MENDEL'S PRINCIPLES APPLIED TO WHEAT II Y MUDS. 



893 



proximate percentages of which would be respectively G 4- 18 + 12 + 3G 

 4- 6 4- 18. 



This Mendelian expectation agrees well with actual percentages 

 respectively of Prof. Spillman's given above, viz. : — G'G + 19*1 + 11 0 

 + 85*4 + G'5 + 17*7. It is quite evident, therefore, that the Mendelian 

 Principles apply to two characters taken together as well as to single 

 characters taken separately, though the expression of them is naturally 

 more complicated. 



Secondly, we will consider the still more complicated case of three 

 characters taken together. In Tables XL and XII. a variety with " long 

 heads " and " brown velvet chaff " is crossed with a variety with " short 

 heads " and " light-coloured glabrous chaff." The result is twenty hybrids 

 with "intermediate heads" and "brown velvet chaff'." These twenty 

 hybrids self-fertilised produced twenty plats containing twelve types, on 

 the average in the following proportions, viz, : — 16*1 (1 4- br + v) + 5-1 

 (1 + br + g) -f 4«4 (1 + li + v) + 1-0 (I li 4- g) + 3P3 (si + br + v) 

 + 8-3 (si + br + g) + 9-8 (si + li + v) + 1-9 (si +■ li + g) + 10-8 (s + br 

 4- v) + 4-1 (s + br + g) + 3-8 (s + li + v) + 1G (s + li + g). The Men- 

 delian formula* for the three single characters are respectively 1 1 + 2 si 

 4- 1 s, 3 br + li, and 3 v + 1 g, and the possible combinations between 

 these would be 9 (1 4- br 4- v) 4-3 (1 4- br 4- g) + 3 (1 4- li 4- v) 4- 1 

 (1 + li 4- g) + 18 (si 4- br 4- v ( 4- G (si 4- br + g) 4- 6 (si + li + v) + 2 

 (si 4- li 4- g) + 9 (s 4- br 4- v) + 8 (s + br 4- g) + 3 (s 4- li 4- v) 4- 1 

 (s 4- li 4- g), the approximate percentages of which would be respectively 13-5 

 4- 4-5 4- 4-5 4- 1-5 -f k ^7-0 4- 9-0 4- 9-0 4- 3-0 4- 18'fi 4- i'5 4- i'6 4- 1*5. 



This Mendelian expectation agrees fairly with the actual percentages 

 respectively of Prof. Spillman's given above, viz, lG'l 4- 5*1 4- 4*4 

 4- l'G 4- 31-3 4- 8-3 4- 9-8 4- P9 + 10*8 4- 4'1 4- 3-8 4- 1*6. It is quite 

 evident, therefore, that the Mendelian Principles apply equally to three 

 characters taken together as well as to two characters and to single charac- 

 ters, though the expression is necessarily much more complicated. 



Prof. Spillman's facts, on the whole, as he himself says, prove to the 

 practical hybridist that in the self-fertilisation of first-crosses between 

 constant varieties it is possible to know beforehand exactly what types 

 will be obtained, and further to calculate the average percentage of each. 

 It reflects the greatest possible credit on Prof. Spillman that he should 

 have arrived at this result independently, not having apparently heard of 

 Mendel's work on similar lines, and the thanks of all hybridists are due to 

 him for his independent confirmation of Mendel's Principles. 



Since the above paper was sent to the press Mr. Bateson has kindly 

 drawn my attention to a further paper by Prof. Spillman in " Science," 

 1902, xvi. p. 794, in which he himself clearly notes the Mendelian 

 significance of his experiments. — C. C. H. 



