TYPES OF MENDELIAN HEREDITY 37 
There is a third kind of white race of poultry, 
namely, white Leghorn, in which white is dominant. 
Crossed to colored birds the offspring are white 
(with often a few colored feathers, which indicates 
that dominance is not complete). 
In the silkworm also a dominant white and a reces- 
sive white factor have been found. The genetic 
results are comparable in all respects to those in the 
fowl. 
There are also cases of blacks or melanic types, 
that have different factorial bases. There are three 
black races of Drosophila—called sable, black, and 
ebony—that belong respectively to the first, second, 
and third groups. These are mueh alike, but close 
scrutiny reveals slight differences. Any two crossed 
together give gray F, flies. 
There are three pink eye colors in Drosophila, one 
whose locus is in the third chromosome (pink), and 
two sex linked eye colors which are so similar that no 
certain difference between them can be observed. 
Not only pigment but also structural characters 
may parallel each other in aremarkable manner. For 
example, in Drosophila the mutant stocks ‘‘bow” 
(sex linked) and ‘‘are” (IJ chromosome) have wings 
that curve evenly downward over the abdomen. 
There are also two kinds of flies whose wings turn 
up sharply near the ends. These stocks are “‘jaunty”’ 
(second chromosome) and “jaunty I,’’ which is sex 
linked. Two types, called “fringed” (II chromosome) 
and “spread” (III chromosome), are characterized 
by thin textured wings held out nearly at right 
