xii HISTORICAL SKETCH. 



M. Isidore Geoffroy Saint-Hilaire, in his lectures deliv- 

 ered in 1850 (of which a Resume appeared in the *' Revue 

 et Mag. de Zoolog.," Jan., 1851), briefly gives his reason 

 for believing that specific characters ''sont fixes, pour 

 chaque espece, tant qu'elle se perpetue au milieu des 

 memes circonstauces: ils se moditient, si les circonstances 

 ambiantes viennent a changer." '^En resume, Vobserva- 

 tion des animaux sauvages demontre deja la variabilite 

 limit ee des especes. Les experiences sur les animaux 

 sauvages devenus domestiques, et sur les animaux domes- 

 tiques redevenus sauvages, la demontrent plus clairement 

 encore. Ces memes experiences prouvent, de plus, que les 

 differences produites peuvent etre de valeu7' generique.'* 

 In his ^aiist. Nat. Generale'' (tom. ii, p. 430, 1859) he 

 amplifies analogous conclusions. 



From a circular lately issued it appears that Dr. Freke, 

 m 1851 {'' Dublin Medical Press," p. 332), propounded 

 the doctrine that all organic beings have descended from 

 one primordial form. His grounds of belief and treat- 

 ment of the subject are wholly different from mine ; 

 but as Dr. Freke has now (1861) published his Essay on 

 ^he ^' Origin of Species 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 pub- 

 lished 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 em- 

 bryos of many species undergo, from the difficulty of dis- 

 tinguishing species and varieties, and from the principle of 

 general gradation, that species have been modified ; and 

 he attributes the modification to the change of circum- 

 Btances. The author (1855) has also treated Psychology 

 on the principle of the necessary acquirement of each 

 mental power and capacity by gradation. 



In 1852 M. Naudin, a distinguished botanist, expressly 

 stated, in an admirable paper on the Origin of Species 

 (•'Revue Horticole," p. 1k)Z \ since partly republished in 

 the *']SIouvelles Archives du Museum," tom. i, p. 171), his 

 belief that species are formed in an analogous manner as 



