GAMETIC COUPLING AND REPULSION IN THE SILKWORM. 
119 
Some of the Chinese strains used in the present experiments having 
been heterozygous for the moultinism, I often met with a mixture of tri- 
moulting and tetra-moulting larvae derived from the same parents. But in 
the following account this character is not altogether touched upon, since as 
yet it has not been fully studied. 
IV. Gametic Repulsion. 
I shall first describe cases of repulsion or spurious allelomorphism. 
1. Complete repulsion between the normal pattern (N) and the yellow 
colour (Y). 
a) The Chinese normal yellows isolated from the above mentioned 
mixed population in 1910 were paired inter se, and two matings of them 
gave the following results in 1911 : 
Lot No. Normal yellow Normal white Plain yellow Total. 
X. l.’lO 84 5 41 130 
N. 2. ’10 154 66 86 306 
Total 238 71 127 436 
From these results, it may be inferred that the parental normal yellows 
were heterozygous for marking characters (normal and plain) as w r ell as for 
cocoon colors (yellow and white), their formula being NnYy. From such 
a zygotic constitution we should expect four phenotypes in the subsequent 
generation, i. e. normal yellow, normal w r hite, plain yellow and plain white 
in the ratio of 9 : 3 : 3 : 1. But actually only the first three of these 
expected foims were obtained, no plain w'hite larva having occurred. These 
results can be easily comprehended if w r e assume the occurrence of complete 
repulsion between normal and yellow. On this assumption we have only 
three forms, normal yellow (NynY), normal white (NyNy) and plain yellow 
(nYnY) in the ratio of 2 : 1 : 1. If this assumption is correct the hetero- 
zygous normal yellow ought to produce, when mated among themselves, 
