Fig. 9. Results of analyses comparing frog spectral reflectances as discriminated by only the achromatic channel of frog or bird visual systems. Data plotted here represent results for the `Green' illuminant, but overall results were similar for all illuminants; see also Table 4. (A) Frog spectral pairs, as seen by frog vision. (B) Frog spectra compared to background spectra, as seen by frog vision. (C) Frog spectral pairs, as seen by bird vision. (D) Frog spectra compared to background spectra, as seen by bird vision.