During a residence in Paris in the spring and summer of 1899, I spent my leisure hours in gathering material for this biography. I visited the place of his birth--the little hamlet of Bazentin, near Amiens--and, thanks to the kindness of the schoolmaster of that village, M. Duval, was shown the house where Lamarck was born, the records in the old parish register at the _mairie_ of the birth of the father of Lamarck and of Lamarck himself. The Jesuit Seminary at Amiens was also visited, in order to obtain traces of his student life there, though the search was unsuccessful. My thanks are due to Professor A. Giard of Paris for kind assistance in the loan of rare books, for copies of his own essays, especially his _Leçon d'Ouverture des Cours de l'Évolution des Êtres organisés_, 1888, and in facilitating the work of collecting data. Introduced by him to Professor Hamy, the learned anthropologist and archivist of the Muséum d'Histoire Naturelle, I was given by him the freest access to the archives in the Maison de Buffon, which, among other papers, contained the MS. _Archives du Muséum_; _i.e._, the _Procès verbaux des Séances tenues par les Officiers du Jardin des Plantes_, from 1790 to 1830, bound in vellum, in thirty-four volumes. These were all looked through, though found to contain but little of biographical interest relating to Lamarck, beyond proving that he lived in that ancient edifice from 1793 until his death in 1829. Dr. Hamy's elaborate history of the last years of the Royal Garden and of the foundation of the Muséum d'Histoire Naturelle, in the volume commemorating the centennial of the foundation of the Museum, has been of essential service. My warmest thanks are due to M. Adrien de Mortillet, formerly secretary of the Society of Anthropology of Paris, for most essential aid. He kindly gave me a copy of a very rare pamphlet, entitled _Lamarck. Par un Groupe de Transformistes, ses Disciples_. He also referred me to notices bearing on the genealogy of Lamarck and his family in the _Revue de Gascogne_ for 1876. To him also I am indebted for the privilege of having electrotypes made of the five illustrations in the _Lamarck_, for copies of the composite portrait of Lamarck by Dr. Gachet, and also for a photograph of the _Acte de Naissance_ reproduced by the late M. Salmon. I have also to acknowledge the kindness shown me by Dr. J. Deniker, the librarian of the Bibliothèque du Muséum d'Histoire Naturelle. I had begun in the museum library, which contains nearly if not every one of Lamarck's publications, to prepare a bibliography of all of Lamarck's writings, when, to my surprise and pleasure, I was presented with a very full and elaborate one by the assistant-librarian, M. Godefroy Malloisel.