102 
Brae her, — Observations on Englena deses. 
Its movements in response to the stimulus are very slow as compared 
with results obtained by Wager (8) on Englena viridis. He mentions 
that if a cloud passes over the sun these organisms immediately leave 
the position which they occupy on the surface of a pond and swim down 
into the water, to reappear as soon as the cloud has passed. Also a number 
Fig. 6. (i) Position of Euglenae at commencement of experiment: A, stiff mud; B, wet 
mud; c, mud covered by water; d, water only. (2) Position of Euglenae after five days’ 
illumination from one side. 
of Euglenae in a saucer illuminated from one side will pass towards the 
source of light in a few minutes. 
Influence of temperature. Cultures of Englena were kept at tem- 
peratures ranging from 3 0 C. to 2o°C.,and in these the organisms appeared 
to flourish equally well. By changing the temperature, however, one is 
able to observe a marked difference in the rate at which the organism 
responds to stimuli. 
At low temperatures, i. e. below 4 0 C., it was found that the Euglenae 
became rounded off, very sluggish, and slow in response to stimuli, but as 
the mud was gradually warmed up, they became more active and expanded 
to their fullest length. 
During the winter of 1916-17 the periods of frost were very severe. 
From December 6 to December 17 the average minimum temperature 
was -3 0 C. The mud in the vessels was frozen each night, but during the 
warmest part of the day, when the mud thawed and rose to a temperature 
of 3 0 C., Euglenae were visible in small numbers for a few hours. 
From January 20 onwards the mud was completely frozen for 
a period of twenty-nine days. The temperature frequently fell as low as 
- io°C., and the mud did not thaw at all during the day-time. When the 
thaw did set in, however, the mud was closely watched for any traces of 
Euglenae either in the vegetative or encysted form. Five days later, a faint 
green colour on the mud showed, on examination, that some of the Euglenae 
had withstood the severe frost. 
