The reactions of Planarians to light . 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
The reactions of Planarians to light . 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-. Fig. 12 Bdelloura Candida. This path was traversed with much wigwagging; there was indif-ference to the source of light and locomotion was not of long duration. ing the angle formed at the junction of the sides and floor of theaquarium, as well as by its manner of finally coming to rest. A typical Phagocata (Fig. n), on the other hand, exhibited The Reactions of Planarians to Light 103 almost no goniotaxis, although the worm repeatedly crossedthe line of the angle. The response to the directive influenceof the light, too, was in this case even less than that of the Fig. 13 Planaria maculata. Considerable activity was shown over this course and a decidedinability to approach the source of the light beyond about the middle of the aquarium. Dendroccelum just described, as is evident from the general wan-dering character of the course. Although the Phagocata in ques-tion frequented both sides of the aquarium—that which was toward 104 Herbert Eugene Walter the light, as well as the oppos
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