60 



Sfiidlrs oil Siiil Protozoa 



cysts sliow practically no cliange as a result of the variations in the 

 treatment. 



Experiment II. In this case the original sample was divided 

 into two portions. One was allowed to dry for nine days: the other 

 was kept saturated for seven days. Bacterial counts were also made 

 on the samples, agar at 22° (1. being used as medium. Otherwise the 

 procedure was the same as in Experinuuit 1. Table 9 shows the 

 results. 



Table 9. 



Drying has again resulted in a reduction in the number of protozoa 

 while the saturation of the soil with water has produced a slight increase 

 in total numbers and a very decided decrease in the number of cysts. 

 The bacterial content has in both cases fallen considerably and it is 

 noteworthy that from the saturated soil more bacteria have disappeared 

 than from that which has been exposed to drying. But the conditions 

 in the saturated soil cannot be regarded as very unfavourable for 

 bacterial growth, for the layer of soil and water is quite a thin one 

 (about \ inch). 



Experiment III. The plan in this case was similar to that 

 adopted in Experiment I, but bacterial counts on agar at 22° were 

 added. The dried soil was kept for 16 days: the 70% sample for 

 15 days and the saturated sample for 14 days. Table 10 contaiiis the 

 results. 



Here the drving has caused no decrease in the total numbers of 

 protozoa. The latter appear all to have been able to encyst before 

 the soil became too dry foi' active life. This view is supported by the 



