11.   The embryos developed into mass of about one hundred cells, including an inner core of embryonic stem cells, which were scooped out.

12.   The goal is to pinpoint the genes that govern how an embryo develops into a fetus and perhaps how to prevent or treat birth defects.

13.   The resulting embryos develop right in the pouch, protected by a collection of bent spines that keeps predators from reaching them.

14.   The sperm would fertilize the egg while the cytoplasm, they hoped, would allow the embryo to develop.

15.   Mifepristone blocks the action of progesterone, which allows an embryo to develop.

16.   Mountford said his company would not consider allowing an embryo to develop into a cloned person.

17.   The scientists were able to manipulate the depth at which the embryos developed, and thus their exposure to ultraviolet radiation.