An Introduction to a Biology 



that it is impossible while this process is going on to term 

 anything whatever Mendelian as far as theory is concerned." x 



But should we be right in refusing to commend the 

 efforts of a well-digger if, in sinking his well, he alternately 

 used a spade, a pickaxe, and dynamite, according as he 

 had to deal with gravel, sandstone, or granite, provided 

 that he found, or even that he thought he would find, water 

 at last ? 



The aims of the Mendelian and the well-sinker are the 

 same to discover something ; and they each employ a 

 definite method, but the tools they use are continually being 

 changed. That is why I think that the method is at least 

 as essential a part of Mendelism as the theory. And that 

 is why I think that there is no more connection between 

 Pearson's generalised theory of alternative inheritance (with 

 special reference to Mendel's Law), and Mendelism, than 

 there is between the second law of thermo-dynamics and 

 the Maxwellian demon's knowledge of atoms plus the method 

 by which he has acquired it. 



There is a definite relation between a generalised theory 

 of alternative inheritance and that particular doctrine on 

 which it is based : it is the same as the relation between 

 the second law of thermo-dynamics and the theory held, 

 ex hypothesi, by the demon as to the nature of the atom. 



But there can be no relation between any generalised 

 theory of inheritance and Mendelism 2 unless that term 

 signifies the Mendelian theory only ; and, even so, this re- 



1 Pearson, :036, p. 53. 



2 I do not, of course, intend to imply that Pearson tries to establish 

 any relation between a generalised theory of inheritance and Mendelism : 

 I know his was a generalised theory of alternative inheritance based on the 

 theory of the pure gamete. All I wish to insist on is that the theory which 

 Mendelians happen to be testing at the moment is, to my mind, not the 

 essential thing in Mendelism. If the commonly accepted explanation of 

 the proportion 1DD : 2DR : 1RR were shown to be false, would experi- 

 ments, called Mendelian, now in progress be prosecuted with less zeal ? 

 By no means. Such a discovery would even be an incentive to more 

 strenuous search. 



