Expression of onychophoran Hox genes (lateral/ventral views). (A-H) Lateral views. (I-J) Ventral views. In all cases anterior is to the left. Upper row: schematic drawing of Hox gene expression. Middle row: bright-field photography (A-J). Lower row: DAPI staining (A’-J’) of the same embryos as shown in exactly the same position as in the middle row (A-J). Darker shading in schematic drawings indicates stronger expression. Lighter shading indicates weaker expression. Note that the expression of Ek-Ubx mRNA forms a posterior to anterior gradient with unclear anterior expansion (marked with a question mark (?)). Arrows in I-J point to expression in the anal valves. Abbreviations: e, eye; j, jaw; L1-L15, first to fifteenth walking limb; saz, segment addition zone; sp, slime papilla.