16 ELEMENTARY ZOOLOGY 



formed, and the body must be so arranged or composed 

 as to be capable of performing these necessary life- 

 processes. All animals take food, digest it, and assimi- 

 late it, that is, convert it into new body substance ; all 

 animals take in oxygen and give off carbonic acid gas; 

 all animals have the power of movement or motion (not 

 necessarily locomotion) ; all animals have the power of 

 sensation, that is, can feel; all animals can reproduce 

 themselves, that is, produce young. These are the 

 necessary life-processes. It is evident that the toad could 

 still live if it had no eyes. Seeing is not one of the 

 necessary functions or processes of life. Nor is hearing, 

 nor is leaping, nor are many of the things which the toad 

 can do ; and animals can exist, and do exist, without any 

 of those organs which enable the toad to see and hear and 

 leap. But the body of any animal must be capable of 

 performing the few essential processes which are necessary 

 to animal life. How surprisingly simple such a body can 

 be will be later discovered. But in most animals the 

 body is a complicated object, and is able to do many 

 things which are accessory to the really essential life- 

 processes, and which make its life complex and elaborate. 



