96 EVOLUTION OF BRITISH CATTLE 



The following table shows the average numbers 

 of calves of each of these colours that may be 

 produced by all the possible matings : — 



Thus it will be seen that, although by crossing 

 white cattle and red a new colour, roan, is 

 produced, that new colour itself is unstable and 

 throws back constantly to one or other parent 

 race. A similar result follows when white cattle 

 are crossed with black : the intermediate hybrid, 

 as it is called in Mendelian phraseology, being in 

 this case a blue roan. 



But, although these intermediate hybrids are 

 unstable, they may be the means of transferring 

 the colour of one kind of cattle from that kind to 

 another kind. The transference of the white 

 colour of the Roman cattle to the black Welsh 

 cattle is a simple case. A white Roman bull 

 breeds with black Welsh cows and produces blue- 

 roan calves. These again breed together, and 

 25 per cent, of their calves are white. In other 

 respects some of these white calves are Romans, 

 some Welsh, and thus, in two generations only, 

 some black Welsh catde may be turned white. 



Perhaps, for exposition's sake, a more striking 



