(A) Estimated order of signaling strength of the Admp, Efna.d, Fgf9/16/20 and Gdf1/3-r pathways in the animal hemisphere, from which ectodermal cells are derived, of a mid-to-late 32-cell embryo. This estimation is based on the data shown in S1 Table. (B) Sensing patterns for Admp, Efna.d, Fgf9/16/20 and Gdf1/3-r signaling that are not inconsistent with Otx expression in normal and experimental embryos (S2 Table). These sensing patterns are compatible with 16 or 8 Boolean functions shown in S2 Fig. (C) Otx expression in a control, a morphant for Admp and Fgf9/16/20, and a morphant for Fgf9/16/20 and Gdf1/3-r. Black arrowheads indicate the expression of Otx in the neural lineage (a6.5 and b6.5 blastomeres). White arrowheads indicate that the expression of Otx in the neural lineage was lost. Arrows indicate Otx expression in the vegetal hemisphere. (D) Boolean function to direct Otx expression.