ii 4 AMEBOID MOVEMENT 



2 2.9$ 



xi/ ""* 



2'52 



Figure 34. The path of an Amoeba discoides under light controlled 

 conditions. At 2 142% the light was turned off until 2 :52, except for a 

 ten-second flash at 2:47. The smoothness of the wavy path was thus 

 maintained in complete darkness. Length of the ameba, about 400 microns. 



Figure 35. Path of an Amoeba discoides showing that continuous light 

 is unnecessary for the maintenance of a -wavy path. The ameba moved 

 under light controlled conditions from 3:02% to 3:13/4. From then 

 until 3:43 the light was turned off except for lo-second flashes at 3:18, 

 3 :22^, 3 124, and so on. The ameba had probably come to rest for 

 some reason between 3 :24 and 3 '.30^2, for an unexpectedly small amount of 

 space was covered in that time. In spite of this disturbance, however, 

 the evidence indicates that light is without causal effect in the wavy path 

 of the ameba. Length of the ameba, 450 microns. 



darkness the ameba merely kept on in the direction it was going 

 when the light was turned off. But during the second period of 

 darkness the ameba changed its course in such a way as to make 

 a smooth curve. In the third period of darkness the ameba con- 

 tinued on its course completing the wave. It is thus apparent 

 that continuous light is not necessary to the formation of waves 

 nor is it detrimental to their formation. Figure 35 shows essen- 

 tially the same thing as Figure 34. The light was turned on from 

 3 : 3^ to 3 :32. During this time the behavior of the ameba 

 was irregular, but whether this was caused by the light or not, 

 cannot be stated. At 3 :43 the ameba came into contact with a 

 small particle which changed its course. The slow speed of 

 movement of these two amebas was due to the low temperature 

 (20 C), the experiments being performed in January. The 



