EDITOR'S INTRODUCTION xxiii 



Agassiz planned and wrote the Essay, was a time of significant con- 

 ceptual transformation in biology. These were the years when Dar- 

 win, Huxley, Joseph Dal ton Hooker, and Gray worked at the elab- 

 oration of a new conceptual framework for natural history, one that 

 would supplant what they had come to regard as the sterile and out- 

 moded concept of special creationism. Gray's and Hooker's re- 

 searches had shown, for example, that there were important re- 

 semblances and affinities between plants of one geographic region 

 and those of another. Such findings made it more reasonable to 

 suppose that animal and plant forms had originated from single 

 pairs in common centers of creation. Their present dispersal and 

 divergencies from the original stock could be accounted for by the 

 action of physical agencies such as the effects of climate in the 

 present or the action of glaciers in the past. While Darwin would 

 elaborate such findings into a general theory of variation as the 

 result of natural selection, one did not have to be a convinced 

 evolutionist to believe in the unity of origin of zoological forms. 



Naturalists identified with this new intellectual persuasion were 

 notable for one common trait: they wished for a free interchange of 

 theory and opinion regarding the new data that were being dis- 

 covered. Thus Gray wrote the Yale naturalist, James Dwight Dana, 

 in 1856 



The right way to bring a series of pretty interesting general questions towards 

 settlement is perhaps in hand . . . viz., for a number of totally independent 

 naturalists, of widely different pursuits and antecedents — to environ it on all 

 sides, work towards a common centre, but each to work perfectly independently. 

 Such men as Darwin, Dr. Hooker, [Alphonse] De Candolle, Agassiz, and myself, 

 — most of them with no theory they are bound to support, ought only to bring 

 out some good results.^ 



As Gray would discover, Agassiz was wedded to the defense of special 

 creationism. This unyielding conviction set him apart from some 

 fellow naturalists in the years immediately preceding and subse- 

 quent to the publication of Darwin's work. By the 1860's Agassiz's at- 

 titude made him one of the few scientists in America publicly 

 opposed to a conception of nature like evolution not grounded on 

 a belief in the permanence of species imposed from without. 

 For example, Agassiz denied the possibility that animals and 



® December 13, 1856, in Jane Loring Gray (ed.). Letters of Asa Gray (2 vols., Boston, 

 1893), II, 424. 



