Permeability to Water and Staining Rate of Developing and Resting Sea Urchin Eggs. ∗

Summary and Conclusions

Immature eggs of the sea urchin S. franciscanus, like fertilized eggs, stain more rapidly in solutions of Methylene Blue, Gentian Violet, and Methyl Violet than do resting unfertilized eggs. Like the fertilized eggs they are also more permeable to water. The immature and fertilized eggs are developing while the unfertilized egg is in a state of developmental inhibition. Increase in water permeability, as well as staining rate, at fertilization (when the egg is released from inhibition) is thus the converse (in direction) of the change when the immature egg enters the resting stage.