<p>We consider strategies of drawing comparisons between conceptually different approaches as practiced by scientists in mid-twentieth century molecular biology or biochemistry. The two accounts of spatial complementarity and sequential order used to explain biological processes at the molecular level, and in particular genetic mechanisms are non-commensurable: they share no significant conceptual common ground. This conceptual divide is dealt with by the relevant scientific community through three strategies: privileging one standard of comparison and thereby creating common ground, often achieved by using ambivalent language (semantic fuzziness); assigning the contrasting accounts to disjunctive fields (conceptual demarcation); and introducing intermediate steps that span the conceptual divide (local meshing). The epistemic benefit of drawing comparisons is to bring order to a field and to stimulate conceptual change by bridging the space between two extremes. We seek to attract attention to drawing comparisons at the conceptual level as an important and neglected part of research activity.</p>