Fig. 3. Treatment of dissociated cells with bFGF and BMP4. Descendant cells of the isolated B4.1 blastomeres were dissociated at the 16- and 32-cell stages. Endoderm formation was detected by expression of ALP, and muscle formation was monitored by expression of myosin. (A,B) During dissociation, blastomeres were treated with bFGF protein in sea water. In A, ALP-negative partial embryos consist of very small cells that look like mesenchyme cells. (C,D) Blastomeres were treated with BMP4 protein.