SYSTEBIATIC ARRANGEMENT OF PISHES. 73 



upon principles that are not merely applicable to them, 

 but to all other portions of the animal or vegetable cre- 

 ation. Now, if the simple question were put to any- 

 reflecting mind, which of these plans was the most phi- 

 losophical, or the most likely to exhibit the true series 

 of nature, no one would hesitate to decide upon the last. 

 This is only a different method of stating the true 

 nature of artificial and of natural systems. The former, 

 indeed, cannot be said to be founded on any general or 

 fixed principles, extending their influence to other 

 branches of zoological science; for although, in one 

 sense, each class may be arranged on a principle, yet 

 that principle is altogether arbitrary. There may be 

 principles of ichthyology, of ornithology, and of all the 

 other classes, but there cannot be principles of zoology, 

 unless the whole of its divisions present a consistent 

 uniform harmony in their arrangement. Upon this 

 vantage ground, therefore, the philosophic naturalist 

 takes his stand; and while he willingly confesses the 

 advantages, nay, the absolute necessity, of availing him- 

 self of the artificial mode of arrangement in little known 

 groups, he feels fully persuaded that the very first im- 

 perfect gHmpse of the natural system should be seized 

 and adopted, since its very errors will eventually lead to 

 truth, and accelerate the discovery of those principles 

 upon which alone zoology can be rendered a science of 

 demonstration, at least in the opinion of those who have 

 given laws for the prosecution of the physical sciences, 

 of which zoology, vast as it is, forms but a small 

 part. 



(71.) One of the consequences involved in the 

 law of representation (or that by which one group of 

 animals represents another group in a totally different 

 class) is, that the primary divisions of a class are no 

 longer arbitrary. We advert to this subject more par- 

 ticularly in the present volume, because, although we 

 have adopted, in almost every instance, the higher 

 groups pointed out by our predecessors, we have not 

 given to them that rank in the class which some have 



