DescriptionBritannica 1911 Arthropoda - Crustacea and Hexapoda compound eye derivation.png	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.
Date	published 1911
Source	Encyclopædia Britannica (11th ed.), v. 2, 1911, p. 678
Author	Edwin Ray Lankester, modified from Watase, “On the Morphology of the Compound Eyes of Arthropods,” Studies from the Biol. Lab. of the Johns Hopkins University, vol. iv. pp. 287-334
Permission (Reusing this file)	Public domainPublic domainfalsefalse This image comes from the 13th edition of the Encyclopædia Britannica or earlier. The copyrights for that book have expired in the United States because the book was first published in the US with the publication occurring before January 1, 1929. As such, this image is in the public domain in the United States.

Caption:

Fig. 12. — 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. B represents an intermediate hypothetical form in which the cells beneath the lens are beginning to be superimposed as corneagen, vitrella and retinula, instead of standing side by side in horizontal series. The black represents the cuticular product of the epidermal cells of the ocular area, taking the form either of lens, cl, of crystalline body, cry, or of rhabdom, rhab; hy, hypodermis or epidermal cells; corn¹ , laterally-placed cells in the simpler stage, A, which like the nerve-end cells, vit¹ and ret¹, are corneagens or lens-producing; corn, specialized corneagen or lens-producing cells; vit¹, potential vitrella cells with cry¹, potential crystalline body now indistinguishable from retinula cells and rhabdomeres; vit, vitrella cell with cry, its contained cuticular product, the crystalline cone or body; ret¹, rhab¹, retinula cells and rhabdom of scorpion undifferentiated from adjacent cells, vit¹; ret, retinula cell; rhab, rhabdom; nf, optic nerve-fibres.