154 STUDIES IN GENERAL PHYSIOLOGY 
in the screen, or to move off the screen entirely. If, 
as soon as the animal has assumed the position shown .in 
Fig. 26, the wire screen is turned over so that the foot of the 
animal is directed upward, the foot is not withdrawn, but 
begins to bend vertically downward from the tip. The bend- 
ing then passes from one ele- 
ment of the body to the next, 
from the foot to the head. As 
soon as the tip of the foot again 
touches the screen, it pushes 
itself through it as far as pos- 
sible. If the wire net is again 
turned over, the whole process 
is repeated anew. In this way 
the animal can be compelled, 
by the help of gravity alone, to weave itself through the 
meshes of the screen several times ‘“‘of its own accord.” 
Fig. 83 shows a Cerianthus which has thrice passed 
through the meshes of the screen in this way. The drawing 
is taken from life. 
4. Such a bending downward, which has been accurately 
studied in negatively geotropic roots, has never been demon- 
strated, so far as I know, in animals. I will therefore cite 
another experiment which better illustrates the course of 
this reaction. If a Cerianthus be put into a test-tube filled 
with sea-water, and the test-tube be placed so that the head 
of the animal is down and the foot up, while the long axis of 
the animal is vertical, the tip of the foot begins after some 
minutes to bend vertically downward. In Fig. 84 is shown 
the course of such an experiment. Several minutes before 
12 o’clock the animal was placed in a test-tube in the posi- 
tion described. At 12 the foot of the animal had begun to 
bend downward (Fig. 34, a); in the next thirteen minutes the 
bending gradually advanced toward the head (Fig. 34, b). 
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