Figure 34. The path of an Amoeba discoides under light controlled conditions. At 2:42¼ 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 3:02¼ to 3:13¼. From then until 3:43 the light was turned off except for 10-second flashes at 3:18, 3:22½, 3:24, and so on. The ameba had probably come to rest for some reason between 3:24 and 3:30½, 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 continued 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 essentially the same thing as [Figure 34.] The light was turned on from 3:30½ 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 apparent connection between longer waves and darkness has not yet been investigated.
[Figure 36] shows the path of an Amoeba proteus under controlled light conditions as above described, but instead of moving over a polished plate glass surface as in the previous experiments, the ameba in this experiment moved over a fine ground-glass surface. It will be observed that for the first twenty minutes the path shows smooth waves, although at 11:53 and 11:55 there was a slight disturbance which was associated with the formation of numerous pseudopods. From 12:07 on, however, the path becomes irregular, the wave-like character being almost obliterated. Associated with this irregularity is the presence of numerous pseudopods. This is a sample of a number of records which indicates that in proteus and discoides the presence of numerous pseudopods in some way prevents the ameba from moving in a path marked by smooth and conspicuous waves.
