Age specific cell sorting within aggregates of chick neural retina cells.

Chick retinal cells of different stages of development, and of different areas of the retina, were stained with two vital fluorescent stains, reaggregated, and analysed for sorting-out. Sorting-out of cells within aggregates occurred if one cell sample was derived from the retinae before and the other after day 7 of incubation. No such cell-sorting effects were found in experiments performed on cells of different areas at the same stage. It is suggested that the sorting-out reflects either a change in cell population around day 7 (such as an increase in postmitotic neuronal cells), or the effect of a stage specific signal which changes the surface properties of a substantial part of most or all cell types.