William Healey Dall 1845-1927

William Healey Dall was one of the great, late 19th century American naturalists. And like many naturalists of his time, his expertise spanned a broad array of taxa, epochs and biological thought, including physical and cultural anthropology, oceanography, paleontology, and invertebrate and vertebrate zoology. He published over 1600 papers, reviews and commentaries in many of the most prestigious journals of his day, including Nature, Science, American Naturalist, Proceedings of the National Academy of Sciences, and the various publication series of the Smithsonian Institution. His expedition and field work centered in Alaska, but he also conducted field studies in Nicaragua and along both the east and west coasts of the United States. He was an elected member of numerous American societies, including the American Association for the Advancement of Science, National Academy of Sciences, National Geographic Society, Philosophical Society of Washington, as well as numerous European societies with whom he met during his travels abroad.

Although a polyglot, Dall's greatest scientific contributions were in the field of malacology. As a malacologist working on both fossil (Tertiary) and living molluscs, W. H. Dall described over 5300 species. While many of these works were short taxonomic papers, several were comprehensive monographs often including anatomical descriptions and phylogenies of the taxa under consideration.

Throughout his career Dall attempted to reflect evolutionary relationships in his molluscan classifications. From 1865-1877 Dall's evolutionary scenarios were built almost exclusively around heterochronic processes (primarily peramorphosis). Biogeographic congruence and natural selection were also invoked. The patterns Dall saw and the processes he intimated were likely derived from the training he received from L. Agassiz and others at the Museum of Comparative Zoology, Harvard University. By 1882 Dall had formalized his heterochronic arguments in terms of Edward Cope and Alpheus Hyatt's patterns of acceleration and retardation. Variation and de novo structures appeared through the interaction of physical forces with the organism, and past onto progeny by the inheritance of acquired characters. By 1890 Dall was an active participant in the Neo-Lamarckian movement in America. Dall's evolutionary models determined how he evaluated character polarities, transformations, and their import. In his monographs and revisions he ordered his species and higher taxa from primitive to derived reflecting his best interpretation of their "natural order." The recognition of Dall's intent and the rules by which he interpreted history requires us to carefully consider the implications of using his classifications today.

From: Lindberg, D. R. 1998. William Healey Dall: A Neo-Lamarckian View of Molluscan Evolution. The Veliger 41(3):227-238.

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