THE METHOD OF EUGENICS 



17 



(Red 

 aiK«stnl ronn). 



iWhite 

 ucestrdfoiBt. 



Zyg 



Ind 



1 



(Second filial generation) ^^^m 



zyg 00 



Ind 



(Third filial generation' 



Fig. 6. — Illustration of laws of inheritance drawn from the crossing of 

 red (a) and white (6) flowered four-o'clocks {Mirabilis jalappa). The offspring 

 of this cross, having the determiner for red from one side only, produced pink 

 flowers only (c). But when these pink-flowered plants were bred together 

 they produced plants of which one in four had red flowers (duplex, d), two in 

 four had pink flowers (simplex, e. /.), while one in four had no red pigment 

 (nulliplex, g). In the lower part of the chart is a diagram showing for each 

 generation the sort of germ cells involved in the union (zygote), the color of 

 the adult, and the nature of the germ-cells he produces; all carried out to the 

 third generation of descendants. From V. Haeckek: "Wandtafeln zur all- 

 gemeinen Biologic" (Nageli: Leipzig). 



