A SOUTHERNER by birth, Walter Millis graduated from Yale in 1920, a time when there was a literary yeast in the New Haven bread, as has since become evident in the work of Stephen Benet. John Farrar, Thornton Wilder, Philip Barry, Phelps Putnam, and Charles R. Walker. Serving his apprenticeship in journalism, Mr. Millis followed the usual course of gravitation to New York; a reporter on the Baltimore News, he was later called to the New York Sun and thence to the editorial staff of the New York Herald-Tribune. Apart from his newsprint he has found time to write a novel. Sand Castle, a number of short stories, and The Martial Spirit.