CHILDHOOD AND YOUTH 5 



divisions of science are concessions to the human mind rather than 

 forms of nature. 



Further consideration of the first group need not detain us 

 long. The very small animals known as amoebae (Fig. 2), the 

 largest of which are visible as specks to the naked eye, are mere 

 droplets of granular protoplasm, creeping over the mud in fresh 



M 



I 



-. ,-- 



m 



FIG. 2. Reproduction of Amoeba (highly magnified). To the left a full-grown 

 amoeba ; to the right successive stages of division. 



water or in the sea, or lurking in the bodies of other animals or of 

 plants. The soft, jelly-like material of which they are formed 

 makes it possible for little particles of food to be engulfed wherever 

 these come in contact with the surface of the body. The simple 

 business of their life is to creep in search of food, to digest the food 

 as quickly as possible, and to grow bigger. But although the 

 different kinds of amoeba differ in size, there is a limit beyond 

 Which each kind does not grow. When that limit has been reached, 

 or sometimes before it has been reached for reproduction is a good 

 deal more complicated in its causes than a mere escape from incon- 



