. The dynamics of living matter. Reproduction; Regeneration (Biology); Biochemistry; Reproduction; Biochemistry. HELIOTROPISM 127 move toward the window, gathering at the window end c of the tube, ahhough by so doing they go from the sunshine into the shade. This shows that the effect of hght consists in turning the head of the animal, and subsequently its whole body, toward the source of light, so that the symmetrical points of the photosensitive surface of the body — in this case the eyes — are struck by the rays at the same angle. The animals will remain at the window side of the tube at c
. The dynamics of living matter. Reproduction; Regeneration (Biology); Biochemistry; Reproduction; Biochemistry. HELIOTROPISM 127 move toward the window, gathering at the window end c of the tube, ahhough by so doing they go from the sunshine into the shade. This shows that the effect of hght consists in turning the head of the animal, and subsequently its whole body, toward the source of light, so that the symmetrical points of the photosensitive surface of the body — in this case the eyes — are struck by the rays at the same angle. The animals will remain at the window side of the tube at c (Fig. 25). The experiment disproves the anthropomorphic idea that the animals go to the brightest spot in space. It can also easily be shown that in these animals, just as in plants, the more refrangible blue rays are more effective than the red rays, and that the latter act like weak light. Let us suppose that a test-tube containing the animals be placed on a table near the window (ww. Fig. 26), through which diffused light D enters; and that one half of the test-tube, namely, that near the window, be covered with blue glass ah. At the beginning of an experiment the animals are gathered at the room end of the test-tube. They behave as if the /////////^ test-tube were entirely uncovered, and move toward the window side of the test-tube, where they remain. The same experiment may be repeated, only with the difference, that the window side ah of the test-tube is covered with red instead of blue glass. The animals now creep in the direction of the window to that c^ point in front of a where ^^-^ the light, filtered by the red glass, begins to strike them. Here they gather, migrat- ing constantly in a narrow circle at the limit between red and diffused light. The explanation of the latter experiment is as follows: As long as the animals are at the room end of the test-tube, they are struck simultaneously by the diffused daylight D which falls through the win- dow, and by the we
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