LONDON.- The first exhibition to explore art and theatre in eighteenth-century England through portraits of women opens at the National Portrait Gallery. With 53 portraits, some brought together for the first time and others not previously seen in public, the exhibition shows the remarkable popularity of actress-portraits and provides a vivid spectacle of eighteenth-century femininity, fashion and theatricality. The First Actresses: Nell Gwyn to Sarah Siddons shows large paintings of actresses in their celebrated stage roles, intimate and sensual off-stage portraits and mass-produced caricatures and prints, and explores how they contributed to the growing reputation and professional status of leading female performers. The exhibition combines much-loved works by artists such as Joshua Reynolds, Thomas Gainsborough, John Hoppner, Thomas Lawrence, Johan