1.   A thinner ozone layer allows more ultraviolet light to reach the Earth, he points out, and ultraviolet light has damaged frog embryos in lab experiments.

2.   Jonathan Slack, professor of developmental biology at Bath University and a leading embryologist, said he could create headless frog embryos relatively easily by manipulating certain genes.

3.   Thomas King, whose early research in frog embryos foreshadowed the cloning of sheep and other mammals decades later, died last Wednesday at Johns Hopkins Hospital in Baltimore.

4.   Scientists create headless frog embryo.