104 
B r acker. — Observations on Englena deses . 
A graph showing these results is given in Fig. 8. 
E, deses is therefore capable of withstanding extremes of temperature 
for short periods, but is less able to withstand long periods of adverse con- 
ditions. The organisms become very .sluggish if subjected to temperatures 
above 25 0 C. or below 5 0 C., and below 2-5° C. no response to stimuli has 
been observed. The rate at which the organism responds to stimuli is 
Fig. 8. Graph showing the time taken for Euglena deses to respond to the stimulus 
of light at different temperatures. 
dependent on the temperature. It is increased as the temperature is raised, 
but above 15 0 C. its activities grow less. 
Depth to which E. deses burrows in Mud. 
Experiments were performed with a view to finding the depth the 
Euglenae burrow in the mud in response to stimuli. By means of a Gillette 
razor-blade the surface mud was scraped off in several dishes to a depth of 
J in.. Jin., and Jin. respectively. The time chosen was after the cultures 
had been placed in the dark, i. e. when the Euglenae had burrowed into the 
mud. 
As a result it was found that in the § inch experiment a large number 
of Euglenae reappeared when placed in the light, in the J inch a few, and in 
the Jinch none at all. 
Therefore one would conclude that the majority of Euglenae do not 
burrow deeper than J inch. The experiment was repeated by inserting a 
strip of Bolton silk, mounted on a frame at an angle of 45 0 , in the mud. 
The organisms burrowing down became entangled in the meshes, and by 
