Slime molds in the group Eumycetozoa are amoeboid protists which produce spore-bearing fruiting bodies and have amoebae with acutely pointed pseudopodia. The more commonly recognized members of the group are the widely studied myxomycetes, or "true" slime molds, and dictyostelid cellular slime molds. Members of both groups have been used as model systems in cell and developmental biology. However, a third group, the protostelids, has received far less attention. The protostelids have very simple fruiting bodies, but many different types of amoebae are found in various species. If the protostelids can be demonstrated to be a monophyletic group, then they would provide an excellent model for: (1) the study of the evolution of patterns of amoeboid cell motility and (2) the study of phylogeny in amoeboid protists in general. Previous work by Dr. Spiegel of the University of Arkansas has shown that the seven genera of protostelids with an amoeboflagellate state in the life cycle are members of a monophyletic lineage along with the myxomycetes, and phylogenetic analysis gives a clear picture of the relationships within the group. The present study will attempt to determine whether members of the protostelids that have only nonflagellate amoebae in the life cycle are related to these seven flagellate genera. The work will concentrate primarily on the two large genera Protostelium and Schizoplasmodiopsis. Preliminary work suggests that the former is polyphyletic and will have species related to several flagellate genera while the latter may be monophyletic. The species in these genera will be examined with light microscopy, immunofluorescence microscopy, and electron microscopy to determine the details of amoebal structure, fruiting body development, and some aspects of mitosis. the characters that are discovered will be used to compare the various species to the flagellate protostelids and to other protists to which they might be related. It is hoped that the study will result in a strongly supported phylogenetic classification of the protostelids.