Spores of Henneguya exilis, taken during the summer of 1968 from the gills of Ictalurus punctatus caught in the Des Moines River near Knoxville, Iowa, and of a species of Myxosoma apparently closely related to Myxosoma ovalis, taken from the gills of Carpiodes velifer from the same locality, were subjected to storage at room temperatures, 4° C, and deep freezing. Repeated measurements of spores under different pretreatment showed that the dimensions of the spores and polar capsules remained remarkably stable, as did ratios of the dimensions of spore parts. Abnormalities in the details of spore architecture were seen under conditions under which dimensions remained stable. It is recommended that, wherever possible, unfixed spores be used for measurements, and preserved spores be used for other observations on which species descriptions are to be based
