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; 



