These time-lapse cinematographic studies provide measurements and descriptions of the pathways and speeds of displacement of cell groups in the forming neural plate of a newt. At speeds ranging from 4 to 95 μ per hour, cell groups are displaced almost as much as 1 mm (896 μ) on a 2.5 mm embryo during plate development prior to neural tube formation. Changes in area of regions of the surface of the neural plate are presented and are found to correlate inversely with changes in height of the neural plate epithelium. Observations with high magnification time-lapse films establish that cells retain their contact relationships with neighboring cells throughout the period of study. The newt neural plate is a sheet of cells just one cell thick. Observed displacements of groups of neural plate cells are the consequence of deformations of the sheet. Observations and correlations indicate that these deformations are the result of regional differences in the amounts of change in cell shape of the constituent cells. Thus one consequence of primary embryonic induction is a patterned change in the height of the cells in the forming neural plate with concomitant displacements of cell groups and regional changes in area that give the neural plate its characteristic shape. © 1969.
