80 EVOLUTION 



the roots; whereas animals obtain their 

 nitrogenous supplies from the complex pro- 

 teids formed within other organisms. Most 

 plants, therefore, feed at a lower chemical 

 level than do animals, and it is characteristic 

 of them that, in the reduction of carbon 

 dioxide and in the manufacture of starch 

 and proteids, the kinetic energy of sunlight 

 is transformed by the living matter into the 

 potential chemical energy of complex food- 

 stuffs. Animals, on the other hand, get their 

 food ready-made; they take the pounds 

 which plants have, as it were, accumulated 

 in pence, and they spend them. For it is 

 characteristic of animals that they explo- 

 sively convert the potential chemical energy 

 of food-stuffs into the kinetic energy of loco- 

 motion and other activities. In short, the 

 great distinction — an average one at best — • 

 is that most animals are more active than 

 most plants. 



Changing the point of view a little, we may 

 notice that, because of their mode of nu- 

 trition, typical animals are bound to be 

 active and locomotor either in whole or in 

 part. Similarly we may say that the plant- 

 cell, by shutting itself up in a wall of cellulose, 

 instead of fully oxidizing this substance, 

 and perhaps also by less efficient elimination 

 of nitrogenous waste, doomed itself to fixity 



