A notion of experimental series is developed, in which experiments or experimental sets are connected through experimental suggestions arising from previous experimental outcomes. To that end, the justification of Howard Temin’s DNA provirus hypothesis is examined. The hypothesis originated with evidence from two exploratory experimental sets on an oncogenic virus and was substantiated by including evidence from three additional experimental sets. Collectively these sets comprise an experimental series and the accumulative evidence from the series was adequate to justify the hypothesis by persuading the virology community of its veracity. The notion of crucial experiment is also discussed in terms of experimental series.