GROWTH 543 



A usable source of C, H, O, N, Ca, K, P, and Na is probably required 

 by all Protozoa. Inorganic media have been used by Hall and Schoen- 

 born (1938) to separate strains of flagellates, by choosing media in 

 which one strain will survive and others perish. Some Protozoa can ob- 

 tain nitrogen from nitrates or ammonium salts, while others require 

 amino acids, proteoses, or peptones. Sodium acetate, glycerate, or glyc- 

 erophosphate are among the simplest carbon sources required by the 

 nonphotosynthetic organisms. Loefer (1935) has summarized the carbo- 

 hydrate requirements. The growth of Chilomonas para7necium requires 

 sodium acetate, magnesium, sulphur, and silicon (Mast and Pace, 1933), 

 and vanadium and copper increase the rate of growth (Bowen, 1938). 

 Colpidium needs phosphate and a minimum three-carbon source, ac- 

 cording to Peters (1920). Potassium and magnesium may be omitted 

 from glass cultures, but are required when quartz vessels are used. 

 Uranium salts cannot be substituted for potassium (Peters, 1921). The 

 addition of pimelic acid to a glycerine- dextrose medium permitted growth 

 of Colpidium (Hall, 1938b). Bacteria-free P. bursaria grew in propor- 

 tion to the concentration of the culture medium (Loefer, 1938d). 



Polytoma grows better when aneurine (synthetic B^) and thiazol 

 compounds are present (Lwoff and Dusi, 1937, 1938); and trypano- 

 somes need hematin and cholesterol. Ameoha and Paratnecium grow bet- 

 ter in the presence of sulfhydryl, and this may be a general requirement 

 of Protozoa. Hammett (1929) obtained an increased growth of Parame- 

 cium, although it was not proportional to the SH content. Hall (1938) 

 found that manganese stimulated the growth of E. anabaena, but failed 

 to stimulate Astasia sp. and Colpidium campylum. 



Culture media have been improved by the addition of yeast extract 

 for Uroleptus, Dallasia, P. bursaria, Pleurotricha, and Stylonychia, and 

 Gregory (1925-28) found that the stimulation or depression of the 

 division rate of Uroleptus mobilis depended on the age of the culture. 

 Beef extract has proved a suitable food for mixed cultures. Plant hormones, 

 indoleacetic, indolebutyric, and indoleproprionic acids increase the 

 growth of chlorophyll-containing Protozoa, while pantothenic acid 

 stimulated those tested by Elliott (1935a, 1938) which did not have 

 chlorophyll. Mottram (1939) reported that 3 : 4 benzpyrene is a growth 

 stimulant for Paramecium. 



Beers (1928a, 1928c) grew two parallel lines of Didinium nasutum 



