PREFACE vii 



vertebrates to select one species as a type to be examined in 

 considerable detail, and then to compare species belonging 

 to the other classes with it. The animal usually chosen for 

 detailed study is the frog, and this form has therefore been 

 treated more fully in this book than any other vertebrate type. 

 The vertebrates are, as a rule, larger than the invertebrates, 

 are fewer in number, and are usually more interesting to be- 

 ginning students ; they are, on the whole, better known than 

 the invertebrates and more easily observed. For these reasons 

 they have been discussed largely from the natural history stand- 

 point, and it is hoped that this treatment will give students 

 a better idea of the everyday events in the lives of the more 

 common vertebrates than can be obtained from a purely morpho- 

 logical course. 



A book covering such a large field as this one must necessa- 

 rily be more or less of a compilation, and the facts and figures 

 must be selected from numerous textbooks and scientific peri- 

 odicals. The sources from which the author has obtained a 

 large part of his material are as follows : 



Bourne, G. C. Comparative Anatomy of Animals, 2 vols., 1909. 

 Bronn, H. G. Klassen und Ordnungen des Tierreichs. 

 Calkins, G. N. Protozoa, 1901. 



- Protozoology, 1909. 

 Cambridge Natural History, 10 vols. 

 Dean, B. . Fishes, Living and Fossil, 1895. 

 Dickerson, M. C. The Frog Book, 1907. 

 Ditmars, R. L. The Reptile Book, 1907. 



- Reptiles of the World, 1910. 



Flower, W. H., and Lydekker, R. Mammals, Living and Ex- 

 tinct, 1891. 



Hertwig, R. Manual of Zoology, 1905. 

 Holmes, S. J. Biology of the Frog, 1906. 

 Jennings, H. S. Behavior of the Lower Organisms, 1906. 

 Jordan, D. S. Guide to the Study of Fishes, 2 vols., 1905. 



- and Evermann, B. W. Fishes of North America, 4 vols., 

 1900. 



