Criteria of stream pollution may be all too evident in turbid, highly colored, offensive smelling streams. But often relatively clear sparkling streams need laboratory examination to determine the nature and extent of their pollution. Biological examinations may include several features as the microscopic life present, or the animals living in or on the bottom. For sometime it has been stated that the presence of certain microscopic organisms in abundance is a sure indication of organic pollution, usually domestic sewage. One of the groups used in this fashion has been the 'Euglenas and their allies', a related group of green flagellates. The report discusses their presence on the Scioto River in Ohio.