410 
R. P. COWLES 
V 
b 
13 
question arises : Are we dealing here with the effect of light stimuli 
or with the effect of stimuli produced by contact with the wall 
of the dish or with both? 
The following experiment among many others shows that the 
stimulus due to contact is to be reckoned with; in other words, 
that the stimulus produced by the contact of ray 1 with the solid 
walls of the corner of the dish or the stimulus produced by the 
breaking of this contact has an effect on the direction of righting, 
on the rays employed in this righting, and on the direction of 
locomotion directly after the completion of the act. An ophiu- 
roid (fig. 11) resting at a against the corner walls was inverted 
and placed at h, so that ray 1 was not directed in a diametrically 
opposite direction to that in position a. The result was that the 
ophiuroid righted itself on rays 3 and 4, and then moved, with 
- ray 1 as the directing ray, apparently under the influence of the 
stimulus given to ray 1 when it was resting in the corner a. For 
