The reactions of Planarians to light . ive Light. When worms wereplaced on the middle of a rectangular aquarium floor and sub-jected to a directive light their movements showed both genericand specific differences. By experimenting with one worm at atime it was possible to plot on a sheet of paper with sufficientaccuracy for general comparison the entire course of the wormduring a considerable period. This was done many times andtypical records of such observations are given in Figs. 10-14. Insuch instances the worm was exposed to a light of approximately147 cm., placed so as to correspond to
The reactions of Planarians to light . ive Light. When worms wereplaced on the middle of a rectangular aquarium floor and sub-jected to a directive light their movements showed both genericand specific differences. By experimenting with one worm at atime it was possible to plot on a sheet of paper with sufficientaccuracy for general comparison the entire course of the wormduring a considerable period. This was done many times andtypical records of such observations are given in Figs. 10-14. Insuch instances the worm was exposed to a light of approximately147 cm., placed so as to correspond to the right side of thefigures. The central rectangular area bounded by the broken linesindicates the limits of the floor of the aquarium, while the smallerexterior adjacent areas represent its vertical sides so rotated as to 100 Herbert Eugene Walter bring them into the plane of the floor. The course taken by aplanarian is indicated by the tortuous line. The full line showsthe course taken on the solid surface of the aquarium; the dot-. Fig. 10 Dendrocoelum lacteum. The shortness of the path shows comparatively little persistencein locomotion, and the direction, considerable indifference to the sourceof light. and-dash lines, the course of the worm on the surface film. Thedotted line indicates a hiatus in the path, made necessary by theattempt to represent on a flat surface a continuous line which tra-verses vertical as well as horizontal surfaces. A succession of The Reactions of Planarians to Light 101 abrupt kinks in the line signifies that at that point the worm exe-cuted decided wigwag movements with its anterior end. Thefigures are reduced in size from the original records. In Fig. 10 is given a specimen record of a Dendrocoelum which
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Keywords: ., bookcentury1900, bookdecade1900, bookidreactionsofp, bookyear1906
