48 DARWINISM AND HUMAN LIFE 



Huxley compared a living creature to a whirlpool 

 ia a river ; it is always changing, yet always 

 apparently the same ; matter and energy stream 

 in and stream out ; the whirlpool has an individu- 

 ahty and a certain unity, yet it is wholly dependent 

 upon the surrounding currents. One may push 

 the whirlpool metaphor too far, so as to give a 

 false simplicity to the facts, for when vital whirl- 

 pools began to be there also emerge/i what cannot 

 be discerned in crystal or dewdrop — the will 

 to live, a capacity of persistent experience, and 

 the power of giving rise to other lives. To ignore 

 this is to attempt a falsely simple natural history. 

 But what Huxley's metaphor of the whirlpool 

 does vividly express is the dependence of living 

 creatures on their surroundings. We cannot under- 

 stand either the whirlpool or the trout apart from 

 the stream. 



When we think out this fundamental dependence 

 upon surroundings, we see, for instance, that all 

 our supplies of energy, all our powers of every 

 kind — with our own hands, or by the use of animal^, 

 or by means of machinery — are traceable to the 

 sun. Or again, it is easy to show that our society 

 depends fundamentally not on gold, but on iron. 

 We depend for food on plants and animals, and 

 through these animals on plants ultimately ; 

 the plants feed upon air, water, and salts, which, 

 with the aid of the energy of the sunlight, they 

 build up into complex organic compounds ; they 

 cannot do this unless the sun shines through a 

 screen of green pigment called chlorophyll ; there 

 cannot be chlorophyll without iron ; therefore our 

 whole social framework is founded on iron. 



Nutritive Chains. — Plants feed on their in- 



