Fig. 4. Sea urchin embryo observed by confocal laser scanning microscopy in fluorescent (A,C,E) and in transmitted (B,D,F) light. (A) Fluorescent three-dimensional image of the untreated embryo (16-blastomere stage) stained with TUNEL. Bar, 30.6 µm. (B) The same embryo as in A observed in transmitted light. Bar, 28.2 µm. (C) Fluorescent three-dimensional image of the sea urchin embryo incubated at the 8-blastomere stage in 5 µg ml^-1 DD for 60 min and stained with TUNEL. Bar, 29.8 µm. (D) The same embryo as in C observed in transmitted light. Bar, 26.8 µm. (E) Fluorescent three-dimensional image of the sea urchin embryo incubated at the 8-blastomere stage in 5 µg ml^-1 DD for 120 min and stained with TUNEL. Bar, 30.6 µm. (F) The same embryo as in E observed in transmitted light. Bar, 28.9 µm.