TUXEDO NOUVEAU: At Stella McCartney, the tux looked more like a roomy suit; at Lanvin, a single white-satin lapel appeared on a black formal vest. Simons, meanwhile, showed tuxedo-bar hybrids at Dior, some with subtle skirt pleats. The Givenchy version, with curved short sleeves, was most original of all.Benoit Tessier/Reuters