The error due to assuming constant curvature is estimated. (a) The relative error, , of each nucleus defining the yolk-cells interface and the cells-medium interface is calculated (inset). This relative error is evaluated in dependence of latitude, ϕ, by averaging over the values in bins of size . The plot shows data of all performed contact-angle measurements of embryos for the yolk-cells (red circles) and cells-medium (blue diamonds) interfaces. (b) To check a possible time dependence of the relative error, it is plotted here for an individual embryo with color-coding depending on time and latitude. This is done for yolk-cells (top) and cells-medium (bottom) interfaces. The same embryo is used as in Fig. 1. Black indicates areas for which no data were available. To see this figure in color, go online.