ommatidium

In an insect, each ommatidium in the compound eye has a corneal lens, a crystalline cone and a light-sensitive organ at its base.

The ommataeum, as already stated, tends to segregate into retinulae which correspond potentially each to an ommatidium of the compound eye.

The lateral eyes of Scorpio consist of groups of separate small lenses each with its ommatidium, but they do not form a continuous compound eye as in Limulus.

Each ommatidium is an elongated cone with its broad extremity abutting against the corneal lenticle.

The ommatidium is from the first segregate and consists of few cells.