LIFE 357 



description of how it came to be a factor in organic 

 evolution. Now there are two elements in natural selection 

 — environment, which may be either organic or inorganic, 

 and death, as a process of eliminating those less fitted to 

 this environment. In the case of purely inorganic sub- 

 stances we can conceive that, under the physical conditions 

 which follow the azoic period of a planet, all sorts of 

 chemical products with varying physical structures might 

 appear. Scientifically we might describe these products 

 as the complex dances of corpuscular groups. In the 

 meeting of group and group some groups would retain 

 their individuality, others would lose it or be dissolved 

 and possibly re-combined in new forms. Any group 

 which retained its individuality would be spoken of 

 physically as a stable product ; and in the early history 

 of a planet, although we are far from being able to describe 

 accurately what might actually take place, it is not un- 

 reasonable to suppose that a physical selection of stable 

 and destruction of unstable products might go on. We 

 do not know why one element is more stable than a 

 second, why it is better suited to its environment (we 

 might describe the stability by aid of atomic accelerations, 

 but this would not explain, only resume it) ; we can only 

 suggest a selection of certain compounds which, because 

 they are selected, we describe as more stable. Now this 

 selection of stable compounds is a very possible feature 

 of physical evolution,^ but it must be noted that it is not 

 precisely the same as natural selection. The environment 

 is in this case purely inorganic, and " death " corresponds 

 to the dissolution and ultimate reabsorption into more 

 stable compounds. The competing substances form, in- 

 deed, their own environment ; and it is the special structure, 

 not the corpuscle, which is conceived to disappear in the 

 struggle. This physical selection is possibly the truest 

 description of the stages which led up to the complex 

 chemical substances endowed with special molecular 



1 It has been applied witli remarkable power by Crookes {British Associa- 

 tion Address, Section B, 1886), to give a suggestive sketch of how even the 

 chemical elements might be conceived as evolved from profylc or prime-atoms. 



