166 ESSAY ON CLASSIFICATION. 



the oldest known Fishes partake of characters, which, 

 at a later time, are exclusively found in Eeptiles, and no 

 longer belong to the Fishes of the present day. It may 

 be said that the earliest Fishes are rather the oldest 

 representatives of the type of Vertebrata than of the class 

 of Fishes, and that this class only assumes its proper 

 characters after the introduction of the class of Eeptiles 

 upon the earth. Similar relations may be traced between 

 the Keptiles and the classes of Birds and Mammalia-, 

 which they- precede. I need only allude here to the 

 resemblance of the Pterodactyli to Birds, and to that 

 of the Ichthyosauri to certain Cetacea. Yet, tlirough all 

 these intricate relations there runs an evident tendency 

 towards the production of higher and higher types, until, 

 at last, Man crowns the whole series. Seen, as it were, 

 at a distance, so that the mind can take a general survey 

 of the whole, and perceive the connection of the successive 

 steps, without being bewildered by the details, such a 

 series appears like the development of a great conception, 

 expressed in proportions so harmonious that every link 

 appears necessary to the full comprehension of its mean- 

 ing, and yet so independent and perfect in itself, that it 

 might be mistaken for a complete whole, and again so 

 intimately connected with the preceding and following 

 members of the series, that one might be viewed as 

 flowing out of the other. What is universally acknow- 

 ledged as characteristic of the highest conceptions of 

 genius is here displayed in a fullness, a richness, a 

 magnificence, an amplitude, a perfection of details, a 

 complication of relations, which baffle our skill and 

 our most persevering efforts to appreciate all its beau- 

 ties. Who can look upon such series, coinciding to 

 such an extent, and not read in them the successive 



