 Considering epigenetic control systems as providing a regulatory function allowed Nanney to suggest that they may be expected to (1) be less stable, (2) be more susceptible to extrinsic control than genetic systems, and (3) exhibit a limited number of “states”, since they are constrained by the information available in the genetic system at each particular time (Nanney 1958). These properties are indeed exhibited by the cellular epigenetic systems that have since been identified, which play a role in cellular (e.g., genomic) regulation. DNA methylation and histone modifications can lead to gene silencing, for example. The transgenerational hereditary properties of epigenetic markings may be subsequent to their regulatory function; however, in multicellular organisms, transgenerational heredity of epigenetic marks is constrained by their developmental role, since parental epigenetic markings may have to be reset in gametes so that they can fulfill their developmental function anew in offspring (Shea et al. 2011; see also Lachmann &amp; Libby 2016).