MR. Gr. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSAE. 
163 
importance to demand its final publication in as complete a form as possible, I have 
sought and obtained the permission of the Royal Society to withdraw this subsection 
from the proof. .... The facts of which it treats form in themselves a connected body 
distinct from all the other facts which are detailed in the rest of this communication ; 
so that, while their omission from the present paper does not entail any furthur modi¬ 
fication of the latter, they will admit of being introduced en masse in my next paper. 
When, therefore, I shall have completed the further experiments which in this con¬ 
nexion I have devised, I shall hope to communicate to the Royal Society, in a single 
connected series, all the facts and inferences which bear upon this subject.” 
Although I have not even yet completed all the experiments wdiich it is desirable 
to make with reference to this subject, I have this year so far added to their number 
that I feel the research is now sufficiently ripe for publication. As already stated, an 
epitome of the main facts regarding artificial rhythm has previously appeared in the 
‘ Proceedings of the Royal Society’; but of course it will now be necessary to give a 
more detailed account of these facts, no less than of those which I have more recently 
observed. Stating, then, all the facts as concisely as possible, they are as follows. 
(6.) If the umbrella of Aurelia aurita has been paralyzed by the removal of its 
lithocysts, and if it is then subjected to faradaic stimulation of minimal intensity, the 
response which it gives is not tetanic, but rhythmic. The rate of this artificial rhythm 
varies in different specimens, but the limits of variation are always within those which 
are observed by the natural rhythm of different specimens. The artificial rhythm is 
not in every case strictly regular; but by carefully adj usting the strength of the 
current, and by shifting the electrodes from one part of the tissue to another until the 
most appropriate part is ascertained, the artificial rhythm admits in most cases of 
being rendered tolerably regular, and in many cases as strictly regular as is the 
natural rhythm of the animal. To show this, I append a tracing of the artificial 
rhythm, which may be taken as a fair sample of the most perfect regularity that can 
be obtained by minimal faradaic stimulation.'"' 
Fig. 1. 
-1— .1_1 _l _L 1 1 1 L 
L 1 _l_ i 
i/i 
J__L 
1,/! 
_1_ 
_1_: 
Seconds 
This artificial rhythm may be obtained with a portion of irritable tissue of any size, 
and whether a large or a small piece of the tissue employed be included between the 
electrodes. 
* This and all the subsequent tracings I obtained by the method already described in my previous paper. 
