Cell division patterns in embryos of the placental viviparous onychophoran Epiperipatus isthmicola (Peripatidae). The full number of leg-bearing segments (30-32 in females and 27-29 in males) has not been established yet. Double-labelling with the DNA-selective dye Hoechst (Bisbenzimide, blue) and anti-phospho-histone H3 antibody (α-PH3, red). (A) Gastrula stage embryo. (B) Elongating germ band embryo with separate mouth and anus openings. (C) Elongating embryo with 10 leg-bearing segments. (D) Elongating "coiled stage" embryo with 20 leg-bearing segments. Arrowheads indicate concentric rings of proliferating cells in the antennal segment. (E) A "coiled stage" embryo with 26 leg-bearing segments. Abbreviations: an, antennal segment; as, anus; at, presumptive antenna; bp, blastopore; jw, jaw segment/presumptive jaw; mo, embryonic mouth; sp, slime papilla segment/presumptive slime papilla. Scale bars: A, 25 μm; B, 50 μm; C and D, 100 μm, E, 150 μm.