Oct. i8. 191S 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 sterihzed (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 



(i) BiFFi, 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 Joiu-. Agr. Sci., v. 7, pt. i, p. 49-74. 



(4) Fred, E. B. 



191 1, tjber die Beschleunigtmg der Lebenstatigkeit hoherer und niederer 

 Pflanzen dutch kleine Giftmengen. In Centbl. Bakt. [etc.], Abt. 2, 

 Bd. 31, No. 5/10, p. 185-245. Literatur, p. 242-245. 



