 Richard Burian (1985), like Kitcher, is concerned with the facts that theoretical terms can pick out natural kinds even when a theory turns out to be mistaken and that researchers who disagree in their theories can use a concept that refers to the same natural kind. Burian illustrates these points with the case of Bateson, who held theoretical views that are now seen as false (e.g., regarding the presence/absence hypothesis, see  §1.1),  but who is still taken to have referred successfully to genes on most occasions where he used the term or synonyms. Furthermore, Bateson was able to discuss the chromosome theory held by the Morgan group (see  §1.2),  despite rejecting it. This only makes sense if it is assumed that despite disagreement, both parties used the term “gene” to refer to the same natural kind. Burian aims at a hybrid account combining extensionalist views based on causal theories of reference and intensionalist views relying on the notion of theoretical descriptions. Theoretical differences among accounts put forward by various groups simultaneously or across time can thus be bridged by a gene concept exhibiting “referential openness” achieved by indefinite, rather schematic descriptions that are not committed to the material nature of genes but nonetheless characterize them through their causal effects and in that sense operationalize the concept. While such concepts facilitate continuity in scientific change, any given research project will operate with a specification of the description that provides criteria to individuate genes and that relies on a mix of functional and structural characterizations. How genes are identified depends among other things on how and on what level the phenotype is determined (e.g., as qualitative or quantitative, molecular or morphological). Such specific gene concepts then account for the discontinuities observed in the history of genetics (Burian 1985; [1995] 2005). In the light of the complex cellular processes in which DNA is involved, both Kitcher and Burian suggest that molecular biologists ultimately study the genetic material rather than genes, but importantly, they are still interested in functional units; a gene then becomes “anything a competent biologist chooses to call a gene” (Kitcher 1992: 131). Genomics or post-genomics can be understood as enhancing this shift (see  §1.5;  Dupré 2004; Stotz et al. 2006; entry on  genomics and postgenomics).