24 LUTHER BURBANK 



There were many reasons why the muUtion 

 theory appealed to oootemporaiy biologists, thus 

 aooouDting for its very cordial reception. 



For example, there are numberkas instanres 

 in nature where the development of a uaeful 

 organ is exceedingly hard to explain on the basis 

 of natural aelectton* because the organ in itit 

 incipient stages could have no titili' ^ 

 a modification in the location of an organ — ^y 

 the shift in the flatfidi*s e>*e 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 ha%'e 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 fiat 

 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 fiatfish having both eyes 

 on one side. 



