COUPLING 201 
When blue-oval is crossed with red-spherical, the 
F, plants are all blue-oval. But in F,, instead of 
getting g blue-oval, 3 blue-spherical, 3 red-oval, and 
I red-spherical, the numbers of the different kinds of 
plants obtained closely approached the following 
proportion—I77 : 15:15: 49. 
Such a series would be produced if the allelomorphs 
concerned were associated in the gametes in the 
following proportion, 7 blue-oval, 1 blue-spherical, 
r red-oval, 7 red-spherical, as may easily be verified by 
multiplication. Enormous numbers of plants must 
naturally be examined before it can be asserted that 
the series actually chosen is really the correct one ; 
in fact, mere statistics are hardly capable of proving so 
complicated a proportion as this in the absence of 
independent considerations. 
In a second case, in which the characters concerned 
were fertility and sterility of the anthers, and presence 
and absence of pigment in the axils of the leaves, 
there was evidence to show that the gametic series 
was I5:1:1:15, instead of being 7:1:1:7. In fact, a 
series such as the following appears to be suggested : 
AB. aB. Ab, ab. Total. 
No coupling ans 9 3 3 I 16 
3Z:1:1: 3 ae 41 7 7 9 64 
7 aoe te tee ore 177 15 15 49 256 
I5:1:1:15 oie 737 31 31 225 1,024 
It is remarkable that coupling of the type 3: 1:1:3 
has not yet been observed. The search has, however, 
