166 CLASSIFICATION. 



species ; thus, the name of Chickweed is Stellaria 

 media. Because there are mostly several species in 

 a genus ; so that if the name of the genus only were 

 used, the species meant would be uncertain ; and as 

 there are often species of the same name in different 

 genera, if the name of the species only were used, the 

 genus meant would be doubtful. 



The classification of animals and plants serves two 

 important purposes : one is that the structural pecu- 

 liarities and affinities of the groups may be contrasted 

 and a knowledge of their absolute and their differ- 

 ential characters acquired, and for this a natural 

 system is eminently serviceable ; the second is that of 

 enabling any animal or plant to be simply distin- 

 guished from any other, for which an artificial or 

 analytical system is extremely useful. 



