1915~\ Outline on the Theory of Descent 17 



cient to warrant classifying the form as a species distinct 

 from the parent type. 



From the flood of criticism that fell upon the "origin" 

 two ideas may be singled out for consideration. First is the 

 view that imperceptibly small variations in the direction of 

 producing a new structure could be of no possible service and 

 therefore would have no selection-value. Second, that geo- 

 logic time is too short for the evolution of the complex living 

 forms that we know out of simple undifferentiated organisms. 

 Without entering into a discussion of these objections, sufiice 

 it to say that their weight was felt to be great by many Dar- 

 winians. To such, and many others, the mutation theory was 

 most welcome. 



MUTATION 



It was ably presented to you at the Wake Forest meeting 

 five years ago by President Poteat. I shall therefore at this 

 time attempt only a brief outline. The mutation theory is 

 the great life-work of Hugo De Vries of Holland already 

 referred to in connection with the rediscovery of Mendel's 

 results. Appearing in 1901 it embodied the extensive ex- 

 perimentation of the preceding twenty years. As a basis 

 for the operation of natural selection, De Vries takes the 

 more striking variations, the previously called "sports" to 

 which he gave the name — mutants — such for example as the 

 sudden appearance of a rose-comb in an apparently pure bred 

 race of single comb fowls, or a white English sparrow, sev- 

 eral times recently reported in "Science," and which I ob- 

 served some months ago on the streets of Durham. Darwin 

 was familiar with this phenomenon and cited numerous 

 cases in his "Animals and Plants under Domestication," but 

 after mature deliberation and after it had been urged upon 

 him by some of his closest scientific friends, he reached the 

 conclusion that "sports" were without important effect on the 

 origin of species — an opinion it would now seem destined 

 to receive recruits. 



These sports or mutants breed true from the beginning 

 and thus furnish a foundation for the view that new species 



