Fig. 8
From: Exceptional Variation on a Common Theme: The Evolution of Crustacean Compound Eyes
A series of schematic diagrams to suggest the evolution of complex photoreceptor sets in stomatopod crustaceans (mantis shrimp). The receptor arrangement illustrated in ‘Step 1’ is typical of that found in many crustaceans, as well as in some ommatidia of mantis shrimps. The other arrangements are found only in the stomatopods. See the text for an explanation of the figure