A man was arrested Sunday in the stabbing of another man on an MBTA bus in Roslindale, officials said. The stabbing occurred on the 34 bus at the intersection of Washington and Beech streets at 12:35 p.m. Sunday. Gasner Jean, 49, was detained by people on the bus until police arrived and arrested him, said MBTA spokesman Joe Pesaturo. No other details about the attack were released. The 24-year-old victim was taken to Brigham and Women’s Hospital and is expected to survive, Pesaturo said. Jean is scheduled to be arraigned Monday in West Roxbury District Court.