THE FOUNTAIN OF CHANGE 239 



it has bred true. Our knowledge of the origin of 

 cultivated plants is meager, but there is considerable 

 reason to believe that they began in mutations. 

 We know that this was the origin of the Laciniate 

 Greater Celandine, which appeared without warning 

 in 1590 and has been breeding true ever since. 

 Some fluctuations seem to be transmissible, and to 

 reappear in varying degrees in the offspring, so that 

 the possibility of man's reaching a desired end by 

 persistent selection remains; but the balance of 

 present-day evidence inclines to the view that the 

 .essential step may be taken brusquely. The 

 momentous prehistoric origin of " thrashable " 

 wheat, for instance, may have come about abruptly 

 and in one plant. Similarly, in regard to the origin 

 of domesticated races of animals our knowledge is 

 very unsatisfactory, but there are strong reasons for 

 believing that the essential steps were due not to 

 sifting fluctuations, but to breeding from transilient 

 mutations. In recent years we have come to know 

 of mutants arising in wild species and persisting. 

 Thus the black mutant of the Peppered Moth 

 has been very successful, and a similar variety of 

 a certain West Indian Sugar-bird has practically 

 supplanted the parent species. Now, whatever we 

 may conclude as to the cause of these two novelties, 

 we cannot at all events say that they were the 

 results of a slow selection of individuals fluctuating 

 in the direction of blackness. It is one of the 

 marked changes in modern evolution-lore that 

 increasing importance is being attached to mutations 



