Henry and Martindale (1987) stained individual blastomeres with 1% Nile blue sulfate in 1% agarose. They report having tried microinjection of horseradish peroxidase (HRP) with poor results. We (Eckberg and Palazzo, 1992) have vital-stained chromosomes by immersing eggs in 1 µg/ml Hoechst 33342 (Sigma Chemical). We have microinjected fluorescein-tagged aequorin (Eckberg and Miller, 1995), but have not attempted to follow the development of individual blastomeres so injected. The usefulness of any vital staining procedure in these eggs is limited by the opacity of the egg.