COLLECTION, CULTIVATION, OBSERVATION 881 



Mixed cultures of many free-living Protozoa are easily maintained 

 by adding from time to time a small amount of ripe hay-infusion or 

 dried lettuce powder to the collected water mentioned before. Chilo- 

 monas, Peranema, Bodo, Arcella, Amoeba, Paramecium, Colpoda, 

 Stylonychia, Euplotes, etc., often multiply in such cultures. To ob- 

 tain a large number of a single species, individuals are taken out 

 under a binocular dissecting microscope by means of a finely drawn- 

 out pipette and transferred to a suitable culture medium. Such a 

 culture is called a mass or stock culture. If a culture is started with a 

 single individual, the resulting population makes up a clone or a 

 pure line 



Aside from the cultures of blood-inhabiting Protozoa and of some 

 100 free-living forms, the protozoan cultures are by no means "pure" 

 cultures in the bacteriological sense, even if only one species of Pro- 

 tozoa is present, since bacteria and other microorganisms are in- 

 variably abundantly present in them. 



A. Free-living Protozoa 



To deal with all the culture media employed by numerous workers 

 for various free-living Protozoa is beyond the scope of the present 

 work. Here only a few examples will be given. For further informa- 

 tion, the reader is referred to Belaf (1928), Needham et al. (1937), 

 etc. 



Chromatophore-bearing flagellates. — There are a number of culture 

 fluids. Two examples: 



(a) 



(b) 



Peranema, Chilomonas, Astacia and other colorless flagellates. — A 

 number of culture fluids have been advocated. A simple yet satis- 



