Fig. 3. Embryos injected at the two-cell stage showed random distribution of labeled cells. Embryos showed spotted distribution of X-gal-positive cells, and this pattern was seen evenly throughout the body axis (A,B) without regard to any embryonic axes. C and D are higher magnifications of B. In all cell layers, X-gal-positive and -negative cells were randomly intermingled. (E) Quantitative analysis. Classification of cell layers, and the result from one embryo, 2-8, are shown. Left panels indicate the origin of the each layer at 3.5 days and 4.5 days based on classic studies, and the name and abbreviation of the each tissue is also shown. The actual numbers of positive and negative cells are given and also represented by the histograms. F,G,H and I,J,K show the results of embryos 2-2 and 2-34, respectively. In the amnion of embryo 2-2, all the cells were positive for X-gal, however, this was an exceptional case because positive cells were intermingled with negative cells in other embryos. Scale bars: 300 µm (A) 150 µm (B), 30 µm (C).