262 Toyama. 



The yellow derived from the dominant white mating and the 

 white from the recessive white mating, when paired inter se will remain 

 true to parents in the succeeding generations, while the white from 

 the former or dominant white mating and the yellow from the latter 

 in the proportion of 75 % will again segregate into white and yellow 

 according to the following gametic combinations which are normal 

 Mendelian figures in F3. 



1. F2 white from the dominant mating paired inter se. 



a. white x white = WW x WW = WW = all white (constant form) 



b. „ X ,, = WW :< WY = WW + WY = all white (a mixture) 



c. „ X ,, = WY :< WY = WW -1- 2 WY -|- YY = 3 whites : i yellow. 



2. F2 yellow from the recessive white mating paired inter se. 



a. yellow x yellow = YY x YY = YY = all yellow. 



b. „ X „ = YY X wY = YY + wY = all yellow. 



c. ,, X ,, = wY X wY = WW -f- 2 wY -f- YY = one white : 3 yellows. 



That is to say, some matings remain true to parents, while the 

 rest segregate into white and yellow; in dominant white series into 

 3W : lY and in the recessive i w: 3Y. Thus in the descendants of the 

 Fl white, whiteness is always dominant to yellow, while in F^ yellow 

 it is always recessive. 



The F^ white mated with Fj yellow or vice versa, on the con- 

 trary will produce both sorts in an equal number as shown below: 



Fl white X Fl yellow = WY X wY = Ww + WY + wY + YY = 

 2 W : 2 Y = I white ; i yellow. 



A result apparently the same as that of monohybrid back-crossings 

 generally met with but as their zygotic constitutions are not the same, 

 neither white nor yellow will remain true to parents, some of them 

 being disintegrated into white and yellow as are shown below: 



whites inbred. 



1. white X white = Ww x Ww = WW -|- 2 Ww -\- ww ^ a mixture of three Kinds 

 of whites. 



2. white X white = Ww X WY = WW -|- WY + Ww -f w Y= 3 whites : i yellow. 



3. „X „ = WY X WY = WW + 2 WY -|- YY = 3 whites : i yellow. 



Some of the white matings give all white broods, and the rest 

 mixed broods in which we find two different kinds in the proportion 

 of 3 whites : i yellow proportions, in one, the zygotic constitutions 

 being ww, WY, Ww (whites) and wY, (yellow) while in another ww, 

 WY (whites) YY (yellow), and consequently the yellow extracted 



