THE 
ZOOLOGIST’S TEXT-BOOK. 
INTRODUCTORY. 
OF THE ANIMAL KINGDOM IN GENERAL. 
Systems are conventional arrangements, to enable naturalists 
the more easily to classify species,' so that their identity may he 
traced, and compared, and investigated. As new species were 
discovered, the task of ascertaining them became so difficult 
and uncertain, that the necessity of Systems was the more 
apparent. Accordingly, systematic arrangement was practised 
to a limited extent before the time of Linnaeus, but to him we 
are indebted for the production of a new and comprehensive 
classification. He reduced all natural objects into three great 
divisions : these he called Kingdoms; viz. the Animal, Vege¬ 
table, and Mineral Kingdoms. These kingdoms he divided into 
Classes, Orders, Genera, Species, and Varieties. 
\ A plurality of species constitute a genus, a variety of genera 
an order, and several orders a class. When, therefore, an ob¬ 
ject presents itself, with which we are totally unacquainted, our 
first business is to consider what is the class to which it be¬ 
longs -. having ascertained this, we next compare it with the 
characters of the orders ; and having determined to which it is 
allied, we proceed to investigate its generic characters : when 
we have satisfied ourselves as to this, we come to the last and 
most difficult point, namely, the discovery of its species ; which 
often rests on very trivial distinctions. 
A 
