Heackel was a prolific writer and natural history illustrator. His books included titles such as The History of Creation, Systematic Phylogeny, The Riddle of the Universe, Last Words on Evolution, and The Last Link. His natural history illustration culminated in the publication of Kunstformen der Natur (Artforms of Nature) in 1904. The book included 100 lithographic and autotype prints of a variety of organisms including arachnids, turtles, bryozoa, sea anemones, and many others.


