CHARACTERS OF DISTINCT PAIRS 109 



the fact that when two individuals, each of which 

 possesses one of them, are mated, a hybrid is produced 

 in which one of them, which is called the dominant, 

 exists to the more or less complete exclusion of the 

 other. 



This is the general conclusion, as to the relation 

 between the two characters of a pair, which was 

 derived from a consideration of Mendel's own experi- 

 ments with peas. Now, it will be seen that from the 

 breeder's point of view it is very desirable to possess 

 some sign by which a dominant character may be 

 known before the crosses are made ; also one is 

 naturally curious to know what it is that makes one 

 character of a pair dominant and the other recessive. 

 A conception of the nature of dominant, in contra- 

 distinction to recessive, characters has already been 

 hinted at in the explanation which was given of the 

 result of crossing a fowl with a " pea " comb with 

 one with a " rose " comb. The two pairs of characters 

 involved in that cross were supposed to be the 

 character of the comb known as " pea " (dominant) 

 and the absence of that character (recessive) ; and 

 the character of the comb known as " rose " 

 (dominant) and the absence of that character (reces- 

 sive). In both cases the presence of a particular 

 character constituted the dominant member of the 

 pair, and the absence of that character the recessive 

 member. The dominant character is due to the 

 presence of something — the recessive to the absence 

 of that something. It is not easy at present to see 

 how this conception may be applied to the pairs of 



