10 STRUCTURE OF THE VERTEBRATES 



scales of ectodermal tissue, and agree with the 

 following two classes in having fluid-filled 

 embryonic membranes surrounding the embryo; 

 and in being lung-breathing animals which never 

 develop gills. 



Class 5. Aves or birds are vertebrates with feathers. 

 Structurally they can be described as warm- 

 blooded reptiles with feathers. 



Class 6. Mammalia, the mammals, are w^arm-blooded ani- 

 mals with milk glands, and are usually covered 

 externally with hair. All mammals have some 

 hair, though it may be reduced to a few whiskers. 



The classification of man illustrates the method used, and 

 how any species can be identified with the use of a key to the 

 particular phylum. 

 Classification of Man: 

 Phylum — Chordata 



Sub-phylum — ^Vertebrata 

 Class — Mammalia 



Order — Primates (Monkeys, Apes and Man) 



Family — Hominidae (Extinct and living genera 

 of men) 



Genus — Homo (A few fossil types and all 

 living men) 



Species — sapiens (all living men.) 

 For proper identification both the genus and species are 

 always given, the genus capitalized, and written Homo sapiens. 

 The specific name may be given to other, widely different, 

 species; but by agreement there can be only one genus with 

 the name. 



A species is often divided into varieties or races. Living men 

 are all included in one species, though divided into four races: 

 Caucasian or white; ^Mongolian, the yellow, brown and red; 

 Ethiopian or African dark-skinned people; and the Negrito, or 

 blacks of the Pacific islands. Similar racial divisions may be 

 used whenever a species shows variations in different parts of its 

 range of habitat. 



