Date of Award


Document Type


Degree Name

Master of Arts (MA)



First Advisor

Dr. A. Thomas Weber


Introduction: In the life cycle (Fig. 1) of members of the Acrasiomycetes, the cellular slime molds, growth is separate from differentiation allowing independent study of these stages. The earliest stage in the life cycle is the spore. Each spore may germinate releasing a single amoeboid cell, the myxamoeba. Myxamoebae feed and grow independently until there is a depletion of the food supply. At this time growth virtually stops and the myxamoebae cease to move independently, streaming instead toward aggregation centers. By the end of aggregation, two morphogenetically different cell types appear, pre-spore cells and pre-stalk cells, which coexist in a structure resembling a common garden slug, called the pseudoplasmodium. The pseudoplasmodium migrates in a direction influenced by various physical conditions such as heat, light, pH and ionic content of the medium. Culmination follows migration and begins when the pseudoplasmodium assumes a vertical position on the substratum. The individual cells then complete differentiation with the pre-spore cells being raised up off the agar surface on a vertical, cellular stalk. The result is a mature, stalked structure, the sorocarp, with spores at the apex.


A Thesis Presented to the Department of Biology and the Faculty of the Graduate College University of Nebraska at Omaha In Partial Fulfillment of the Requirements for the Degree Master of Arts. Copyright 1975 Nancy Taylor Morris.