Incorporation of 5-bromo-2'-deoxyuridine (BrdU) and subsequent immunohistochemical detection at the posterior end in embryos of the onychophoran Euperipatoides rowelli (Peripatopsidae). Triple-labelling with the DNA-selective dye Hoechst (Bisbenzimide, blue), and anti-BrdU (green) and anti-phospho-histone H3 antibodies (α-PH3, red) after 3 hours incubation in BrdU. Confocal micrographs. Arrows point to areas of intense anti-BrdU immunolabelling corresponding to the developing ventral organs. Note that neither anti-BrdU nor α-PH3 immunolabelling reveals an increased number of cell divisions at the posterior end. (A) Posterior end of an early stage 3 embryo. (B) Posterior end of a late stage 3 embryo. (C) Posterior end of a stage 4 embryo. Leg-bearing segments numbered. Abbreviations: as, anus; ve, ventral extra-embryonic ectoderm. Scale bars: A-C, 200 μm.