INTRODUCTION TO CLASSIFICATION. 



CHAPTER II. 



THE CHAEACTEES OF THE CLASSES OF THE INVEETEBRATA. 



MORPHOLOGICAL classification, then, acquires its highest import- 

 ance as a statement of the empirical laws of the correlation of 

 structures ; and its value is in proportion to the precision and 

 the comprehensiveness with which those laws, the definitions of 

 the groups adopted in the classification, are stated. So that, 

 in attempting to arrive at clear notions concerning classification, 

 the first point is to ascertain whether any, and if so, what 

 groups of animals can be established, the members of which 

 shall be at once united together and separated from those of all 

 other groups, by well-defined structural characters. And it 

 will be most convenient to commence the inquiry with groups 

 of that value which are commonly called CLASSES, and which 

 are enumerated in an order and arrangement, the purpose 

 of which will appear more fully by and by, in the following 

 table. 



TABLE OF THE CLASSES OF THE ANIMAL KINGDOM. 



The Limits of the Four Cuvierian Sub-Kingdoms are indicated 

 by the Brackets and Dotted Line. 



BADIATA. 



Gregarinida. Infusoria. 

 Rhizopoda. 

 Radiolaria. 

 Spongida. 



Hydrozoa. 

 Actinozoa. 



Polyzoa. 



Scolecida (?). 

 Eehinodermata. 



Choetognatha. 

 Annelida. 



Crustacea. 

 Arachnida. 

 Myriapoda. 

 Insecta. 



ARTICULATA. 



