They may have been expressed in ciliary cells of larval eyes, which were subsequently resorbed into the brain on metamorphosis to the adult form. C-opsins are also found in some derived bilaterian-invertebrate eyes, such as the pallial eyes of the bivalve molluscs; however, the lateral eyes (which were presumably the ancestral type for this group, if eyes evolved once there) always use r-opsins. Cnidaria, which are an outgroup to the taxa mentioned above, express c-opsins—but r-opsins are yet to be found in this group. Incidentally, the melanin produced in the cnidaria is produced in the same fashion as that in vertebrates, suggesting the common descent of this pigment. Additional images
See also
Adaptation (eye) (night vision)
Emission theory (vision)
Eye color
Eye development
Eye disease
Eye injury
Eye movement
Eyelid
Nictitating membrane
Ophthalmology
Orbit (anatomy)
Simple eye in invertebrates
Tapetum lucidum
Tears

Notes
References
Citations
Bibliography
Ali, Mohamed Ather; Klyne, M.A. (1985). Vision in Vertebrates. New York: Plenum Press. ISBN 978-0-306-42065-8. Further reading
Yong, Ed (14 January 2016). "Inside the Eye: Natures Most Exquisite Creation". National Geographic. External links

Evolution of the eye
Anatomy of the eye – flash animated interactive. (Adobe Flash)
Webvision. The organisation of the retina and visual system. An in-depth treatment of retinal function, open to all but geared most towards graduate students. Eye strips images of all but bare essentials before sending visual information to the brain, UC Berkeley research shows
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