The purpose of these experiments was to determine if there were major qualitative differences in the colonization process at different points in a lake at approximately the same point in time given that the lake was sujected to influent streams, outfalls, seiches, and currents. Another way of phrasing this problem: Is the protozoan fraction of the biota of a lake repeatedly distributed throughout the ecosystem in a manner that allows minimal and reliable sampling? In order to approach this problem, sets of artificial substrates made of polyurethane foam were positioned at various points in Douglas Lake, Michigan (area: ca 13 Km2) in relation to major currents, influent streams and outfalls. The artificial substrates were examined principally during the summer of 1972. Some stations were sampled in October after fall overturn, and samples of natural substrate material were taken from under ice cover in March 1973. The analysis of data shows a marked similarity among samples.