Christiaan Huygens again observed little animals using dark-ground illumination

September 17, 1678

Huygens wrote in French:

Je regardois tous ces animaux non pas directement contre la lumiere mais en detournant un peu le microscope, ce qui les fait paroistre sur un fond noir. On decouvre mieux par ce moyen les moindres animaux ayant vie, et l'on distingue aussi mieux les parties des grands.

In English translation:

I looked at all these animals not directly against the light but by turning the microscope a little, which makes them appear on a black background. We discover better by this means the smallest living animals, and we also better distinguish the parts of the large ones.