GFP-expressing Mes1 cells in 10-day-old chimeras. (A) Number of GFP-expressing Mes1 cells per chimera. (B) Number of distribution sites of GFP-expressing Mes1 cells per chimera. (C) Sites of GFP-expressing Mes1 cells in chimeras. “Head” includes the brain, gill operculum, jaws, otic vesicle; “trunk” includes the tail, spinal cord, notocord, and somites; “eye” means the retina and lens; and “heart” includes the atrium, ventricle, ventral body wall, aorta, and conus arteriosus.