No. 587] VARIABILITY AND AMPHIMIXIS 671 



TABLE IX 



Types (No. 3 and 8) with Variability in Separate Parental Types 

 (No. 1, 2, 6 and 7), in the First Hybrid Generations (No. 4 and 9) 

 and in the Second Hybrid Generations (No. 5 and 10). No. 3 and 8 

 Calculated from Data by Hayes in Tables noted. Other Constants 



XV-XVI 401+403 



XVII 403 X401 



XVIII 403X401-1- 



Here the constants of No. 3 and No. 8 have been ob- 

 tained by combining the two parental types (401 and 403) 

 both for the number of leaves and the height of the plant, 

 and it may be noted that the coefficient of variation has 

 dropped from 19.55 to 9.40 in the one case and from 17.35 

 to 13.60 in the other case. Thus variability as measured 

 statistically lias decreased. Those who have advo- 

 cated an increased variability as the result of hybridiza- 

 tion are correct when comparison is made of the F 2 gen- 

 eration with the F x generation or with a single parental 

 generation. They are not correct, however, in making a 

 general statement that cross breeding increases varia- 

 bility since the variability of the group composed of both 

 parental types must be considered and upon so doing, it 

 may normally be found that there has actually been a 

 decrease in variability. 



The possibility exists however that the variability will 

 appear to have been increased when forms having the 

 same phenotypebut different genotypes are bred together. 

 Such a condition may be illustrated by the two strains of 

 white sweet peas crossed by Bateson which produced 

 purple flowers in the first (F a ) generation, and purple, 



