Fig. 1. Schematic representation of the notochord lineage. Primary notochord precursors are indicated in dark pink and secondary notochord precursors in light pink. (A) Eight-cell stage embryo. Lateral view. Anterior is towards the left, animal is upwards. (B) 24-cell stage. (C) 44-cell stage. (D) 110-cell stage. Vegetal view, anterior is upwards in B-D. (E) Mid-tailbud. The 32 anterior cells constitute the primary notochord, while the eight posterior cells form the secondary notochord. (F) Lineage tree of the primary notochord starting from the eight-cell stage. (G) Lineage tree of the secondary notochord. Red rectangles correspond to blastomeres that develop into notochord after isolation.