DIFFEREN'T BANK OF GROUPS. 269 



tected in nature : for although, when a sub-genus is very- 

 perfect, it sometimes contains the five types of form 

 common to all circular groups ; yet, as vie have just 

 observed, no instance has yet been pointed out, wherein 

 each of these types is also circular. 



(329-) It is clearly impossible to define any of these 

 groups by characters which are applicable to all such as 

 hold the same rank ; nor can their value be known by 

 any other rules than those resulting from analysis and 

 comparison. The characters which belong to a family 

 in one tribe, are totally different from those which cha- 

 racterise a family in the next; while such as are 

 exhibited in a third, will be very different from either. 

 Nor can we tell, at first sight, the difference between a 

 tribe and a family ; or whether any particular form is 

 the representation of a genus or a sub-genus. The 

 true rank of a natural group, in short, can only be de- 

 tected by analysis and analogy ; and the more extensively 

 these enquiries are carried into the neighbouring groups, 

 the more hkely are we to understand its true rank. But 

 as this mode of investigation is not only laborious, but 

 too difficult to be extensively prosecuted, it is the cus- 

 tom with most writers to throw several genera into a 

 group, and call that group a family, or a sub-family. 

 This is all very well, and really useful, if it be consi- 

 dered, as it truly is, but a temporary expedient, — a 

 mode of abridging labour, by assuming what has not 

 been proved, and pointing out to the reader the most 

 probable station of the group or species under his con- 

 sideration. But no faith can be placed in such tables or 

 scales of gradation*, until their circular arrangements 

 and analogies have been made out by analysis. We 

 shall now proceed to make some general remarks upon 

 these groups. 



(3.30.) The common consent of mankind has sanc- 

 tioned tlie belief in the three kingdoms of nature, — the 



* Sucl), for instance, as that in tlie Introduction to Entomology, 

 vol. iv. p. ci'J'j. > 



