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A major question in developmental biology is how precursor cells give rise to diverse sets of differentiated cell types. In most systems, it remains unclear whether the precursors can form many or all cell types (multipotent or totipotent), or only a single cell type (predetermined). The question of cell lineage is central to the neural crest because it gives rise to numerous and diverse derivatives including peripheral neurons, glial and Schwann cells, pigment cells, and cartilage. Although the sets of derivatives arising from different populations of neural crest cells have been well-documented^1,2, relatively little is known about the developmental potentials of individual neural crest cells. We have iontophoretically microinjected the vital dye, lysinated rhodamine dextran (LRD)³ into individual dorsal neural tube cells to mark unambiguously their descendants. Many of the resulting labelled clones consisted of multiple cell …