236 BREEDING 



ancestry behind the green in this case will make itself 

 felt by increasing the proportion of yellows and 

 diminishing that of greens in the second hybrid 

 generation produced." 



The actual result is entirely in accord with 

 Mendelian expectation. Our interest, of course, is 

 focused on the second hybrid generation. The first 

 is yellow, as in the normal cross. The ratio of greens 

 in the second hybrid generation is 24*88 per cent., 

 as close an approximation as is ever obtained to 

 25 per cent. This ratio, 24*88 per cent., is based 

 on what is, I believe, the largest second hybrid 

 generation that has been observed. It consisted of 

 139,837 individuals (in this case, of course, seeds), 

 the actual number of yellow ones being 105,045, 

 and of greens 34,792. 



To anyone brought up solely on Mendelian prin- 

 ciples — and it is possible that this book may, some 

 day, fall into the hands of such an one — this result will 

 not seem in the least unexpected. But I would remind 

 the reader that this is written at a time when the 

 number of people who have derived their notions of 

 heredity solely from teaching given in post-Mendelian 

 times (namely, since 1900) is very small, and that I 

 myself derived my ideas of heredity from teachers who 

 held exactly the same views on heredity as those 

 expressed in the last paragraph but one. 



The conformity of the result with Mendelian 

 expectation is seen directly we pay attention, not to 

 the somatic characters of the individuals in the 

 pedigrees on the preceding page, but to the contents 



