252 ESSAYS OF A BIOLOGIST 



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subsidiary direction towards the production of more 

 and more complex forms of matter. If our general 

 ideas are correct, there must have been a time when 

 matter in our ordinary sense of the word did not 

 exist — there can have been no atoms, only free elec- 

 trons. From this state, there evolved one in which 

 the various electron-systems that we call atoms first 

 appeared; later still, atoms could join with atoms to 

 produce molecules. Leaping over vast periods, we 

 would come to the time when radiation had brought 

 the temperature of the earth surface below 100 de- 

 grees centigrade; water then could form from steam 

 and solution occur. Through solution, all soluble 

 elements, which would othen\dse remain locked in the 

 inactivity of the solid state, are enabled to enter upon 

 a new phase of mobility, of chemical life, as we may 

 say. Only in water could colloid carbon compounds 

 first be built up, and only from such substances could 

 life originate. 



Living substance, or at least much of it, must be 

 formed of molecules containing thousands of atoms, 

 each atom in its turn a system of circling electrons. 

 Here already is a vast increase of complexity: it re- 

 mains to be seen whether the same tendency is per- 

 petuated later. 



The evolutionary concept is to biology what the 

 doctrine of the conservation of energy has been in 

 the physico-chemical sciences — an indispensable pre- 

 liminary to proper methods of attack. But while 

 great stress has been laid on the various methods by 



