You must read Inside the Eye: Nature’s Most Exquisite Creation — National Geographic Magazine this is so fascinating about EYEs.

DAN-ERIC NILSSON, LUND UNIVERSITY, SWEDEN via – National Geographic Magazine

This box jellyfish (Tripedalia cystophora) is only about half an inch across, yet it possesses 24 eyes, housed in four rhopalia. Four of the six eyes in each rhopalium (left) are simple photo sensors, but two have light-focusing lenses. A floating crystal weight called a statolith keeps the top lensed eye always pointing upward, scanning for mangrove canopies that signal food and shelter.

As Ed Young, the author poses “But what about the box jelly? It is among the simplest of animals, just a gelatinous, pulsating blob with four trailing bundles of stinging tentacles. It doesn’t even have a proper brain—merely a ring of neurons running around its bell. What information could it possibly need? Inside the Eye: Nature’s Most Exquisite Creation — National Geographic Magazine