 The focus of discussions about replicators concerns just which organic entities actually meet the definition of replicator. Answering this question obviously turns on what one takes the definition of replicator to be. In this connection the revision of the original meaning of “replicator” turned out to be central. The revised meaning refined and restricted the meaning of “replicator,” which was defined as “an entity that passes on its structure directly in replication” (Hull 1980: 318). The terms replicator and interactor will be used in this latter sense in the rest of this entry.