146 DOMESTICATED ANIMALS AND PLANTS 



oi x^ -\- 2 xy + j^, in which x'^ and jj/^ are pure as to this character, 

 though descended from mixed parents on both sides. 



Now the x'^- part of this offspring, having no y characters, will 

 continue to breed pure x as well as if no y were involved in the 

 make-up of its ancestry, and likewise for the y'^. 



The 2 xy part of this generation is hybrid like the parents, 

 and, when bred together, will reproduce again the same general 

 character of offspring as their hybrid parents of the last genera- 

 tion, namely, x'^ + 2 xy-\-y'^; that is to say, when hybrids of 

 nonblending characters are bred together they will produce three 

 kinds of offspring. One will be like the one pure parent ; another 

 will be like the other pure parent, and the third group, consti- 

 tuting one half the total numbers, will remain hybrid. The two 

 others will breed pure, but the hybrid will not. 



Dominant and recessive characters. In truth, it is seldom in 

 practice that all these three classes stand clearly out. Some char- 

 acters are dominant over others ; that is, more easily detected, 

 such as strong colors over weak, huge size over small, etc. 



Suppose now that we take such a case, representing the 

 dominant or easily detected character by the letter JJ, and the 

 recessive, as it is called, or the obscure character by the letter r. 

 The result of breeding Dr hybrids with themselves will then 

 be I)^+2nr+r^. 



Now what will this kind of a population look like ? The 17^, 

 being pure, will of course be easily seen. The same is true of 

 the r^, though less distinct, because the recessive characters are 

 less conspicuous ; that is, 2 5 per cent of the population is clearly 

 D^ and another 25 per cent is as certainly r^. But what about 

 the remaining 50 per cent } 



Clearly this 50 per cent {Dr) will look like pure D, because 

 the r character, though actually present, will not be noticed, 

 being recessive. 



Accordingly the whole population, instead of looking like 

 25 /)2+ ^oDr+ 2^r^, as it really is, will appear like 75 i^ + 

 2 5 r^, the eye being unable to distinguish between the 2 5 /> and 



