The anatomy of the compound eye ofPeriplaneta americana L.

The fine structure of the retina was studied using light and electron microscopy.The eye is of the typical fused-rhabdomere, eucone, apposition type, with no unusual features or specializations.Each ommatidium consists of a distal dioptric apparatus with cornea and four cells forming the crystalline cone. Proximal to this is a retina composed of eight retinula cells. Each ommatidium is surrounded distally by two primary pigment cells and proximally by several accessory pigment cells.All retinula cells are similar and contribute to the rhabdom.In the light-adapted state, retinula cell screening pigment particles congregate around the rhabdom, contrasting with the dark-adapted state where a palisade separates the screening pigment from the rhabdom.