228 Professor L. Agassiz on the Principles of 



and even arbitrary decision, beyond what the knowledge of 

 facts would justify ; for the brilliant results which the intro- 

 duction of comparative anatomy, as the foundation of the 

 classification of the animal kingdom, has brought to light 

 must naturally have blinded us to the imperfections and de- 

 ficiencies which constantly accompany the most important 

 improvements in the natural arrangement of every class. 

 Nevertheless, our confidence in the possibility of ascertaining 

 the natural relations of all animals has been increased by the 

 growing agreement between the different systems ; and there 

 is no philosophical observer who has not noticed this process 

 of gradual approximation towards a greater uniformity in 

 the view taken by different observers of the natural affinities 

 of animals, however concealed this agreement has often been 

 in consequence of changes of name or transposition of the 

 order in which the objects were introduced. 



The time has, however, gone by when the mere translation 

 of family names, or of more general or minor divisions, into 

 another language, could be presented as a new system, and 

 the raising of a secondary division into the rank of a primary 

 group, or the lowering of a primary division into a subordi- 

 nate position, constituted an improvement in the knowledge 

 of the natural relations of animals. Nothing short of a ma- 

 terial addition to the information we possess respecting any 

 group of animals, can now be considered as a real advance 

 in zoology. 



It should be further considered that our object is not 

 merely or chiefly to ascertain the structural relations of ani- 

 mals, but to know all the various relations which have been 

 established between them, and which they sustain toward 

 the world in which they live. The knowledge of the natural 

 embryonic development — of the order of succession in geolo- 

 gical tiipes, — of the geographical distribution upon the sur- 

 face of our globe — and of the habits arising from the natural 

 relations to the elements in which they live, — all these con- 

 siderations are of as great importance in our zoological 

 studies as the knowledge of the structure and functions of 

 their organs, to which, of late, more exclusive attention has 

 been paid. 



