Fig. 8. Comparison of recruitment of neural precursors in fly and spider. (Top) In Drosophila, Delta/Notch signalling specifies differences in a single cell within a field of initially equivalent cells leading to the recruitment of one neural precursor (neuroblast) from a proneural cluster. (Bottom) In the spider, groups of cells that are located within a field of initially equivalent cells adopt the neural fate simultaneously. Dark blue, cells that have the competence to adopt the neural fate; light blue, cells that have not adopted the neural fate.