The following comments are designed to aid the instructor in handling and maintaining protozoan units. They concern the fundamental factors affecting the most frequently studied laboratory culture.

Shipments leave our laboratory in excellent condition but sometimes encounter delays or are exposed to temperature extremes which kill the specimens. CULTURES RECEIVED IN POOR CONDITION SHOULD BE REPORTED AT ONCE, AND NO LONGER THAN 48 HOURS AFTER RECEIPT.

Allow the cultures to settle for about fifteen minutes before use. This will permit the organisms to regroup in the areas where they are most readily collected; that is Amoeba and Pelomyxa on or near the bottom; Euglena and similar chlorophyll-bearing species on the lighted side. Paramecium, Stentor, Blepharisma, Spirostomum, Peranema, and other free-swimming types throughout the medium. Often the protozoa will be found grouped together at the bottom of the culture, concentrated about the wheat or rice grain. Locating the organisms can be facilitated by a prelimimary examination of the culture under a low power stereoscope.

Note: As all protozoans are shipped with a food source, some of these may yet remain in the culture. Culture should be used for classrooms study before experimentation and subculturing is attempted. Mixed protozoan cultures should be studied immediately since the larger forms eat the smaller and variety is quickly reduced.

Equipment: Keeping units free of contaminating elements is of major importance in producing healthy, viable cultures. To ensure such an environment, it is necessary to begin with clean (sterile if possible) labware. Containers should be free of all chemical residue and should not have been previously used for fixatives or other toxic materials.

Medium: Pond or stream water which has been sterilized will, under normal conditions, also prove a growth-producing medium. Water which is prepared for any length of time before use should be stored in airtight containers to prevent contamination; it may be necessary to re-aerate this liquid by agitation before use.

Temperature: Most protozoans will grow normally at room temperature (68-75 degrees F). Cultures should be kept with lids lightly placed over the jars. Never place cultures in a refrigerator or indirect sunlight.