Oct. 18, 1915 
Separation of Soil Protozoa 
139 
It will be observed from Table I that the large ciliates are not able to 
pass through the filter paper at all, which fact is in agreement with the 
experience of Russell and Hutchinson (9, 10). The noteworthy feature, 
however, is that the number of small ciliates decreases rapidly in increas¬ 
ing the thicknesses of the filter paper from two to four. Thus, with four 
thicknesses of filter paper all of the ciliates found in the solution em¬ 
ployed were separated from the flagellates. Likewise it was a simple 
matter to separate the small from the large ciliates. In this way it 
becomes possible to employ mass cultures of flagellates, small ciliates, or 
large ciliates, as may be necessary in the problems indicated at the 
outset. 
In an effort to determine the effect of filtration on the separation of 
soil protozoa from bacteria, a bacterial count was made of the stock- 
culture solution previously employed, known to contain soil micro¬ 
organisms. Ten c. c. of this solution were then filtered through five 
thicknesses of sterilized (with alcohol) filter paper (S. & S. No. 589). 
The residue on the filter paper, consisting of all of the protozoa originally 
present, together with some adhering bacteria, was then plated out on 
Lipman and Brown's (7, p. 132) synthetic agar. The bacterial count 
showed that 90 per cent of the bacteria had passed through the filter 
paper (after making due deduction for contamination from the air by 
exposing agar plates for the same length of time as was necessary for 
filtration), thus leaving the protozoan residue comparatively free from 
bacteria. 
This method in all probability would not allow complete separation of 
the protozoa from the bacteria. Consequently the work was not car¬ 
ried out any farther. However, this method, because of its rapidity and 
simplicity, might prove of value in investigations concerned with the effect 
of protozoa on mixed but not on pure cultures of bacteria. 
While these preliminary experiments do not warrant any definite 
conclusions, they are, nevertheless, indicative of some of the difficul¬ 
ties which the soil protozoologist encounters. 
LITERATURE CITED 
(1) Bieei, U., and Razzeto, O. 
1907. Sulle applicazioni della filtrazione in microbiologia e sulla permeability 
di alcuni filtri ai protozoi delle acque. In Sperimentale, ann. 61, 
fasc. 1/2, p. 45-82, pi. 1-4. Indicazioni bibliografiche, p. 80-82. 
(2) Cunningham, Andrew. 
1914. Studies on soil protozoa. II. Some of the activities of protozoa. In 
Centbl. Bakt. [etc.], Abt. 2, Bd. 42, No. 1/4, p. 8-27, pi. 2. 
(3) — 
1915. Studies on soil protozoa. In Jour. Agr. Sci., v. 7, pt. 1, p. 49-74. 
(4) Fred, E. B. 
1911. Uber die Besehleunigung der Lebenstatigkeit hdherer und niederer 
Pflanzen durch kleine Giftmengen. In Centbl. Bakt. [etc.], Abt. 2, 
Bd. 31, No. 5/10, p. 185-245. Literatur, p. 242-245. 
