4 PLANT AND ANIMAL LIFE 



Building materials of animals. Certain of the or- 

 ganic substances produced by plants, such as starch, oil 

 and sugar, together with such inorganic materials as 

 water, lime and other salts, are used by animals as food 

 and from them they build up their bodies. 1 The bodies 

 thus built may be so simple as to consist of but a single 

 speck of living matter or so complicated as to have the 



FIG. 2. Ameba at rest and branching (viewed from above). After micro-photo- 

 graphs by Dellinger. 



various organs and tissues possessed by the higher ani- 

 mals and man. 



A simple type of animal. One of the simpler ani- 

 mals which has been most studied because it is commonly 

 found in stagnant waters, is the ameba. The ameba has 

 neither eyes nor ears, nose nor mouth, head nor legs, 

 but is just a minute mass of a living jelly-like substance 

 called protoplasm. Within this is a more solid body 

 known as the nucleus. The entire mass is filled with 

 granules and when at rest is more or less spherical in 

 form. When active, it assumes various shapes and is 

 able to move about by throwing out from its body pro- 

 jections which serve as feet. Although it has no mouth, 

 it is able to swallow particles of food when they come 

 in contact with its body and later to expel their undi- 

 gested portions. This bit of independent, self-directing 

 1 Many animals also eat the flesh of other animals. 



