THE CLASSIFICATION OF ANIMALS. 235 



But there are types within types. Thus, there are five 

 modifications of the Vertebrate type Fish, Amphibian, 

 Reptile, Bird, and Mammal; and these are again divided 

 and subdivided, for Mammals, e. g., differ among them- 

 selves. So that in the end we have a constellation of 

 groups within groups, founded on peculiar characters of 

 less and less importance, as we descend from the general 

 to the special. 



Individuals are the units of the Animal Creation. An 

 animal existence, complete in all its parts, is an individual, 

 whether separate, as Man, or living in a community, as the 

 Coral. 127 



Species is the smallest group of individuals which can 

 be defined by distinct characteristics, and which is sepa- 

 rated by a gap from all other like groups. A well-marked 

 subdivision of a species is called a variety. Crosses be- 

 tween species are called hybrids, as the Mule. 



Genus is a group of species having the same essential 

 structure. Thus, the closely allied species Cat, Tiger, and 

 Lion belong to one genus. 



Family, or Tribe, is a group of genera having a simi- 

 lar form. Thus, the Dogs and Foxes belong to different 

 genera, but betray a family likeness. 



Order is a group of families, or genera, related to one 

 another by a common structure. Cats, Dogs, Hyenas, and 

 Bears are linked together by important anatomical features; 

 their teeth, stomachs, and claws show carnivorous habits. 



Class is a still larger group, comprising all animals 

 which agree simply in a special modification of the type 

 to which they belong. Thus, Fishes, Amphibians, Rep- 

 tiles, Birds, and Mammals are so many aspects of the Ver- 

 tebrate type. 



Subkingdom is a primary division of the Animal King- 

 dom, which includes all animals formed upon one of the 

 various types of structure ; as Vertebrate. 



