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 animal is directed upward, the foot is not withdrawn, but 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. 33 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. 34 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). 



