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 now 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 calling 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 
different 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 g7voup as is the family of crows. When 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 Sy/. 
via and Muscicapa of the Linnean school, for instance, 
are good examples of artificial groups: every small 
bird, with a slender bill, was placed in the first ; and all 
