Properties of a Myxomycete Plasmodium . 185 
spreading upon it can be kept uppermost, and so brought 
near the objective To transfer the plasmodium to the glass, 
a portion was separated from the mass by cutting the strands 
across and then loosening it from the substratum with a soft 
camel’s-hair brush. In order that it may have time to recover 
from the shock of the transfer, and become well spread out. it 
is best to do this the day before it is needed for use. 
One of these cages placed upon the stage of a microscope 
contained in an apparatus similar to Sachs 5 warm-chamber 1 , 
gives excellent opportunity for observing the plasmodium 
and noting any changes in currents or position. 
The space surrounding the well containing the microscope 
was packed with snow and salt, and a temperature of from 
— 2° to — 3 0 C. could thus be easily attained. Down to about 
i° C. there was no change from lowering the temperature, 
either in position or rapidity of the currents. But from this 
point to about — i° C. there was a gradual slowing of the 
currents, and between —2° and — 3 0 all movement stopped. 
If the exposure to this latter cold were but for a few minutes, 
the currents would soon start if the temperature were raised 
to i°— 2° C. ; but if the exposures were made for an hour, 
in no case was it possible to revive them. So it appears that 
while a temperature of from —2° to — 3 0 C. does not instantly 
kill this plasmodium, it will do so if the plasmodium is 
exposed to it for any length of time. 
Summary. 
Concerning rheotropism, it is found that up to a certain 
point the plasmodium is positively rheotropic, but that a very 
slight increase in the strength of the current causes it to 
become negatively so, and that any considerable increase in 
the strength of the current causes it to move entirely away 
from the water. But the question of why the organism has 
taken on the habit of positive rheotropism is regarded as 
1 This apparatus is figured on p. 608 of Sachs’ Lectures on the Physiology 
of Plants, Eng. trans. 
