 A fundamental requirement for evolutionary change via natural selection is the existence of variation in the population. However, for variations to have evolutionary effect they need to be (at least partly) hereditary or heritable (see entry on  heritability;  I will here focus on hereditary variations and hereditary transmissibility as defined above, and will not discuss the notion of heritability which is a population term). It is hereditary variations that fuel evolution through natural selection (Lewontin 1970, 1985). Thus, if we aim to give a general account of possible evolutionary change we may start by examining and classifying hereditary variations (Jablonka &amp; Lamb 2005). Hereditary variation, in turn, may be accounted for in terms of inheritance mechanisms, hence by accounts of inheritance systems. As a starting point we can understand the notion of inheritance system as referring to mechanisms, processes, and participating factors, that are involved in transmission between parents and offspring leading to hereditary relations. Several influential accounts of inheritance systems that are of philosophical interest are discussed in  section 3.