I2 o Phylum Protozoa 



time the color of the infusion indicates the chemical condition of the cul- 

 ture. When fresh, the cabbage leaf culture medium is light reddish 

 purple in color, but about 24 hours after being seeded with Paramecium, 

 it turns red, indicating the formation of acid. In four or five days to two 

 weeks, as the Paramecia increase in number, the medium gradually be- 

 comes alkaline, as is shown by its change of color to green. 



The culture, as far as quantity of Paramecia is concerned, is at its 

 height when it becomes a brilliant green and has lost its early turbidity. 

 The behavior of the cultures may be varied considerably by adding a trace 

 of sodium bicarbonate or a weak acid. In from one to two months, the 

 culture becomes the color of an old hay infusion, fails to react to acids or 

 alkalies and the Paramecia have either wholly or almost wholly died off. 



Bibliography 

 Bragg, A. N., and Htjlpieu, H. 1925. A method of demonstrating acidity of 



food vacuoles in Paramecium. Science 61:392. 



M. E. D. 



PARAMECIUM* 

 William LeRay and Norma Ford, University of Toronto 



PARAMECIUM is a form which is easily reared. From the bottom of 

 a permanent pond the foul-smelling debris is taken and kept in a 

 bowl barely covered with water and at a temperature of approximately 

 73 F. As the debris fouls, the Paramecium become abundant. From 

 time to time (about once a week) a half-inch cube of fish is added to 

 the bowl to maintain a supply of food. Such a culture as this will carry on 

 for months. It is advisable to select a large race and to rear in sepa- 

 rate containers. Should some small forms be present in the new bowls 

 they are usually unsuccessful in the competition with the large ones. 



A CULTURE MEDIUM FOR PARAMECIUM** 



THIS medium has proven very satisfactory for culturing various 

 species of Paramecium in pure line cultures. The main result of the 

 use of the medium is that the organisms do not exhibit a lowering of their 

 normal metabolism after continuous culturing. 



* Editor's Note: For the technique used by Prof. L. L. Woodruff of Yale University in 

 maintaining his famous pedigreed cultures of Paramecia the reader is referred to the 

 following articles: 



Woodruff, L. L. 1908. The life cycle of Paramecium when subjected to a varied 

 environment. Amer. Nat. 42:520. 



1911. Two thousand generations of Paramecium. Archiv. f. Protist. 21:263. 



1932. Paramecium aurelia in pedigreed culture for twenty-five years. Trans. Amer. 



Micr. Soc. 51:196. 



Woodruff, L. L., and Erdmann, Rhoda. 1914- A normal periodic reorganization 

 process without cell fusion in Paramecium. /. Exper. Zool. 17:425- 



♦♦Reprinted, with slight changes, from Science 75:364. 1932, by Lauren E. 

 Rosenberg, University of California. 



