342 
THE GEOLOGIST. 
I 
and vegetable kingdoms are constructed, and which have been 
selected by naturalists as the principles on which to ground ihose 
arbitrary divisions and sub-divisions of scientific aiTangement so 
necessary for facilitating the acquirement of knowledge and for the 
progress of investigation. 
All animated or hving things belong to one of two markedly dis- 
tinct groups — the animal or vegetable ; hence in scientific nomen- 
clature the greatest distinctions are given to these thoroughly 
decided divisions, and they are consequently termed kingdoms. 
Taking either plants or animals it is apparent that of either we have 
many sorts, and also that these sorts are evidently constructed on 
different plans, as for example seaweeds and trees, insects, Crustacea, 
starfish, shells, quadrupeds ; hence we have principal divisions into 
sub-Jiingcloms, classes, and orders. Taking the members of any one 
of these divisions, we find that, though there may be a common 
resemblance on the whole, yet the typical form, upon which all of 
them are more or less constructed, is nevertheless variously modi- 
fied, and that numerous forms, although subservient to the type, are 
still modelled more directly upon some certain deviation or pecu- 
liarity. For example, the class Mammalia has the characteristic 
features of the Vertebrata in the possession of an internal bony 
skeleton, consisting of a cranium, vertebral column, and two fore 
and two hind limbs for teiTcstrial locomotion. But how distinctly is 
this veHehrate tyj^e modified to suit the particular exigencies, habits, 
and conditions of other vertebrate classes, such as fish, reptiles, 
birds, whales, man. Each of these classes again displays maiiy dis- 
tinctive modifications, as, for example, the eagle and the sparrow, 
the herring and the shark ; hence arise other subdivisions or orders, 
and these again exhibit siibservnent modifications, as for instance the 
eagle and the hawk. Those which have thus a great resemblance 
for each other are included in one fnmihj, and are distinguished from 
ench other by a generic name, or in other words each family is made 
up of different sorts or (jenera. These again are susceptible of divi- 
sion by individual or special characters, whence the denomination of 
species, the still minor variations of which — brought about by 
difference of existence, physical conditions, or local circumstances — 
are indicated by the term vari'rfles. 
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