Fig. 8. Scoring mitotic figures in unfused and fused chorionic ectoplacental junctions for data in Table 5. Brightfield photomicrographs of a late-headfold stage exposed to colcemid for 2 hours and prepared for histochemistry (see Materials and Methods). Arrows in B-D indicate examples of mitotic figures in metaphase. (A) The chorionic area scored for mitotic figures is indicated between the ‘brackets’. The three arrows point to the region of ChE shown in B-D. (B) ChE median of A showing the fused chorionic area beneath the broken lines and bordered on the left by a unbroken black line. (C) Unfused ChE perimeter to the left of the unbroken black line of B, the extent of which is enclosed by a ‘bracket’. (D) Unfused ChE perimeter to the right of the fused ChE median, the extent of which is also enclosed by a ‘bracket’. Abbreviations: ac, amniotic cavity; am, amnion; EPCav, ectoplacental cavity; EPC, ectoplacental cone; x, exocoelomic cavity; ys, yolk sac. Scale bar: 100 µm for A; 25 µm for B-D.