300 Saunders. 
altogether from the pollen; moreover in this latter race W appears 
to be coupled with one of the factors required for singleness. We 
may represent the gametic series in this sulphur-white race thus: 
Ovules Pollen 
ya 
n-ı XYW all xyw 
FEN 
ı XxW 
I xYw 
-I 
n-I xyw 
Now the conclusion stated under (xr) is based on a long series 
of records, and the fact that the eversporting strains employed do 
produce an excess of doubles must, I think, be considered to be 
completely established. A considerable amount of evidence on this 
point is to be found in my paper in the Journal of Genetics (see 
Table III pp. 372 and 373). A glance at the records contained in 
this Table is sufficient to show that the number of families in which 
doubles preponderate are overwhelmingly greater in number than 
those in which there is a majority — almost always inconsiderable — 
of singles. Let us analyse some of these results further. The two 
cases in which the largest number of families were obtained, viz. those 
of the red and sulphur-white strains will serve our purpose. In the 
case of the red strain 87 families were raised representing five gene- 
rations of descendants from one individual. In 5 of these families 
the number of singles and doubles recorded was equal; leaving these 
5 out of consideration together with ı other family in which only a 
solitary individual was obtained, we have left 81 families. Of these 
63 gave an excess, often considerable, of the double form, whereas 
in the remaining 18 families in which there was a deficiency of 
doubles, the amount of the deficiency is usually slight. In one of 
these 18 families the excess of singles was proved not to be genuine, 
for a further sowing made later gave an excess of doubles. Only 
indeed in one case among the whole number is the deficit greater 
than we might expect as a chance variation from the expected ratio, 
regard being paid to the size of the families. In this one case the 
numbers obtained were 23 single and 8 double. In view of all the 
facts it is most improbable that even here we have a genuine 
exception. Actual proof one way or the other is not, however, now 
obtainable. It is perhaps worth mentioning that the parent of this 
family was planted next to a batch of non-double-throwing reds of 
another strain, and it is therefore just possible that accidental fertili- 
