20 MODES OF RESEARCH IN GENETICS 



perhaps too much to say that the law of segre- 

 gation and recombination would never have been 

 discovered by study of the ancestry alone, but 

 such a result would at any rate have been highly 

 improbable. 



The difference in viewpoint between the bio- 

 metric and Mendelian methods has its most im- 

 portant practical consequence in the fact that it 

 renders possible the application of the experi- 

 mental method in the latter case, while practically 

 excluding it in the former. One can experiment 

 in regard to one's progeny but not in regard to 

 one's ancestors. Herein lies the great advantage of 

 Mendelian method as a mode of research. While 

 Mendelism is philosophically a statistical method 

 primarily, as has already been pointed out, it is 

 not solely such, but instead formulates its problem 

 in such a way as to permit the experimental mode 

 of attack. 



The essential thing which Mendelian studies 

 of heredity do is to determine the distribution 

 of hereditary differences amongst the progeny of 

 a particular individual or pair of individuals. 

 In other words, it studies the distribution of 

 hereditary specificities. This is obviously a higher 

 level of attack on the problem than the biometric. 

 Because it is so is the reason that it has been so 

 much more fruitful of results. 



That the method is essentially statistical is 

 evident. It deals with masses of individuals, 



