MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
177 
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 spontaneity 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 unmutilated specimen 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 polypite begins to retract by rhythmical twitches, the rate of this rhythm rapidly 
increasing until it ends in tonic contraction. When the polypite has just become fully 
retracted—or very often a little earlier—the bell suddenly begins its forcible and well- 
pronounced rhythmic contractions, which rapidly increase 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 normal swimming movements in response to natural or ganglionic stimulation. 
And, as already observed, this peculiarity of the excitable tissues is also well marked 
in the case of the artificial stimulation of deganglionated specimens under otherwise 
similar circumstances. 
The only facts which still remain to be considered regarding these shivering move¬ 
ments of paralyzed Sarsia are those which have reference to electrical stimulation. 
It will be remembered that in my first paper ( loc . cit.) I described these shivering 
movements as ensuing, not only when the paralyzed bells are immersed in chemical 
stimulants, but also when they are immersed in normal sea-water immediately after 
having been submitted to electrical stimulation. As the passage in my former 
paper which describes this effect of electrical stimulation is a short one, I will here 
transcribe it:— 
“ When the swimming-bell of Sarsia has had its margin removed, and so, as proved 
by hundreds of similar experiments, has been entirely deprived of its locomotor centres, 
nevertheless, in response to electrical stimulation, instead of giving a single contraction 
to make or break, it may begin a highly peculiar motion of a flurried, shivering 
character, which lasts without intermission for periods varying from a few seconds to 
half an hour. I never but once saw a similar motion in the perfect animal, and this 
was in the case of a specimen which was dying from having been poisoned with iron 
rust. The motion, I think, can be explained by supposing that the various parts of 
the muscle-layer are contracting without co-ordination; but why they should sometimes 
do this in response to stimulation, and why when they do this they should continue 
the action so long, these questions I cannot answer. In the case of so peculiar a 
MDCCCLXXX. 2 A 
