M. Agassiz on the Classification of Fishes. 133 



to be completed ; and the design would have to represent 

 the relief itself as much as possible. Then the time may 

 come, perhaps, when the requirements of science will go so 

 far as to render, in most instances, real reliefs indispensable ; 

 that is to say, the material reproduction of forms, reduced to 

 certain dimensions, will one day become a necessary accom- 

 paniment to topographical works. 



May we not say the same thing of systems in natural his- 

 tory ? There was a time when vague approaches were suffi- 

 cient to give an idea of the limited number of beings, imper- 

 fectly known, which constituted the subject of the naturalist's 

 study. They were grouped according to some conspicuous 

 characters, easily perceived ; sometimes all that was attempted 

 was to place them after one another, according to their size, 

 their manner of life, or the places which they inhabited. 

 However incomplete these methods were, they still satisfied 

 tjie wants of inquirers at that period ; and notwithstanding 

 their imperfection, they even contributed to the progress of 

 the natural sciences. Some author or other, by remarking the 

 gaps in such arrangements, completed the method; others 

 collected new materials calculated to facilitate the researches 

 of their successors, and by degrees new systems arose, founded 

 on good characters. From that period the progress was rapid ; 

 monographical works came to extend the field of comparisons, 

 by fixing new bases for the study of details. New ideas led 

 to the discovery of new aspects in subjects supposed to have 

 been exhausted. It was thus, without leaving the domain of 

 zoology, and without going back to the first attempts at classi- 

 fication proposed for the animal kingdom, that naturalists 

 confined themselves for a long tinie to seek for the distinctive 

 characters of species, and to group them in a small number of 

 genera, often founded on a very imperfect acquaintance with 

 their organisation. This tendency is particularly characteristic 

 of the works belonging to the school of Linna)us, which caused 

 the science to make immense progress, by simplifying the metho4 

 and limiting it to the most concise expression of known facts. 

 It was soon perceived, however, that this system could be 

 regarded only as a frame-work fitted to include, in one view, 

 all the classes, but the compartments of which were poorly fur- 

 nished. Every day, in truth, enriched science with important 



