16 MODES OF RESEARCH IN GENETICS 



born in the experiment it becomes an absolute 

 logical impossibility ever to determine critically 

 whether any apparent result of the selection is 

 due, on the one hand, to a sorting out of preex- 

 istent hereditary differences, or, on the other 

 hand, to a cumulative change in the hereditary 

 determiners themselves. This proposition is not 

 only absolutely unassailable from the logical 

 standpoint, but that it is also practically demon- 

 strable, has, I think, been proved by Surface's 1 

 analysis of the Illinois corn work, East's and 

 Hayes' 2 selection experiments with tobacco, the 



than the correlation table, which is a device admirably calculated 

 under certain conditions — and those just the conditions which 

 obtain in the study of selection problems — to obscure to the point 

 of complete concealment facts which are perfectly clear and evident 

 so long as the individual is made the unit of study. To lump material 

 into a correlation table, with complete loss of any opportunity there- 

 after to get any useful knowledge about the individual, is only justi- 

 fied when from the nature of the material little or nothing is or can 

 be known about the individual case beyond the fact of its occurrence. 

 Then may we properly turn to the statistical method as a last resort 

 in the search for knowledge. But surely in fully pedigreed material 

 we are a very long way from knowing nothing about the individual. 

 On the contrary, we know a most important thing about each indi- 

 vidual ; namely, its own particular ancestry. 



The logical points regarding the statistical method here touched 

 upon are more fully discussed farther on. (See p. 69.) 



1 Surface, F. M. "The Result of Selecting Fluctuating Varia- 

 tions." Data from the Illinois Corn Breeding Experiments. IV e 

 Cong. Int. de Genetique, Paris (1911), pp. 222-237 (1913). 



2 East, E. M., and Hayes, H. K. "A Genetic Analysis of the 

 Changes Produced by Selection in Experiments with Tobacco." 

 Amer. Nat., Vol. XLVIII, pp. 5-48, 1914. 



