Scientists in Wisconsin have mixed ear of pig and egg of cow and a series of other cross species combination into clone living embryos of pigs, rats, sheep and monkeys. The series of experiments, being described at a meeting in Boston, represents a new and surprising twist on the cloning technology that led to the birth of Dolly, the sheep. The work suggests that cow eggs, available by the thousands from slaughterhouses, contain all the ingredients and molecular machinery needed to grow embryos of any species to be cloned.