CHAPTER III 



NUMERICAL CONSEQUENCES AND RECOMBINATIONS. 



Representations of the F^ Generation and Novelties due 

 to Re-combination of Factors — Compound Characters — ■ 

 Combs of Fowls — Heterostylism — White Flowers from 

 Red X Cream. 



The unity of characters being recognized, we may next 

 examine some of the statistical consequences of this pheno- 

 menon. In order to determine the number of units and 

 allelomorphic pairs which are concerned in any practical 

 case, we have to be guided first by the visible statistical 

 composition of F^ ; and next by such tests of the gametic 

 constitution of the several F^ individuals as can be made by 

 breeding from them. 



To those who are familiar with algebraical methods, the 

 employment of F^ numbers to discover the number of terms 

 in the gametic series may present small difficulty, but to 

 others the following graphic method of demonstration 

 may be of service. For the introduction of this system, 

 which greatly simplifies difficult cases, I am indebted to 

 Mr Punnett. 



Take the simplest example, of one pair of allelomorphs, 

 say Tall ( T) and Dwarf (t). The parent zygotes of the 

 pure strains are then TT and tt. Their gametes are T, Z, 

 and /, t, respectively. The F^ heterozygote is Tt, and its 

 gametes are all either T or t in equal numbers. As this 

 is true both of the female germs and the male germs, there 

 are four possible combinations. Make therefore four 



