Dec. 13, 191S 



Activity of Soil Protozoa 



485 



ratory. Examinations were made from time to time for a period, and 

 then the samples were placed outside in the open air where the tempera- 

 ture variation was great and examinations were again made. (See 

 Table V.) 



Table V. 



-Presence of active protozoa in water-logged soils, under constant and variable 

 temperatures 



«S. C. ■= small ciliates; L. C.=large ciliates; F.=flagellates; A.=ameb2e; t=few, tt=several; ttt=many. 



The data given in Table V indicate that living protozoa were always 

 present in all of the water-logged soils during incubation at outside 

 temperature as well as at room temperature. It was noted that the 

 sudden change from the room temperature to the outside temperature 

 did not have any marked effect upon the existence of the organisms in 

 the active condition. 



PERIOD OF EXCYSTMENT OF SOIL PROTOZOA 



Since active protozoa were not found in normal field soils, the question 

 at once presented itself, How long a period of time was required for 

 soil protozoa to become active in the presence of sufficient moist- 

 ure, as, for instance, during a heavy fall of rain, and How long will 

 they remain in the active state ? In his work with Colpoda cucullus 

 Goodey (3) in 191 3 found that at 30° C. many were active after an hour. 

 It was suggested by Martin and Lewin (8), as previously noted, that 

 they may become active in a few minutes. To prevent misunderstand- 

 ing as to the presence of motile protozoa in the soil, the writer in his 

 method of examination proposed a 2 -minute examination of each sam- 

 ple — i. e., the soil was in contact with free water no longer than two min- 

 utes at each examination. In no case during the entire course of the 

 many examinations of field soils were any protozoa noted to have excysted 



