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sunlight was essentially the same. There was in many specimens, 
a sHght decrease in rate of movement, in some a momentary 
cessation, and in others no apparent reaction whatever. In the 
green the effect was similar to that in red, yellow and violet, only 
somewhat more marked. To obtain the effect described above 
it is necessary (1) to have amoebae in a certain condition, (2) to 
keep them in as low light intensity as possible before making 
the exposure, and (3) to use very intense light. When exposed 
in blue after having become active in any other color or in diffuse 
sunlight all movement stopped instantly in nearly all specimens 
observed. But there was no apparent contraction, the animals 
retained almost the exact form they had before the exposure. In 
some instances after remaining quiet a few seconds the streaming 
of the protoplasm in the anterior pseudopods slowly began again. 
In others new pseudopods were formed at the posterior end, and 
as these developed the old ones were slowly withdrawn. The 
movement ordinarily increased at such a rate that after 30 to 60 
seconds it was again normal. If any other part of the spectrum 
was flashed on an amoeba which had become active in the blue 
there was no apparent reaction, but if such a specimen was ex- 
posed to direct sunlight it was clearly seen, in some instances, 
that the streaming ceased again. 
The fact that the same reactions are obtained in the impure 
colors produced by means of filters and in the relatively pure 
colors of the spectrum, is significant. It shows that a few foreign 
rays have no appreciable effect on the reactions of organisms which 
are not very sensitive to light. Moreover in case of Amoeba the 
response to the blue is so striking and that to the other colors so 
very slight that there can be no question as to the specific effect 
of the blue (430-490mm) . That is, the effect of different parts of 
the prismatic solar spectrum on Amoeba is not proportional to 
the energy contents, for the energy gradually increases as one 
proceeds from the violet toward the red end, whereas the region 
of maximum stimulation for Amoeba is in the blue, from which 
it decreases toward both ends. . Nor is it proportional to the brignt- 
ness as judged by the human eye, for the yellow is much brighter 
than any other part of the spectrum. In fact, under the conditions 
