240 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 



series of animals, we can never compare a typical group 

 in one circle with an aberrant group in another ; for 

 these groups, being of different denominations, would 

 destroy at the very outset the harmony of the com- 

 parison : it would render the law in question indeter- 

 minate, and, therefore, no law. Every perfect group 

 has its own typical and aberrant forms ; and these are 

 represented by the typical and aberrant forms in an- 

 other perfect group. When, therefore, the toucans 

 {RamphastideB), as a whole, are made to represent the 

 entire group of Conirostres, the analogy or represent- 

 ation is false ; because the Ramphastidce are admitted 

 by all to be an aberrant family in the scansorial circle ; 

 and the Conirostres are likewise admitted to be the 

 typical group of another circle. But when, on the other 

 hand, the Conirostres are stated to represent the Inses- 

 sores, then the analogy is true, because both of these 

 groups are pre-eminently typical in their respective 

 circles : although unequal in their rank or extent, they 

 are equal in their denomination. This rule, however, 

 by no means affects the comparison of the contents of a 

 typical with those of an aberrant group ; for as each 

 have types of perfection, so these types should justly 

 represent each other. To vary our examples, we shall 

 take an instance from two famihar animals in the class 

 of quadrupeds. The Ferce and the Ungulata are two 

 natural orders ; but one is typical, and the other aber- 

 rant : yet as each of these are circular, so their re- 

 spective typical and aberrant groups may justly be 

 compared as representing each other ; and this they ac- 

 cordingly do. The tiger is one of the typical forms of 

 Ferae, and we see how beautifully it corresponds to the 

 zebra, which is a typical form in the Ungulata. This 

 analogical resemblance does not consist merely in 

 the remarkable similarity of stripes on the two ani- 

 mals, but actually extends to their moral character : 

 both are vicious, wild, and untameable, and both are 

 inferior to that form which is pre-eminent in each 

 genus ; namely, the lion in one, and the horse in the 



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