American journal of physiology . animals passed has beenreduced from 100° to 80° ;the region of most frequentemergence was 10° eitherside of zero instead of 20° ;and the position of averageemergence was removedfrom 27° to 24°. The move-ments of the animals werethus limited to a narrowerfield. The conclusions to bedrawn from the three setsof experiments on plana-rians witJi eyes are, first,that planarians moving hor-izontally toward a source oflight are deflected furtherfrom an ideal course (to 0°)than when moving under vertical light, and, secondly, that when moving horizontally aivayfrom a so
American journal of physiology . animals passed has beenreduced from 100° to 80° ;the region of most frequentemergence was 10° eitherside of zero instead of 20° ;and the position of averageemergence was removedfrom 27° to 24°. The move-ments of the animals werethus limited to a narrowerfield. The conclusions to bedrawn from the three setsof experiments on plana-rians witJi eyes are, first,that planarians moving hor-izontally toward a source oflight are deflected furtherfrom an ideal course (to 0°)than when moving under vertical light, and, secondly, that when moving horizontally aivayfrom a source of light, they are kept more closely to an idealcourse than when moving under vertical light. It is also to benoticed that the effect of horizontal light is much greater on ani-mals started toward than on those started away from the sourceof light. These are the natural consequences of a peculiarity whichthese animals possess of moving away from a source of light whenthe rays fall upon them in an effective Figure 3.— Distribution of points at which pla-narians without eyes passed over the circum-ference of the circle, (1) when affected byhorizontal light and directed toward itssource (right half of figure), and (2) whenunder vertical light and directed toward 0°(left half). For further explanation seepage 379. 382 G. H. Parker and F. L. Burnett. Planarians without Eyes. — To what extent planariaiis without eyesreact toward light can be seen from the remaining three sets ofexperiments. The first of these, Hke the first one on planarians witheyes, was carried out in horizontal light with the animals directedtoward the source of light. The records are given on the right sideof Fig. 3. The circumference was passed over anywhere between0° and 140° ; the region of most frequent emergence was not veryclearly marked, but presumably lay between 30° and 40° ; and theangle of average emergence was 57°. The reactions of eyeless animals in vertical light ar
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