SEPARATION OF SOIL PROTOZOA 1 
By Nicholas Kopeloff, H. Clay Lint, and David A. Coleman, 
Research Fellows, The New Jersey College for the Benefit of Agriculture and Mechanic Arts 
Some interesting problems have been suggested by the contention of 
Russell and Hutchinson (9, io) 2 that protozoa are one of the limiting 
factors in soil fertility, because they feed upon and consequently limit 
the numbers of soil bacteria. Before the agricultural scientist can 
successfully formulate a complete explanation of the phenomena con¬ 
cerned with the function of protozoa in soils it is essential to establish 
certain fundamentals in methodology. Russell and Hutchinson (9, 10) 
and Cunningham (2, 3) have presented some valuable information con¬ 
cerning the depression of bacterial numbers as a result of inoculation 
with cultures of protozoa. The writers entered upon an investigation of 
a similar nature, with an attempt to base their work upon the use of 
protozoa-free cultures of bacteria, and bacteria-free cultures of protozoa. 
But little mention is to be found in the literature regarding the separa¬ 
tion of the different kinds of protozoa from each other and from bacteria. 
Russell and Hutchinson (9, 10) and Fred (4) have employed an efficient 
method of filtration for obtaining cultures of protozoa, but they do not 
offer any further experimental data concerning such separations. Cun¬ 
ningham (2, 3) has made use of a single-drop method for obtaining 
protozoa-free cultures of bacteria, based on the transfer to a suitable 
medium of a drop from a protozoan culture which upon microscopic 
examination revealed no protozoa. On the other hand, he does not 
describe any direct method for obtaining a bacteria-free culture of 
protozoa. Jordan (5, p. 469) mentions a method which might prove 
somewhat tedious—that is, having protozoa pass through concentric 
rings of dead bacteria on a culture plate until they had no living adher¬ 
ing bacteria. He refers also to Frosch’s 3 method of separation by 
means of a sodium-carbonate solution. Richter (8) suggests the use of 
a high-gelatin medium which would suppress the bacterial growth of 
liquefying organisms. Biffi and Razzeto (1) give an account of the 
passage of protozoa through semipermeable filters after a considerable 
period of time has elapsed. 
The writers are in agreement with Biffi and Razzeto regarding the 
importance of the time element in filtration, since it has been observed 
that protozoa have been able to work through the pores of a filter in a 
short time. 
In the work under consideration—namely, the separation of flagellates 
from ciliates—an ,8-day-old culture of soil organisms was employed. 
1 From the Departments of Soil Chemistry and Bacteriology, New Jersey Experiment Station, New 
Brunswick, N. J. 
2 Reference is made by number to u Literature cited,” p. 139-140. 
8 Frosch, P. Zur Frage der Reinziichtung der Amoben. In Centbl. Bakt. [etc.], Abt. 1, Bd. 21, No. 
24/25* P* 926-932. 1897. 
(137) 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
ah 
Vol. V, No. 3 
Oct. 18, 1915 
N. J.—2 
