24 LUTHER BURBANK 



There were many reasons why the mutation 

 theory appealed to contemporary biologists, thus 

 accounting for its very cordial reception. 



For example, there are numberless instances 

 in nature where the development of a useful 

 organ is exceedingly hard to explain on the basis 

 of natural selection, because the organ in its 

 incipient stages could have no utility. Similarly 

 a modification in the location of an organ say 

 the shift in the flatfish's eye until both eyes are 

 on one side is difficult to explain as a process 

 taking place by infinitesimal stages, on the basis 

 of natural selection. 



A slight shift in position of the eye of the flat- 

 fish would have no utility whatever. It is only 

 when the shift has become sufficient to bring the 

 eye on the upper side of the fish that the creature 

 would have any advantage over other flatfish 

 whose eye is on the under side. 



If we imagine a mutation in which a fish 

 appears with an eye distorted in location suffi- 

 ciently to be usable while its owner lies flat 

 on its side in the mud, we can readily under- 

 stand how such a mutation might be favor- 

 able to the individual and thus might furnish 

 material for the development through natural 

 selection of a race of flatfish having both eyes 

 on one side. 



