FACTORS IN THE BEHAVIOR OF OPHIUROIDS 397 
of the rock, for if the specimen is turned around while being taken 
away from the rock it will usualh^ move with the ray or rays 
directed forward, which were originally against the rock, even 
though this behavior may take the ophiuroid directly away from 
the shelter. The influence of handling by the investigator at once 
suggests itself as a factor in the behavior just described. In fact, 
experiments below show that echinoderms do tend to move away 
from the side of the body which has been handled, but the explan- 
ation of the behavior given above nevertheless holds good, as 
is shown by changing the manner of holding. 
CONTACT WITH SOLID WALLS 
It has been mentioned above that stmiuli produced by con- 
tact with solid walls, such as the surface of rocks, are very im- 
portant factors in the life of the ophiuroid. Experiments which 
will be described below indicate that they are even more important 
than stimuli produced by small differences in intensity of light. 
The following rather crude experiment shows the lasting effect 
of a stimulus produced by contact with the solid walls of the 
corner of a rectangular glass dish. This dish, 36 cm. long, 23.5 
cm. wide and 7.5 cm. high, was partly filled with sea-water and 
placed in front of a wide-open window. Light from many sources 
entered the dish but that from the open window was of the greatest 
intensity. An ophiuroid (Ophiocoma riisei) was placed in the 
dish and it moved at once to the corner indicated, (Fig. 1, a) plac- 
ing one of its rays in the angle. After allowing the specimen to 
remain there for several minutes, its was pushed diagonally across 
the dish to the position shown (fig. 1, 6). The orientation of the 
ophiuroid with reference to the original resting place was not 
changed during this procedure and its rays were not allowed to 
touch the sides or corners of the dish. Almost immediately the 
creature moved back to the corner from which it had been 
removed, (Fig. 1, a) even though in so doing it went toward the 
strongest source of light. It did not turn the disc but moved with 
the ray forward that had originally been in contact with the 
corner. This experiment was repeated many times, using different 
corners for the starting point, and in nearly every case the ophiur- 
