138 ROBERT H. HUTCHISON 



oped in abundance at least two distinct forms were easily seen. 

 Some were large, much vacuolated, comparatively sluggish in 

 movement and of a bright pink color. Others were smaller 

 (especially in breadth), vacuoles small and few, more active in 

 their movements and of a duller color. The larger forms were 

 always killed a short time before the others. Spirostomum and 

 Urostyla were found developing in the same culture and both 

 were present in the dishes during the experiments and therefore 

 they were subjected to exactly the same conditions. The sur- 

 rounding medium, the time of exposure,, the time allowed for 

 recovery, and so forth, were identical, yet the two forms are more 

 strikingly different in their ability to withstand heat than any 

 two of the forms experimented on. 



Experiments with other forms gave some interesting results, 

 although not extensive enough to warrant the construction of 

 curves. One experiment with Glaucoma showed that it was 

 killed at 35°C., while one species of Stylonychia under the same 

 conditions is more resistant, its death temperature being ca. 40°. 

 In another case Stylonychia were observed alive and active at 

 40° when all of 95 Paramecia in the same drop were dead. Among 

 the flagellates some specific differences were observed. Peranema 

 is killed at 40°; Chilomonas at 38°; Gonium at about 37° and 

 Synura at some point below 28°. Synura was found but twice 

 and only one experiment was successful. The dishes were re- 

 moved in order starting at 28°, but even in that one removed 

 at 28° all Synura were dead. The colonies had disintegrated 

 and no recovery or formation of new colonies was observed within 

 a week. The very interesting observations of H. N. Parker ('11) 

 give further evidence of a very low death point. The case of 

 Synura seems to be an unusual one. Grosse-Allerman ('09) men- 

 tions one case which is even more unusual. He states that 

 Amoeba terricola is killed by a few minutes' exposure to 25°. 

 By way of contrast, it is rather striking to read of Amoeba 

 limax and Nassula elegans living in hot springs at a temperature 

 of 50° or 52° (Issel '10), and of parasitic forms such as Trypano- 

 soma brucei and Trypanosoma elmassani killed only after five 

 minutes' exposure to 45°C. (Jackimoff '09). But leaving such 



