For over thirty years the Lamarckian factors of evolution have seemed to me to afford the foundation on which natural selection rests, to be the primary and efficient causes of organic change, and thus to account for the origin of variations, which Darwin himself assumed as the starting point or basis of his selection theory.

It is not lessening the value of Darwin's labors, to recognize the originality of Lamarck's views, the vigor with which he asserted their truth, and the heroic manner in which, against adverse and contemptuous criticism, to his dying day he clung to them.
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 _Lecon d'Ouverture des Cours de l'Evolution des Etres organises_, 1888, and in facilitating the work of collecting data.

Introduced by him to Professor Hamy, the learned anthropologist and archivist of the Museum 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.