Developing embryos from early blastula to gastrula stages. (A, B) Animal pole view of early blastula stages. Two different live embryos from same clutch. (C, D) Two magnifications of same embryo cut in half at the beginning of gastrulation, showing bottle cells. White arrows point to apical end of bottle cells. (C) Lower magnification view that shows large yolky cells near the center of the embryo. (D) High magnification view of the dorsal lip region showing bottle cells. Black arrowhead points to basal edge of one bottle cell. (E, F) Two views of a live embryo at a mid-gastrula stage. (E) Animal pole view showing the blastocoel roof; (F) vegetal pole view of the blastopore. The dorsal side of the blastopore is towards the top (white arrowhead). (G, H) Animal pole view of cells migrating along the blastocoel roof of a live embryo. Arrow points to front of migrating cells. The cells are migrating to the right. (G) low magnification; (H) high magnification. (I, J) Vegetal pole view of the blastopore of a late gastrula stage embryo. Dorsal region is towards the top. (I) low magnification; (J) high magnification. Scale bars = 1.0 mm.