360 THE FIRST ORGANISMS 



circle and branching only occurred at definite points on the 

 circle leading to the constantly repeated formation of this 

 or that metabolic product. This constant repetition of con- 

 nected reactions, co-ordinated in a single network, also led 

 to the emergence of a property characteristic of living things, 

 that of self-reproduction. This may be taken as the origin 

 of life. At this stage in the evolution of matter natural 

 selection assumed its full biological meaning and formed the 

 basis for the faster elaboration of higher and higher degrees 

 of adaptation of living organisms to the conditions under 

 which they existed, of the exact correspondence of all the 

 details of their internal structure to their vital functions. In 

 other words, there appeared that striking ' purposefulness ' 

 of the structure of living bodies upon which we have already 

 remarked. 



The opinion is fairly widely held in contemporary scien- 

 tific literature that the capacity for self-reproduction is to 

 be found even in the chemical form of the motion of matter, 

 that it can be a property of isolated molecules. Until com- 

 paratively recently many biologists regarded the constant 

 formation of particular substances within the organism as 

 being the result of the presence in the organism of ready- 

 made moulds for those particular substances. These moulds 

 were supposed to ' multiply ' in some way and thus be 

 responsible for the constancy of the composition and structure 

 of the organism and for its reproduction. 



In particular this opinion was once very clearly expounded 

 by N. Kol'tsov.^" He believed that the formation, not only 

 of proteins, but also of other components of the living cell, 

 such as chlorophyll and the anthocyanins, occurred because 

 the protoplasm already contained corresponding molecules 

 which acted as templates for their formation. These mole- 

 cules * multiplied ' and thus exactly reproduced their own 

 structures. 



The factual evidence of contemporary biochemistry was, 

 however, radically opposed to this opinion and revealed a 

 completely different mechanism of biosynthesis based on the 

 constancy of certain sequences of biochemical reactions. For 

 example, butyric acid is formed by some species of bacteria, 

 not because it was present in them beforehand, but because 



