Editing Eye (section)

====Apposition eyes====
Apposition eyes are the most common form of eyes and are presumably the ancestral form of compound eyes. They are found in all [[arthropod]] groups, although they may have evolved more than once within this phylum. Some [[annelids]] and [[bivalves]] also have apposition eyes. They are also possessed by ''[[Limulus]]'', the horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point.<ref name=Land1992/> (Some caterpillars appear to have evolved compound eyes from simple eyes in the opposite fashion.)

Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the [[ommatidium]].