PROGRESS OF ICHTHYOLOGY. 429 



des which it may present, and of the reasonings, labors, cautions, and 

 varied resources, by means of which its solution is sought, when a 

 great philosophical naturalist girds himself to the task. We see here 

 most instructively, how different the endeavor to frame such a natura 

 system, is from the procedure of an artificial system, which carries 

 imperatively through the whole of a class of organized beings, a sys 

 tern of marks either arbitrary, or conformable to natural affinities in a 

 partial degree. And we have not often the advantage of having the 

 reasons for a systematic arrangement so clearly and fully indicated, as 

 is done here, and in the descriptions of the separate orders. 



This arrangement Cuvier adhered to in all its main points, both in 

 the second edition of the Regne Animal, published in 1821, and in his 

 Histoire Naturelle des Poissons, of which the first volume was published 

 in 1828, but which unfortunately was not completed at the time of his 

 death. It may be supposed, therefore, to be in accordance with those 

 views of zoological philosophy, which it was the business of his life to 

 form and to apply ; and in a work like the present, where, upon so 

 large a question of natural history, w r e must be directed in a great 

 measure by the analogy of the history of science, and by the judgments 

 which seem most to have the character of wisdom, we appear to be 

 justified in taking Cuvier's ichthyological system as the nearest 

 approach which has yet been made to a natural method in that depart- 

 ment. 



The true natural method is only one : artificial methods, and even 

 good ones, there may be many, as we have seen in botany; and each 

 of these may have its advantages for some particular use. On some 

 methods of this kind, on which naturalists themselves have hardly yet 

 had time to form a stable and distinct opinion, it is not our office to 

 decide. But judging, as I have already said, from the general analo- 

 gy of the natural sciences, I find it difficult to conceive that the ich- 

 thyological method of M. Agassiz, recently propounded with an espe- 

 cial reference to fossil fishes, can be otherwise than an artificial method. 

 It is founded entirely on one part of the animal, its scaly covering, and 

 even on a single scale. It does not conform to that which almost all 

 systematic ichthyologists hitherto have considered as a permanent 

 natural distinction of a high order; the distinction of bony and cartila- 

 ginous fishes ; for it is stated that each order contains examples of 

 both. 15 I do not know what general anatomical or physiological 



16 Dr. Buckland's Bridge-water Treatise, p. 270. 



