326 PRACTICAL AND SCIENTIFIC ZOOLOGY. 



are trifling ; but it must be remembered that no facts 

 supplied by one part of creation to illustrate another 

 part, can deserve that epithet. On the contrary, the 

 more simple the illustration, and the more familiar the 

 example, the greater force does analogical reasoning 

 acquire. 



(395.) The nature of a circle of affinity, and the 

 number of natural divisions which compose all such 

 circles, have novr been sufficiently explained. As these 

 constitute the first principles of natural arrangement, the 

 student would do well, by frequent perusal, to retain 

 them in his memory, or he may consider these familiar 

 illustrations as introductory to the fuller exposition, 

 already given on these subjects, in the second portion 

 of this volume. 



{396.) We shall now lead the student a step farther, 

 by calHng his attention, first, to the properties of 

 natural groups ; and, secondly, to the means by which 

 such groups are to be detected and proved. An atten- 

 tive consideration of the relations subsisting between 

 diflferent groups of animals has led to the discovery of 

 certain properties peculiar to each of those which we 

 have, in the last section, denominated typical and aber- 

 rant. A few of the most remarkable circumstances so 

 elicited we shall now briefly explain. 



(397») By the word group, the reader is to under- 

 stand an assemblage, large or small, of individual 

 species or higher assortments, possessing among them- 

 selves certain characters definite and peculiar. The term 

 is used, in a general way, to express either a class, an 

 order, a family, a genus, or any other division which 

 is employed in system, the class of birds being as 

 much a group as is the family of crows. WTien such 

 an assemblage is formed upon characters or circum- 

 stances which have no general reference to primary 

 laws, the group is termed artificial. The genera Syl- 

 via and Muscicapa of the Linneean school, for instance, 

 are good examples of artificial groups : every small 

 bird, with a slender bill, was placed in the first ; and all 



