432 STUDIES IN GENERAL PHYSIOLOGY 
This time I also made the reverse experiment. The 
polyps formed in blue light were exposed to red light (the 
blue glass was replaced by a red one on September 6). After 
five days all the newly developed polyps had perished. By 
September 13 only a few diminutive polyps had developed. 
Experiment 3.—On August 25 eight stems of Euden- 
drium culture were placed behind light-red glass (which 
allowed also some blue light to pass through), and nine 
stems of the same culture behind blue glass which was not 
very dark. On August 30 a number of polyps had devel- 
oped, not only behind the light-blue, but also behind the 
light-red glass. The light-red screen was then replaced by 
a dark-red one; while thé number of polyps constantly 
increased in the blue light, development soon ceased behind 
the dark-red screen. On September 1 the eight stems in the 
red light had only sixteen small polyps, while the nine in the 
blue light, which were of the same size and from the same 
culture, had eighty polyps. On the following day eighteen 
polyps had developed in the red light, while the stems in the 
blue light were literally covered with them. 
On September 5 the glasses were exchanged; the animals 
which up to this time had been behind the red screen were 
now exposed to blue light, while those which had been 
exposed to blue light were placed behind the dark-red screen. 
The number of polyps on the stems in the blue light (which 
had formerly been in the red) increased rapidly; on Septem- 
ber 9 the number had grown to 27, on the 10th to 40, and 
soon. The polyps on the animals in the red light (which 
had formerly been in the blue) not only did not increase in 
number, but they began to die, and on the 11th only a few 
were left which looked sickly. 
A fourth experiment corroborated the result that numerous 
and vigorous polyps are formed behind a dark-blue screen, 
while in red light only roots are formed. 
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