18 MODES OF RESEARCH IN GENETICS 



all others. This directly implies a necessity for 

 the application of statistical methods. It means 

 that it will always be necessary in studying 

 heredity to use as large a number of individuals 

 as possible and so determine average effects of 

 the different causal factors. We have, of course, 

 in genetics a special case of the general proposition, 

 more fully developed in a later chapter (cf . infra, 

 pp. 54-61), that in practice the statistical method 

 is a logically necessary adjunct to the experi- 

 mental method generally. 



What we have to distinguish clearly between 

 is, on the one hand, the biometric school of 

 genetic study, which stands off by itself in sharp 

 distinction to other modes of attacking the prob- 

 lems of heredity, and which is criticized in what 

 has preceded ; and, on the other hand, the statisti- 

 cal method as a general method of science, which 

 as such is indispensable, as well in the study of 

 genetics as elsewhere. 



To summarize : it is believed that our analysis 

 has shown that the purely statistical mode of 

 attacking the problem of heredity, as it has actu- 

 ally been developed, finds its chief limitations in 

 that, first, it deals only with the most superficial 

 aspects of the problem, and second, that the par- 

 ticular method pursued is based upon a logically 

 and biologically unsound assumption. At the 

 same time statistical methods in general are found 

 to be essential in dealing with the problems. 



