51 8 Journal of Agricultural Research voi. iv.No. 6 



Jena Erlenmeyer flasks were placed loo c. c. portions of a 3 per cent 

 dried-blood extract + 0.05 per cent of dibasic potassium phosphate 

 (KjHPOJ prepared by boiling 30 gm. of dried blood with i ,000 c. c. of 

 tap water for one hour and then adding 0.05 per cent of KjHPO^. In 

 like manner 100 c. c. portions of Lohnis's (11, p. 118) soil extract with 

 the addition of 0.05 per cent of dibasic potassium phosphate were put 

 into another series of flasks. These flasks were plugged with cotton and 

 sterilized in an autoclave and all the precautions taken as in bacterio- 

 logical work. They were then carefully inoculated with i, 2, 3, 5, 10, 

 20, 50, and 100 gm. portions of moist and dry soils. The solutions were 

 examined under the microscope for living protozoa by carefully trans- 

 ferring a film of the culture solution to a clean glass slide. The inoculated 

 flasks were then placed in a constant-temperature incubator and incu- 

 bated at 22° C. Daily examinations at the same hour for a period of 

 30 days were made and the different types of protozoa enumerated by 

 the improved loop method described on p. 512. 



In order to compare the development of protozoa of different green- 

 house soils, three other compost soils were collected : 



(i) A 10 per cent manure and 10 per cent sand mixture upon which 

 roses were grown in the greenhouse the previous year. At the time of 

 collection this soil was exposed to the weather and contained 21.1 per 

 cent of moisture. 



(2) A 50 per cent manure mixture, which was also exposed to the 

 weather and had a moisture content of 30.3 per cent. Roses were grown 

 upon this soil the previous year. 



(3) A 30 per cent compost which was planted to soy beans and com 

 seedlings. This was a dry soil, having a moisture content of 14.9 per 

 cent. 



Erlenmeyer flasks of 200 c. c. capacity containing 100 c. c. of the same 

 extracts of dried blood and soil, as described above, were inoculated 

 with I, 20, 50, and 100 gm. portions of the four composts. These solu- 

 tions were examined for protozoa and then incubated at 22° C. for eight 

 days. At the same hour each day examinations and counts of the 

 different types of protozoa were made. 



The classification of the protozoa which was followed throughout this 

 problem was as follows : ^ 



The small ciliates included all organisms from the smallest to and 

 including Colpidium colpoda Ehrb. The vorticellae were also included. 



The large ciliates included all forms larger than Colpidium colpoda. 



The flagellates included all the forms that were observed. 



It was found at the outset that there were many minute organisms 

 that could not be recognized easily under the low power, but which were 

 easily seen with the high power of the microscope. Even under the 

 high power it was impossible to distinguish between large bacteria and 



