Fig. 3. Confocal sections of a blastocyst that shows correspondence of the clonal border of the two-cell stage progeny with a plane separating the embryonic and abembryonic parts. Blastomeres were labelled at the two-cell stage with dyes of different colours. The boundary zone is marked with broken red lines and the border of the blastocoel was traced on a central section and is shown projected onto each of the other sections as a broken white line. (A-I) Individual optical sections at 7.5 µm intervals in the ‘z-dimension’. (J,K) The dissociated cells of this blastocyst observed by fluorescence or DIC optics, respectively.