The reactions of Planarians to light . Fig. 10 Dendrocoelum lacteum. The shortness of the path shows comparatively little persistencein locomotion, and the direction, considerable indifference to the sourceof light. and-dash lines, the course of the worm on the surface film. Thedotted line indicates a hiatus in the path, made necessary by theattempt to represent on a flat surface a continuous line which tra-verses vertical as well as horizontal surfaces. A succession of The Reactions of Planarians to Light 101 abrupt kinks in the line signifies that at that point the worm exe-cuted decided wig
The reactions of Planarians to light . Fig. 10 Dendrocoelum lacteum. The shortness of the path shows comparatively little persistencein locomotion, and the direction, considerable indifference to the sourceof light. and-dash lines, the course of the worm on the surface film. Thedotted line indicates a hiatus in the path, made necessary by theattempt to represent on a flat surface a continuous line which tra-verses vertical as well as horizontal surfaces. A succession of The Reactions of Planarians to Light 101 abrupt kinks in the line signifies that at that point the worm exe-cuted decided wigwag movements with its anterior end. Thefigures are reduced in size from the original records. In Fig. 10 is given a specimen record of a Dendrocoelum which. Fig. ii Phagocata gracilis. This path shows great activity on the part of the worm, and, althoughit is mostly laid down away from the source of the light, it shows that the worm experienced no greatdifficulty in moving toward the light. came to a standstill after 18 minutes of locomotion. The firstmovement of this worm was diagonally away from the light, butit soon came back toward the light traversing almost the entire 102 Herbert Eugene Walter width of the aquarium and in doing so showed considerable indif-ference to the directive influence of the light. Its susceptibilityto goniotactic stimulus is plainly shown by its behavior upon reach-
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