104 Phylum Protozoa 



Glaucoma pyrijormis (35-60/z)* grows as vigorously as any ciliate 

 found in freshwaters. [See also p. 54-] It will grow on heavy suspen- 

 sions of Bacterium colt, and is unique in that it adjusts promptly to, and 

 grows vigorously in, sterile 0.5% Difco powdered yeast extract. Indi- 

 viduals are sufficiently large to be counted under the low powers of 

 binocular dissecting microscopes. 



Several strains have been described. Lwoff's (1932) and Elliott's 

 (1933) grow on peptone, Butterfield's (1929) grows for several transfers 

 on peptone, but ultimately demands yeast extract, while a strain isolated 

 by Hetherington (1936) shows no growth on peptone. Elliott (1935) 

 observed nutritive differences between peptone-growing strains. Glaser 

 and Coria (1935) isolated strains from hot springs which will tolerate 

 temperatures of 37 C. 



Extensive trials of different media (Hetherington, 1936) for Glaucoma 

 Pyrijormis resulted in the following optimum medium: 



Yeast Extract, Difco 0.5% 



Powd. Whole Yeast, Difco B13412 0.2% 



This is made up in Peters' medium (see p. 000), an inorganic physio- 

 logical salt solution, and autoclaved at 15 lbs. for 15 minutes. For stock 

 cultures, 125 cc. Erlenmeyer flasks are convenient vessels. Division 

 rates observed were rather constant, varying from 7.97 to 8.03 at 25 C. 

 Glaucoma scintillans (50-65/x), a typical holotrichous ciliate, was first 

 grown in pure culture by Chatton in 1929, later by Hetherington (1933). 

 [See also p. 56.] Neither investigator achieved dependable growth. Un- 

 published recent work by the writer resulted in the following medium: 



Yeast Extract, Difco 0.5% 



Powd. Whole Yeast, Difco B13412 1.0% 



Division rates observed vary from 2 to 2.7 at 25 C; the ciliates 

 appear normal and well nourished. While these rates are much lower 

 than those resulting from culture on single strains of bacteria, growth in 

 pure culture is now satisfactory for many experimental purposes. 



Other freshwater ciliates which have been obtained in pure culture are 

 Colpoda cucullus, C. steinii, Chilodon cucullulus, and Loxocephalus 

 granulosus. These investigations are reviewed by Hetherington ( 1934b) . 



* This ciliate was called Paramecium in the first paper of Peters (1920). Lwoff 

 (1923) first, and Peters (1929) later, called it Colpidium colpoda. It was called Colpidium 

 by Butterfield (1929), Colpidium campylum by Hetherington (1933) and by Taylor, et 

 o-l- (i933), Colpidium striatum by Elliott (1933), and Saprophilus oviformis by Glaser 

 and Coria (1935). Saprophilus oviformis, Glaucoma pyrijormis, and Colpidium striatum 

 are probably synonyms (Kahl, personal communication), but Colpidium campylum is a 

 common and distinct ciliate which is distinguished by the possession of a conspicuous 

 gullet, inconspicuous oral membranes, and by the fact that it will not grow in pure culture 

 in Difco yeast extract (or peptone, tryptone, or neopeptone, Difco). 



