742 
MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAS. 
responsive to stimuli applied at the tentacles, and sometimes two or three contractions 
will follow such a stimulus, as if the spontaneity of the animal were slightly aroused 
by the irritation. Soon, however, only one contraction is given in response to every 
tentacular irritation, and by-and-by this also ceases — the Medusa being thus no longer 
responsive to central stimulation. It remains, however, for a long time responsive to 
stimulation of the nervo-muscle sheet ; indeed the strength of the alcohol solution 
must be very considerable before loss of muscular irritability supervenes. It may thus 
be made to do so, however; and on then transferring the animal to normal water, 
recovery begins in from three minutes to a quarter of an hour. The first contractions 
are very feeble, with long intervals of repose ; but gradually the animal returns to its 
normal state. 
The above remarks apply also to Tiaropsis. In T. indicans the polypite recovers in 
normal water sooner than does the nectocalyx. Both in Sarsia and Tiaropsis the 
polypite and tentacles are retracted while exposed to alcohol, and, after transference to 
normal sea-water, the animals float on the surface — presumably in consequence of their 
having imbibed some of the spirit. The period during which floatation lasts depends, 
(a) on the strength of the alcohol solution used, and ( b ) on the time of exposure to its 
influence. It may last for an hour or more ; but in no case is recovery complete till 
some time after the floatation ceases. 
§ 10. Cyanide of Potassium. — On Sarsia the first effect is to quicken the contractions 
and then to enfeeble them. The animal assumes an elongated form, as already described 
under atropin. Spontaneity ceases very rapidly even in weak solutions ; and for an 
exceedingly short time after it has done so, the bell continues responsive both to tenta- 
cular and to direct stimulation. For a long time after the bell ceases to respond to any 
kind of stimulation, the nervous connexions between the tentacles and between the ten- 
tacles and polypite remain intact, as also do the nervous connexions of these organs with 
all parts of the bell. This interesting fact is rendered apparent, first, by stimulating 
a tentacle and observing that all the four tentacles and the polypite respond ; and, 
second, by irritating any part of the nervo-muscular sheet of the bell and observing 
that while the latter does not respond, both the tentacles and the polypite retract. 
Recovery from this stage occupies several hours. 
In the case of Tiaropsis the convulsions are, as usual, more pronounced, being 
marked by the occurrence of a gradually increasing spasm, which differs from a normal 
spasm in the respects already described under strychnia. In all the species both 
of Sarsia and Tiaropsis , the polypite and tentacles are retracted during exposure to 
this poison. 
§11. Pemarks. — The above are some among the poisons which I have tried; but to avoid 
undue length I will not proceed further with the list on the present occasion. Enough, 
I think, has been said to show how surprising is the resemblance between the actions of 
these various poisons on the Medusse and on the higher animals. When the physiologist 
bears in mind that in Sarsia we have the means of testing the comparative influence of 
