26 ANIMAL KINGDOM CLASSIFICATION. 



AJHMAL KINGDOM, 



CLASSIFICATION. 



SUB-KINGDOMS. In classifying animals they are first divided into 

 four large groups, called Sub-kingdom*. These are: 



I. Sub-kingdom Vertebrata. 



II. Sub-kingdom Articulata. 



III. Sub-kingdom Mollusca. 



IV. Sub-kingdom Radiata. 



The first of these four great divisions is so named because all 

 the animals which compose it, without exception, possess an in- 

 ternal skeleton, that is, a bony framework covered with flesh, like 

 that of man, and consequently a vertebral column i.e., a column 

 composed of vertebras. This is the origin of the name of vertebrate, 

 which is applied to this sub-kingdom. It comprises Four Classes 

 Mammals, Birds, Reptiles, and Fishes. The sub-kingdom Arti- 

 culata is composed of animals whose body is formed of segments, 

 or separate rings, arranged in a regular series. Moreover, they 

 have no internal skeleton, and, on the contrary, the external parts 

 are generally the hardest and toughest, as in the crayfish and 

 the centipede. Sometimes these animals are only protected by a 

 hard skin, like that of the earth-worm, or the leech. The princi- 

 pal classes of this sub-kingdom are Insects, Crustacea, and 

 Worms. 



