54 JELLY-FISH, STAR-FISH, AND SEA-URCHINS, 
the cylinder being stationary during each response, 
and rotated a short distance with the hand during 
each interval of repose. 
Fig. 2. 
The second tracing (Figs. 3 and 4) is a record of 
the difference between the lengths of the latent 
period, and also between the strengths of the con- 
traction, in the case (w) of the first of such a series 
of responses (Fig. 3), and (b) of the last of such a 
series (Fig. 4). 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. 
In accordance with the now customary termi- 
nology, I shall ca'l such a series of responses as are 
given in Fig. 2 a “staircase.” Such a staircase has 
a greater number of steps in it if caused by a weak 
current (compare Figs. 2 and 5); and if the strength 
of the current be suddenly increased after the 
maximum level of a staircase has been reached by 
using a feeble current, this level admits of being 
sightly raised (see Fig. 5). Moreover, I find that a 
