194 



GENETICS 



coming from each parent respectively. If all of these 

 independent determiners are equal as regards excess 

 ear-length, each factor would represent an excess of 

 20 mm. above the normal ear-length found in short- 

 eared rabbits, that is, 



220 mm. - 100 mm. 



= 20 mm. 



When according to this computation a lop (20 

 mm. X 6 + 100 mm. = 220 mm.) and a pure short- 

 eared rabbit (20 mm. X + 100 mm. = 100 mm.) 

 are crossed, if imperfect dominance occurs, which 

 is a very common phenomenon, it is true that 

 the offspring might present a "blended" appear- 

 ance. If now these cross-breds of the first gen- 

 eration prove to be trihybrids with respect to excess 

 ear-length, there would be sixty-four possibilities 

 in their progeny segregating out just as in the red- 

 kerneled wheat. 



These possibilities would be arranged in the fol- 

 lowing frequencies: 



