In 1901, he published a book Die Descendenztheorie which attacked Darwinism, evolution and theories of common descent.
[3] In 1907, Vernon Lyman Kellogg described Fleischmann as the "only biologist of recognized position, of whom I am aware, who publicly declares disbelief in the theory of descent.
"[4] Palaeontologist William Berryman Scott noted that because of his anti-evolutionary views, Fleischmann was "almost entirely alone in modern biological literature.
"[5] His anti-evolutionary writings were criticized by biologist August Weismann and zoologist Sinai Tschulok.
[1] He was the author of a popular zoology textbook and a book which contained a series of lectures held in 1921–1922 at the University of Erlangen.