World Oceans Day: Ernst Haeckel and Art Forms in Nature

This post is the fifth in our series leading up to the celebration of World Oceans Day on June 8. This series explores publications that represent important milestones in the progress of marine bioscience research and ocean exploration. This post is an abbreviated version of a longer feature published on the Smithsonian Ocean Portal. View the entire article here.

From recent articles published via premier scientific journals to monumental volumes marking the beginning of our study of the natural world, the Biodiversity Heritage Library‘s collections include information about species from every corner of the globe and ecological niche. They also include works authored by some of the most influential men and women scientists in history.

One such individual is German zoologist Ernst Haeckel.

Born in 1834 in Potsdam, Germany (then Prussia), Ernst Haeckel served as a professor of comparative anatomy and director of the Zoological Institute at the University of Jena, named and described several thousand new species of marine invertebrates, and was a member of more than 90 learned societies during his lifetime. He studied an array of zoological topics but is widely remembered for his work on many invertebrate groups, including marine organisms like radiolarians, poriferans (sponges), and cnidarians (jellyfish, anemones, and corals). He had a deep personal interest in evolution, becoming the preeminent proponent of Darwinism in Germany (though some of his evolutionary ideas did diverge from Darwin’s theories) and helping to popularize this theory throughout Europe. He also served as a consultant on the Challenger expedition – the first non-commercial exploration of the deep-sea environment – that revolutionized the field of oceanography. The author of over 40 works and thousands of drawings, one of Haeckel’s most iconic publications is Kunstformen der Natur.

Kunstformen der Natur, translated into English as Art Forms in Nature, is a landmark publication in the field of naturalist illustration. Published in sets of ten from 1899-1904 and together in two volumes in 1904, the work contains 100 lithographic prints produced by Adolf Giltsch from Haeckel’s original sketches and watercolors.

While much of it is stylized for artistic effect, the exquisitely drawn, detailed plates exhibiting Art Nouveau techniques alongside commentary accessible to even the general public made Kunstformen der Natur an instant success and helped popularize science and many little-known marine organisms. Indeed, while Kunstformen der Natur covers a wide range of biological diversity, a majority of the illustrations depict marine life.

The timelessness and accuracy of Haeckel’s illustrations are evident even today. Just last year, an Atlas of the larval stages of all crustaceans worldwide, co-written by Joel W. Martin, Curator of Crustaceans at the Natural History Museum of Los Angeles County (a BHL Affiliate), featured one of Haeckel’s exquisite illustrations on the cover.

Learn more about Ernst Haeckel and Kunstformen der Natur in this online exhibit from The MBLWHOI Library. View the book in its entirety for free on the Biodiversity Heritage Library, digitized by Smithsonian Libraries, and browse all of the amazing illustrations in Flickr.


Of all of the species Haeckel described, he is arguably most famous for the radiolarians. Planktonic, unicellular marine eukaryotes, radiolarians are found in all of the world’s oceans and represent a staple component of marine ecosystems. The multiple body compartments of radiolarians are surrounded by and elaborate mineral skeletons called the test, which exhibits the exquisite designs that so captivated Haeckel. Haeckel first encountered these beauties while at Messina in Sicily, and it was this experience that prompted him to pursue doctorate studies in zoology. Haeckel helped popularize these animals with the public through his 1862 monograph Die Radiolarien, his 1887 report as part of the H.M.S. Challenger expedition, and his illustrations in Kunstformen der Natur.



Siphonophorae is an order of marine animals in the phylum Cnidaria (the same phylum containing jellyfish). Although they superficially resemble jellyfish, each siphonophore specimen is actually a colony of many genetically-identical individuals, called zooids. Each zooid is specialized to serve a particular function within the colony, so much so that most cannot survive alone. The infamous and venomous Portuguese man o’ war is a member of this order. Certain siphonophore species can emit light. A species in the Erenna genus found off of the coast of Monterey, California has stinging cells that glow red, probably to attract the small fish upon which it preys. This species is only the second life form known to produce a red light, the first being the scaleless dragonfish Chirostomias pliopterus.

Rhizostomae Jellyfish

Haeckel was inspired by nature to create not just stunning illustrations but decorative pieces for home interiors as well. Haeckel discovered a species of rhizostomae jellyfish in Bellagemma, Ceylon, in December 1881. He was so impressed with the form that he used it as a model for ceiling decorations in his Villa Medusa home in Jena. Today, all jellyfish species fished on a commercial basis for human consumption are from the rhizostomae order, which are typically dried and/or salted before eating. China is the first documented country to eat jellyfish, with the practice dating back to at least 300 CE.


Nudibranchs (often casually called sea slugs) are soft-bodied, marine snails that have lost all trace of an external shell. The name “nudibranch” translates from the Latin as “naked gills.” Consisting of about 3,000 species, some have developed impressive defensives, including the ability to synthesize toxic compounds (such as sulfuric acid) or the ability to “hijack” and repurpose the stinging cells of the cnidarians (jellyfish, anemones, and, corals) that some of them eat.

Learn more about marine organisms and Haeckel’s amazing illustrations in the full article on 

More World Oceans Day Resources

  • Follow us on Twitter, Facebook, and this blog all this week as we explore marine biodiversity and awesome related publications in BHL.
  • Check out some monumental publications in historic and present-day marine bioscience research in our BHL collection.
  • Browse a selection of marine biodiversity illustrations in Flickr and Pinterst
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Grace Costantino served as the Outreach and Communication Manager for the Biodiversity Heritage Library from 2014 to 2021. In this capacity, she developed and managed BHL's communication strategy, oversaw social media initiatives, and engaged with the public to excite audiences about the wealth of biodiversity heritage available in BHL. Prior to her role as Outreach and Communication Manager, Grace served as the Digital Collections Librarian for Smithsonian Libraries and as the Program Manager for BHL.