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- 
ingly, instead of cutting off 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 
recognize that in so doing 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- 
