Here is a scan of Haeckel's Kunstformen der Natur --its a big pdf file that is 260MB but worth it as it really gives a view into Ernst Haeckel's mind, aesthetic and scientific understanding. It's interesting as his name keeps popping up on websites that validate Genesis--anti-Darwin thinking which is curious as Haeckel, after reading Darwin's treatise On the Origin of Species viewed his work as a confirmation of this theory. He proceeded to send a copy of his book, Monograph on Radiolarians when it was published in 1862 to Darwin. Darwin was apparently delighted "The images were the most magnificent works which I have ever seen, & am proud to possess a copy from the author" he wrote.
There is a recent film, Proteus, a Nineteenth Century Vision (a film by David Lebrun) that showcases Ernst Haeckel and his little sea organism, the radiolarian. Haeckel discovered, described, classified and painted four thousand species of these one celled creatures. They are among the earliest forms of life. In their intricate geometric skeletons, Haeckel saw all the future possibilities of organic and created form. His work influenced not only biology but also movements, thinkers and authors as disparate as Art Nouveau and Surrealism, Sigmund Freud and D.H. Lawrence, Vladimir Lenin and Thomas Edison.