HISTORICAL SKETCH. ix 



forms may be generated " without the presence of any 

 mold or germ of former aggregates." I am not sure that 

 I understand some passages; but it seems that he attributes 

 much influence to the direct action of the conditions of 

 life. He clearly saw, however, the full force of the prin- 

 ciple of natural selection. 



The celebrated geologist and naturalist. Von Buch, in 

 his excellent "Description Physique des Isles Canaries" 

 (1836, p. 147), clearly expresses his belief that varieties 

 slowly become changed into permanent species, which are 

 no longer capable of intercrossing. 



Eafinesque, in his " New Flora of North America," pub- 

 lished in 1836, wrote (p. 6) as follows: "All species might 

 have been varieties once, and many varieties are gradually 

 becoming species by assuming constant and peculiar char- 

 acters;" but further on (p. 18) he adds, "except the 

 original types or ancestors of the genus." 



In 1843-44 Professor Haldeman (^" Boston Journal of 

 Nat. Hist. XT. States," vol. iv, p. 468) has ably given the 

 arguments for and against the hypothesis of the develop- 

 ment and modification of species: he seems to lean toward 

 the side of change. 



The "Vestiges of Creation" appeared in 1844. In the 

 tenth and much improved edition (1853) the anony- 

 mous author says (p. 155): "The proposition determined 

 on after much consideration is, that the several series 

 of animated beings, from the simplest and oldest \x^ to 

 the highest and most recent, are, under the providence 

 of God, the results, J?rs^, of an impulse which has been im- 

 parted to the forms of life, advancing them, in definite 

 times, by generation, through grades of organization ter- 

 minating in the highest dicotyledons and vertebrata, these 

 grades being few in number, and generally marked by in- 

 tervals of organic character, which we find to be a practi- 

 cal difficulty in ascertaining affinities; second, of another 

 impulse connected with the vital forces, tending, in the 

 course of generations, to modify organic structures in ac- 

 cordance with external circumstances, as food, the nature 

 of the habitat, and the meteoric agencies, these being the 

 ' adaptations ' of the natural theologian." The author ap- 

 parently believes that organization progresses by sudden 

 leaps, but that the effects produced by the conditions of 



