Vorticella, from Christian Gottfried Ehrenberg, Die Infusionsthierchen, 1838.

28. Ehrenberg, Christian Gottfried (1795-1876).
Die Infusionsthierchen als volkommene Organismen. Leipzig: L. Voss, 1838.

The term “infusoria” was the commonly-used term in the nineteenth century for what we now call protozoa.  Infusoria were generally microscopic life, and quite a few had been observed by naturalists like Schaeffer and Müller when studying larger invertebrates (see items 23 and 24).  But the definitive study of infusoria was this large folio work by Ehrenberg, who was one of the leading German authorities on invertebrates.  He championed the idea that infusoria had circulatory, gastric, and nervous systems just like higher animals, and in this he would prove to be in error.  But his illustrations of the diversity of microscopic life have seldom been rivaled. We see here just two of the thirty plates in his book; one shows Volvox colonies in various stages of development, and the other depicts a variety of Vorticella, an organism which looks like an inverted bell on a stalk.  At the middle right of this plate, one can see, at a different scale of enlargement, a copepod, to which some tiny Vorticella are attached.

Volvox colonies, from Christian Gottfried Ehrenberg, Die Infusionsthierchen, 1838.
Linda hall Library