176 
MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSiE. 
die in this condition of strong systole. But if the bell be transferred to normal sea¬ 
water immediately after, or still better, slightly before the tonic spasm has become 
complete, an interesting series of phenomena present themselves. The spasm persists 
for a long time after the transference without undergoing any change—the length of 
this time depending on the stage in the severity of the spasm at which the transference 
is made. After this time is passed, the spasm becomes less pronounced than it was at 
the moment of transference, and a reversion takes place to the rhythmic contractions. 
The spasm may next pass off entirely, leaving only the rhythmic contractions behind. 
Eventually these too fade away into quiescence; but it is remarkable that they leave 
behind them a much more persistent exaltation of irritability than is the case with 
acid. For in the case of glycerine the paralyzed bell which has been exposed to 
the influence of the irritant and afterwards become quiescent in normal sea-water, 
will often continue for hours to respond to single stimuli with a bout of rhythmic 
contractions. This effect of glycerine in producing an extreme condition of exalted 
irritability is also rendered apparent in another way. For if, during the soaking stage 
of the experiment—he., before the first of the rhythmic contractions has occurred—the 
bell be nipped with the forceps, the effect may be that of so precipitating events that 
the whole of the rhythmic stages are omitted, and the previously quiescent bell enters 
at once into a state of rigid tonic spasm. This effect is particularly liable to occur 
after prolonged soaking in weak solutions of glycerine. 
As in the case of stimulation by acid, so in that of stimulation by glycerine, the 
artificial rhythm never begins in any strength of solution until the epithelial surface 
has become opalescent to a considerable degree. 
In the case of stimulation by glycerine the behaviour of the polypite is more 
unequivocal than it is in the case of stimulation by acid. 1 have therefore reserved 
till now my description of the behaviour of this organ under the influence of constant 
chemical stimulation. This behaviour is of a very marked though simple character. 
The polypite is always the first to respond to the stimulation—its retraction preceding 
the first movements of the bell by an interval of several seconds, so that by the time 
the bell begins its rhythmic response the polypite is usually retracted to its utmost. 
The initial response of the polypite is also rhythmic ; and the rhythm which it 
manifests—especially if the glycerine solution be not over strong—is of the same slow 
character which has already been described as manifested by this organ when under 
the influence of mechanical stimulation. The rhythm, however, is decidedly quicker 
in the former than in the latter case. 
Lastly, with regard to the marginal ganglia, it is to be observed that in the case of 
all the chemical irritants I have tried, if unmutilated specimens of Sarsia be immersed 
in a sea-water solution of the irritant, which is of a sufficient strength to evoke 
artificial rhythm in paralyzed specimens, the spontaneity of the ganglia is destroyed 
in a few seconds after the immersion of the animals— i.e., in a shorter time than is 
required for the first appearance of artificial rhythm. Consequently, whether the 
