28 THE MENDEL JOURNAL 



of male and female germ-cells are entirely a 

 matter of chance. For under these conditions 

 the only possible unions among the germ-cells- 

 are : — 



■■•• 2 Dominant x d Dominant 



2 „ X d Recessive 



2 Recessive x 6 Dominant 

 2 ,, X J Recessive 



As the nnmbers of each type of both male 



and female germ-cells are equal, it follows that, 



on the average, each 2 D will have an equal chance 



of being fertilised by either a c? D or a d' R, and 



each 2 R an exactly similar chaiice. As the 



chances are eqiial therefore in all cases, the 



numbers of matings of each of the four types 



will be equal also, and the result must be on the 



average : — 



1 D : 2 D (R)t : 1 R. 



So Mendel's Law amounts to this, that when a. 

 pair, or am^ number of pairs, of contrasted 

 characters are combined in one individual {i.e., 

 when that individual is hybrid with regard to those 

 characters) the two factors for each pair are 

 separated from one another during the formation of 

 the germ-cells, so that half the latter contain the 

 factor for one character and half the factor for the 

 other character, the various pairs of characters 

 behaving in an absoluteh^ independent manner and 

 giving rise, therefore, to germ-cells containing 



* The sign 2 represents female and J" indicates male. 

 t It was ascertained by reciprocal crossing that there was no 

 difference between 2 D x c? R and 2 R x J D, 



