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S. O. MAST 
(1876) and Stahl (1884) state that if a portion of the plasmodium 
of certain myxomycetes is strongly illuminated the protoplasm 
in that portion stops and later tends to flow toward the part not 
illuminated. In view of all these facts it seems strange that Ver- 
worn and Davenport observed no reactions in amoebae as they 
crawled from a shadow into an intensely illuminated region. 
My observations were all made on Amoeba proteus taken from 
a culture which Professor H. S. Jennings kindly put at my dis- 
posal. The amoebae came up in a hay infusion used in rearing 
paramecia. They were so abundant that hundreds were often 
found in a few drops taken from the surface of the debris where 
they collected, forming a dense grayish layer in many places. In 
all the observations numerous specimens were mounted in a 
clear solution under a large cover glass supported by a ring of 
vaseline so as to give them ample room for movement. It was 
found that they can be kept on a slide in this way in excellent 
condition for several days. 
REACTIONS TO CHANGE IN LIGHT INTENSITY 
By means of a mirror direct sunlight was flashed on specimens 
on a slide mounted in diffuse daylight and it was found that the 
increase of intensity caused all streaming to stop immediately 
regardless of the direction of the rays of light . There was however, 
no immediate contraction similar to that observed by Engelmann 
on Pelomjoca. After a few minutes' exposure new pseudopods 
usually formed at or near the posterior end and as these ex- 
tended the old ones were withdrawn. It is an important fact 
that after the amoebae have been exposed to direct sunlight for 
a short time they appear to move as rapidly as they did in diffuse 
light and that if the intensity is gradually increased there is no 
apparent decrease in rate of movement, for it shows that the 
response described above is dependent primarily upon the time 
rate of change in light intensity and secondarily upon the amount 
of change. 
These results agree in general with those of Harrington and 
Leaming and others mentioned above, but they do not bear on 
