32 BREEDING 



other two are hybrids, and will produce dominants 

 and recessives in the proportion three to one, 

 just as the hybrids of the first hybrid genera- 

 tion did. 



We see, therefore, that when the recessive 

 reappears in the second hybrid generation (an 

 extracted recessive, as it is then called), we may 

 count on its being pure, and be confident that 

 it will breed true ; but we cannot tell whether 

 the dominants which occur in the second hybrid 

 generation are pure dominants or hybrids until 

 we have bred from them. This can be done in 

 the case of self-fertilising plants by allowing self- 

 fertilisation to take place and by sowing the seed 

 thus set. If dominants only are produced, it is 

 pure ; if dominants and recessives, it is hybrid. But 

 there is another way which is much more suitable 

 in the case of animals, in which the sexes are separate. 

 It has been found that if a hybrid of the first hybrid 

 generation is mated with a recessive, half of the 

 offspring are hybrids (bearing the dominant character, 

 of course), and half are recessives. 



