THE BEGINNINGS OF LIFE. 95 



one of the atoms of hydrogen by an atom of methyl, so 

 producing methyl-amine, N(CH 3 )H 2 ; and then under 

 the further action of methyl, ending in a further substi- 

 tution, there is reached the still more compound sub- 

 stance dimethyl-amine, N(CH 3 )(CH 3 )H. And in this 

 manner highly complex substances are eventually built 

 up. Another characteristic of their method is no less 

 significant. Two complex compounds are employed to 

 generate, by their action upon one another, a compound 

 of still greater complexity ; different heterogeneous 

 molecules of one stage, become parents of a molecule 

 a stage higher in heterogeneity. Thus having built up 

 acetic acid out of its elements, and having by the 

 process of substitution described above changed the 

 acetic acid into propionic acid, and propionic into 



butyric, of which the formula is I^S^ltSS 3 ^; 



( UJ (HO) \ 



this complex compound by operating upon another 

 complex compound, such as the dimethyl-amine named 

 above, generates one of still greater complexity, butyrate 



of dimethyl-amine | C ( 3 ^<^ 3)H j N(CH 3 ) (CH 3 )H. 



See then the remarkable parallelism. The progress 

 towards higher types of organic molecules is effected 

 by modifications upon modifications; as throughout 

 Evolution in general. Each of these modifications is 

 a change of the molecule into equilibrium with its 

 environment an adaptation, as it were, to new sur- 

 rounding conditions to which it is subjected ; as through- 

 out Evolution in general. Larger, or more integrated, 



