The “slender but consistent” series of investigators responsible for early progress in the understanding of cytokinesis produced an appreciable body of thought and observation that seems to stand to a great extent by itself. The importance of understanding contraction, deformation, surface formation, and other manifestations of cell activity that seemed especially important during cytokinesis was recognized, but fundamental information concerning the nature of these activities was lacking. It was not usually possible to explain by adducing relevant supporting data from other fields because they did not exist. W. H. Lewis's (1942) insight concerning the similarities among cytokinesis, amoeboid locomotion, and cell shape change drew attention to the probable importance of surface contractile activity in cell biology, but it did not at that time offer a way to understand the underlying mechanisms.

The 50-year efflorescence of comment and conjecture about cytokinesis that was produced by some of the best-known minds in cell and developmental biology was not accompanied by marked advances in an understanding of the details of the process or by improvements in general methods of analysis of dynamic cell activity. Attempts to understand cytokinesis by reasoning from descriptive information were usually unsuccessful because of the nature and scale of the process.