Fig. 1. Cell lineage of endoderm in the ascidian. (A) Positions of the anterior (orange) and posterior (yellow) endoderm and their precursor blastomeres. Eight-cell embryo is lateral view. Anterior is towards the left, animal pole is upwards. Sixty-four-cell embryo is vegetal view. Anterior is upwards. (B) Lineage tree starting from B4.1 posterior-vegetal blastomeres of an eight-cell embryo. Endoderm lineage is yellow. Minor fates are indicated in parentheses.