INTRODUCTION. 11 



In studying each animal, if we ask, (1) What is its food, 

 how obtained and how used ? How does it get oxygen from 

 the air? How does it get rid of waste and worn-out mate- 

 rial from its body? (2) How does it reproduce its kind? 

 How numerous are its progeny and to what danger exposed? 

 (3) How does it move ? What are its specially movable 

 parts ? (4) What powers of sense, of instinct, and of intel- 

 ligence has it, and what sort of a nervous system as the 

 seat of these powers ? and if we follow patiently where 

 Nature leads until we have found satisfactory answers to 

 these questions, we shall arrive at a better comprehension 

 of the animal's activities, and in the end shall have learned 

 many lessons of perennial interest and profit. This four- 

 fold division of animal phenomena will be of service as an 

 outline for our future study, leading us to learn for each 

 animal all we can about 



I. Nutrition, and its subservient organs. 

 II. Reproduction, and the adaptation of the reproduc- 

 tive process to varying conditions of life. 



III. Voluntary Motion and motor organs. 



IV. Sensation, as manifest through a nervous system in 

 senses, instinct, and intelligence. 



