484 



Journal of Agricultural Research 



Vol. V, No. II 



Table IV. — Presence of active protozoa in different soils at different temperatures when 

 the moisture conditions were favorable 



oS.C.=sniall ciliates, L.C.= large ciliates, F.= flagellates, A.= ameb3e, t=few, tt=several, t+t=many. 



The data presented in Tables III and IV again point to the fact that 

 the supply of sufficient moisture is the limiting factor which influences 

 the presence of protozoa in the active state in the soil, while the tem- 

 perature, the presence of organic matter, and the soil structure seem 

 to be only secondary factors. 



On examining Table IV it becomes apparent that the temperature 

 influences the period of excystment, in that a higher temperature may 

 encourage a more rapid excystment of a greater number of protozoa and 

 that the physical character of the soil may be more or less influential 

 in the movement of the organisms in the soil ; yet ,if the moisture content 

 is not high enough, the protozoa will not be present in the active state. 



To find out whether protozoa were always present in the active state 

 in water-logged soils, samples of six soils, three greenhouse and three 

 field soils, which were kept in the laboratory for some time, were put 

 into small bottles, water-logged, and the bottles plugged with rubber 

 stoppers to prevent evaporation, and then allowed to stand in the labo- 



