238 Toyama and Mori. 
The results of crossing between various whites and yellow. 
Let us now suppose that crossing between such various whites 
and yellow takes place at random. What results would be produced ? 
I. If the SSYY white was mated with the yellow, ssYY, simple 
monohybrid combinations will result. 2. The same will be the case 
when the ssyy white is mated with the yellow; the difference between 
the first and the second matings being that in the former the white 
is dominant and in the latter it is recessive towards the yellow. 3. In 
the mating between the SSyy white and the ssYY yellow, the Fy 
offspring are dihybrid white (SsYy) which segregate into white and 
yellow in F, in the proportion 13 w:3 y (as in the cross, SSYY x ssyy). 
4. In the heterozygous white forms, such as SSYy and Ssyy, the segre- 
gation will take place and their offspring will be a mixture of three 
different sorts of white forms, i. e. (SSYY + SSYy + SSyy) in the former, 
and (SSyy + Ssyy + ssyy) in the latter. Practically, however, both are 
white breeds which breed true to the whiteness. If such white breeds 
were mated with the yellow, the following combinations would be 
expected: 
a) The Mixed white (SSYY + SSYy + SSyy) crossed with the yellow 
(ssYY). 
F= SsYY + SsYy. 
w.| ar u 
| Sst ee 
Fy = (3 W+ 1 Y) (6 W:2 Y) (13 W+3 Y) 
b) The mixed white (SSyy + Ssyy + ssyy) crossed with the yellow 
(ssYY). 
F= SsYy (SsYy + ssYy) ssYy. 
Ww. WHY. Ve 
| Z R | 
135 (3) WY BE} NS) (13 W+ 3 Y) (1 W:3 Y) (ZSWI: 33%) 
The former cross (a) gives F, broods which are all white and 
disintegrate into three sorts of mixed broods in Foy, i.e., 3 W:ı Y, 
6 W:2Y and 13 W:3Y. The latter cross (b) gives three sorts of Fy 
broods, i. e., all whites, all yellows, and a mixture of 1W:1Y. Of 
the three sorts of F, broods thus produced, the white is a dihybrid 
combination which disintegrates into 13 W:3 Y in Fs, while the yellow 
is a monohybrid form and segregates into 1 W: 3 Y. Hence both white 
and yellow in F, are heterozygous. 
As Toyama (13b, c) has already noticed in his papers, both 
COUTAGNE (3) and KELLOGG (9) obtained the three sorts of F, broods 
