208 READINGS IN 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 xutritive 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, ravra pei, 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 fleshis 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— 
