THEORY OF RESULTS 213 



will be yellow and green in the ratio of three to one ; 

 on the remaining plant they will be yellow wrinkled 

 only. These, when sown, will produce nothing but 

 yellow wrinkled. Similarly with the isolation of the 

 green rounds. The green rounds in the second hybrid 

 generation are sown ; two out of every three plants 

 produced will bear round as well as wrinkled green, 

 the remaining plant will produce green rounds only. 

 These, when sown, will do likewise. 



It is not, in my opinion, necessary to give any 

 further instances of the application of this sixteen- 

 square Table to practical problems. What the 

 breeder wants is a working familiarity with this 

 Table. If the reader understands it properly and 

 has cases which can be dealt with by its help, there 

 will be no difficulty in applying it to them. It is 

 convenient for this purpose to have this Table in a 

 general form, as on p. 214. "A" and "a" stand 

 for the dominant and recessive members of one pair ; 

 " B " and " b " for those of another pair. 



There is one point in regard to the criticism of 

 Mendelian theory which may be emphasised here. 

 The fact that the 9:3:3:1 ratio can be deduced 

 from a theory of the gametic contents of the germ 

 cells of the hybrid does not prove that theory to be 

 true, because not only can the 9:3:3:1 ratio be 

 shown to follow from the mere combination of two 

 3 : 1 ratios, but the existence, and frequency of 

 occurrence, of the nine zygotic types described on 

 p. 211 follows from the combination of two 1:2:1 

 ratios, as explained on p. 100. My point is this: 



