No. 614] FACTOR MUTATIONS IN EVOLUTION 123 



clature we have the conception of evolution, recently sug- 

 gested by Bateson and expanded by C. B. Davenport, 

 which holds that ''the foundation of the organic world 

 was laid when a tremendously complex, vital molecule, 

 capable of splitting up into a vast number of kinds of 

 other vital molecules, was evolved," and that the process 

 of evolution may be described as the unpacking of this 

 "original package" by the process of loss of factors or 

 portions of factors. Various lines of evidence indicate 

 that changes in species are the result of some process of 

 factor changes. But those who adopt a physico-chemical 

 conception of factors and factor changes will find it un- 

 necessary to imagine the "primordial amoeba" in which 

 was laid the foundation of the organic world as possessing 

 in some mysteriously generalized condition all the genetic 

 factors that comprise the hereditary complex of the genus 

 Homo, since it is not by the "loss" or "fractionation" of 

 factors that hereditary changes have been wrought. A 

 gene does not "drop out" or " split up" into two or more 

 —rather a gene or factor is altered so that its reactions 

 conditio)/ a different somatic end product. It is not by 

 loss of factors, but by changes in the composition of fac- 

 tors, supplemented by intercrossing, that new races, new 

 varieties, and new species having the same chromosome 

 number, originate. 



Definite organization of the "hereditary substance par 

 excellence," the chromatin, probably occurred in certain 

 prototypes of existing organisms, in which the chromatic 

 substance was not differentiated from the remainder of the 

 cell plasm. The recent papers of Minchin on the evolution 

 of the cell and of Troland on the enzyme theory of life 

 show that the most probable early course of evolution was 

 from that unorganized state typical of the Chlamydozoa, 

 which are supposed to consist of free chromatin material, 

 i!]) through advancing degrees of differentiation between 

 the specialized hereditary substance and the remainder of 

 the protoplast. Between this fairly satisfactory concep- 

 tion of the earliest steps in evolution and the ever- 



