Question

1912 note on the negative reaction under light-adaptation in the planarian

Answer 1

Answer:

Studied negative reaction under light-adaptation in planarian. Activities of a planarian were traced for 5 mins under normal illumination. It was then left in the dark for sometime, after which light was thrown on it. As the S was brought into activity by the light and turned away from it, another light was thrown, so that the same side of the animal was lighted. Results show that if planarians were placed in non-directive light after being in directive light, they turned consistently in the direction from which the light 1st came. This indicated that planarian became light adapted on one side during the exposure to directive light. After continued turning in one direction, planarian tended to make frequent changes of direction toward light, but on very strong stimulation, they may disappear. Rate of movement decreased with increased fatigue, and was less under intense, opposing, directive illumination.

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