Fertilization of investment-free Xenopus eggs.

The vitelline envelope of unfertilized Xenopus egg can be removed manually after treating the dejellied eggs for 10 min with 20% (w/v) sucrose in F-1 saline. Fertilization occurred in 52% of the eggs denuded in this way when UV-solubilized jelly was added to the sperm-egg mixture; without the jelly the level of fertilization was only 6%. Fertilization did not occur synchronously in the denuded eggs; the average delay between insemination and fertilization was 19 +/- 18 min.