The cross-eyed beakworm isn't really cross-eyed. In fact, it only has one eye. Its one eye, however, has developed a unique, elliptical, dual-pupiled eye, which also has semi-separated retinas. In order for it to look around, it has developed an eye where the retinas move instead of the eye. This has allowed them a small amount of depth perception, which in turn allowed them to form much larger schools.