^38 



Journal of Agricultural Research 



Vol. V. No. 3 



This was prepared by adding loo gm. of Penn clay loam soil to i liter of 

 a ID per cent hay infusion plus 0.5 per cent of egg albumin, which the 

 writers had previously found to be best adapted to the large and rapid 

 development of protozoa in such soil (6) . 



The method of procedure was as follows : The numbers of protozoa in 

 the stock culture solution were first counted by the new method described 

 i;i a previous paper (6) and recorded under classes of (i) flagellates, 

 (2) small cihates (12 to 20m), and (3) large ciliates (25 to 60^1). No 

 amoebse developed in the short period of incubation. Ten c. c. of the 

 culture solution were then placed (by means of a sterile pipette) on filter 

 paper, previously sterilized with alcohol, and allowed to filter through 

 for one minute. The protozoan content of the filtrate was then recorded 

 in tripUcate and the filtrate incubated for five days at 22° C, in order 

 to allow the excystment of any encysted forms. The filtration and 

 incubation processes were then repeated, if necessary, until all the living 

 protozoa of the desired type had been separated out. The filter paper 

 was used in from one to five different thicknesses (Schleicher and Schiill's 

 No. 589). The results are recorded in Table I. 



Table I. — Number of protozoa per 10 c. c. of filtrate through varying thicknesses of 

 filter paper 



■ Stock protozoan solution. 



