Fig. 3. Multifocal optical systems were found in all studied groups of terrestrial vertebrates, ranging from amphibians (A,B) to primates (C-F). Ring-like structures are visible in the photorefractive images (A,C,E). Because of larger eye size, the rings are more prominent in the primates (C,E) than in the toad (A). All three species have slit pupils; horizontal in the toad (B) and vertical in the primates (D,F). Scale bars are 5 mm. Species: Bufo marinus (A,B), Nycticebus coucang (C,D), Galago senegalensis (E,F).