Fig. 2. How the total densities of EphA receptor in the EphA3⁺ cells (green) and the EphA3^- cells (black) vary along the nasotemporal axis of the retina, for the six experimental cases analysed.(A,B) Homozygous/heterozygous EphA3 knockin; (C,D) homozygous/heterozygous EphA3 knockin coupled with heterozygous EphA4 knockout; (E,F) homozygous/heterozygous EphA3 knockin coupled with homozygous EphA4 knockout. The two arrows at the side of each graph indicate the extent to which the range of variation in EphA density within the EphA3⁺ population overlaps with the range of variation within the EphA3^- population. The six curves are calculated from the empirical result (Reber et al., 2004) that total EphA receptor density in a RGC at a distance x along the nasotemporal axis is 0.26e^-2.3x + K ₀ for the EphA3 cells and 0.26e^-2.3x + K₀ + K _A3 for the EphA3 cells. The values of the constants K₀ and K_A3 in the six cases are: A, 1.05,1.86; B, 1.05,0.93; C, 0.54,1.77; D, 0.51,0.93; E, 0.0,1.80; F, 0.0,0.90.