Leeuwenhoek's discoveries and drawings of 'little animalcules' opened up a whole new world for naturalists. Protozoa, and microorganisms generally were discovered. Christian Gottfried Ehrenberg's book "Die Infusionsthierchen" summarised what was known in 1838. Lorenz Oken (1779–1851) in 1805 wrote that infusoria (microscopic forms) were the basis of all life. 