SEX INHERITANCE 129 
If a Japanese female is crossed to a European male, 
the F, female and male may be represented in the 
following formula: 
F, ¢ (FF) Mm F, ¢ (FF) M M 
100 60 100 80, 60 
Both ‘‘normal” female and male offspring are 
expected in equal numbers. The reciprocal cross 
gives a different result viz.: 
F, ¢ (FF) Mm F, ¢ (FF) M M 
80 =—80 80 80, 60 
The F, female is FF —- M=0; and is therefore 
represented as intersexual. It will be observed that 
the so-called ‘‘female factors” in these formule 
are supposed to be inherited entirely through the 
mother. 
By assigning different values to FF and M in 
the different races it is possible to express the results 
in such a way that the sexes obtained by various 
crosses have different minimal values—those less 
or more than any assigned value for a given sex 
are interpreted as intersexes. In the example 
cited, an exact balance (= 0) between the con- 
flicting factors produces an individual that is neither 
male nor female, but made up of a mosaic of parts 
each of which is roughly comparable to the same 
part in a male or a female. 
A series of crosses between species of Biston 
have been made by J. W. Harrison. The sex ratios 
are altered and in some cases intersexual females 
