PHYSIOLOGY OF ASCIDIA ATRA LESUEUR YRS 
If these phenomena are to be explained in terms of the animal’s 
adaptation to the repeated stimulus, as maintained by Kinoshita 
(11) for Ciona and Styela (Parker, ’17, p. 221), it follows that the 
continued rhythmic application of the stimulus should cease to 
be effective after the animal has once stopped reacting to it, 
that is, once it has adapted itself. In Ascidia this is not 
the case. In the curve in figure 2, for instance, the break after 
the point marked a means that the animal failed to respond 
Fig. 1 Record of response to intense, rhythmic, mechanical stimulation, 
resulting in arapid exhaustion. The base line marks five-minute intervals. 
Fig. 2 Record of response to rhythmic, mechanical stimulation, less intense 
than in figure 1. For further explanation see test. The base line marks five- 
minute intervals. 
though stimuli were applied at the rate of one every 15 seconds. 
This continued for three minutes when suddenly it again began 
to react and continued to do so for twenty minutes. At the 
point marked 6 the animal failed to contract to one impact but 
responded to the next (c). It then ceased responding for four 
more stimulations. The fifth produced a contraction (d) but 
several more after that failed to call forth a reaction. A process 
of adaptation can, therefore, hardly be said to be responsible 
for the cessation of the reaction. 
