CORRELATED VARIABILITY. 59 



Gen. 1. 



3en. 2 



Gen. 3. 



31 y (hybrid) peas produced 12 plants; 

 these bore: 



77.5 y (hybrid + y) peas ( =75.8%) 247 g (pure-blooded) 



21 plants were produced: peas ( =24.2%). 



7 (33%) pure- 14 (66%) hybrids^ 



blooded y, because they 20 plants bore : 



because they bore: 



bore : | 



292 y peas 462 y 149 g 670 green peas. 



(hybrid + y) (pure-blooded) 

 peas (=76.4%) peas (-23.6%) 



It is clear that if this process of crossing of the hybrids 

 continues, the proportion of hybrids to the whole population 

 will diminish; for the share of pure-blooded forms breeds 

 true; while the originally equal share of hybrids is repeatedly 

 halved. 



If the hybrid is crossed with one of the parents instead of 

 with another hybrid, we will get 



(1) (d+r)d=d, d+d, r, and 



(2) (d + r)r=d, r+r,r. 



in (1) all of the progeny will appear of the dominant type. 

 In (2) one-half will appear of that type. This again agrees 

 with experiment. 



Second Case. The two parents differ in respect to two 

 characters case of dihybrids. Imagine a lot of ripe germ- 

 cells with the antagonistic qualities of any pair separated 

 according to the second principle stated at the outset. A 

 indicates the one pair of qualities and B the other; then we 

 shall have nine classes of zygotes, the proportion of each of 

 which is as follows: 



A. 25%d,d 



B. G.25%d, d; 12.5%J, r; 6.25%r, r. 

 A. 



B. I2.5%d, d; 25%d, r; 12.5%r, r. 

 A. 25%r, r 



B. 6.25%d,d', 12.5%d,r] 6.25%r, r. 



