398 
R. P. COWLES 
oid returned to the corner in which it had been resting, although 
sometimes, especially when fatigued, the return was not so direct 
as that shown in fig. 1. 
One naturally asks if the behavior just described is due to the 
persistence of the contact-stim^ulus? May not bilateral symmetry. 
EXPLANATION OF FIGURES 
The large rectangle in the thirteen figures of this article representes the 
outline of the large rectangular glass dish; the arrow outside of the rectangle 
indicates the direction from which the most intense light comes; the plain 
arrows inside the rectangle show the direction of locomotion; the arrows with 
hooks on the end indicate that the ophiuroid has been turned on its back or 
that it has righted itself; the ophiuroid is represented by a five armed star 
and in any one figure it is alwaj^s the same arm or ray that is marked by a short 
cross line, 
method of handling, intensity of the lighted field, or currents in 
the water, due to pushing the ophiuroid away from its resting 
place be factors? 
In order to see if bilateral symmetry or any structural peculi- 
arity were factors in the above behavior, many trials were made in 
