692 
ME. G. J. EO MANES ON THE LOCOMOTOE SYSTEM OF MEDUS2E. 
strong faradization does cause a more or less well-pronounced tetanus. The continuity 
of the spasm is, indeed, often interrupted by momentary and partial relaxations. These 
interruptions are the more frequent the weaker the current ; so that at a certain strength 
of the latter, the tetanus is of a wild and tumultuous nature ; but with strong currents 
the spasm is tolerably uniform. That in all cases the tetanus is due to summation of con- 
tractions, may he very prettily shown by the following experiment. An Aurelia is cut into a 
spiral strip, and all its lithocysts are removed ; single -induction-shocks are then thrown in 
with a key at one end of the strip — every shock, of course, giving rise to a contractile wave. 
If these shocks are thrown in at a somewhat fast rate, two contractile waves may be 
made at the same time to course along the spiral strip one behind the other ; but if the 
shocks are thrown in at a still faster rate, so as to diminish the distance between any 
two successive waves, a point soon arrives at which every wave overtakes its predecessor; 
and if several waves be thus made to coalesce, the whole strip becomes thrown into a 
state of persistent contraction. 
In this way sustained tetanus, or single contractile waves, or any intermediate phase, 
may be instantly produced at pleasure. In such experiments, moreover, it is interesting 
to observe that, no matter how long the strip may be, whatever disturbances are set up at 
one end are faithfully transmitted to the other. For instance, if an Aurelia be cut into 
the longest possible strip with a remnant of the disk left attached at one end — as 
represented by Plate 33 in my previous paper — then all the peculiar time relations 
Between successive contractions which are intentionally caused by the experimenter at 
one end of the strip, are afterwards accurately reproduced at the other end of the strip 
by the remainder of the disk. Now as this fact is observable however complex 
these time relations may be, and however rapidly the successive stimuli are thrown in, 
I think it is a point of some interest that these complicated relations among rapidly 
succeeding stimuli do not become blended during their passage along the thirty or forty 
inches of contractile tissue. The fact, of course, shows that the rate of transmission is 
so identical in the case of all the stimuli originated, that the sum of the effects of any 
series of stimuli is delivered at the distal end of the strip with all its constituent parts 
as distinct from one another as they were at starting from the proximal end of the strip. 
IY. SECTION. 
In this division I shall treat of all the evidence I have been able to collect regarding 
the distribution of nerves and the physiological character of the contractile tissues in 
the various species of Medusas which have this year fallen within my observation. By 
the word “ nerves ” here I mean certain physiologically differentiated tracts of tissue 
which either stimulation or section prove to perform the function of conveying impres- 
sions to a distance ; and by “ physiological character of the contractile tissues ” I mean 
the character of these tissues in respect of the degree in which the nervous element 
shows itself to be physiologically differentiated from the muscular element. 
§ 1. Distribution of Nerves in Sarsia. (A) Deflex Action . — The occurrence of reflex 
