Cell division patterns in early embryos of the ovoviviparous onychophoran Euperipatoides rowelli (Peripatopsidae). Double-labelling with the DNA-selective dye Hoechst (Bisbenzimide, blue) and anti-phospho-histone H3 antibody (α-PH3, red). (A) Mitotic cells from an early segmenting embryo. The nuclei of Hoechst stained cells show diffuse chromatin whereas chromosomes (ch) are seen in Hoechst/α-PH3 double-labelled cells. (B) Blastula stage embryo with mitotic cells scattered throughout the blastoderm (bd). (C) Early gastrula stage embryo with dividing cells in the extra-embryonic ectoderm (ee) and in the germ disc (arrowhead). (D) Early germ band embryo with cell divisions scattered throughout the germ disc. Paired germ band (dotted line) extends anteriorly on each side of the slit-like blastopore (bp). Abbreviations: bd, blastoderm; bp, blastopore; ch, chromosomes; ee, extra-embryonic ectoderm. Scale bars: A, 10 μm; B and C, 200 μm; D, 100 μm.