70 Phylum Protozoa 



Place natural pond cultures in shallow glass or earthenware dishes 

 and keep covered to prevent evaporation. If pond scums and Euglena 

 are wanted or if these are needed for the food of any desired protozoan, 

 set the cultures in diffuse light, never in direct sunlight. Label each cul- 

 ture. Use one pipette for each culture. This precaution is of great 

 importance in examining the subcultures. 



Examination of cultures. At intervals each culture should be ex- 

 amined carefully. In making the examination, take samples of scum, of 

 clear liquid, scrapings from sides of vessel, from the light side and from 

 the dark side, from the vegetation, and from the bottom. These situa- 

 tions may furnish different forms because some forms swim freely while 

 others creep. Some require much oxygen while others can exist on less. 



Subcultures. If at any time any culture is yielding a large number of 

 desirable species such as Paramecium, Euglena, Amoeba, etc., sub- 

 cultures should be made as follows: Clean thoroughly short stender 

 dishes or finger bowls. Place in these filtered cistern or distilled water. 

 Do not use raw tap water. If neither cistern nor distilled water is 

 available, filter some water which has stood for a long time in an aqua- 

 rium or tank. Such water seems to have lost many of its noxious prop- 

 erties. Place a few straws of clean hay in the water and allow it to stand 

 36 to 48 hours before the desired Protozoa are placed in it. In place of 

 dry hay, the hay may be boiled in distilled or cistern water and the hay, 

 not the hay water, added to the water in the dish. Boiling the hay will 

 sterilize it so that sterilization of the hay in an autoclave is probably 

 unnecessary. Allow to stand before inoculating. In such cultures bac- 

 teria will develop and on these Paramecium and certain other forms feed. 



PURE CULTURES 



Isolation of particular species is not an entirely simple matter. How- 

 ever, individual Protozoa may frequently be secured by using a mouth 

 pipette. This is a glass tube with a finely drawn tip in one end of a 

 rubber tube 12 to 15 inches long with a short piece of glass tubing to 

 place in the mouth in the other end. Place a small dish of the culture 

 containing the organism sought on the stage of the binocular microscope 

 and put the glass tube in the mouth. When a desired individual is found 

 bring the point of the pipette near it and suck on the tube. With some 

 practice the protozoan may be caught and may be put on a slide in a 

 small drop of water and examined. In this way individual Protozoa 

 may be isolated for the inoculation of cultures and by washing them in 

 one or several changes of water the worker can be reasonably sure that 

 other species are not present. ^^J 



Amoeba. In culturing Amoeba tap water may be harmful and must 



