ii2 Phylum Protozoa 



ciently nutritive to permit the growth of contaminating micro-organisms. 

 Justification for this may be seen in the fact that molds were never 

 observed to develop during the experiments. 



All experiments were carried out in a constant temperature room at 

 72 ° F. with north light. 



The containers for the culture of Colpoda are watch glasses of about 

 2 mm. diameter enclosed in petri dishes of suitable size containing in the 

 bottom a small amount of water and so used as moist chambers. 



References 



For the culture of Colpoda cucullus see also p. 104. 

 For the culture of Colpoda steinii see pp. 56 and 104. 

 Family Urocentridae 



For the culture of Urocentrum turbo see p. 106. 



Bibliography 



Osterhout, W. J. V. 1906. Extreme toxicity of sodium chloride and its prevention 

 by other salts. /. Biol. Chem. 1:363. 



Family parameciidae 



SOME METHODS FOR THE PURE CULTURE OF PROTOZOA 



William Trager, Rockefeller Institute for Medical Research 



I. SEPARATION OF THE PROTOZOA FROM 

 OTHER MICRO-ORGANISMS 



Migration through Pipettes. The technique developed by Glaser and 

 Coria (1930), and used by them for the separation of certain Protozoa 

 from their contaminating bacteria, depends essentially on the exhibition 

 by the Protozoa of a geotropic response which causes them to swim away 

 from the bacteria through a column of sterile liquid. Two methods for 

 bringing this about are available. In the first, sterile pipettes are used, at 

 least 14 inches long with a % inch bore, a tapering point, and a cotton 

 plug at the large end. For negatively geotropic Protozoa such a pipette, 

 by suction through a rubber tube attached to the large end, is filled with 

 sterile tap water to within 2 inches of the top. Then about 2 cc. of a 

 heavy culture of the contaminated Protozoa is carefully sucked up into 

 the pipette, so as to form a layer beneath the sterile water. The tapering 

 end of the pipette is then sealed by heat, care being taken not to permit 

 the formation of air bubbles. The pipette, sealed end down, is set upright 

 in a test tube rack. In from 5 to 30 minutes, negatively geotropic Proto- 

 zoa will be present at the top of the column of liquid. Even motile 



