744 Fluctuations 



selection of species complies as closely as possi- 

 ble with existing terminology, and does not 

 seem liable to any misunderstanding. 



It is a selection between species. Opposed to 

 it is the selection within the species. Manifest- 

 ly the first should precede the second, and if this 

 progression is not conscientiously followed it 

 will result in confusion. This is evident when 

 it is considered that fluctuations can only appear 

 with the pure and normal type in pure strains, 

 and that each admixture of other units is liable 

 to be shown by the form of the curves. More- 

 over, selection chooses single individuals, and a 

 single plant, if it is not a hybrid, can scarcely 

 pertain to two different species. The first 

 choice therefore is apt to make the strain pure. 



In contrasting selection between species with 

 that within the species, of course elementary 

 species are meant, including varieties. The 

 terms would be meaningless if it were taken to 

 mean that the real systematic units are indi- 

 cated. In this sense we might designate the 

 last named process with the term of intra- 

 specific selection, and it is obvious that this term 

 is applicable both to natural and to artificial 

 selection. 



Having previously dealt with species-selec- 

 tion at sufficient length, we may now confine our- 

 selves to the consideration of the intra-specific 



