MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSiE. 
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In this particular species the polypite never exhibits any spontaneous motion after 
the ganglia of the nectocalyx have been removed. But if it be nipped with the 
forceps, or otherwise irritated, it contracts strongly and suddenly; it then very slowly 
and gradually relaxes until it has regained its original length. After a considerable 
interval, and without the application of any additional stimulus, it gives another 
single, sudden, though slight contraction, to be again followed by gradual relaxation 
and a prolonged interval of repose, which is followed in turn by another contraction, 
and so on. These sudden and well-marked contractions occur at intervals of many 
seconds, and show a decided tendency to rhythmic periodicity, though the rhythm 
is not always perfectly exact. This intensely slow rhythm as the result of injury 
may continue for a long time, particularly if the injury has been of a severe character. 
There can be no doubt, therefore, that the mechanical (or other) injury in this case 
acts as a source of constant irritation ; so that here again we have evidence of rhythmic 
action independent of ganglia and caused by the alternate exhaustion and recovery of 
contractile tissues.* 
With regard to artificial rhythm caused by chemical stimuli, by far the most 
conspicuous instance that I have observed is that of the paralyzed nectocalyx of 
Sarsia. It wall be remembered that in my first paper, under the heading 
“ Stimulation,” I drew prominent attention to “a highly peculiar motion of a 
flurried, shivering character,” which is manifested by this organ when its marginal 
ganglia have been removed and it is exposed to the influence of faintly acidulated 
water. As previously remarked, at the time when this description was published I 
had not observed the phenomena of artificial rhythm in any of the other cases in 
which I subsequently observed it, and I was therefore completely at a loss to interpret 
the facts in the case which I described. I was thus under the necessity of stating the 
fact merely as “ a highly remarkable phenomenon, and one which I was quite unable 
to explain, though I was persuaded that it was a phenomenon well meriting the 
attention of physiologists.” Now, however, when read in the light of the foregoing- 
facts, there can be no doubt that the present one falls into its place very satisfactorily; 
it is an additional and very valuable instance of the display of artificial rhythm under 
the influence of a constant stimulus of low intensity. For the shivering motions of 
* We may pretty safely conclude tliat ganglia are altogether absent in the polypite of Sarsia, not only 
because Schultz bas failed to detect them in this organ microscopically, but also because of the complete 
absence of spontaneity -which it manifests. I may here mention that this case of the polypite of Sarsia is 
precisely analagous to another which I have observed in a widely different tissue, namely, the tongue of 
the Frog. Here, too, the presence of ganglion cells has never been observed microscopically, though 
specially sought for by Dr. Klein and others. Yet under the influence of mechanical and other modes of 
stimulation, I find that I am able to make the excised organ pulsate as rhythmically as a heart. As 
however I intend to devote a separate paper to the subject of artificial rhythm in tissues other than those 
of the Medusae, I shall not here enter into details with regard to the singularly beautiful instance which 
I have just mentioned; but I have felt that it is desirable to point out in this place the analogy which it 
presents to the case of the polypite of Sarsia. 
