Fig. 11. (A-D) The epidermis overgrows the ventral nerve cord after formation of the neuropil. Flat preparations (A,B) and transverse semi-thin sections of the ventral nerve cords at stage 6. (A) Apical optical section of the ventral nerve cord of an embryo stained with phalloidin-rhodamine. The ventral neuromeres sink into the embryo (asterisk) and the epidermis overgrows the nerve cord (arrow). (B) Basal optical section of the same region shown in A. A ladder-like neuropil has been formed by the invaginated cells (arrow). (C) Transverse section of the hemineuromere of leg segment 1 at early stage 6. At this stage a medial thickening forms (arrowhead). The asterisk indicates the midline. (D) At late stage 6 an additional thickening has formed at the lateral border of the hemineuromere and the central part sinks into the embryo. The asterisk indicates the midline. l1 to l3, leg segments 1 to 3. Scale bars: 10 µm.