The entanglement of individuation and explanation in the discovery of xenogastrulation.

This paper analyzes an episode of scientific work that was prompted by observations of a novel defect in early embryonic development, which was unexpectedly induced in an experimental context and has tentatively been dubbed "xenogastrulation." The researchers worked to individuate this as a novel phenomenon-both by distinguishing it from what it is not (e.g., exogastrulation) and by forming a positive conception of what it is-in order to facilitate further inquiry. Our analysis provides new insights into the role of explanatory reasoning in nascent experimental research programs. We argue that the researchers' efforts to individuate the novel phenomenon were entangled with their efforts to explain it. By this, we mean that tentative answers to the individuative question, "what is it?" also served as tentative answers to the explanatory question, "by what means does it occur?" This case study therefore demonstrates that explanation need not wait until an explanandum has been clearly individuated but instead can be deeply entangled with the process of individuating the explanandum in the first place.