318 PRINCIPLES OF SOIL MICROBIOLOGY 



The green Paramoecium bursaria was cultivated 21 on a medium consisting of: 



Ca(N0 3 ) 2 0.20 gram NaCl 0.20 gram 



MgS0 4 -7H 2 0.02 gram FeS0 4 Trace 



K 2 HP0 4 .02 gram Water 1000 cc. 



Peters' glycerophosphate medium, described below, has been used successfully 

 for the cultivation of ciliates. Colpidium and Oicomonas were grown on the 

 following medium: 22 



Ammonium lactate. .. . 0.1 gram KC1 0.3 gram 



Glucose 0.4 gram MgS0 4 -7H 2 0.001 gram 



NH4CI 0.03gram CaCl 2 0.02 gram 



Na 2 HP0 4 0.01 gram 



The reaction is adjusted to pH 7.0-7.4. Phenol red may be added to the cul- 

 tures to follow changes in the acidity and alkalinity during the growth of the 

 culture. Giltay solution and a synthetic glycerin medium may also be em- 

 ployed. 23 



However, the majority of the media used for the isolation of protozoa 

 are based upon a previous development of bacteria, which, either alive 

 or dead, may serve as food for the protozoa. Such substances as soil, 

 straw, hay, grass, lettuce, leaves, etc. cooked in water are favorable. 



Thirty to 40 grams of hay are cooked in one liter of water for thirty minutes; 24 

 solution is filtered, made up to volume; to prepare a solid medium 15 grams of 

 agar are added. 0.025 per cent meat extract in distilled water was found 26 to be 

 favorable for Paramoecium aurelia. Other media containing one to two per cent 

 of nutrose, somatose, or peptone and 1.5 per cent agar are also favorable. Martin 

 and Lewin 26 used a medium prepared by boiling three lumps of horse dung in 500 

 cc. water for 1£ hours, filtering through cloth and adding 6 grams of agar. A 

 small amount of water or dilute albumin added to the culture plates to a depth 



21 Pringsheim, E. G. Die Kultur von Paramoecium bursaria. Biol. Centrbl. 

 36: 375. 1915; Zur Physiologie saprophytischer Flagellaten (Polytoma, Astasia, 

 and Chilomonas). Beitr. Allg. Bot., 2: 88-137. 1921. 



22 Cutler, D. W., and Crump, L. M. The rate of reproduction in artificial 

 culture of Colpidium colpoda. Biochem. Jour., 17: 174-186, 878-886. 1923. 



23 Cutler, D. W. Methods for the study of soil protozoa. Abderhald. 

 Handb. biol. Arb. Method. Abt. XI, T. 3. 1926. 



24 Further information on hay infusions is given by Woodruff, L. L. Observa- 

 tions on the origin and sequence of the protozoan fauna of hay infusions. Jour. 

 Exp. Zool., 12: 206-264. 1912; Fine, M. S. Chemical properties of hay infusions 

 with special reference to the titratable acidity and its relation to protozoan 

 sequence. Ibid., 12: 265-289. 1912. 



26 Woodruff, L. L. Jour. Exp. Zool., 12: 205. 1912; 14: 575. 1913. 

 26 Martin, C. H., and Lewin, K. B. Some notes on soil protozoa. Phil. 

 Trans. Roy. Soc. B, 205: 77-94. 1914; Jour. Agr. Sci., 7: 106-119. 1915. 



