Our group studied both types of phage, virulent and temperate, in continuous culture. We used a Coulter Counter to follow total numbers of bacteria and used plate counts for the types of bacteria. Phage were counted by preparing Petri dishes covered with sensitive bacteria and allowing them to grow after very dilute suspensions of phage had been spread over them. There were clear zones of lysed bacteria where ever a phage particle or an infected cell had started a localized infection