 Griesemer’s classification of reproducers is an abstraction hierarchy. It provides a formal taxonomy of reproducers, arranging them in a series of nested classes. The classification of inheritance systems suggested by Jablonka and Lamb (Jablonka 2001; Jablonka &amp; Lamb 2005/2014) discussed in the next section, in contrast, enumerates types of concrete inheritance systems found in the living world.