A and B. In 3A, from top to bottom in this ventral view of larval medaka during first wk after hatching, are the 3 major veins associated with yolk sac and abdominal viscera: left duct of Cuvier, median yolk vein (deep to oil droplet) and right duct of Cuvier. Note that the liver (asterisk) remains in the left lateral portion of the abdominal cavity. In 3B, a ventral view of 2 wk old hatchling, note absence of major veins at the abdominal surface. Liver has now assumed a transverse position extending across the full extent of the rostral portion of abdomen. Heart now occupies concavity associated with rostral liver surface. Bar = 0.1 mm.