Plankton organisms (mostly protists) from waters near Kiel, Germany, by Hans Lohmann (1908, Figure 7).

Lohmann, following Kofoid, found that most of the planktonic organisms were small and not apparent with nets usually used. Most plankton nets will only catch copepods (like the #8 Oithona) and big diatoms (like the #32 Coscinodiscus). The numerical and ecological importance of protists was 're-discovered' in the 1970's.