Hill & Knowlton and Gray & Co. will merge.

Under the definitive merger agreement, shareholders of Gray & Co. Public Communications International will get about $8.75 in stock of JWT Group Inc., parent of Hill & Knowlton, for each Gray share. Gray shareholders will vote in August on the merger, which will be accomplished on a pooling-of-interests basis. The proposed merger marks the return to Hill & Knowlton of Robert Gray, chairman and chief executive of Gray & Co., who resigned as vice chairman of Hill & Knowlton in 1981 to start his own firm.