10 



NATURAL HISTORY OF VERTEBRATE ANIMALS 



introduction. As in the ensuing chapters on Morphology and 

 Physiology, the frog and man will be most frequently cited for 

 purposes of illustration. 



The Frog as a Representative Vertebrate 



Classification. — It is a familiar fact that animals fall into 

 restricted groups called species (singular, species, not " specie ")• 



E. Cyclostbme 

 Fig. 1.— Representatives of the Sub-phylum Vertehrata {cf. Figs. 2 and 3). 



Since the most effective manner of explaining what is meant by 

 the term species is through concrete examples of such animal 

 groups and their place in classification, we may proceed at once to 



