PHYSICAL SELECTION AND GEOWTH 229 



according to these side-chain combinations — that the different 

 benzene derivatives are formed. 



It is interesting to note that even among these relatively 

 simple carbon compounds — those familiar with chemistry will 

 appreciate the virtue of that term " relatively " — we find already 

 that there is indication of selective activity. I mean this, that 

 once one of these bodies or derivatives has been formed and 

 becomes partially broken down, it is found more easy to obtain 

 new associations after the original type rather than new associa- 

 tions of a different order. Even among the simpler carbon 

 compounds we see the faint origin of what, biologically, we speak 

 of as habit. The same is true of radicles in general. Once 

 certain compounds are formed, the adhesions or attachments are 

 more close, more fixed. So now to continue. Let us suppose 

 this simple annule of living matter with certain side-chains 

 already attached, floating about in a fluid medium in which, 

 through a concatenation of circumstances, various odd ions are 

 similarly floating free. The unsatisfied arms of the ring are 

 liable to be satisfied, that is, to attract and fix on certain other 

 ions. All that we have to do is to suppose this particular annule 

 attaches to one unsatisfied arm a floating ion of carbon, that this 

 then so attaches itself to other carbon ions until a second ring is 

 formed in association with the first. Then this ring similarly 

 attaches to itself side-chains in the identical order seen in the 

 first instance. 



Now behold, there is built up a second annule of identical 

 nature, which, when once formed, may break loose. In place of 

 one annule we have two, and as the properties of any chemical 

 compound depend upon its composition, the composition deter- 

 mining how, and how much, energy is liberated under certain 

 conditions, so, if the composition of the first annule, as we 

 agreed, was such as to confer upon it the properties we term 

 vital, the second annule will possess the identical properties. 

 In place of one living molecule we have two ; in short, we have 

 growth. 



But stop, you will be saying. By what earthly right do you 

 assume that chance ions floating in a fluid medium come to 

 attach themselves one to the other in due and regular order, so 

 as to form a ring with side-chains identical with the original 

 ring with its side-chains, with which the first of these wandering 



