Largely self-educated, Dujardin, who was born in Tours, France, studied geology, botany, optics, and crystallography while working variously as a hydraulics engineer, librarian, and teacher of geometry and chemistry at Tours. In 1839 he was elected to the chair of geology and mineralogy at Toulouse, and in the following year was appointed professor of botany and zoology and dean of the Faculty of Sciences at Rennes. As a skilled microscopist, Dujardin carried out extensive studies of the microorganisms (infusoria) occurring in decaying matter. These led him, in 1834, to suggest the separation of a new group of protozoan animals, which he called the rhizopods (i.e. rootfeet). He was the first to recognize and appreciate the contractile nature of the protoplasm (which he termed the sarcode) and also demonstrated the role of the vacuole for evacuating waste matter. Such studies enabled Dujardin to refute the supposition, reintroduced by Christian Ehrenberg, that microorganisms have organs similar to those of the higher animals. Dujardin also investigated the cnidarians (jellyfish, sea anemones, corals, etc.), echinoderms (sea-urchins, starfish, etc.), as well as the platyhelminths, or flatworms, the last mentioned providing the basis for subsequent parasitological investigations.