WASHINGTON  The Obama administration released final rules governing stem cell research on Monday that will allow many older stem cell lines to be eligible for federally financed research.

The changes came in response to criticism from scientists that the rules that the administration proposed in April  requiring that donors of fertilized eggs sign extensive consent forms  would have made even some of the stem cell lines approved by the Bush administration ineligible for further money.

Dr. Raynard S. Kington, acting director of the National Institutes of Health, said in a news conference that his agency would insist that any scientists creating stem cell lines after Tuesday follow the new rules to the letter for their work to be eligible.

Scientists using stem cell lines created before Tuesday may seek review by a group of the Advisory Committee to the Director. If the lines were created under conditions that met the spirit but not the letter of the new rules, they will be approved, Dr. Kington said.