24 
Psyche 
[February 
sume distribution and equal interbreeding of all the genetic 
types (given in Gabritschevsky’s Table II) we may expect 
animals appearing in the proportion of the three types shown in 
the table. If we convert the tabular figures into percentages we 
find that they give us an expectation of about 53% b; 14% h; 
33% p. However, these ratios will shift from year to year in 
nature and instead of having equal numbers of six genetic types 
the second year to breed from there will be six types in the 
ratios (6 + 17 + 17) bombylans, 7 hcemorrhoidalis, 16 + 6 plumata , 
causing the gradual piling up of the heterozygous classes. 
The percentages for the region near Moskow are also given. 
It is marked by a dearth of the dominant bombylans. These are 
20% bombylans, 30% hcemorrhoidalis, 50% plumata. A shift 
caused by interbreeding could not take care of these ratios. 
True it is that the presence of even 20% bombylans will distort 
the relative appearance of hcemorrhoidalis and plumata types. If, 
however, we neglect this and compute the percentages for the 
two varieties of yellow thoraxed flies observed, we find that 
about 62.5% of them were p. and 37.5 were hcemorrhoidalis. 
When we consult the table mentioned above and classify the' 
animals resulting from yellow thoraxed parents we find that we 
should expect 70% plumata and 29 . 1% hcemorrhoidalis. 
The above is entirely a theoretical consideration. Actual 
numbers are not given in the text. Percentages for these two 
places only are given. It is unknown whether or not these per- 
centages were based on fair samples of the population. 
I prefer to use Mendel’s type of formulae for simplicity’s sake. 
Let Y = black thorax 
y = lack of black thorax=yellow thorax 
W = white abdomen 
w = lack of White abdomen=red abdomen 
Then a bombylans may be: 
YYww 
YYWW 
Yyww 
possibly YYWw 
YyWW 
YyWw 
