236 STUDY OF NATURAL HISTORY. 



CHAP. V. 



ON THE CHARACTERS OF NATURAL GROUPS. 



(162.) The characters by which natural groups, 

 like those we have hitherto contemplated, are 

 to be known and designated, has been a fruitful 

 subject of disquisition among writers. It has 

 been customary, until within the last few years, for 

 naturalists to decide, a priori, upon those charac- 

 ters which a group of species, or a single one, 

 should possess, in order to constitute a genus. This 

 mode of proceeding, as may naturally be supposed, 

 led every one to follow his own opinion ; so that 

 almost every part of an animal, in turn, had been 

 singled out as the most important for this purpose. 

 Thus, Linnaeus founded his genera of birds entirely 

 on the form of the bill and the construction of the 

 feet ; totally disregarding the formation of their 

 wings, — which is one of the chief characteristics 

 of birds, — and entirely overlooking their manners, 

 habits, and food. In entomology, however, he con- 

 structed his genera on a totally different principle. 

 Here he considers the wings of insects as affording 

 the most important characters ; and he has accord- 

 ingly founded all his great divisions, and most of his 

 lesser ones, in the different modifications which these 

 members present; while the mouth and the feet, 

 which were so highly regarded in his arrangement 

 of birds, are scarcely noticed in his classification of 



