THE METHOD OF EUGENICS 



17 





(Third filial generatloni 



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

 red (a) and white (&) flowered four-o' clocks {Mirabilisjalappa). 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. Haecker: " Wandtaf eln zur all- 

 gemeinen Biologie" (Nageli: Leipzig). 



