PHENOMENA OF INHERITANCE 253 



ble combinations of these determiners in the 

 gametes is (2) 7 or 128. That is, in this case 

 128 kinds of germ cells may be produced, each 

 having a different inheritance formula; and 

 since each of these 128 kinds of male germ 

 cells may unite with any one of the 128 kinds 

 of female germ cells, the number of possible 

 combinations is (128) 2 or 16,384, which repre- 

 sents the number of combinations of these char- 

 acters which are possible in the F 2 generation. 

 Every one of these more than sixteen thousand 

 genotypes may be represented by various com- 

 binations of the letters ABCDEFG and 

 abcdefg. 



When many characters are concerned it is 

 difficult to remember what each letter stands 

 for, and consequently it is customary in such 

 cases to designate characters by the initial let- 

 ter in the name of that character. By this 

 form of short hand one can show in a graphic 

 way the possible segregations and combina- 

 tions of hereditary units in gametes and zy- 

 gotes through successive generations, and as a 

 result many modern works on Mendelian 

 inheritance look like pages of algebraic 

 formulae. 



