Julia Barlow Platt (14 September 1857 in San Francisco – 1935) was an American embryologist and politician.
She studied at Harvard University and obtained her doctorate at Freiburg in 1898. She investigated embryogenesis, in particular the head development, from studying sharks and salamanders. Her most notable contribution to the field was her demonstration that neural crest cells formed the jaw cartilage and tooth dentine in salamanders, but her work was not believed by her contemporaries. Her claim went counter to the belief that only mesoderm could form bones and cartilage. Her hypothesis of the neural crest origin of the cranial skeleton gained acceptance only some 50 years later when confirmed by Sven Hörstadius and Sven Sellman.
Unable to secure a university position, she said "if I cannot obtain the work I wish, then I must take up with the next best" and then became active in politics, including tearing down a fence to give the public access to the beach at Lover's Point in Pacific Grove, California. In 1931, at the age of 74, she became mayor of Pacific Grove, California. According to Steve Palumbi and Carolyn Sotka, her prescient pioneering setting up of a marine protected area was crucial to the recovery of the sea otter.Platt, J. B. (1890): "The Anterior Head-Cavities of Acanthias (Preliminary Notice)", Zool. Anz. 13: 239
Platt, J. B. (1892): "Fibres connecting the Central Nervous System and Chorda in Amphioxus", Anat. Anz. 7: 282-284
Platt, J. B. (1893): "Ectodermic Origin of the Cartilages of the Head", Anat. Anz. 8: 506-509
Platt, J. B. (1894): "Ontogenetische Differenzirung des Ektoderms in Necturus", Archiv mikr. Anat. 43: 911-966
Platt, J. B. (1894): "Ontogenetic Differentiations of the Ectoderm in Necturus" Anat. Anz. 9: 51-56
Platt, J. B. (1898): "The development of the cartilaginous skull and of the branchial and hypoglossal musculature in Necturus", Morphol. Jahrb. 25: 377-464