Fig. 1. Cell lineages of the ascidian larval CNS. Cell lineages are indicated as follows: the a-line is coloured red (anterior sensory vesicle precursors) or pink (anterior epidermis and pharynx/neurohypothesis precursors); b-line is green and A-line yellow at the 8-cell stage and light yellow (medial cells) or tan (lateral cells) from the 32-cell stage. Bars connecting two blastomeres on the right side of the drawings indicate sister cell relationship. Small circles in the lateral-A-line precursors on the left side indicate that these blastomeres give rise to the motoneurons; the final position of the motoneurons in the visceral ganglion is also indicated on the drawing of the larvae. At the neural plate stage, only the neural plate is shown and the dark blue ovals represent the secondary muscle lineage.