104 EMINENT NATURALISTS. 



discovered that the scales of fishes correspond by four 

 kinds of structures to f our grand natural divisions, which 

 he called Granoids, Placoids, Cycloids, and Ctenoids. 

 With this basis, and aided by an intimate knowledge 

 of the skeleton, he was enabled to tabulate all the 

 known fossil species. These formed his gigantic work 

 published as "Recherches sur les Poissons Fossiles," the 

 publication of which at Neufchatel extended over ten 

 years. It formed five quarto volumes, with 311 folio 

 plates. Eighty of the greatest museums of Europe 

 had furnished the materials for it, and the number 

 of described species amounted to 1,700 in about 20,000 

 examples. This is, undoubtedly, the greatest work of 

 Agassiz, and forms, with Cuvier's and Valenciennes' 

 " Histoire Naturelle des Poissons," and Johann Miiller's 

 Treatises, the foundation of our present knowledge of 

 fishes, while it does not confine itself to the region of 

 ichthyolites, but extends over the entire wide field of 

 the anatomy and classification of fishes, essentially 

 modifying the latter. Agassiz considered, and with 

 justice, that the separation of the ganoids from the 

 other fishes into the rank of a special order was the 

 greatest step towards progress for which science was 

 indebted to him, and on the basis of the comparison 

 of the fossil fishes of formations with living forms, 

 he enunciated several generally valid laws, which have 

 had an important bearing on the development theory 

 of the whole organic world. 



The preparation of this work was laborious in the 

 extreme. Agassiz was obliged to travel with an artist, 

 in order to examine and figure the specimens which 



