Ill 



MENDEL'S WORK 21 



plants from which the tall character has been 

 eliminated, i.e. to pure recessive dwarfs. Conse- 

 quently from the ^x ovules of the self - fertilised 

 hybrid we ought to obtain "^^x tall and x dwarf 

 plants. And of the ix tails x should breed true to 

 tallness, while the remaining 2x, having been formed 

 like the original hybrid by the union of a " tall " 

 and a "dwarf" gamete, ought to behave like it 

 when bred from and give tails and dwarfs in the 

 ratio 3:1. Now this is precisely the result actually 

 obtained by experiment (cf p. 18), and the close 

 accord of the experimental results with those deduced 

 on the assumption of the purity of the gametes as 

 enunciated by Mendel affords the strongest of 

 arguments for regarding the nature of the gametes 

 and their relation to the characters of the zygotes in 

 the way that he has done. 



It is possible to put the theory to a further test. 

 The explanation of the 3 : i ratio of dominants and 

 recessives in the F2 generation is regarded as due 

 to the Fi individuals producing equal numbers of 

 gametes bearing the dominant and recessive elements 

 respectively. If now the F^ plant be crossed with 

 the pure recessive, we are bringing together a series 

 of gametes consisting of equal numbers of dominants 

 and recessives with a scries consisting solely of 

 recessives. We ought from such a cross to obtain 

 equal numbers of dominant and recessive individuals, 

 and further, the dominants so produced ought all to 

 give both dominants and recessives in the ratio 

 3 : I when they themselves are bred from. Both 

 of these expectations were amply confirmed by 

 experiment, and crossing with the recessive is now a 



