10 A MANUAL OF MENDELISM 



ratios for the two pairs, thus (putting initial letters for 

 the characters) : 



3 R + 1 w 

 3 Y + Ig 



9 RY + 3 Rg + 3 wY + 1 wg ; 



that the progeny of hybrids whose parents differed in 

 three pairs are ranged in a series which is developed by 

 combining the ratios for the three pairs, thus (putting 

 C for coloured and c for white) : 



9 RY + 3 Rg + 3 wY + 1 wg 

 3 C + 1 c 



27 RYC + 9 RgC + 9 wYC + 3 wgC + 9 RYc + 

 3 RgC + 3 wYc + 1 wgc ; 



and so on. 



This statement might be simplified still farther, thus : 

 The result of the first pair of characters is to divide the 

 hybrids' progeny into two groups in which the dominant 

 group is to the recessive in the ratio 3:1. The result 

 of the second pair is to subdivide each of these two 

 groups again in the ratio 3:1, and, if the number in the 

 smallest group is to be represented by the figure 1 as 

 unit, the numbers in the other groups must be trebled ; 

 and so on, for any number of pairs, thus : 



