Fig. 6. Developmental potential of vegetally marked four-cell blastomeres when surrounded in chimaeras by four-cell blastomeres from random positions. Three chimaeras recovered at E5.5 to observe the distribution of H2B-GFP marked cells in comparison to progeny of not expressing GFP. (A,B) Two sides of the embryo in which the e2+-derived progeny contributed mainly to epiblast and extra-embryonic ectoderm. The contribution of labelled cells appears to be stronger on one side of the embryo (A). (C) Chimaera of e2+ four-cell stage blastomere (visible bead) and four wild-type blastomeres of F1 (wild-type) strain. (D,E) Two sides of embryo in which e2+ blastomere contributed to epiblast, extra-embryonic ectoderm and some visceral endoderm. (F,G) Two sides of chimaera in which e2+ contributed predominantly to visceral endoderm. Scale bar: in A, 50 µm for A,B,D-G; in C, 30 µm for C.