JPMorgan Chase & Company and Morgan Stanley, forced to split by lawmakers more than 70 years ago, may reunite, one of Wall Street’s top-rated bank analysts said.

“We are raising the possibility of a merger between JPMorgan and Morgan Stanley,” Prudential Equity Group’s Michael Mayo wrote in a note to clients yesterday. He cited “our view that both managements are willing to pursue acquisitions, expectations that both stand-alone will lag peer performance, and the need for merger-related synergies to achieve longer-term goals.”

A merger of JPMorgan, the no. 3 American bank, and Morgan Stanley, the world’s no. 1 securities firm, would bring together companies with a combined market value of more than $175 billion. The so-called House of Morgan dominated American finance in the early 20th century, bailing out the U.S. Treasury, creating the nation’s steel monopoly, and advising chief executive officers and presidents alike.

Congress, in passing the Glass-Steagall Act of 1933 and related legislation, banned J.P. Morgan & Company from selling securities. Several of its partners left to form a separate investment bank, called Morgan Stanley. J.P. Morgan was acquired by Chase Manhattan Corporation in 2000.

Glass-Steagall was repealed in 1999. JPMorgan has since competed with Morgan Stanley to provide investment banking services such as stock underwriting and merger advice. Both companies are based in New York.

“As a matter of policy, we don’t comment on market rumor or speculation,” a Morgan Stanley spokesman, James Badenhausen, said. A JPMorgan spokesman, Joseph Evangelisti, declined to comment. Mr. Mayo also declined.

Mr. Mayo, whom investors ranked third among bank analysts in last year’s survey by Institutional Investor magazine, said the modern-day JPMorgan may pursue acquisitions to counter ebbing profit at its investment-banking and credit card arms. Meantime, Morgan Stanley wants to expand its services and increase assets to compete more effectively with larger companies, he wrote.

The president of JPMorgan, Jamie Dimon, 49, who joined though the 2004 purchase of Bank One and is slated to become CEO next year, said in July that the company would be prepared to make a big acquisition in early 2006. Morgan Stanley’s John Mack, 60, a former president of the firm who rejoined as chief executive in June, may have expressed an interest in merging with J.P. Morgan before the bank’s sale to Chase, Mr. Mayo wrote.

JPMorgan’s current CEO, William Harrison, said in May that it wouldn’t pursue mergers with securities firms such as Morgan Stanley and Bear Stearns because of the challenges of combining such large businesses.

“It wouldn’t work for us,” Mr. Harrison, 62, told Harvard Business School students in an interview on the Charlie Rose show. “We’re pretty far down the road in our global product client set.”

Mr. Mayo also noted the risks in yesterday’s client note, saying they would “include potential culture clashes and loss of intellectual capital.”