I. THE ORIGIN OF VIRUSES 141 



highly probable that such particles can act as viruses. It may, how- 

 ever, be unreasonable to postulate these particles to be only agents 

 able to become viruses. Nucleic acid is contained in most abundance 

 in genes themselves and there is a good reason to consider that these 

 particles, the genes, have the greatest template action in the cell. 

 Therefore, genes are most likely to behave as viruses when they are 

 liberated from the cell. On the other hand, it has been suggested by 

 a number of authors that viruses may be genes that have gone wild, 

 acquiring in the process the ability to exist independently in the cell 

 and to move from cell. Thus the "free gene" theory has been advanced 

 by MuUer (32) and Duggar and Armstrong (33). 



