Müller became a strong supporter of Darwin. He wrote "Für Darwin" in 1864, arguing that Charles Darwin's theory of evolution by natural selection was correct, and that Brazilian crustaceans and their larvae could be affected by adaptations at any growth stage. This was translated into English as "Facts and Arguments for Darwin" in 1869. If Müller had a weakness it was that his writing was much less readable than that of Darwin or Wallace; both the German and English editions are hard reading indeed, which has limited the appreciation of this significant book.