GAMETIC COUPLING AND REPULSION IN THE 
SILKWORM, BOMBVX MORI. 
By 
YOSHIMARO TANAKA. 
Assistant Professor of Zotlogy, College of Agriculture, 
Tohoku Imperial University, Sapporo, Japan. 
With PL IX. 
I. Introduction. 
In the gametogenesis of an individual heterozygous for a factor or factors, 
all possible kinds of gametes as regards the presence or absence of the factor 
or factors are formed in equal numbers. For instance, in the case of a 
zygote heterozygous for two factors, A and B, the gametes to be produced 
is represented thus : 
1 AB : 1 Ab : l aB : 1 ab, 
and by the combination of these gametes there will be formed four classes 
of the offspring, AB, Ab, aB and ab, in the ratio of 9 : 3: 3: 1. 
But a number of cases are known in which certain deviations from the 
above general rule have been observed. Bateson obtained, for example, the 
following result in the cross of the Sweet Pea BL x bl, where B is purple 
(blue factor); b, red; L, long pollen; 1, round pollen. The F, plants were 
all purples with long pollen, and F., consisted of 1528 BL : 106 Bl: 117 
bL: 381 bl- Here the numerical ratio is remarkably different from the 
normal 9 : 3 : 3 : 1 series. 
To account for such an anomalous case, Bateson and his collaborators 
put forth a suggestion that here the possible gametic forms are not produced 
in equal numbers, but that certain gametes occur more frequently than others, 
i. e. a partial coupling takes place between B and L. The gametic series in 
