CLASSIFICATION. 3 



the field mouse, Mus sylvaticus ; and the harvest 

 mouse, Mus messorius, all of which are species more 

 or less resembling the Mouse, but all distinguishable 

 from each other by minor characters ; these, there- 

 fore, constitute a genus. 



An Order is a far more extensive group, including 

 several genera, allied to each other by some important 

 feature in their economy. The rats and the mice, 

 for example, are all remarkable for their chisel-like 

 front teeth, but there are other animals that have 

 their teeth of the same construction, although they 

 have not the same long and tapering tail, e.g., the 

 squirrel, the beaver, the hare, and the porcupine; 

 these, therefore, form the order Rodentia, or animals 

 distinguished by their chisel-like teeth. 



A Class embraces all the Orders related to each 

 other by some grand and general character possessed 

 by them all in common. Thus, the Kodentia suckle 

 their young, but so do dogs, so do monkeys, hedge- 

 hogs, cats, whales, elephants, cows, ant-eaters, and 

 kangaroos ; a circumstance whereby they are dis- 

 tinguished from birds» reptiles, or fishes. All animals 

 that give suck are, therefore, associated to form one 

 gi-eat class — the Mammalia. 



Or we may take the converse of all this. Thus, in the 

 animal kingdom there is a Class of creatures recog- 

 nisable by the circumstance that they suckle their 

 young ; among these is an Order, distinguished by 

 having chisel-like teeth in the front of their mouths ; 

 belonging to this Order is a Genus, remarkable for 

 the possession of a long tapering tail, and the smallest 

 Species belonging to this genus is the harvest mouse, 

 Mus Messorius. An arrangement such as this en- 

 ables us to find out the name of any animal, and is 

 called a system, which, in fact is a dicti'onary with 

 this difference, that here the properties enable us to 

 find out the name, whereas in ordinary dictionaries, 

 the known name serves to acquaint us with the 

 properties. Thus, the study of Zoology is one 

 eminently calculated to accustom the mind to habits 



B 2 



