Seite - 16 - in The Origin of Species

16 HISTORICAL SKETCH qu'elle se perpetue ou milieu des memes circonstances : ils se modifient, si les circonstances ambiantes viennent a changer." "En resume, I'cbservaiion des animaux sauvages demontre deja la variabilite limitee des especes. Les experiences sur les animaux sauvages devenus domestiques, et sur les ani- maux domestiques redevenus sauvages, la demontrent plus clairement encore. Ces memes experiences prouvent, de plus, que les dififerences produites peuvent etre de valeur generique." In his ' Hist. Nat. Generale' (torn ii. p. 340, 1859) he amplifies analogous conclusions. From a circular lately issued it appears that Dr. Freke, in 1851 ('Dublin Medical Press,' p. 322), propounded the doc- trine that all organic beings have descended from one pri- mordial form. His grounds of belief and treatment of the subject are wholly different from mine; but as Dr. Freke has now^ (1861) published his Essay on the 'Origin of Spe- cies by means of Organic Affinity,' the difficult attempt to give any idea of his views would be superfluous on my part. Mr. Herbert Spencer, in an Essay (originally published in the 'Leader,' March, 1852, and republished in his 'Essays,' in 1858), has contrasted the theories of the Creation and the Development of organic beings with remarkable skill and force. He argues from the analogy of domestic productions, from the changes which the embryos of many species under- go, from the difficulty of distinguishing species and varie- ties, and from the principle of general gradation, that species have been modified; and he attributes the modification to the change of circumstances. The author (1855) has also treated Psychology on the principle of the necessary acquire- ipent of each mental power and capacity by gradation. La 1852 M. Naudin, a distinguished botanist, expressly stated, in an admirable paper on the Origin of Species ('Revue Horticole,' p. 102; since partly republished in the 'Nouvelles Archives du Museum,' tom. i. p. 171), his belief that species are formed in an analogous manner as varieties are under cultivation ; and the latter process he attributes to man's power of selection. But he does not show how selec- tion acts under nature. He believes, like Dean Herbert, that species, when nascent, were more plastic than at present. He lays weight on what he calls the principle of finality;