II0 Phylum Protozoa 



sun. Cultures which were not exposed to the air, and hence did not 

 become moldy, continued to thrive for long periods of time. 



STOCK CULTURES OF COLPODA* 



DURING the course of investigation with Protozoa, a rather con- 

 venient and easy method of obtaining and keeping stock cultures 

 of Colpoda was found. 



Colpoda, as is well known, usually occur early in soil cultures from 

 which they may be obtained, in the active state, in large numbers. Later 

 in the life of the culture the animals encyst and it is upon this condition 

 that the following method is based. 



From a young soil culture active Colpoda are isolated, transferred to 

 Syracuse watch glasses and ordinary hay infusion added. After one or 

 two days the culture fluid in the watch glass is allowed to evaporate 

 slowly by exposure to the air. During this slow evaporation the animals 

 encyst. The dried up culture is left exposed for one or two days, when 

 new hay infusion is added. The animals, having divided within the 

 cysts, revive and are found in greatly increased numbers. This drying 

 process may be repeated until a more or less concentrated culture of 

 organisms is obtained. The concentrated culture of organisms is then 

 pipetted into a petri dish in which a piece of ordinary filter paper, cut so 

 as to exactly cover the bottom of the dish and moistened with hay infusion, 

 is placed. The petri dish is then left uncovered to evaporate slowly. The 

 filter paper, with the encysted organisms on it, when thoroughly dry, may 

 be cut into small pieces and kept indefinitely. 



To start fresh cultures, pieces of the filter paper are put into watch 

 glasses or other containers and hay infusion added. In a short time the 

 animals revive and new cultures of the original are thus obtained. 



This method of keeping stock cultures seems to be especially adapted 

 for schools and colleges where only a limited amount of time is devoted 

 to the Protozoa and where no time for the ordinary culture preparation 

 work is available. 



M. E. D. 



Reference 

 For the culture of Colpoda see also p. 63. 



THE CULTURE OF COLPODA CUCULLUS 



H. Albert Barker and C. V. Taylor, Stanford University 



Colpoda cucullus may be cultured in finger bowls containing 10-20 cc. 

 of a dilute hay infusion. These infusions, however, are singularly unsuit- 



* Reprinted with slight changes from an article in Science 53:92, 192 1, by Joseph H. 

 Bodine, Iowa State University. 



