eyespots
...that the eyespots of green algae and euglenids are the simplest and most common "eyes" found in nature?
...that the <b id="mwBac"><a href="./Eyespot_apparatus" id="mwBag" rel="mw:WikiLink" title="Eyespot apparatus">eyespots</a></b> of <a class="mw-redirect" href="./Green_alga" id="mwBak" rel="mw:WikiLink" title="Green alga">green algae</a> and <a href="./Euglenid" id="mwBao" rel="mw:WikiLink" title="Euglenid">euglenids</a> are the simplest and most common "eyes" found in nature?