1926] Inheritance of Color Varieties in V olucella bombylans 23 
done justice to himself or his material, for although he tabulates 
the data and shows that they may all fit a simple Mendelian 
scheme, yet he does not attempt to show the snugness of this fit. 
This I have tried to do, for one is not content with knowing that 
an hereditary formula may be applied successfully, but desires as 
well to know the probability of its being the most exact inter- 
pretation possible for the given facts. It is when too many 
multiple factors, lethals, normal overlaps, distorted chromosomes 
and the like must be resorted to to elucidate materials of great 
complexity and difficult handling, that many workers take leave 
of this form of analysis. 
The data under consideration show results of matings be- 
tween the three varietal forms, bombylans, hcemorrhoidalis and 
plumata. There are eighteen matings in which both parents are 
known and twelve in which the mother only was observed. Ac- 
cording to the Mendelian scheme as given by Gabritschevsky 
there are twenty-one different genetic types of matings possible. 
Among the forms considered there are two pairs of alter- 
natives. Either the thorax and base of abdomen are black or 
■they are yellow with a rusty red tinge on the central portion of 
the mesonotum. The fourth abdominal segment is either rusty 
red or white. 
The black thorax and red abdomen are characteristic of 
bombylans. The yellow thorax and red abdomen distinguish 
hcemorrhoidalis from plumata which bears the yellow thorax and 
white abdomen. 
The fourth possible combination, that of a black thorax and 
white abdomen does not appear in nature. This may be taken 
to mean that the presence of a black thorax tinges the abdomen 
regardless of those factors affecting it specifically. True it is that 
there is variation in intensity of the rusty red abdominal color in 
bombylans. Such a condition would give us reasons for at least 
three such variations according to whether the specific color 
factors which the animal contained were homozygous for red, 
for white or heterozygous for both. 
In Kurst Stad (Russia) the three color varieties are distri- 
buted in the proportion of 50% b; 20% h; 30% p. If we as- 
