On Friday, Watson's publicist said he had pulled out of his British book tour and gone home.
The comments had prompted three organisations, including the Science Museum in London, to cancel his talks.
Watson was also suspended from administrative duties at the Cold Spring Harbor Laboratory in New York.
The laboratory released a statement saying its "Board of Trustees decided to suspend the administrative responsibilities of Chancellor James Watson pending further deliberation by the board".
Bruce Stillman, the laboratory's president, said that the comments were Watson's "own personal statements and in no way reflect the mission, goals, or principles of Cold Spring Harbor Laboratory's Board, administration or faculty".
Watson said he was sorry for the comments in an appearance at the Royal Society in London.
"I am mortified about what has happened," he told a group of scientists and journalists. "I can certainly understand why people, reading those words, have reacted in the ways they have.
"To all those who have drawn the inference from my words that Africa, as a continent, is somehow genetically inferior, I can only apologise unreservedly.
"That is not what I meant. More importantly from my point of view, there is no scientific basis for such a belief."