Cell dispersion in the VE of the embryonic region specifically increases after E5.5. Examples, shown as a fluorescent projection of a confocal z series merged with a transmitted light section, of coherent (A-C) and dispersive (E-G) distributions of labelled cells at the early egg cylinder (EEC) stage (A, E), E5.5 (B, F) and E6.5 (C, G). For each stage, the number of conceptuses considered and the percentage of coherent and dispersive cases are indicated. (D) Schematic representation of the localisation of labelled cells in coherent distributions. The number of conceptuses considered at each stage is indicated (n) and the percentage of cases with labelled cells in the extra-embryonic region (grey), the embryonic region (blue) or spanning both (vertical bar) is shown. (H) Schematic representation of the characteristics of dispersive distributions of labelled cells in the extra-embryonic region (grey) or embryonic regions (blue). The number of conceptuses considered at each stage (n) is indicated. The average and the standard deviation of the number of clusters per conceptus are shown in black. The number of conceptuses considered with clusters in the extra-embryonic and embryonic regions respectively is 9 and 12 at the early egg cylinder stage, 20 and 21 at E5.5, 26 and 27 at E6.5. Some conceptuses have both extra-embryonic and embryonic clusters. The average and the standard deviation of the number of cells per clusters are shown in dark blue. The number of clusters considered in the extra-embryonic and embryonic regions respectively is 14 and 21 at the early egg cylinder stage, 40 and 53 at E5.5, 92 and 431 at E6.5. *,°,+,~ are significantly different (Mann-Whitney test, p < 0.05). nb, number; SD standard deviation. Scale bars 20 μm.