How did Lamarck become a professor at the National Museum of Natural History in Paris?

Lamarck became a professor at the Muséum National d’Histoire Naturelle in 1793, following a major institutional reorganization. During the French Revolution, the former Jardin du Roi was transformed into the new national museum, and all 12 scientists who had served as officers of the previous establishment were appointed as professors and coadministrators of the new institution.1

Although Lamarck had established his scientific reputation as a botanist, the two available professorships in botany were claimed by Antoine-Laurent de Jussieu and René Desfontaines. Consequently, Lamarck was assigned the professorship of "insects, worms, and microscopic animals." While this represented a significant shift in his professional focus, it was supported by his personal interest as an ardent shell collector. He subsequently dedicated himself to classifying this group, eventually inventing the term invertebrate to describe these organisms.1