The Effect of Soil Storage and Water Content Ox the Protozoan Population

Summary. Experiments are described showing that it is possible to conduct laboratory experiments on micro‐organisms in stored soil, providing the surface of the soil is large relatively to its volume. Experiments on the influence of moisture on the soil protozoa show that active forms are found in soils containing a very low per centage of water. The flagellate Cercomonas crassicauda was found to excyst and reproduce in air‐dried soil brought to 1/6 the water‐holding capacity. The numbers of the bacteria also in this experiment nearly doubled their numbers in 24 hours. Four common soil protozoa were found to behave normally in soil of 1/2 and 1/3 the water‐holding capacity, which previously had been air‐dried and then brought to the desired water content Field soils having water contents of 6 per cent, in one case and 4 per cent. in another corroborated the laboratory experiments In all of these samples active Cercomonas were found, other protozoa being present only in the form of cysts.