Fig. 15. (A) Iridophore of the mantle ‘red’ stripe (see Fig.5B) showing three observers (X, Y and Z), each viewing reflections of light from the iridophore. The line styles of this figure and the symbols given in the text are the same as shown in Fig.14. The thickness of each line roughly indicates intensity, i.e. the thicker the line, the greater the intensity. While the reflections seen by observer X are unpolarised, those seen by observers Y and Z are maximally polarised. m, mantle. (B) The reflective patterns seen looking along the length of the mantle ‘red’ stripe. The shading of the ‘red’ stripe indicates intensity of reflection, i.e. the lighter the shading, the higher the intensity. Dotted lines indicate the position of the eye of the observer opposite the midpoint of the ‘red’ stripe. Observer X: within an angle of view of less than ±30°, the intensities of the reflections will equal the background light. For a larger angle of view, the reflections (shown in white) become brighter than the background and polarised. Observer Y: the reflections seen within an angle of view of approximately ±30° will be polarised and approximately four times brighter than the background. Observer Z: the brightness of the reflections will equal the background light over the entire visual field.