MEASUREMENT OF VARIABLE PROPERTIES 139 



sorts exist, but as often as a germ cell D meets an R, the 

 property R is latent ; and in a similar way r is latent when d 

 meets r. Therefore the 9 sorts are reduced to 4 — viz. 



The seeds DH'^ are Dd (round, yellow) 



zDRd^ 

 2DHr 

 4DdRr 

 RW 

 2drR^ 



J52y2 



2DRr^ 

 R^r^ 



) 



) 



Dd ( 

 Dd ( 



Dd ( „ „ ) 



Rd (wrinkled, yellow) 

 Rd ( „ „ ) 



Dr (round, green) 

 Dr ( „ „ ) 



Rr (wrinkled, green) 



1+2+2+4 _ 9 



rS T5" 



1+2 _ 3 



T8 TW 



1+2 _ 3 



~T~S T8" 



1 1 



TV ~ IB 



(Compare (4), p. 120.) The numerical value of each term is 

 the frequency of the corresponding sort of seeds — viz. 



Round, yellow (Dd) 

 Wrinkled, yellow (Rd) 

 Round, green (Dr) 

 Wrinkled, green (Rr) 



or 9 : 3 : 3 : 1 (relative frequencies). 



In MENDEL'S experiment (556 seeds yielded by 15 Fj 

 plants) the figures were ^ : 



Observed Calculated ' 



Rr (wrinkled, green) 

 Dr (round, green) 

 Rd (wrinkled, yellow) 

 Dd (round, yellow) 



Considering the four above groups with reference to their 

 hereditary possibilities, we discern : — 



Among the plants raised from round, yellow seeds : 



(a) Plants raised from seeds D^d^, which are expected to 

 yield i sort of seeds (round, yellow) ; this is expressed by the 

 coefficient of the term, which is i. 



(P) Plants raised from zDRd^ ; coefficient 2 ; 2 sorts of 

 seeds (round, yellow; wrinkled, yellow). 



(y) Plants raised from 2D^dr ; coefficient 2 ; 2 sorts of 

 seeds (round, yellow; round, green). 



(8) Plants raised from ^DRdr ; coefficient 4 ; 4 sorts of seeds 

 (round, yellow ; round, green ; wrinkled, yellow ; wrinkled, 

 green). 



1 MENDEL, in BATESON. loc. cit., p. 333. Compare the method of cal- 

 culation adopted by Mendel and the method followed here. 



" These experimental results are very satisfactory. Compare the figures 

 obtained by tossing 500 times one coin, p. 119. 



