DIFFERENT KINDS OF LIVING MATTER. 25 



referred in the scheme of another, since men differ 

 greatly, not only in knowledge, but in opinion. 



Types represent general plans of structure. Classes 

 are formed by the special modification of a type. 

 Orders are groups of the same class related by a com- 

 mon structure. A Family or Genus is a still smaller 

 group having generally the same essential structure. 

 A Species is the smallest group whose structure is 

 constant. Species are so much alike that they may 

 have descended from the same parents. Individuals 

 are the units of organic life, forming a complete ani- 

 mate existence. Peculiarities of races or breeds are 

 called varieties. Vegetables and animals are distin- 

 guished from each other by the term Kingdom, and 

 the types in each kingdom are called Sub-kingdoms. 



4. The names which naturalists use to designate 

 kinds or groups of living things are formed from the 

 Latin or the Greek language. There ^re good rea- 

 sons for this. In the modern languages common things 

 have many different names. But the majority of 

 plants and animals are new or rare, and have no name 

 in any modern language. If there must be a new 

 name it may as well be Latin or Greek as any other. 

 Then the latter languages have the advantage of ex- 

 pressing by their combinations some peculiarity which 

 is distinctive, and which is readily recognized by the 

 learned. As to the difficulty of learning these terms, 

 it is only apparent. They can easily be mastered by 



