CHEMICAL ORIGIN OF LIFE 17 



material. The complexity of the protein 

 molecule is enormous, and its capacity of 

 entering into chemical or physical combina 

 tions with other molecules is so great that in 

 it we seem to see the possibilities of the evolu 

 tion of something possessing the primitive 

 characteristics of life. We can imagine such 

 molecules combining by aggregation until the 

 aggregate becomes unstable and divides into 

 two aggregates, each possessing all the original 

 properties of the first, and being capable of 

 similarly growing and dividing. If the con 

 ditions are such that this process can go 

 on continuously, and that new protein can 

 constantly be produced, as is actually the case 

 in vegetable tissues, natural selection will soon 

 come into play, and the evolution of a less 

 imperfect, and more definite and complex, 

 form of organism will gradually take place. 



A further part of the case for the mechan 

 istic theory consists in criticisms of alternative 

 theories. The traditional opponents of the 

 mechanistic theory may be classed as either 

 vitalists or animists. The former maintain 

 that the behaviour of living organisms is so 

 peculiar, and so different from anything met 



