The reactions of Planarians to light . f the directive influence of light can be accom-plished by means of various devices. (1) The light may be madeto fall vertically from above upon a horizontal field; (2) it may bereflected vertically from below so as to pass through a transparentfield at right angles to the plane of the field; (3) methods 1 and2 may be combined. The apparatus finally used in the majorityof experiments with non-directive light, was based upon the methodfirst mentioned. The Reactions of Planarians to Light 53 Fig. I shows a diagrammatic vertical section of this
The reactions of Planarians to light . f the directive influence of light can be accom-plished by means of various devices. (1) The light may be madeto fall vertically from above upon a horizontal field; (2) it may bereflected vertically from below so as to pass through a transparentfield at right angles to the plane of the field; (3) methods 1 and2 may be combined. The apparatus finally used in the majorityof experiments with non-directive light, was based upon the methodfirst mentioned. The Reactions of Planarians to Light 53 Fig. I shows a diagrammatic vertical section of this light {A), an incandescent electric lamp, was mounted in ablack sheet-iron hood (B) to prevent the escape of any laterallight. This hood was suspended from the ceiling of the darkroom where the experiments were carried on and was arranged sothat it could be easily raised or lowered, thus changing the heightand consequently the intensity of the light with reference to anyfixed point below. In the hood, beneath the light, was supported. Fig. i A, light; B, walls of hood; C, heat screen; DD, diaphragm; E, roof of hood; F, plate-glassfloor of aquarium; G, paraffine wall of aquarium; HH, diaphragm to cut off light reflections fromparaffine wall; J, wall of reflector box; J, open side of reflector box; K, mirror; L, walls of tunnel;MM, black draperies; N, table. a flat-bottomed, clear-glass dish (C) containing distilled water toa depth of about three centimeters. The heat screen thus obtainedeffectually filtered out the heat rays, allowing only the light raysto pass through. A few inches under the heat screen was inserteda diaphragm (D), painted black, the purpose of which was to aidin cutting out side reflections besides allowing only a central col-umn of light to escape below. A black sheet-iron roof (E) con- 54 Herbert Eugene Walter fined the upward rays to reflections within the hood itself, at thesame time permitting the escape of heated air. On a table directlyunder the suspen
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Keywords: ., bookcentury1900, bookdecade1900, bookidreactionsofp, bookyear1906
