- Single Ommatidium of Cockroach's Eye (after Grenacher).
Each such unit is termed an "ommatidium."
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.
The ommatidium (soft structure beneath the lens-unit of a compound eye) is very simple in both Scorpio and Limulus.
The cells of tl ommatidium are a good deal larger than the neighbouring common cells of the epidermis.
23) each ommatidium has a peculiar ganglion cell developed in a central position, whilst the ommatidium of the lateral eyelets of Scorpio shows!
that the lateral eyes of Scorpio have a single cell-layered or " monostichous " ommatidium like that of Limulus.
Each such complex of cells underlying the lenticle of a compound eye is called an " ommatidium "; the entire mass of cells underlying a monomeniscous eye is an " ommataeum."
The ommataeum, as already stated, tends to segregate into retinulae which correspond potentially each to an ommatidium of the compound eye.
The ommatidium is from the first segregate and consists of few cells.
One single, complete eye, situated in a compound eye, is called an ommatidium.
The surface of a compound eye is seen to be covered with a large number of hexagonal corneal facets, each of which overlies an ommatidium or series of cell elements (fig.
- Diagram to show the derivation of the unit or "ommatidium " of the compound eye of Crustacea and Hexapoda, C, from a simple monomeniscous monostichous eye resembling the lateral eye of a scorpion, A, or the unit of the compound lateral eye of Limulus (see article Arachnida, figs.
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