The specimen is PtK2 marsupial kidney epithelial cells grown in tissue culture, then fixed and double-stained using FITC and propidium diiodide (PI). Photomicrographs were recorded utilizing a UPL 100x apochromatic objective coupled to a WU dichroic filter combination. A 2.5x projection photo eyepiece was used to transfer light from the intermediate image plane to the photographic emulsion.