162 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



great disturbance was observable in regularity of 

 the rhythm ; for before the removal of the manu- 

 brium, the Medusa had been swimming for hours 

 with perfect regularity. 



Before concluding my description of these experi- 

 ments, it may perhaps be as well to mention one 

 other, which was designed to meet a possible 

 objection to the inferences which, as I shall imme- 

 diately argue, these experiments seem to sustain. It 

 occurred to me as a remote possibility that the 

 slowing and irregularity of the rhythm, which are 

 observable about a quarter of an hour after the 

 operations described, might be due to the depriva- 

 tion of adequate nourishment suffered by the ganglia, 

 in consequence of the escape of nutrient matter 

 from the cut ends of the nutrient tubes. Accord- 

 ino-lv, instead of cuttino^ ofi* the manubrium, I tried 

 the effect of momentarily immersing it in hot water, 

 and found that the subsequent disturbances of the 

 rhythm were precisely similar to those which result 

 from removal of the manubrium. 



Now, to draw any inferences from such meagre 

 facts as the above would be hazardous, unless we 

 recop^nize that in so doinor our inferences are not 

 trustworthy. But, with this recognition, I think 

 there will be no harm in briefly stating the deduc- 

 tions to which the facts, such as they are, would 

 seem to point. 



Physiologists are undecided as to the extent in 

 which many apparently automatic actions may not 

 really be actions of a reflex kind. Given any 

 ganglio-muscular tissue which is rhythmically con- 



