1926] Inheritance of Color Varieties in V olucella bombylans 
25 
A plumata is : 
yyWw 
yyWW 
A hcemorrhoidalis is: 
yywuo 
Bombylans and plumata may or may not breed true, but hcemorr- 
hoidalis alway& does. 
The simplest explanation is that the combinations of thorax 
and abdomen are closely linked or that the three color phases 
are allelomorphic. 
If we classify the recorded matings by the types or classes of 
offspring produced we find that the results fall readily into one 
or more of the twenty-one theoretical combinations. 
There is a single exceptional individual. It is in the case of 
a hcemorrhoidalis male appearing in what should be a plumata 
group onl v y. It may be an individual variation resmbling hcemorr- 
hoidalis or a case of mutation. Non-disjunction and contamina- 
tion might account for its appearance. It might be a badly dis- 
torted ratio, for one possible mating could produce these in the 
proportion of 3:1. In a number of instances only a single type 
of mating can account for the results obtained. In others several 
combinations could have produced the observed classes in the 
same proportions. It is impossible to distinguish between homo- 
zygous and heterozygous dominants in either parents or offspring 
unless a very detailed genetic study could be successfully carried 
out. 
If we consider that those matings which produced like 
results in the Fi were identical, although in a few cases there is a 
chance to the contrary, we may combine these data. We may 
then calculate the expectancy under such conditions. The cal- 
culated sizes of the classes expected may then be compared with 
the numbers of individuals in each class actually obtained. 
Upon comparing the expected values with the numbers ob- 
served, it is evident that there is a much better agreement than 
could possibly be found due to chance alone. 
Let us now examine these results as I have analysed them 
by the statistical method. 
