Thaler M M, Cox M C, Villee C A
Science. 1969 May 16;164(3881):832-4. doi: 10.1126/science.164.3881.832.
Actinomycin D is excluded from unfertilized eggs and developing embryos of the sea urchin Arbacia punctulata until the blastula hatches. The rate of uptake of actinomycin D by embryos doubles as development progresses after hatching to the gastrula stage.