Fig. 2. Clones derived from the 2-cell blastomeres of the parthenogenetic embryos do not respect an embryonic-abembryonic boundary in the blastocyst. Blastomeres of 2-cell embryos were labelled with different coloured dyes and the distribution of the progeny of labelled cells were analysed at the blastocyst stage. The frequencies of the four categories of blastocyst scored are indicated. Blastocysts of 4 different groups of embryos: parthenogenetic haploid eggs (A,B); parthenogenetic diploid eggs treated with cytochalasin (C,D); parthenogenetic diploid eggs in which the polar body was fused back to the embryo (E,F); and fertilised eggs (G,H) [data from Piotrowska et al. (Piotrowska et al., 2001)]. Blastocysts were scored ++ if 0, 1 or 2 cells crossed the boundary zone. In cases where 3 cells crossed the boundary, blastocysts were scored +. When 4-5 cells, or more than 5 cells failed to respect the boundary they were scored — and — —, respectively. In the table, the degree to which predominantly embryonic clones extend to the abembryonic part are shown in red. The degree to which abembryonic clones extend to the embryonic part are shown in blue. The micrographs represent individual optical sections mid-way through the embryo to show the cavity, which occupies the lower half of each blastocyst. The boundary zone is marked with white dashed lines and the border of the blastocoel has been traced on to a central section and is shown projected onto each of the other sections as a blue dashed line. The clonal border is marked with a yellow dashed line. The examples shown in the micrographs are all from haploid parthenogenetically activated eggs. Scale bar: 25 µm.