ARTIFICIAL RHYTHM. 197 



artificial rhythm. Consequently, whether the 

 specimens experimented upon be entire or paralyzed 

 by removal of their margins, the phenomena of 

 artificial rhythm under the influence of chemical 

 stimulation are the same. But although the spon- 

 taneity of the ganglia disappears before the artificial 

 rhythm sets in, such is not the case with the reflex 

 activity of the ganglia ; for on nipping a tentacle of 

 the quiescent bell before the artificial rhythm has 

 set in, the bell will give a single normal response to 

 the stimulation. 



Hence, in historical order, on dropping an unmuti- 

 lated specimen of Sarsia into a solution of glycerine 

 of the strength named, the usual succession of events 

 to be observed is as follows. First, increased 

 activity of the normal swimming motions, to be 

 quickly followed by a rapid and progressive decrease 

 of such activity, till in about fifteen seconds after 

 the immersion total quiescence supervenes. Four 

 or five seconds later the manubrium begins to re- 

 tract by rhythmical twitches, the rate of this 

 rhythm rapidly increasing until it ends in tonic 

 contraction. When the manubrium has just become 

 fully retracted — or very often a little earlier — the 

 bell suddenly begins its forcible and well-pro- 

 nounced rhythmic contractions, which rapidly in- 

 crease in their rate of rhythm until they coalesce 

 into a vigorous and persistent spasm. If the animal 

 be now restored to normal sea -water, spontaneity 

 will return in a feeble manner ; but there is always 

 afterwards a great tendency displayed by the bell 

 to exhibit shivering spasms instead of norma' 



14 



