103 
Br acker. — Observations on Euglena deses. 
Experiments were then performed in order to see at what temperature 
the Euglenae become active again after freezing. Four dishes containing 
mud and Euglenae were placed out of doors at nightfall so that the next 
morning the mud in all the dishes was frozen. They were placed in a good 
light and kept at different temperatures as follows : 
(i) Kept all day at o° C. 
(*) „ i°C. 
(3) „ *°C. 
(4) Warmed slowly from o° C. to 4 0 C. 
These experiments were repeated several times and the following 
results obtained : 
In (1), (2), and (3) no Euglenae appeared during the day. 
In (4) the first traces of Euglenae appeared on the surface of the mud 
when the temperature was approximately 2*5° C. 
If the mud is frozen while the organisms are visible and then placed in 
Fig. 7. E. deses. 
1-5, changes in shape of one individual when warmed from 1.5 0 C. to i6°C. 
the dark, the Euglenae will not burrow into the mud until the temperature 
is as high as 2*5° C. At low temperature the Euglenae appear rounded 
off, and Fig. 7 shows the changes in appearance when the organism is 
warmed. 
In order to see at what temperature the organism is most active the 
cultures were kept at different temperatures and covered with a black cloth, 
and the time taken for complete disappearance was recorded. From a large 
number of experiments performed, the following results were obtained : 
Temperature. 
Time to disappear. 
3°C. 
60 minutes (approx. 
6°C. 
4° „ 
9° C. 
30 „ 
I 2° C. 
25 „ 
I 5°C. , 
20 „ 
20° C. 
30 » 
#5 
25° C. 
i| hours 
