[165] This he already touched upon in his _Mémoires de Physique et d'Histoire naturelle_ (p. 342). [166] _Système des Animaux sans Vertèbres_, pp. 16 and 17. [167] I have cited the incontestable proofs in my _Hydrogéologie_, and I have the conviction that one day all will be compelled to accept these great truths. [168] _Ranunculus aquaticus capillaceus_ (Tournef., p. 291). [169] _Ranunculus aquaticus_ (folio rotundo et capillaceo, Tournef., p. 291). [170] _Gramen junceum_, etc. (Moris, hist. 3, sec. 8, t. 9, f. 4). [171] _Discours d'ouverture d'un Cours de Zoologie, prononcé en prairial, an XI, au Muséum d'Histoire naturelle, sur la question, Qu'est-ce que l'espèce parmi les corps vivans?_ (1803). [172] _Recherches sur l'Organisation des Corps vivans_, p. 9. [173] "See at the end of this discourse the sketch of a _Philosophie zoologique_ relative to this subject." [This sketch was not added--only the title at the end of the book.] [174] See the _Annales du Muséum d'Hist. nat._, IV^e cahier. 1., 1802, pp. 302, 303: _Mémoires sur les Fossiles des Environs de Paris_, etc. He repeats in his _Discours_ what he wrote in 1802 in the _Annales_. [175] _Ibid._ This is repeated from the article in the _Annales_. [176] _Ibid._ "See my _Recherches sur les Corps vivans_" (Appendix, p. 141). [177] _Discours d'Ouverture du Cours des Animaux sans Vertèbres, prononcé dans le Muséum d'Histoire naturelle en mai 1806._ (No imprint. 8^o, pp. 108.) Only the most important passages are here translated. [178] "We know that all the forms of organs compared to the uses of these same organs are always perfectly adapted. But there is a common error in this connection, since it is thought that the forms of organs have caused their functions (_en ont amené l'emploi_), whereas it is easy to demonstrate by observation that it is the uses (_usages_) which have given origin to the forms of organs." CHAPTER XVII THE "PHILOSOPHIE ZOOLOGIQUE" Lamarck's mature views on the theory of descent comprise a portion of his celebrated _Philosophie zoologique_. We will let him tell the story of creation by natural causes so far as possible in his own words. In the _avertissement_, or preface, he says that his experience has led him to realize that a body of precepts and of principles relating to the study of animals and even applicable to other parts of the natural sciences would now be useful, our knowledge of zoölogical facts having, for about thirty years, made considerable progress. After referring to the differences in structure and faculties characterizing animals of different groups, he proceeds to outline his theory, and begins by asking: