242 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 



most part, to one department of zoology; and have, 

 therefore, been unprepared to state in what manner 

 the forms therein contained re-appear, as it were, under 

 an almost infinite variety of modifications, in other di- 

 visions of the animal kingdom, totally different from 

 that which has been the object of their peculiar study. 



(299-) Before proceeding, however, to the main ob- 

 ject before us, a few observations become necessary on 

 the characteristic properties of the different denomin- 

 ations of groups. In using the term denomination, we 

 apply it not to the rank or station of a group among 

 its congeners, but solely in reference to its typical or 

 aberrant nature; in other words, whether it exhibits 

 the greatest perfection of any particular structure, or 

 whether this perfection is deteriorated, so to speak, by 

 the admixture of other characters belonging to a neigh- 

 bouring group. 



(300.) As every natural group is first divided into 

 three circles, so it follows that there are three primary 

 denominations of groups ; and these, as we have already 

 explained, are called the typical, the sub-typical, and 

 the aberrant : by these names we express their denomi' 

 nation, and we shall now treat of each in detail. 



(301.) I. The first distinction of typical groups is 

 implied by the name they bear. The animals they con- 

 tain are the most perfectly organised : that is to say, are 

 endowed with the greatest number of perfections, and 

 capable of performing, to the greatest extent, the func- 

 tions which peculiarly characterise their respective circles. 

 This is universal in all typical groups ; but there is a 

 marked difference between the types of a typical circle, 

 and the types of an aberrant one. In the first we find a 

 combination of properties concentrated, as it were, in cer- 

 tain individuals, without any one of these preponderating, 

 in a remarkable degree, over the others ; whereas in the 

 second it is quite the reverse : in these last, one faculty is 

 developed in the highest degree, as if to compensate for 

 the total absence, or very sUght developement, of others. 



(302.) Let us exempHfy this proposition by fami- 



