128 



Cuvierlan System of Zoology, 



the latest observation appears in 1800. The least variation is 

 in the time of the appearance of the migratory birds, and the 

 hatching of young rooks. The greatest range is in the blos- 

 soming of the turnip, the appearance of the yellow butterfly, 

 and the singing of the thrush. 



INDICATIONS OF SPRING, 



Art. III. The Cuvierian, or Natural^ System of Zoology, 



. Essay 3. The Characters of Vertebrated Animals^ and their Divi- 

 sion into Four Classes ; Mammijerous Animals^ Birds, Reptiles, 

 and Fishes. Distinctive Characters of each Class, By B. 



Having given in the preceding essays Baron Cuvier's ge- 

 neral view of animal physiology, and stated the principles on 

 which he establishes four grand divisions of the animal king- 

 dom, I shall, in the present essay, comprise his more ample 

 description of the characters of the first division, Verte- 

 brated Animals ; also the distinctive characters of each of the 

 four classes into which they are divided. It will be shown 

 that this division into four classes is justly founded upon the 

 internal organisation, and not upon the external forms, of ani- 

 mals ; and the reader will not fail to perceive the importance, 

 indeed the absolute necessity, of an acquaintance with the lead- 

 ing facts in animal physiology, if he would obtain a correct 

 knowledge of zoology as a science. 



