1.   A perplexing feature of the hybrid embryo is that it starts off mostly bovine and then becomes mostly yet not entirely human.

2.   Lonza said that recently, Dr. Neil First of the University of Wisconsin formed hybrid embryos using denucleated cow eggs and nuclei from mice, monkeys and other animals.

3.   The human nuclei are thought to take over the cow egg, so that the hybrid embryo quickly becomes human during the few days it lives.

4.   The researchers report that some of the embryo mixtures formed a sort of hybrid embryo, or chimera, that developed enough for stem cells to be present.

5.   The spokesman said the law also bans mixing human and animal cells to create hybrid embryos and forbids implanting hybrid embryos into human or animal mothers.