Authors: Stan Wagon email: wagon@macalester.edu Address: Macalester College, St. Paul, MN 55105 USA Peter Webb email: webb@math.umn.edu Address: School of Mathematics, University of Minnesota, Minneapolis MN 55455 USA Title: Venn Symmetry and Prime Numbers: A Seductive Proof Revisited Abstract: We discuss the proof of the theorem of Henderson which states that symmetric n-Venn diagrams only exist when n is prime, pointing out what appears to be the omission in the literature of part of the argument, and providing a proof of the missing step.