GROUPS FAMILIARLY EXPLAINED. 327 
those with broad bills were referred to the second ; and 
in neither were habits, analogies, or general structure, 
taken into the account. On the other hand, we deem a 
natural group to be an assemblage which is represented 
by other groups in different classes of animals ; and 
which is characterised not by one or two peculiarities, 
but by distinctions drawn both from economy and struc- 
ture. The toucans, the humming-birds, the lamelli- 
corn floral beetles, and numerous others, are natural 
groups, not so much because they are obvious to the 
inexperienced eye, as because they represent analogically 
other groups in totally different departments of nature. 
Strictly speaking, and using the term in its true sense, 
no group can be termed natural, until its circular tendency 
is detected, and its analogical relations pointed out. 
(398.) We are thus led to seek farther information 
upon the question — How are we to prove that a group is 
natural? One naturalist selects oneset of characters, which 
by another are slighted ; some look only to the internal 
structure, others confine their characters to the external; 
and all are prepared with reasons in support of their 
different theories. How are we then to discover which 
are the essential requisites or properties of a natural 
group? Now, as the series in which natural objects 
follow each other is circular, it follows that the circu- 
larity of a group is its primary requisite. Every group, 
therefore, which, upon close investigation, does not form 
its own particular circle, or which does not exhibit a 
tendency thereto, may be considered artificial ; while, 
on the contrary, every one which has its affinities re- 
turning into itself, exemplifies the first general law of 
nature, and wears the aspect of being natural. 
(399.) The first property, therefore, which we must 
look for in a natural group, is, that the affinities of the 
objects it contains proceed more or less in a circle. It 
is rarely that a group, which from other circumstances we 
know to be natural, contains so few subjects, and these 
so wide apart from each other, as to prevent us from 
detecting their tendency to a circle; while, on the 
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