270 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 
animal, the vegetable, and the mineral. These divi- 
sions are palpable ; and our belief in them is not to be 
disturbed by the subtleties of philosophy or the argu- 
ments of metaphysicians. From this point, therefore, 
if we wish to pursue the synthetic mode of investi- 
gation, we may start, as from an incontrovertible truth. 
The animal kingdom is admitted to be a circular group: 
its first divisions are, therefore, into sub-kingdoms. 
Vertebrated animals form one of these swb-kingdoms ; 
and annulose animals, or insects, generally speaking, 
another. These are next divided naturally into classes, 
of which description are quadrupeds, birds, fishes, rep- 
tiles, and Amphibia in one; and winged insects, apter- 
ous insects, barnacles (Cirripeda), &c. in the other. 
So far we can have no doubt as to the kingdom, sub- 
kingdom, or class to which an animal, whose rank we 
wish to ascertain, belongs ; and we will suppose this to 
be the common-bearded titmouse (Parus biarmicus). 
Every one sees that this is a bird not formed either for 
swimming, wading, or running upon the ground: we 
consequently conclude that it perches, and refer it at 
once to the division of birds named, from this circum- 
stance, Insessores ; and by this means arrive at its 
order. Its perfect and well-proportioned feet guide us 
to the particular tribe of JInsessores which is distin- 
guished by these characters; and we then proceed, by 
still further examining its structure, to refer it to the 
family of warblers, and to the sub-family of titmice 
(Pariane).* The sharp conic bill, and other minute 
peculiarities of structure, show that it belongs to the 
genus of Parus ; and to that little group, or sub-genus, 
which contains the most typical examples, or Pari 
proper. But even a sub-genus, as we have already 
seen, contains in its own little circle, when perfect, a 
representation of all the types of nature; and thus the 
bird before us, as representing the natatorial or aquatic 
type, inhabits the marshy borders of lakes and rivers, 
* Northern Zoology, vol. ii. p. 203. 
