xxiv EDITOR'S INTRODUCTION 



plants had originated in common centers of creation, their present 

 distribution being the result of such physical factors as glacial action. 

 The Ice Age had provided, instead, a physical barrier to any unity 

 of development between past and present. As he wrote in the Essay, 



It appears to me ... as facts now point distinctly to an independent origin 

 of individuals of the same species in remote regions, or of closely allied species 

 representing one another in distant parts of the world, one of the strongest 

 arguments in favor of the supposition, that physical agents may have had a 

 controlling influence in changing the character of the organic world, is gone 

 for ever. (p. 39) 



How, then, explain the particular patterns of geographical distribu- 

 tion? "Only the deliberate intervention of an Intellect, acting con- 

 tinuously according to one plan, can account for phenomena of this 

 kind." From these statements it seemed to some that Agassiz had 

 become more dogmatic with the years and had remained uninflu- 

 enced by the course of zoological research. To Lyell, therefore, the 

 Essay showed that Agassiz had "nailed his colors to the mast" and 

 announced for all time his opposition to ideas of change and de- 

 velopment. 



Yet when naturalists like these men criticized Agassiz for his re- 

 liance on old standards, they were in a sense castigating their own 

 high admiration for the idealism that had seemed attractive to Gray 

 when he first heard Agassiz in 1846. Agassiz had not changed; his 

 audience had. Moreover, while it was true that his social involve- 

 ments had not allowed him the time or interest to become familiar 

 with new directions in research, active investigators — Karl Ernst 

 von Baer and Sir Richard Owen for example — were nevertheless 

 equally firm opponents of the developmental concept. Two years 

 before Darwin, it was still true according to all the standards 

 of science Agassiz and men like him respected, that the idea of 

 development was still an unproved hypothesis. He could hardly 

 have been expected to support the theory before 1859, when even 

 Huxley and Lyell, unburdened by Agassiz's idealism, had not yet 

 publicly embraced the idea, although they encouraged Darwin in 

 his efforts. Proponents of evolution criticized Agassiz for his con- 

 tinued opposition in the 1860's, yet his attitude was consistent with 

 views he had held since the I830's. Such supporters of Darwin as 

 Lyell and Gray were men of equal good will, but in their dissatis- 



