Fig. 10. Squid mantle in dorso-ventral section (d and v represent dorsal and ventral regions) showing the directions in which light is reflected from the iridophores of the ventral side. Dashed double-dotted line, normal incidence to iridophore; solid line, incident and reflected light; dashed dotted line, 15° incidence; dotted line, 45° incidence; dashed line, 55° incidence.