There, he attended primary school until his 12th or 13th year. He graduated two years later, and set up practice in Nieuwediep.
Besides translating the first edition of Charles Darwin"s Origin of Species (1860), he wrote a great number of works popularising science, particularly the life sciences. He used his wages to educate himself in French, then German, and then English. This desire for self-education and self-discipline would characterise Winkler throughout his life.
His first patient, a fisherman, complained of being stung by a weever fish.
His studies took him to the library of Teylers Museum in Haarlem, and his subsequent article on the weever in the popular journal Album der Natuur established him as an expert on fishes. At the Museum, he also developed an interest in paleontology and geology.
The curator, professor Van Breda, approached him to describe the fossil fishes from his own and Teylers" collections. This set Winkler up at the museum and his work, duly lauded, was published in the Verhandelingen ("Transactions") of Teylers" Society in 1859.
This was followed up by further work on fishes from the German Solnhofen limestone, and completion of the catalogue of the museum"s fossil fish collection.
A year later he finished the catalogue, despite being forced to work in an unheated room and continuing with his general medical practice. In 1864 Winkler was asked to become curator of Teylers" paleontological and mineralogical cabinet, a post he kept until his death in 1897. He immediately set to work to catalogue the Museum"s entire collection of fossils, which at the time was unnumbered and, frequently, undocumented.
On the advice of the prominent Utrecht natural historian Pieter Harting, he applied a numerical system in which the fossils were divided into Periods (Paleozoic, Mesozoic and Caenozoic) and sorted from "high" to "low".
This system, and the way in which Winkler applied it, already showed the influence of Darwin"s theory of evolution. Completing this catalogue would take until 1896, by which time six volumes and five supplements had been published, documenting a total of 15,458 fossils.
Winkler also catalogued the museum"s mineral collection.