SYMBIONTICISM IX RELATIOX TO HEREDITY 119 



points to a smaller unit than the chromosome, whatever 

 the nature of this unit may be. The genes have been 

 thought of in terms of atoms or molecules. The work ac- 

 comphshed in genetics in which genes have been accepted 

 as the transmitting unit, has enabled biologists to appreciate 

 the nature of the mechanism concerned in hereditary varia- 

 tions. But we must raise the question: Do hereditary 

 variations lead to evolutionary variations? 



The variations that have been experimentally produced 

 by deVries and others, apparently, are hereditary variations, 

 explainable on the basis of the behavior of genes. But 

 have these mutations represented true species? Ivlany 

 modern biologists are not convinced that they are stable 

 species. Such mutations maj^ breed true for a time, but 

 it appears that these variations are not of the character 

 nor of the rank of evolutionary variations. We must 

 attempt to look further into the hypothetical nature of 

 genes, and attempt to correlate "genes" with evolutionary 

 variations. 



It appears from a perusal of the Uterature that ''genes" 

 are to be considered as some sort of molecular entities, 

 of the same nature in all forms of life, but varying in their 

 arrangement and grouping in the chromosomes of different 

 species. This conception, apparently, carries with it the 

 idea that new genes are never added to the chromosomes, 

 but that the genes in an amoeba are the same as those in 

 man; the essential difference being the arrangement and 

 grouping in the chromosomes. It is believed also that the 

 genes may be modified by intrinsic environmental factors. 

 Morgan, perhaps, had this conception of genes in mind 

 when he said, "Evolution consists largely in introducing 

 new factors that influence characters already present." 



This conception of "preformed" or limited genes has 

 led to more or less bizarre hypotheses on the mechanism of 

 organic evolution. 



