Sexuality in the Acrasiales

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Abstract
Dictyostelium discoideum was grown along with Escherichia coli in yeast-starch agar, and at various stages in the life cycle samples were removed and stained with aceto-orcein. In the vegetative stage the myxamoebae fed upon the bacteria and multiplied by cell division. In the early stages of aggregation vegetative amoebae, fusing gametic amoebae and zygotes were found. Syngamy occurred on the outer fringes of the aggregation and when the initial zygotes had formed a center of the aggregation, meiosis was initiated, and continued as long as zygotes joined the aggregation. The zygotes could be distinguished from the vegetative or gametic cells by their larger size. No mitotic divisions occurred in the diploid stage (2n-14), represented by the fusion nucleus of the zygote. The pseudoplasmodium of D. discoideum permits a migration stage. In the formation of the sporocarp, after its stalk had elevated the sporogenous cells, rapid cell division occurred before spore formation, causing a reduction in size of the cells which later became spores.