686 
MR. Gr. J.' ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSiE. 
Now we have here a very remarkable series of phenomena ; and as it is a series which 
never fails to occur under the conditions named, I append 
tracings to give a better idea of the very marked and 
striking character of the results. The first tracing (fig. 1) 
is a record of the successive increments of the responses to 
successive induction-shocks of the same intensity thrown in 
at three seconds’ intervals — the cylinder being stationary 
during each response, and rotated a short distance with 
the hand during each interval of repose. 
The second tracing (figs. 2 & 3) is a record of the difference between the lengths of 
Fig- 1. 
F g. 3. 
the latent period, and also between the strengths of the contraction, in the case, 1st, of 
the first of such a series of responses (fig. 2), and, 2nd, of the last of such a series (fig. 3). 
From these tracings it will be manifest, without further comment, how surprising is the 
effect of a series of stimuli, first in arousing the tissue, as it were, to increased activity , 
and second in developing a state of expectancy. 
Those who are acquainted with Dr. Bowditch’s investigation “ concerning the irrita- 
bility of the muscular fibres of the heart cannot fail to be struck by the great simi- 
* Ludavig, ‘ Arbeiten aus der physiologischen Anstalt zu Leipzig,’ 1871, pp. 139-176. [It is further to be 
observed that a similar summation of stimuli has lately been observed to occur, in the case of reflex action, in 
the frog (Dr. Stirling, ‘Journal of Anat. and Physiol.’ Jan. 1876) and in the excitable leaf of Dioncea (Dr. 
Burdon Sanderson and Mr. Page, Proc. Roy. Soc. No. 177). — 1877.] 
