318 PRACTICAL AND SCIENTIFIC ZOOLOGY. 
looked upon as oracular. It may, nevertheless, hap- 
pen, even in systems grounded upon universal prin- 
ciples, that what appeared in the first instance an 
example of defective, unnecessary, or unnatural com- 
bination or arrangement, may be truly unexceptionable 
when viewed with reference to those general principles 
upon which the system itself is founded. 
(384.) Hence it becomes necessary that a general 
knowledge of the principles of natural arrangement 
should be first acquired ; for, as these principles are as 
conspicuous in the smallest groups of nature as they are 
in the largest, they form the basis of every true com- 
bination above that of a collection of individuals of the 
same species. If the student resolved, for instance, to 
confine his attention to the parrot family, of which there 
are probably 200 species, he will discover that the 
natural arrangement of these species, among themselves, 
is regulated precisely by the same laws as those which 
divide the classes of vertebrated animals. In like 
manner, if he studies the lepidopterous order of insects, 
he will find their natural series to tally not only with 
those of the parrots and the vertebrated classes, but 
also (and, of course, more intimately) with those of the 
apterous and the winged insects. A general idea, there- 
fore, of those fundamental principles of classification by 
which all these dissimilar groups. are naturally arranged, 
is indispensable. When this is acquired, the student is 
qualified to enter upon .the details of that particular 
portion he has selected for study ; he will receive an 
elevated pleasure in tracing these principles in the 
arrangement of the objects before him ; and he becomes, 
in some degree, qualified to judge of their correctness. 
Having, in the last chapter, intimated those requisites 
which should prepare him for this enquiry, we now 
proceed to a familiar explanation of these principles. 
The student, thus prepared, will be qualified not only 
to understand the former disquisitions in this volume, 
but will peruse those which succeed with feelings of 
interest he could not otherwise entertain. 
