740 
ME, J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDITSiE. 
twitches. The polypite and tentacles are now strongly retracted, while the nectocalyx 
is drawn together so as to assume an elongated form. The latter is now no longer 
responsive either to tentacular or to direct stimulation ; but the tentacles and polypite 
both remain responsive to stimuli applied either directly to themselves or to the nervo- 
muscular tissue of the bell. Death always takes place in very strong systole ; and as' 
this is an exceedingly unusual thing in the case of Sarsia, there can be no doubt that, 
in this respect, the action of the digitalin is different on the Medusae from what it is on 
the heart. 
On the various species of Tiarojpsis digitalin at first causes acceleration of the 
swimming-movements, with great irregularity and want of coordination. Next strong 
and persistent spasms supervene, which give the outline of the nectocalyx an irregular 
form; and every now and then this unnatural spasm gives place to convulsive swimming- 
motions. Evidently, however, the spasm becomes quite persistent and excessively 
strong. The polypite of Tiarojpsis indicans crouches to its utmost, and the animal dies 
in strong systole. 
§ 7. Atropin. — In the case of Sarsia atropin causes convulsive swimming-motions. 
The systoles next become feeble, and finally cease. The nectocalyx is now somewhat 
drawn together in persistent systole, with the polypite and tentacles strongly retracted. 
Muscular irritability remains after tentacular irritability has disappeared, but it is then 
decidedly enfeebled. 
In the various species of Tiaropsis the convulsions are strongly pronounced. They 
begin as mere accelerations of the natural swimming-motions, but soon grow into well- 
marked convulsions, consisting of furious bouts of irregular systoles following one 
another with the utmost rapidity, and wholly without coordination. Occasionally 
these movements are interrupted by a violent spasm, on which strong shuddering 
contractions are superimposed. 
§ 8. Nicotin . — On dropping Sarsia into a sea-water solution of nicotin of appropriate 
strength, the animal immediately goes into a violent and continuous spasm, on which a 
number of rapidly succeeding minute contractions are superimposed. The latter, 
however, rapidly die away, leaving the nectocalyx still in strong and continuous systole ; 
tentacles and polypite are retracted to the utmost. Shortly after cessation of sponta- 
neity, the bell is no longer responsive to tentacular stimulation, but remains for a 
considerable time responsive to direct stimulation of its own substance ; eventually, 
however, all irritability disappears, while the tentacles and polypite relax. On trans- 
ferring the animal to normal water, muscular irritability first returns, and then central, 
as shown by the earlier response of the bell to direct than to tentacular stimulation ; 
but if the animal has been poisoned heavily enough to have had its muscular irritabi- 
lity suspended, it is a long time before central irritability returns. Soon after central irri- 
tability has returned, the animal begins to show feeble signs of spontaneity, the motions 
being exceedingly weak, with long intervals of repose ; but the degree of such feeble- 
ness depends on the length of time during which the animal has previously been exposed 
