understand the reasons underpinning their beauty. He exchanged opinions with the noted cryptogamist G. H. K. Thwaites on the topic. In the fourth edition of On the Origin of Species he stated that "Few objects are more beautiful than the minute siliceous cases of the diatomaceae: were these created that they might be examined and admired under the high powers of the microscope"? and reasoned that their exquisite morphologies must have functional underpinnings rather than having been created purely for humans to admire. See also Highly branched isoprenoid, long-chain alkenes produced by a small number of marine diatoms Notes References External links Diatom EST database, École Normale Supérieure Plankton*Net, taxonomic database including images of diatom species Life History and Ecology of Diatoms, University of California Museum of Paleontology Diatoms: 'Nature's Marbles', Eureka site, University of Bergen Diatom life history and ecology, Microfossil Image Recovery and Circulation for Learning and Education (MIRACLE), University College London Diatom page , Royal Botanic Garden Edinburgh Geometry and Pattern in Nature 3: The holes in radiolarian and diatom tests Diatom QuickFacts, Monterey Bay Aquarium Research Institute Algae image database Academy of Natural Sciences of Philadelphia (ANSP) Diatom taxa Academy of Natural Sciences of Philadelphia (ANSP) An Introduction to the Microscopical Study of Diatoms by Robert B. McLaughlin Algae classes