Wrote Letter L-283 of 1695-12-28 to Hendrik van Bleyswijk about herring, their stomach worms, the food in herring stomachs, and how small fish like herring catch food
Text of the letter in the original Dutch and in English translation from Alle de Brieven. The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren
Leeuwenhoek wrote this letter about
Why herring take little food and yet are fat. Worms from the stomach of a herring. Herring use plankton as food, and sometimes eggs of other herring. Worms drill through the stomach wall of the herring; a comparison with chickens that have swallowed pins. Parts of plants and a small snail in herring stomachs. Sturgeon too take food, viz. shrimp. Comparison between herring that grow fat and codfish that put on more flesh when they take food. Small fishes swim against the current and have large eyes, to enable them to catch food more easily.