The Reactions of Planarians to Light 



55 



amount of turning, changes in course, degree of wandering, inter- 

 val of response and manner of coming to rest, could be obtained 

 in this apparatus with approximate correctness. To determine 

 the rate of locomotion, however, required a device which would 

 measure accurately the distance traveled in a unit of time. The 



Fig. 2 ABCF, pantograph; C, fixed point; D, paraffine wall of aquarium; E, plate glass bottom 

 of aquarium; F, place where the arm A is grasped by the operator. A style is located at end of 

 arm A, in contact with under side of aquarium floor. J, style at end of tracing arm B, in contact with 

 smoked paper; J, beginning of a course traced on the smoked paper; K, drawing board for attachment 

 of smoked paper; L, sheet of smoked paper fastened to drawing board; M, actual course of the worm. 



method already mentioned of measuring rate from mucus-tracks 

 developed by means of powdered carmine, proved too tedious and 

 uncertain except for the worm's maneuvers in the dark, when it 

 seemed the only available way. 



