Later in 1905, Kraus and Pribram found that the bacteria, which produced soluble hemolysin, were more related to non-cholera vibrios; therefore, referred to all hemolytic vibrios as El Tor vibrios. In the early 1930s, A. Shousha, A. Gardner and K. Venkatraman, all researchers, suggested that only hemolytic vibrios agglutinated with anti-cholera serum should be referred to as El Tor vibrios. In 1959, R. Pollitzer designated El Tor as its own species V. eltor separate from V. cholera, but six years later, in 1965, R. Hugh discovered that V. cholerae and V. eltor were similar in 30 positive and 20 negative characteristics.