8o BREEDING 



that the character borne by the hybrid is not essential 

 to the Mendelian phenomenon ; in the three cases 

 which we are considering the hybrid has been 

 either (a) indistinguishable from one parent, or (h) 

 intermediate between the two, or (c) it has borne 

 the character of the remote ancestral form of both. 

 What is common to all three cases is the reappearance 

 in the second hybrid generation of the " dominant " 

 parental character, the hybrid character (when 

 different from this) and the " recessive " parental 

 character in the ratios of 25 per cent., 50 per cent, 

 and 25 per cent, respectively — a phenomenon to 

 which the term segregation has been applied. 



The fact that the hybrid frequently bears 

 characters which are peculiar to itself, and the 

 occurrence of segregation, are the two features of 

 the results of crossing which lead to the production of 

 novelties ; and they correspond, in the main, to two 

 distinct practical methods. In the first of these 

 methods the novelty is obtained in the first hybrid 

 generation by virtue of the fact that the hybrid bears 

 characters peculiar to itself. The hybrid in these cases 

 is usually not reversionary, but intermediate between 

 the two parents, as in the case of the Andalusian 

 fowl, and that of the roan colour in cattle, which is 

 produced by crossing red with white, and which, when 

 m.ated with roan, gives 25 per cent, red, 50 per cent, 

 roan, and 25 per cent, white. The novelty which 

 arises in this way is unstable. 



In the second of these practical methods the 

 novelty is not obtained till the second hybrid genera- 



