The Reactions of Planarians to Light 



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titative measure of the amount of turning toward or away from 

 the source of the Hght under the given conditions was obtained. 



The apparatus finally utilized for this experiment was based 

 upon a device employed by Parker and Burnett ('oo) in testing 

 the relative behavior of normal and eyeless planarians when sub- 

 jected to directive light. Its arrangement is shown in Fig. 5. 



On the top of a table {A) in the dark room was placed a rectan- 

 gular aquarium {BCDE), the ends of which {BE and CD) were 



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Fig. 5 A, Top of table; BCDE, rectangular aquarium; BE, glass end; FG, round swinging 

 aquarium; H, copper wire attached to ceiling and supporting the swinging aquarium FG; I, movable 

 light; JJ, diaphragm; K, surface of water in outer aquarium; L, surface of water in inner aquarium; 

 M, lens. 



made of glass while the floor and sides were of wood painted with 

 camera-black. Within this aquarium a second cylindrical one 

 {FG), made entirely of thin glass and measuring 20 cm. in diam- 

 eter, was suspended from the ceiling by means of a fine wire {H) 

 attached to a swivel to allow turning. On the floor of the outer 

 aquarium and directly beneath the inner one was drawn a circle 



