Tucker Anthony & R. L. Day Inc., a large Boston investment and brokerage company operating primarily in New England, has agreed to acquire Julia M. Walsh & Sons Inc. of Washington for an undisclosed price.

The transaction, which is subject to regulatory approval and completion of legal agreements, is expected to be completed in August.

Although details of the transaction are yet to be worked out, Walsh & Sons, the first full-service investment firm to be headed by a woman, will continue to operate under present management but as a division of Tucker Anthony, said John Montgomery, vice president and research director at Walsh & Sons.

The Washington office likely will be renamed Walsh/Tucker Anthony, Montgomery added.

Walsh, who is chairman of the company she founded six years ago, will become a managing partner in Tucker Anthony, which is a wholly owned subsidiary of John Hancock Mutual Life Insurance Co.

"We're expecting that not a great deal will change in how we operate in the future," said Montgomery, one of three Walsh sons who helped found the Washington firm in 1977. The three sons--John and Michael Montgomery and Tom Walsh--will remain with the firm under its new parent company as vice presidents.

Before starting her own firm, Walsh was for more than 20 years a registered representative, general partner, senior vice president and vice chairman of Ferris & Co., a leading Washington-based securities firm.

Although smaller than most local brokerage firms with 30 employes and about 4,000 accounts, Walsh & Sons had carved out a fairly prominent niche in the investment community and recently had been courted by several larger companies.

The decision to go with Tucker Anthony "made a lot of sense to us" said John Montgomery, because, "as we go through deregulation, there will be a lot of new services and products. And we thought it would be advantageous to our clients to be able to offer a wider range of services.

"Philosophically, in terms of how an investment firm should be run, we're very close," Montgomery added. "They're very entrepreneurial," he said of Tucker Anthony.

Ward Carey, president and chief executive officer of Tucker Anthony, said he expects to expand Walsh's operation here but "not by a great degree." The goal, he added, is to maintain a "small, but high quality operation" in Washington.

Carey said Tucker Anthony decided to acquire Walsh & Sons because the local firm is "compatible with what we do" and because "it's the best way of getting into" Washington, where his company hoped to expand.

Tucker Anthony, which was founded in 1892, is a regional broker in the Middle Atlantic area. It employs more than 1,000 persons.