Specificity of cell adhesion: differences between normal and hybrid sea urchin cells.

The adhesive specificity of embryonic sea urchin cells from two species, and the two hybrid crosses between these species was examined by a cell-aggregate collection assay. Cells of normal Lytechinus or Tripneustes embryos were found to adhere to homospecific cell aggregates at a much higher rate than they would adhere to heterospecific aggregates. Hybrid cells adhered to collecting aggregates at an intermediate rate. The observed pattern of hybrid cell adhesion suggested that paternal gene products are capable of modifying cell surface adhesive sites as early as the mesenchyme blastula stage.