 Although these postulates cannot be applied in all cases, they do retain historical importance to the development of scientific thought and are still being used today.The discovery of microorganisms such as "Euglena" that did not fit into either the animal or plant kingdoms, since they were photosynthetic like plants, but motile like animals, led to the naming of a third kingdom in the 1860s.In 1860 John Hogg called this the Protoctista, and in 1866 Ernst Haeckel named it the Protista.