246 LOUIS AGASSIZ. 



tween the fossil fishes of all geological for- 

 mations and those of the present world, is 

 best told by the author.^ " Possessing no fos- 

 sil fishes myself, and renouncing forever the 

 acquisition of collections so precious, I have 

 been forced to seek the materials for my work 

 in all the collections of Europe containing 

 such remains; I have, therefore, made fre- 

 quent journeys in Germany, in France, and in 

 England, in order to examine, describe, and 

 illustrate the objects of my researches. But 

 notwithstanding the cordiality with which even 

 the most precious specimens have been placed 

 at my disposition, a serious inconvenience has 

 resulted from this mode of working, namely, 

 that I have rarely been able to compare di- 

 rectly the various specimens of the same spe- 

 cies from difPerent collections, and that I have 

 often been obliged to make my identification 

 from memory, or from simple notes, or, in the 

 more fortunate cases, from my drawings only. 

 It is impossible to imagine the fatigue, the ex- 

 haustion of all the faculties, involved in such 

 a method. The hurry of traveling, joined to 

 the lack of the most ordinary facilities for 

 observation, has not rendered my task more 



1 Recherches sur les Poissons Fossiles, vol. i. Addition h la 

 Preface. 



