The paper analyzes the impact of the discovery of the division of infusoria on eighteenth-century microscopic iconography. In the fall of 1765, while reproducing the anti-spontaneist experiments of Lazzaro Spallanzani, Horace-Bénédict de Saussure (1740-1799) discovered a new method of producing infusoria animalcules, namely their division, later reinterpreted as mitosis. Drawing a dividing animalcule posed particular problems, especially the question of how to represent the temporal sequence of a microscopic creature. Although Saussure's notebook of microscopic experiments remained unpublished, the discovery soon spread and was recognized by European naturalists, who began to repeat the observations and quickly encountered iconographic problems similar to those experienced by Saussure. In fact, the linearity used to represent time is a construction, and especially for public images, scientists had to contend with the conventions of draftsmen and engravers. The analysis of the microscopic iconographic material of the period 1740-1786 shows that during this period certain naturalists invented new solutions for the representation of time, but the diffusion of their innovations was not immediate. Nevertheless, the use of linearity in the illustration of microscopic creatures was established between 1765 and 1776 as a solution that allowed the public to read an iconographic temporal process as a text.