xxx MUTATION, MENDELISM, ETC. 



third generation would be pure thrum-eyed, and bred 

 together for any number of generations would yield no 

 other form ; another quarter would similarly be pure pin- 

 eyed, while the remaining half would have the appear- 

 ance of thrum-eyed, but when tested by breeding would 

 behave in the same manner as the second generation. 

 Pursuing this process to infinity, if it were possible to do 

 so, 1 we should be confronted by two sets of individuals 

 equal in number, one thrum-eyed, the other pin-eyed. The 

 word ' dominant ', then, only means that the individuals 

 which in each generation contain both conditions, the indi- 

 viduals whose offspring will in the course of future genera- 

 tions divide themselves equally between the two camps 

 — that these have the superficial appearance of one 

 condition alone, and that the thrum-eyed. The pin- 

 eyed condition, equally present, as is proved by breeding, 

 but not superficially evident, is called ' recessive '. 



' Dominant,' then, implies no permanent superiority, but 

 describes a superficial appearance which analysis proves 

 to be misleading. 



It has been necessary to say all this, although often 

 said before, because it is important to explain as clearly 

 as possible what is the nature of the ' solution ' at which, 

 accepting Lock's account, Bateson and Gregory have 

 arrived. And it is desirable that this knowledge should 

 be available for those who have not studied the elements 

 of Mendelism as well as for those who have. 



What does the ' solution ' amount to ? Merely this, 

 — the knowledge that the two conditions ' thrum-eye ' 

 and ' pin-eye ', so far as they follow Mendelian laws, do 



1 In this particular example there is little doubt that the experiment 

 would soon come to an end. Darwin's results, as stated in 6 on p. xxviii, 

 indicate that it would be impossible to produce many generations by 

 ' illegitimate ' unions. 



