Cells and Organizers

This article evaluates historically some of the factors otherthan the new "cell biology" that have influenced embryologiststo think in terms of cells rather than supracellular agencies.Evidence of Spemann's emphasis on organizers as supracellularphenomena is presented, but it is pointed out that Spemann raisedsome cellular questions that were by-passed at the time. Vogtand others who studied morphogenetic movements in the 1920'salso considered these as supracellular processes, although Vogtpreviously (1913) had studied the movements of individual amphibianembryonic cells isolated in vitro. It is pointed out that the number of investigators who studiedisolated cells in vitro before the development of tissue culturewas considerable, including Remak (1855), Stricker (1864), andHis (1899), among others. Holtfreter observed the actions ofisolated cells from 1931 on, in part, at first, because thecells isolated themselves from cell groups in vitro. His studiesof explants, in the 1930's, 1940's, and 1950's, emphasized thatsupracellular phenomena must be explained in terms of cell properties,including membrane properties. In addition, the dramatic resultsof his experiments demonstrating affinity drew attention tocells as organized individuals, just as Spemann's experimentshad done earlier to demonstrate the integrative qualities ofembryos-as-wholes.