188 



LIGHT AXD PROTOPLASM 



[Cn. VII 



11:22 



11:18 



(2). 14:OO to 14:2O 



ft'" 



11:12 



11:02 



10:55 



ft 



10:44 



I 



13:06 



(3). 14:20 to 14:34 



FIG. 53. Camera drawing, showing 

 the successive positions assumed 

 by an amoeba subjected to light 

 falling upon it from one side. The 

 arrow lies in a horizontal projec- 

 tion of the sun's rays. The amoeba 

 retreats from the source of light. 

 The numbers to the right of the 

 outlines of the amoeba give the 

 observed times between 10:28 and 

 11 :22 A.M. Magnified 16 diameters. 



FIG. 54. Camera drawing, showing 

 the successive positions assumed 

 by an amoeba retreating from the 

 light. The position of the infalling 

 ray was successively changed from 

 (1) to (2), (3), and (4). The arrow 

 labelled " First direction of migra- 

 tion " shows the direction of loco- 

 motion of the amoeba before the 

 light fell upon it at the beginning of 

 the experiment. The numbers indi- 

 cate hours and minutes. During the 

 interval from 13:06 (=1:06) P.M. to 

 13:57, the amoeba was not under di- 

 rect observation, since I was called 

 away. Magnified 16 diameters. 



Cases that can be explained only on the ground of the imme- 

 diate effect of light upon the direction of movement are cer- 

 tainly rare. ENTZ ('88), indeed, has intimated that Opalina 

 flees from light, but VERWORN ('89, pp. 53-57) was not able 

 to confirm him in this point. VERWORN'S method was here, 

 as in the case of Amoeba, not satisfactory. Instead of having 

 the light fall from one side only upon the drop containing the 

 Opalinas, he let the light pass vertically from below through a 

 small hole, and could observe no tendency to avoid the illu- 



10:34 



,10:28 



13:00 



12:54 



