Multiplication of Extremes 743 



of the results of the choice of extremes, which it 

 may be easily seen is a matter of the greatest 

 practical importance. This choice is generally 

 designated as selection, but as with most of the 

 terms in the domain of variability, the word 

 selection has come to have more than one mean- 

 ing. Facts have accumulated enormously since 

 the time of Darwin, a more thorough knowl- 

 edge has brought about distinctions, and di- 

 visions at a rapidly increasing rate, with which 

 terminology has not kept pace. Selection in- 

 cludes all kinds of choice. Darwin distin- 

 guished between natural and artificial selection, 

 but proper subdivisions of these conceptions are 

 needed. 



In the fourth lecture we dealt with this same 

 question, and saw that selection must, in the first 

 place, make a choice between the elementary 

 species of the same systematic form. This 

 selection of species or species-selection was the 

 work of Le Couteur and Patrick Shirreff, and is 

 now in general use in practice where it has re- 

 ceived the name of variety-testing. This clear 

 and unequivocal term however, can hardly be 

 included under the head of natural selection. 

 The poetic terminology of selection by nature 

 has already brought about many difficulties that 

 should be avoided in the future. On the other 

 hand, the designation of the process as a natural 



