In the received version of the development of science, natural kinds are established in the preliminary stages and made more precise by measurement. By examining the move from nineteenth- to twentieth-century biology, this paper unpacks the notion of species as ‘natural kinds’ and grounds for discourse, questioning received notions about both kinds and species. Life sciences in the nineteenth century established several ‘monster-barring’ techniques to block disputes about the precise definition of species. Counterintuitively, precision and definition brought dispute and disrupted (...) exchange. Thus, any attempt to add precision was doomed to failure. By intervening and measuring, the new experimental biology dislocated the established links between natural kinds and kinds of people and institutions. New kinds were built in new places. They were made to measure from the very start. This paper ends by claiming that there was no long-standing ‘species problem’ in the history of biology. That problem is a later construction of the ‘modern synthesis’, well after the disruption of ‘kinds’ and kinds of people. Only then would definitions and precision matter. A new, non-linguistic, take on the incommensurability thesis is hinted at. (shrink)