. The dynamics of living matter . Fig. 24. — Positive heliotropism of Serpula uncinata. The light had originally struck the animal in the direction of the arrow ab, and their tubes were parallel with the direction of the rays. When the light fell in the direction cd the tubes began to grow at right angles to their former direction. Partly diagrammatic. 2. Heliotropism of Free-moving Animals We have seen that the essential feature of the heliotropic reaction consists in the fact that the light automatically puts the plant or the animal {Eudendrium, Spirographis) into such a position that the ax
. The dynamics of living matter . Fig. 24. — Positive heliotropism of Serpula uncinata. The light had originally struck the animal in the direction of the arrow ab, and their tubes were parallel with the direction of the rays. When the light fell in the direction cd the tubes began to grow at right angles to their former direction. Partly diagrammatic. 2. Heliotropism of Free-moving Animals We have seen that the essential feature of the heliotropic reaction consists in the fact that the light automatically puts the plant or the animal {Eudendrium, Spirographis) into such a position that the axis of symmetry of the body, or organ, falls into the direction of the rays of light. In the case of positively heliotropic organs, the tip, or head, is directed toward the source of light, while it is the reverse in the case of negatively heliotropic organs. If we imagine that such a positively heliotropic organ, the polyp of Eudendrium, or a worm, like Spiro- graphis, be endowed with the power of spontaneous locomotion, and if for some internal reasons the animal were compelled to be constantly in motion (as is the case with many pelagic larvae), we should notice that these animals had no choice left in regard to the direction of their motion. The light would turn them automatically until their axis of symmetry was in the direction of the rays of light, and the animal could
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectreproduction, bookyea
