part of develops from start stage end stage Kupffer's vesicle TAO:0000001 Small but distinctive epithelial sac containing fluid, located midventrally posterior to the yolk cell or its extension, and transiently present during most of the segmentation period. Kupffer's vesicle has been compared to the mouse embryonic node. ciliated organ of asymmetry ZFA:0000001 zebrafish_anatomy forerunner cell group tail bud embryonic structure segmentation:1-4 somites pharyngula:prim-5