372 EVOLUTION, GENETICS, AND EUGENICS 



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 understand either the whirlpool or the trout apart from 

 the stream. 



When we think out this fundamental dependence upon surround- 

 ings, 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 animals, 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 chloro- 

 phyll without iron; therefore our whole social framework is founded 

 on iron. 



Nutritive chains. — Plants feed on their inanimate environment 

 in a direct way that is impossible to animals, so we pass insensibly 

 from dependence on surroundings to those nutritive chains which bind 

 living creatures together in long series often quaintly suggestive of 

 "The House That Jack Built" and similar old rhymes. We have 

 ceased to wonder at the circulation of the blood in our body; have we 

 begun to wonder enough at the ceaseless circulation of matter in the 

 system of nature ? As Heraclitus said, -iravra pel, all things are in flux. 

 "The rain falls; the springs are fed ; the streams are filled and flow to 

 the sea; the mist rises from the deep and the clouds are formed, which 

 break again on the mountain-side. The plant captures air, water, and 

 salts, and, with the sun's aid, builds them up by vital alchemy into the 

 bread of life, incorporating this into itself. The animal eats the plant 

 and a new incarnation begins. All flesh is grass. The animal becomes 

 part of another animal, and the reincarnation continues." The silver 

 cord of the bundle of life is loosed, and earth returns to earth. The 

 microbes of decay break down the dead, and there is a return to air 

 and water and salts. We may be sure that nothing real is ever lost; 

 we are sure that all things flow. Penelope-like, Nature is continually 

 unravelling her web and making a fresh start. 



Nexus between mud and clear thinking. — To keep a famous 

 inland fish-pond from giving out, some boxes of mud and manure were 

 placed at the sides. Bacteria — the minions of all putrefaction — 



