Fig. 4

Expression of vax at late developmental stages in embryos of the onychophoran E. rowelli. Anterior is up in a–c and left in e; developing limbs are numbered. a Head of a stage V embryo in ventral view. Dashed lines demarcate the cerebral grooves. b Head of a stage VI embryo in dorsal view. Arrows point to uncharacterized regions of the developing brain, arrowheads indicate the putative olfactory lobes. Asterisks indicate the spot-like expression near the base of the antennae. c Head of a stage VI embryo in ventral view. Arrowheads point to the expression in the developing hypocerebral organs. d Cross section of the head of a stage VI embryo, dorsal is up. Arrowheads point to the expression in the developing hypocerebral organs. e Stage VI embryo in ventrolateral view, dorsal is up. Arrowheads point to the expression in the developing ventral nerve cords. Abbreviations: an, antennal tract; at, developing antenna; cl, cephalic lobe; cn, central brain neuropil; cx, brain cortex; de, dorsal extra-embryonic tissue; ho, developing hypocerebral organs; jw, developing jaw; mo, mouth opening; po, proctodeum; sp, developing slime papilla; ve, ventral extra-embryonic tissue. Scale bars: a–d:100 μm; e: 500 μm