PART I 



STRUCTURE, FUNCTIONS, AND DEVELOP- 

 MENT OF ANIMALS 



CHAPTER I 

 THE STUDY OF ANIMALS AND THEIR LIFE 



Our familiar knowledge of animals and their life. 



We are familiarly acquainted with dogs and cats; less 

 familiarly probably with toads and crayfishes, and we 

 have little more than a bare knowledge of the existence 

 of such animals as seals and starfishes and reindeer. But 

 what real knowledge of dogs and toads does our familiar 

 acquaintanceship with them give ? Certain habits of the 

 dog are known to us: it eats, and eats certain kinds of 

 food ; it runs about ; it responds to our calls or even to 

 the mere sight of us ; it evidently feels pain when struck, 

 and shows fear when threatened. Another class of 

 attributes of the dog includes those things that we know 

 of its bodily make-up: its possession of a head with eyes 

 and ears, nose and mouth ; its four legs with toes and 

 claws; its covering of hair. We know, too, that it was 

 born alive as a very small helpless puppy which lived for 

 a while on food furnished by the mother, and that it has 

 grown and developed from this young state to a fully 

 grown, fully developed dog. We know also that our 

 dog is a certain kind cf dog, a spaniel, perhaps, while 



