''Forgive me, if nearing life's end, I see a drama with a tinge, modest, all but ignorable, of the Shakespearean...'' writes Hortense Calisher with characteristically swooping sentence structure as she muses on the discovery that her Southern Jewish forebears may have owned slaves. (The tattoo she summons is a bugle call.) Of course the eminent 92-year-old author is forgiven she's entitled to backward run her sentences after a long, brilliant career of Jamesian literary construction and Whartonian interest in societal strictures. But the wandering, garlanded narrative style makes this memoir (alternately set in Virginia and New York City) an exceedingly drifty amalgam of rummage and reminiscence. ''About family history one always wants to know more,'' she avers. On the particular family in Tattoo For A Slave, it depends.