All vertebrate animals have two eyes, but this was not always the case. Our primitive, fish-like predecessors evolved with a third eye that was directly connected to the brain and was called the pineal eye. Over time this developed into a small organ in the brain that controls hormones, known as the pineal gland. Arachnids have eight eyes to match their eight legs, but other types of insect vary. The praying mantis, for example, has five eyes. On the seabed, things get even more interesting. Starfish have an eye at the end of each arm while scallops can have over 100 eyes, allowing them to easily spot predators from their perch on the ocean floor.