Stocks retreated sharply and Treasury bond prices jumped Monday as investors reacted to a stunning reshaping of the landscape of Wall Street that took out two storied names: Lehman Brothers Holdings Inc. and Merrill Lynch & Co.

The Dow Jones industrial average fell more than 180 points, well off the drop of nearly 350 points seen in the early going.

Stocks posted big losses in markets across much of the globe as investors absorbed bankruptcy plans at Lehman and Merrill Lynch's forced sale to Bank of America for $50 billion in stock. And perhaps most ominously, American International Group Inc. is asking the Federal Reserve for emergency funding. The world's largest insurance company plans to announce a major restructuring Monday.

The swift developments are the biggest yet in the 14-month-old credit crises that stems from now toxic subprime mortgage debt.

Investors are worried that trouble at AIG and the bankruptcy filing by Lehman, felled by $60 billion in bad debt and a dearth of investor confidence, will touch off another series of troubles for banks and financial institutions that may be forced to further write down the value of their own debt assets. Wall Street had been hopeful six months ago that the collapse of Bear Stearns would mark the darkest day of the credit crisis.

But AIG's troubles a week after its stock dropped 45 percent are worrisome for some investors because of the company's enormous balance sheet and the risks that troubles with that companies finances could spill over to the companies with which it does business. AIG, one of the 30 stocks that make up the Dow industrials, fell $5.37, or 44 percent, to $6.76 Monday as investors worried that it would be the subject of downgrades from credit ratings agencies.

Jeffrey Mortimer, chief investment officer at Charles Schwab Investment Management in San Francisco, said stocks' losses aren't steeper because the market expected Lehman would find a buyer or declare bankruptcy.