PLANT HYBRIDIZATION BEFORE MENDEL 255 



spring in question, for the four categories of 4, 3, 2, and 1 tri- 

 color grandparents with both parents tricolor, was 106, lOl, 24, 

 and 8, respectively. The correspondence between the calculated 

 result and the observed numbers, in the case where one parent 

 only was tricolor, and where neither was tricolor, was equally 

 close. The calculations made in a similar manner, where the num- 

 ber of tricolors in the great-grandparents was 8, 7, 6, 5, and 4, 

 respectively; in the grandparents, 4, 3, and 2, respectively, and 

 in the parents 2 and 1, respectively, showed an equally remark- 

 able close correspondence between the calculated results and the 

 observed facts. 



For example, where the tricolors in the great-grandparents 

 were, 7, 6, 5, and 4, respectively, the number of tricolors in 

 grandparents 3, and the number in the parents 2, the relation 

 between the calculated and the observed facts in the four cases 

 was found to be 16 : 17, 18 : 19, 13 : 14, and 5:6, respectively. The 

 summary of all cases gave the relation of calculated to observed 

 tricolor in the offspring as 180:181. 



It would thus appear that the contribution of the immediate 

 ancestors to the color-inheritance, theoretically and experimen- 

 tally, would be as follows : 



Parents each O.2500 



Grandparents (tricolor, calculated) each 0.0625 



Grandparents (tricolor, experimental) ' each 0.0408 



Grandparents (non-tricolor, experimental) each O.0243 



Using these particular coefficients as components of value. Gal- 

 ton constructed a general coefficient to express each set of com- 

 binations of tricolor and non-tricolor, found in the hounds' an- 

 cestry. The cases are as follows, using "T" for tricolor and "N" 

 for non-tricolor. 



The letters represent all possible combinations of tricolor "T," 

 and non-tricolor "N," according as^they occur in the different 

 cases, each pair of letters representing a pair of grandparents, 

 paternal and maternal. 



Case I , 



TT-TT 



Here all four of the grandparents of the tricolor animals were 



