THE FRAGRAXT CALLA 25 



We have every reason to believe that the 

 races of flatfish now existing have recently — 

 in a geological sense — developed their observed 

 condition of having the eyes thus located; indeed, 

 proof of this that amounts to demonstration is 

 furnished by the fact that the young flatfish even 

 to this day is born with its eyes located like those 

 of other fishes, the migration of the eye, so to 

 speak, taking place as the individual develops the 

 racial habit of Ipng on its side. 



But as I said, it is unquestionably difficult to 

 conceive how the useful distortion came about 

 unless it began suddenly as a "sport" or muta- 

 tion. This is one instance among many. 



And so Professor de Vries's observation, which 

 proved that mutations do sometimes seem to 

 occur "spontaneously" in nature, was seized on as 

 affording a solution of one of the puzzles of 

 evolution, and the mutation theory was pretty 

 generally regarded as a valuable supplement to 

 the Darwinian theory of evolution. 



It should be clearly understood, however, that 

 neither Professor de Vries liimself nor anyone 

 else speaking with authority, has thought of the 

 mutation theory as in any sense contradicting the 

 Darwinian theory of natural selection. On the 

 contrary", it is to be regarded as supplementing 

 and supporting that theory. If creatures are 



