436 P. W. WHITING 
D. The physiology of color production 
As regards coloration of the upper side of the fore-wing there 
is striking symmetry of the proximal to the distal half. In the 
type moth there are black marks near the center. The gray mid- 
area is bounded distally and proximally by outer and inner 
transverse, wavy, black lines. Next to these are the outer and 
inner narrow whitish lines and then the gray marginal and basal 
areas. At extreme margin and base are small black marks. In 
the color variations studied, symmetry is not lost, although 
certain of the markings mentioned are obliterated by intensifi- 
cation or dilution of pigment. 
Color variations may be supposed to depend upon relative 
variations in quantity of a color producer and a color inhibitor. 
Figure 1 expresses the genetic and physiological relationships 
of color production in the proximal half of the fore-wing. The 
conditions in the distal half would be shown by a diagram sym- 
metrical to this. Passing from left to right are shown as labeled 
the conditions at extreme base, basal area, inner white line, 
inner black line, inner half of mid-area, and inner half of median 
spots. The solid heavy curved line labeled C expresses the 
quantity of color producer present in the various regions of the 
wing. It is probable that this is not a single substance, but 
rather a color base and an activating enzyme. The color base 
may be present in greatest amount at extreme base of wing, 
black line, and median spots and in least amount in white line. 
The enzyme may decrease constantly in amount towards center 
of wing. The combination of the curves representing quantities 
of base and enzyme would approximate the curve C. 
The other curves express relative quantity of inhibitor in each 
region for each of the color varieties studied. All of these curves 
are of exactly the same form and each is symmetrical with rela- 
tion to a line drawn through the similarly labeled point in the 
ruled rectangle and at an angle of 45° to the horizontal. The 
curves would therefore coincide where the points superposed. 
The displacement of these points relative to each other represents, 
therefore, the displacement of the curves. 
