272 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 



doubt, be easy to divide the family of warblers in twenty 

 different ways, if mere division were the object; and thus 

 to increase or diminish the number of the groups : but 

 to do this in more ways than one, so that each division 

 shall be a circular group, is utterly impossible ; and it 

 therefore follows, that these groups, and their relative 

 value, exist as truly and as absolutely in nature, and are 

 as capable of being defined, as quadrupeds are from 

 birds, or fishes from insects. It will be our object, at 

 a more convenient season, to exhibit an analysis of the 

 second column. This analysis, in short, has been made : 

 and as the results have been procured by the same 

 means, we could not withhold from our readers so in- 

 teresting a coincidence of the definite number and rank 

 of natural groups, taken from two different classes ; al- 

 though the truth of one must at present be assumed. 



"(332.) Although we have not yet been able to detect 

 any circular groups below the rank of sub-genera, the 

 species composing these little assemblages, when they 

 are numerous, always present us with representations of 

 those primary types of form already defined, and to 

 which nature so tenaciously adheres. We see an ex- 

 ample of this in the bearded titmouse, which is the 

 natatorial or aquatic type of a sub- genus ; while Poda- 

 lirius llachaon, in like manner, is an aquatic or fissi- 

 rostral type. The student must not, however, look to 

 these two series with any expectation of tracing trans- 

 verse analogies : for although the two orders of Inses- 

 sores and Lepidoptera really happen to represent each 

 other, and are typical orders, the other groups are of 

 different denominations ; and therefore cannot, as we 

 have already explained, be analogous. 



(333.) In further proof of the universality of these 

 groups, both as regards their number and their rank, we 

 shall now produce two other series : one of which is 

 selected from the class of Mollusca, for the purpose of 

 ascertaining the rank of that lovely shell, the Harpula 

 Vexillum Swains. ; and the other from the sub-kingdom 



