126 PLANTS, THE FOOD OF ANIMALS 



nitrates, sulphates, phosphates and other salts and into free 

 ammonia, carbon dioxide and water. All are returned to the 

 earth or atmosphere to be again taken up by the green plants 

 and animals and drawn once again through the living vortex 

 of matter and energy. 



The food of Hydra thus is only a link in the endless chain 

 of matter- and energy-transformations shown in the diagram 

 (p. 1 1 8). Above and through it all is the silent penetrating 

 agency of the sun, the source of all energy. 



