Activity of Soil Protozoa 



483 



than three times, a new sample being taken every two minutes; during 

 the examinations the respective samples were kept at the different tem- 

 peratures. Sterile tap water of the same temperature as that at which 

 the respective soils were incubated was used in making the examina- 

 tions. Each series of samples were kept screened from the light during 

 the period of incubation. After examination the samples were again 

 weighed to determine the quantity of soil used in examination. Daily 

 examinations of each sample of each soil were made for a period of 

 eight days. (See Table III.) 



Table III. — Presence of active protozoa in different soils, with varying amounts 0/ 

 moisture at different temperatures (constant and variable) for a period of eight day! 



o The writer did not think it advisable to include the remainder of Table III representing samples incu- 

 bated at 5° to 7°, 22° to 24°. 32° to 33°, and at the outdoor temperature, as in no case were any living 

 protozoa found during the period of eight days. 



* S. C t=few small ciliates. 



Upon examining Table III it is seen that in but one sample of soil 

 (the field soil which had an optimum and a half of moisture) were any 

 active protozoa observed. It was noted that there was a little de- 

 pression in the sample of soil and a little free available water was 

 present, thus no doubt accounting for the presence of this organism on 

 the third day of incubation, as on no other day and in no other soil were 

 any motile protozoa seen. 



In order to be certain that these soils contained cysts of protozoa and 

 to collect some data as to the amount of moisture necessary for excyst- 

 ment and also to note the time of excystment of protozoa when condi- 

 tions are favorable, to each series of the three different soil samples con- 

 taining moisture to the amount of half optimum and optimum and a half 

 sterile tap water was added to make the amount two optimums and two 

 and one-half optimums, respectively. These samples were then incu- 

 bated at the same temperatures as before, and daily examinations for a 

 period of four days were made. (See Table IV.) 



