VARIATIONS IN CELL SIZE DURING THE DEVELOPMENT OF THE SLIME MOLD, DICTYOSTELIUM DISCOIDEUM

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Abstract
1. The individual cell size was measured for 300 cells at various stages during the development of the slime mold Dictyostelium discoideum; during two periods of the vegetative stage when the amoebae are actively feeding, during the aggregation stage when the amoebae are streaming together to form cell masses, during the migration stage when the cell mass wanders over the substratum, and finally the mature encapsulated spores. 2. The mean size was large during the vegetative period, dropped severely in the fasting aggregating amoebae, increased slightly during the migration stage, only to fall to their minimum size as mature spores. 3. The variability in size was large and especially so during the periods before, during and after aggregation. 4. Of special interest relative to the problem of differentiation was the fact that during the migration stage, the anterior presumptive stalk cells were significantly larger than the posterior presumptive spore cells, being another example of an early detectable sign of differentiation.