sarsia. One may watch several hundreds of 

 these animals while they are swimming about in 

 the same bell-jar and never perceive, as in the 

 covered-eyed MedusMe, the slightest want of gang- 



* In this description I have everywhei-e adopted the current 

 phraseology with regard to ganglionic action — a phi-aseology 

 which embodies the theory of ganglia supplying interrupted stimu- 

 lation. But although I have done this for the sake of clearness, 

 of course it will be seen that the facts harmonize equally well 

 with the theoi-y of continuous stimulation, to which 1 shall alludo 

 further on. 



