English: Frontal histological sections of Zoea IV (Holländer stain). a - overview of the anterior part of the head with stalked compound eyes and eyestalk neuropils (EyNP), see Fig. ​Fig.2c2c for section plane; b - higher magnification of the right compound eye showing the visual neuropils lamina (La), medulla (Me), and lobula (Lo), proximally adjoined by the complex of the hemiellipsoid body neuropil and the medulla terminalis (HN/TM); b` - visual chiasm (arrow head) between medulla and lamina; c – the compound eye consists of many single ommatidia (one ommatidium surrounded by a line), note that the cornea is detached because of poor fixation (↔ double arrow); c`- cross sections of ommatidia show that the crystalline cones are composed of four cone cells. Each cell of one crystalline cone is indicated by an arrowhead; d - the ommatidia extend bundles of neurites (Neu) into the lamina; e – a branch of the ophthalmic artery (OA) extends towards the eyestalk neuropils; e`- the two main branches of the ophthalmic artery (OA) course towards the eyestalks; f – the protocerebral tract (PCT) connects the eyestalk neuropils and protocerebrum (PC) of median brain. Abbreviations: A1 - first antenna, Cap - capillary, CL - corneal lens, Co - cornea of compound eye, Cry - crystalline cone, Cu - cuticle, DP - distal pigment, Ey - compound eye, EyNP - eyestalk neuropils, HN/TM - complex of hemiellipsoid body neuropil and medulla terminalis, La - lamina, Lo - lobula, Me - medulla, Neu - neurites, OA - ophthalmic artery, Om - ommatidium of compound eye, PC - protocerebrum, PCT - protocerebral tract, Pi - shielding pigment, Rh - rhabdomeres of photoreceptor cell, Ros - rostrum, RS - rostral spine. Spitnzer et al., 2018 (https://dx.doi.org/10.1186/s12983-018-0271-z)