Figure 2
Ommatidial structures and their interpretations. (a) Overview of another sensory unit, fossilised in a different way (red arrow); another, slightly weathered adjacent (pink arrow). Insert: Position of the relics of receptor cells marked. (b) (a) in detail. Note the rhabdom embraced by spherical elements, interpreted as putative ‘palisades’63,64,65. (c–h) More examples of receptor-cell-rosettes with rhabdoms (red arrows) surrounded by palisades, f repeats the spherical elements very clearly. (i) Schematic drawing of (Fig. 1k), the putative thin crystalline cone in blue. (j) Translucent head of Artemia salina (Linnaeus, 1758), showing up the screening pigments inside of the compound eye. (k) Overview of the counterpart of the eye, red arrow indicates the position of the individual visual unit of Figs. 1k, 2i. (l,m) Illustration of how the isolated visual unit may have come up to its position, being stripped of the layer of lenses seen at their proximate surface below. (n) Modern compound eye of a hornet (Vespa crabro Linnaeus, 1758) and schematic drawing of an apposition compound eye, ommatidium and its cross-section. c cavity, formerly containing the receptor unit, cc crystalline cone, p palisade, pc pigment cells, rc receptor cell, rh rhabdom, ru receptor unit, L lens; o–q, s from the right eye.
